HWooldridge had his engine apart and came to the Bulletin Board for some advice as to just how far he should go with the rebuild. "I have an F-134 torn down to bare block for rebuild. The CJ-3B that it came out of has 34,000 miles; it ran okay and didn't knock, but was running very rich, burning oil and had about 60 pounds of compression in each cylinder. In general, the interior of the engine is very clean, but has a lot of sooty black carbon on the exhaust path and valves. All cylinders measure two to three thousandths of an inch out of round in the direction of stroke (side to side), with 3-5 taper and 5-7 diameter out of spec from factory numbers. The pistons are stamped ‘STD’ on top, but do not have a carbon ring near the top.
"My thought is to bore out .010 of an inch over, install new pistons and rings and then leave everything else alone, except maybe lap the valves and reset clearances. My question is --- how much is enough? If this is the original cam, should I replace it? The timing gears, rods and crank all look good so I was planning no change there. I want a reliable stock engine for going into the boonies, but it will not be an everyday driver so probably won't see more than 1-2 thousand miles per year. Any info is appreciated."
Glenn Smith suggested: "Assuming you’re saying that you’ve measured the crank and are not relying on strictly looking at it, why not just hone the cylinders and stay with the standard pistons? Then you wouldn't need any machine work at all. It sounds like the rings were more weak than worn. Does the cam look worn? Like you said, lap the valves if they're not in bad shape. It wouldn't be as good as a total rebuild, but judging from your intended use, you would probably be satisfied with the way it ran. If you do have it bored, have the head done professionally too and let the machine shop look at the crank and cam."
Ed Wilson said: "The rule that I followed in my rebuild a couple years ago was, ‘It'll never be any easier than now,’ whatever rebuild component you are thinking about. A general rule that I have heard from mechanics all my life is don't rebuild only part of the engine. In your case, the increased compression of the work that you mentioned on the bores may over-stress the used rod and main bearings. Also, old cam bearings can be a problem too.
"If budget considerations allow, the best way to go is a total overhaul, then you have an engine in which all components can be built to the proper tolerances and the entire unit has an equal life span. I just fear that you will be unhappy with less at some point in time, wishing that you had done this or that while the engine was apart."
Steve Lane agreed: "I second Ed's comments. I have my engine apart as I write this. I finally talked myself into doing the ‘full meal deal’ before it goes back into the chassis; I'm very glad that I did.
"Once I pulled the pistons, I found evidence of a half-rebuild. The cylinder bores had pits in them, ostensibly from where the rings had rusted in place and then been broken loose. A prior owner had simply used a ridge reamer to take most of the ridge off of the bores and then honed the cylinders as smooth as possible. Still some pits and scratches remain. The rings looked really good, so they must have been replaced. The rod caps had several rounded off heads on the nuts; I’m not sure how, or if, they were torqued accurately. The bearing surfaces on the crank looked pretty good, and polished up nicely with some 400 and 600 grit wet-or-dry paper. It had already been cut .010 of an inch under.
"The valve train was just horrible. Exactly ONE valve out of eight showed a good sealing surface and the 1-2 intake port had fresh oil in it when I removed the manifold from the block. The valve stem seals were nowhere to be found and I found one broken valve spring. All of the valves and guides were worn horribly. Possibly the originals were still in place.
"I finally convinced myself that if I did it halfway and had to do it again in less than 8 or 10 years, I would never forgive myself. I ordered up the requisite parts for the rebuild. The block, head and crank are going to the machine shop on Monday. I’m going .040 of an inch over on the pistons, .020 of an inch under on the crank and stainless valves with hardened exhaust seats are in order.
"Check the block deck for flatness and a light skim cut if necessary, and the same for the head. They're also going to install new cam bearings since the hot-tanking process eats the old ones and press in the new valve guides to the proper depth. I'm going to save a few bucks by lapping in the valves myself and reassembling the valve train.
"As I said before, go for the full whammy. Think of it this way: yes, you will have a few hundred bucks up front, but when you have to redo it somewhere down the road, you will not only have to do everything that you didn't do this time, but you are also going to have to redo everything you did in the half-rebuild too. Besides, the engine is already out. That is often the hardest part!"
Mike voiced his opinion: "Take it to a good machine shop, one that you can trust. I was ready to get new pistons and bore the cylinders and put all new valves in, but the guy said that the pistons were fine. He machined the head and did a valve job; it saved me about $500.00. I told him don't worry how much it cost, just do it right and get what it needs. I am very thankful that I found someone I can trust."
Tom Callahan posted: "My suggestion is that you find a machine shop that you feel comfortable with and have them do the stuff you can't. Bring home the parts and put it together yourself. What a great project for you and your youngster/wife/girlfriend/buddy/etc. Get a service manual, follow the reassembly directions and if you run into a problem, post your question on the Bulletin Board. Someone who follows this page has probably encountered the same problem somewhere along the line, and they probably have found a way to remedy it. As for machine work, my experience is to take off only the material that is necessary. Why bore .040 of an inch over, when .010 of an inch will do it, and still leave material for the next time?"
GSlater posted: "I completed restoring my '63 Willys CJ-5 Tuxedo Park, and had the engine overhauled by a local shop. It runs like a top. The result in having a professional do it is they have the specs, tools, knowledge and patience to do it right. My wife and I started to rebuild this F-head motor and did it halfway, so we were lucky that the rust inside didn't seize it permanently. It's a piece of history and the motor gives my '63 CJ-5 that unique Jeep sound that just doesn't exist with the modern versions that simply carry the name."
HWooldridge made his decision: "I have decided to go ahead and do a .010 of an inch overbore with corresponding new parts. The guy I'm going to use runs an old and well-established machine shop that does industrial engines. I asked a few questions and he seemed very familiar with this engine. He will do all of the machine work on the head and block, grind the crank, install new hardened valves and seats, and sell me the replacement parts for about $1000. Except for the head and valves, I have to put it all back together. My question is whether this sounds like a good price and are there any unique things to look for or do when restoring one of these engines."
One more reply from the Bulletin Board: "For $1200 I just picked up my L-head from the shop. My compression was only really bad in one cylinder but when opened it up, they found that I needed new bearings, etc., so the list is as follows: clean and paint the engine, new rings and hone cylinders, new oil pump, turn flywheel, install a different distributor that I supplied, replace damaged valves and guides, new gasket set and a bunch of little things. I think that I expected $500 for a valve job but once it is there it is tough to say no. Fortunately, the pistons were fine and the crank had never been turned. Hopefully I am good for another 55 years. If I were you, for that kind of investment I would want a shop to assemble it and stand behind it."
Another anonymous reader replied: "It costs about $12-1500 to go through an engine anymore. Ask the old guy to build the engine altogether. He will probably only charge about $150-200 to take it from totally stripped of accessories to completely rebuilt. That should include boring it out and new valves and pistons. Then you have someone to talk to if it does not work. I could write for an hour about the pitfalls of building jeep engines. A good engine is easy if you have done a bunch, but can be a nightmare if you get a few details wrong."
Jerry Brown suggested: "If you are in or near a big city, check out some commercial re-builders. I agree with the previous comment - get it completely re-done."
Someone else proposed a slightly less in depth approach: "In central NY, a completely rebuilt and reassembled F-head was quoted at $1050. All small parts replaced for that and engine painted. If there is no reason to suspect a bad crank, you can just get the valve job and re-ring your pistons by yourself. Should be under $500 to do that and your compression will go way up. If you choose to reassemble yourself, my experience is that these engines will tolerate a ‘looser’ assembly better than they will a ‘tight’ one."
Rusty came to the Bulletin Board seeking information on milling his head to increase performance: "Does any one know the difference between the standard and high compression heads? Can I mill mine to make it high compression? How much should I remove?"
Reed responded: "A very good question. I don't have the answer, though you should be able to calculate it yourself. Original high compression heads, at least from W-O, were supposedly marked with some sort of a blue indication. Some have supposed that the whole head was painted blue. I, personally, surmise that there should have been found a much more diminutive blue dot on the head. Be that as it may, you can still calculate what material has to be removed from the head to reduce the volume to the compression ratio that you desire. The only admonition, as you would suspect, is how much clearance there is between the piston at TDC and the reduced head clearance. The rest is just math and using the specifications."
Ed Wilson said: "When I was rebuilding my '54 F-head last year, I looked into performance modifications, especially regarding the head. I found very little information on this outside of Clifford Performance. I also talked to my engine guru, the one who builds the race engines and did my engine work. His opinion, which I respect, is that any head or block milling that would increase performance appreciably, would get into valve clearance problems with the flat head pistons. In other words, it would require special pistons with cutouts for valve clearance. Doubting the ‘in stock’ status of these pistons, I abandoned this idea.
"I also inquired about porting or polishing this head. Due the configuration of the F-Head, the usual methods and tools used for this are of little value. A NASCAR engine shop with hi-tech equipment might be able to do this, but they don't take any walk-in customers, especially with my lack of a major sponsor! What we did do was a complete overhaul with a .030-inch overbore and .020-inch milling on the head to square the mating surface. The block did not need any milling. I learned from working with my engine builder that the secret is details, details, and details. I wanted a good performer without investing a fortune, and now I have a strong running F-Head that should last longer than I will."
Wes K provided: "The last two digits of the engine code on the water pump boss are the compression ratio (on F4-134 engines built in 1969 and later). I would check that first; you might already be at 6.9 or 7.1 to 1. Both early and late repair manuals give a maximum warp of the cylinder head surface as .010 inch. Therefore, if you're sure you have a 6.7 or 6.9 to 1 head with no warpage, you could assume a .010 inch cut would do no harm. You could also measure the areas involved. Another option is to search for a thinner head gasket."
Joel Haslett had a different idea: "This question reminds me of something that I wondered about a while ago. I have seen the Swamp Buggy races in Naples, Florida, on TV. They have a class for Jeeps and these appear to have the F-134 motors. I'll bet that those guys know a lot of secrets to building F-134 Jeep motors. Does anyone know someone involved in the Jeep racing down there who could answer some questions?"
Bob Christy chimed in: "I've been involved with racing F-head jeeps for years and I can tell you that some of the racers do many things to the F-head to boost performance. I know that most of them shave the head and the block, but of course how much depends on your situation. Another trick is to create an electronic ignition distributor out of one from a V-8; from what I've seen it's pretty easy to do as long as you know a machinist who can make the right rod for you. Other tricks are carburetors and headers."
A question on the CJ-3B Bulletin Board: "I was afraid of this. For several months I could not get my Jeep to start (it's a '55 with a F-head 4 cyl.) When I finally checked the oil level with the dipstick, the oil was all watery-kind of a gray-colored water. I've heard this is a blown head gasket or something like that... What to do? All advice appreciated!"
And Curtis had a similar problem: "I had everything necessary to start the newly overhauled F-134 tonight, and I reached the stage at which I needed to fill the cooling system. I got up to 12 quarts, and water still did not show in the top of the rad. I continued, and realizing the worst might be occurring, paused to check the dipstick. The oil level was nearly twice as high as the full mark. I obtained a plastic tub to place under the oil pan, and slowly unscrewed the oil drain plug until a thin trickle of water dripped out of the drain hole. I continued out with the plug, until the water came gushing out. I would estimate that the pan caught 6-7 quarts, and another quart or so ended up on the floor. The passage of the water from the cooling system to the oil reservoir was so swift that the water I was pouring in did not even back up before draining into the oil pan. Whatever I must do now, I feel that there will probably be a long and hellish road to get back to where I thought I was tonight. If anyone can venture any explanation at all as to why this happened, I would be grateful. I'm not sure that I could have imagined a more disturbing malady."
JC Jenkins: "First, it could be a head gasket, it could be a cracked head or even a cracked block... all of these are NOT life threatening, and with a little patience and a good manual you will overcome it... keep us posted."
Reed Cary: "Your engine is not seized, yet. That is the good news. Were it me, I'd make a quick run to the nearest jobber and buy a few gallons of 'flushing oil'. Drain the crankcase and cooling system completely, fill with new oil, and turn the engine over enough to get oil throughout the engine. (You might repeat this step, for insurance.) Then, you can take your time to find out how the water got in there."
jyotin: "When you put the gasket back on, be sure to get it right side up. It isn't marked, and some people will tell you it doesn't matter, but it does. If you have the manual I believe it is figure 100 that shows the correct side to be up. It is explained in the manual where they talk about tightening sequence. It is really easy -- when you get the gasket, look at the metal that goes around the cylinders. On one side the metal will come together making a solid metal joint between the two cylinders, the other sidethe metal stops and there is a small gap. The solid metal side goes up towards the head."
Jan: "And DON'T forget to scrape off (carefully) the remains of the gasket, and make sure the head and block are clean and flat."
Bob Christy: "I'm not an expert on this but I did replace my head gasket last year after one of those flat freeze plugs blew. A bad gasket is pretty common and an easy fix -- the important part is to find out why it went bad in the first place. I'd take the head off and check to see if the gasket is the problem. If it is, a replacement can be had at NAPA. Don't tell them the year but rather the years it was used (up to 1969 I think). Also, be sure to get the right gasket. The one for the F134 has a large hole for the piston and an oblong end on one side of the hole for the single flathead valve. If you get the wrong one you'll have all kinds of problems."
"The job is fairly easy, should take you 2-3 hours even if you don't know what you're doing. Be sure to beg, borrow or steal a torque wrench and tighten the bolts in the correct sequence. You should be able to find it in any of the service manuals. Don't forget to clean that crap out of the engine and radiator."
Jim Sammons: "My first thought was wrong or improperly fitted head gasket. The next thought was badly cracked head or block. Then maybe a bolt got left out of the head, maybe the short one under the carburetor? The head bolts go right through the water jacket. If one was left out, water would go straight into the crankcase. Not knowing the history of the engine or reason for rebuilding, it's hard to guess."
jyotin: "My money is on the head gasket as well. Is it on right side up? Those gaskets look the same as other ones -- it would be worth a phone call to buy a new one from someone who knows Jeeps -- say, Turner 4WD. Some knuckleheads at the local discount parts store might get it crossed up with another one. It wouldn't surprise me to see that you had the wrong gasket. However, at any case I'd get the head off ASAP because there is always the possibility that the cylinders are full of water too."
Curtis: "Well, I obtained the head and manifold gaskets necessary to properly reassemble the engine, today. According to the fellow at the auto parts store, gasket sealant was not to be used with Fel-Pro head gaskets. The instructions in the overhaul kit confirmed this. I installed the head gasket with the metal side against the block and torqued the bolts evenly to 65 ft-lb in the sequence prescribed. Ecstatic, I rigged a meager wiring harness, which would enable me to run the engine and filled the radiator and oil reservoir. As I grasped the bailing wire loop attached to the carburetor linkage to test the function of my improvised throttle, I noticed a crown of water droplets surrounding the top of the block, just beneath the gasket mating surface. I drained the radiator and block, removed the exhaust manifold, pulled the rocker cover, rocker arms, oil lines, carb, etc., and pulled the head. Everything was dry, except for: those regions surrounding the rectangular water passages around the perimeter of the head, the two triangular casting ports on each end of the generator side of the head, and the two square casting ports on the exhaust side of the head, which lie between the push rod bores. I would expect 65 ft-lb to compress the gasket sufficiently to seal these ports, but there is apparently enough room for them to leak with no pressure at all on the cooling system. Do I need to use a sealant of some sort? If so, what kind of sealant is acceptable? Would red Permatex work? Is there some other defect, which is causing this leakage? I would appreciate hearing any theories, suggestions, or accounts of head installation from other Jeep enthusiasts' overhauls. I hope that this is the last time for a long while that I will have to take the head off. I'm getting too good at it."
Brian: "I had the same problem when I assembled my engine with a Fel-Pro gasket set. I tore it back apart and inspected everything but did not find anything wrong. I went to the local NAPA store and checked out their gasket sets. They are made by Victor -- their head gasket is made with a perforated steel core and covered with a Teflon material. I reassembled my engine, ran it to operating temperature and retorqued all the bolts, and have had no problems."
Bob: "The last time I had a problem like this the head needed resurfacing. If that was already done by a machine shop your head will seal. I have rebuilt many engines and have never used gasket sealer on head gaskets. If the head is warped even a few thousands, torqing will not stop a leak. Good luck!"
Steve: "While you have the head off, use a steel straightedge to check the flatness of the block. With the straightedge on edge, hold it against the top of the block in various places, but especially in the spots where you saw leakage. Have a friend shine a flashlight against one side of the straightedge, while you check for warping. Any amount of warping is unacceptable, and will result in a leak that you cannot seal.
"Repeat the whole procedure with the head. This is where most warping occurs. If it is only the head that is warped (very likely) then you are good to go. A light milling job at your local machine shop will get the job done. If it is the block, then it will need to be disassembled and taken to the machine shop for a 'deck' job. As one of the other posters said, even a couple of thousandths will ruin a head gasket seal, and give you headaches as long as you own this engine. I have never heard of using any type of sealant on a head gasket, with the exception of a pure copper spray used on some racing engines with turbo/superchargers. Follow the manufacturers' recommendations to the letter."
Howard: "Try Fel-Pro copper gasket sealant. I recently pulled the head on my F-134 and used it on the installation. Seems to do the trick"
Vern: "One more quick thing to check is to take a tap and clean out the threads in the block for the head bolts. Crud builds up in there and causes a false torque reading. It would be quick and simple to do. You may even want to thread the bolts into the bare block and double-check the exposed length before you clean out the threads. The bolts could be stopping short due to crud so the head looks tight but really isn't."
Curtis wanted to ensure that his rebuild went back together properly and came to the Bulletin Board for advice: "For guidance in the process of rebuilding the F-134 from my 3B, I have employed the Jeep service manual, Haynes repair manual, and F-134 overhaul guide available on CJ3B.info. Work has gone fairly smoothly up to the crankshaft, which I am fairly concerned about installing correctly. My most critical uncertainty lies in assessment of endplay. A dial indicator and feeler gauges have indicated that it is currently about 0.008 of an inch. The online manual on CJ3B.info states that 0.004 -0.008 of an inch is acceptable, while the Haynes and Jeep manuals list 0.004 - 0.006 of an inch as correct endplay. Shims are available in 0.002 of an inch thickness. Should I go ahead and assemble the engine, or wait until I can obtain the shims? Would I need to use Jeep shims, or could I make my own from shim stock?
"Am I making entirely too big a deal out of this? This is my first automotive engine overhaul, so I am, for the first time, applying theory, which I know very well, toward physical assembly, to which I am virgin. I would appreciate some practical advice. Also, I expect that there will certainly be some wearing-in period for the main bearings, but I am not sure what acceptable taper should be. On the front and rear mains, the plastigage indicates about 0.0005 of an inch of taper which attenuates toward the inside of the crankcase. Is this fairly normal, or should I have another go at the mains? How should I more effectively clean the bearing bores?"
Jim Sammons replied: "If you were building this engine for a boat or something where you might have more than normal thrust on the crankshaft, you would probably want to shim the crankshaft to eliminate some of the end play. Also this is a low rpm engine and not a racing engine so tolerances are not that critical. You will most likely be okay with the endplay you have, but if you want it to be letter perfect, put the recommended shims in, not ones you build yourself. I doubt seriously that you will ever have a problem with that engine if the endplay is at the max recommended. You probably will never have a problem with the taper either. I have put together engines with worse tolerances than that and had them perform just fine. As long as you remember that it is not a racing engine and treat it with due respect, it should give many miles of trouble free service. As for cleaning the crankshaft bore, you just need to wipe it out with solvent or clean it lightly with fine emery or steel wool."
Eric Lawson recommended: ".0005 of an inch of taper in the bearing clearance measurements is actually pretty good. As long as you have the minimum bearing clearances, you are okay. Adding shims increases the endplay of the crankshaft. If you have .008 of an inch of endplay without any shims, go ahead and put it together. .008 inch of endplay, while at the maximum limit, is not excessive.
"I too have seen the various specifications change as I referred to different service books. The only ‘excuse’ I can think of is that the specifications were changed to reflect Willys' increasing experience with the engine. As more engines were built, they had a better idea what they could get away with, and what they could not.
"Check the crankshaft endplay several times as you tighten up the crankshaft nut. If the endplay seems to disappear, you will need to add a shim or two. The first few steps on page 5 of the rebuild page deal with estimating the required shim pack thickness. It usually gets pretty close, within one shim. Because of this, it is wise to measure the endplay as you tighten the crankshaft nut. The tighten-measure-tighten-measure, etc. routine will keep you from hurting the front main bearing if the initial estimate was incorrect.
"When the crank is in place in the block, the machined thrust surface at the front of the #1 crank throw touching the rear lip of the front main bearing stops further forward movement of the crank. The thrust washer touching the front lip of the front main bearing stops further rearward movement of the crankshaft. The shims go between the crankshaft main journal and the thrust washer and the shims are smaller in diameter than the journal diameter. Adding shims spaces the thrust washer further forward on the crankshaft. This will allow more rearward movement of the crank before the thrust washer contacts the front main bearing's front lip. The total front to rear movement of the crank is the endplay.
"It isn't that unusual to have a crankshaft that has a near maximum endplay measurement without using any shims. The thrust surface on the front crank throw gets worn during normal use, or ground away when someone who isn’t paying attention to their job regrinds the crank. This is what causes the increased endplay. If you look at the fifth image on page 5 of the rebuild page, you can see the thrust surface in the picture of the crankshaft (the picture with the thrust washer installed on the crank). The thrust surface is the machined surface on the crank throw.
"If the endplay is very excessive, this thrust surface can be built up with the hard chrome process. If you do this, be prepared to spend $75 to $100. I looked into some cheaper alternatives to fix the excessive endplay problem, but decided hard chroming was the only way to fix things and not cause other problems."
Thomas had a bit of difficulty while trying to replace the rear main seal. "I need some HELP!! I have spent two day and two sets of packing trying to install the two round seals in the rear main. I am to the point of trying anything. I have tried water and oil and even put them in the freezer, which did help a little. The packing seems to be too large; the farthest that I have been able to push it into the hole is about 2/3 of the way. This was done with great difficulty and continually twisting the packing. I wonder if the replacement packing that I have is made differently than the OEM? If this is just a plug to stop oil from leaking, could silicone be put into the holes just as well? I really hate the idea of that much silicone, but I'm desperate. Is there an alternate way to seal this? Any help or suggestions will be greatly appreciated."
Wes K said: "If you insist on using the rope style seal, then you need to buy the appropriate tools. You should also consider removing the engine or loosening the crank bearing caps. I prefer to use the newer two-piece preformed seal. The Willys and Kaiser manuals both give detailed instructions on changing either style seal. See also "Rebuilding an F-head Engine" Page 5 and Page 7."
Eric Lawson responded: "I don't think that the silicone would help here. It would probably seal the sides of the cap, but I'm not sure if it would help at the bottom of the bore where the seals are installed. The only places I've used silicone are where the parts are pushed together. In the bearing cap, the bead is going to be wiped off of the cap as the cap is placed into position. There is really no compression on the sides of the bearing cap and I think it would be likely that the oil would move between the cap and the silicone seal.
"I assume that you have made sure there isn't any crud in the bores where the seals are installed? I've come to the same conclusion about some of the packings; they are too large. I don't know why this is the case. I've asked some folks who I thought would have a good answer and the best answer that I've received is that the information on why they were designed as they were is long gone.
"I've tried the following things and if they didn't work, went out and got another seal set: water or light oil on the packings along with twisting them as I install them; leaving the bearing cap bolts slightly loose and then trying to install the seals and installing the seals first and then installing the bearing cap. I have also tried reducing the diameter of the seals and that has always resulted in oil leaks. A friend tried increasing the diameter of the bores and he too ended up with an oil leak, this time unrepairable."
Chuck provided: "Although I have not done the job, the man that I purchased my 3B from states that you should soak the seal in kerosene."
Steve said: "I had the same problem inserting the round rubber seals. They came in a gasket set for an engine overhaul and I could not get them in. I determined that they were oversized, got new ones and they inserted with no problem."
Drac replied: "If you still have the original seal, you can tighten it up by using a wire between the seal and block. This was an old trick and was usually done with the engine still in place. There was a commercially available kit for doing this. If you no longer have the original, then try the following: Plasti-gage the bearing surface first and make sure the clearance is correct. Then push the seal in as far as you can, place the crank in place and keep working the crank back and forth. Eventually, the seal will become longer. Next, you trim the excess off, leaving a little bit, about 1/8 inch, on both sides. This will compact and increase the pressure against the crank when the cap is installed. Repeat this procedure with the cap side of the seal. When you are done, there will be a significant amount of force required to turn the crank due to drag from the seal."
B.C. answered: "I used plenty of assembly lube and installed the seals and cap together. It was tight and hard to do, but no leaks."
Russ asked: "Anyone ever tried putting them in the freezer for a while before installing them? I’m only wondering, as I will be doing a rear seal before long. I am thinking of replacement without pulling the engine or crank."
Dave Strader posted: "I think that you guys are talking about installing a new rope seal on the rear main. There are two ways to go here. For the F-head motors, you can use the later style neoprene two-piece seal. When you’re at the parts store, just ask for a rear main seal kit for a 1970 134 motor. For the earlier L-head motors, only the rope seal kit is available. While at the parts store getting your parts, ask for a ‘Sneaky-Pete.’ It is a small piece of woven wire with a T-handle on one end. The other end has the woven wire expanded out. I know that Cal-Van and Lisle make them.
"After you get home, pull the oil pan and the two bolts attaching the lower half of the rear main. Remove the lower rear main. Pull the old rope seal from the upper half of the main with a needle nose pliers or the Sneaky-Pete. You might have to use a brass punch to get it started out. Clean off all of the crud. Loop the Sneaky-Pete over the crank and attach the end of the rope seal to it. Now pull the seal into place. Sometimes a little assembly lube or oil helps. Even up the rope seal. Leave about 3/8 inch of rope past the upper main half. Now install the lower half of the seal and leave the same amount of extra sticking out. Some lower half seals are rope and others are rubber. Install the little rubber dowel pieces if they are required for your motor. Clean off any oil or assembly lube from the seal ends. Dab on a little gasket sealer. Replace the lower main cap and torque the bolts. Put the pan back on and you're done."
Lou Hill had some questions while replacing his rear main seal: "I am replacing my rear main crankshaft seal. The original had a rubber lip with a metal ring inside. This allowed me to drive on the metal ring portion and remove the original seal from the engine block. My new seal does not have this rubber coated metal lip. I think it will be very difficult to install the replacement upper seal into the engine block. I want to find an original style seal. Can anyone tell me where to find one?"
Oldtime answered: "I believe that the Felpro #BS3165 will do you fine. Another seal, Napa Victor brand #JV687 also is metal backed. In fact, these two seals appear to come from the same manufacturer, as they look identical to me. One professional suggestion for installation is to make sure that the two seal halves do not meet at the journal parting line. In other words, rotate the seal just past the half way point."
Lou Hill came back: "Great advice on rotating the seal slightly! One other item that I'm not too sure about; should I try to install the two packings before or at the same time as I reinstall the bottom of the seal holder, or should I install everything and then lube the packings and try to shove them up into the two seal packing openings? It seem like it may hard doing the latter."
Oldtime: "Basically what you need to do is lube then rotate the seal halves into position. Next, clean the bearing cap and mating block surfaces with solvent. Put some non-hardening or elastic type sealer on the areas prone to oil seepage. Install the cap, torque and rotate test the crankshaft. Satisfied with the fit? Now insert the rubber seal rods with a little sealer on either side of the bearing cap. Check the protrusion length of the rubber seal rods. These should be about ¼ inch long. The extra length will compress the side cap seals to a tight fit once the oil pan is installed."
Ken asked: "My flywheel ring gear has several teeth that are about 30% worn off. Do I need to replace it, and if so, is replacing the ring gear something that is manageable in a home shop?"
One anonymous poster said: "There are two ways to get the old ring gear off. The first is with a chisel. Make a cut, not touching the flywheel of course, and pop it off with a brass punch and hammer. The second way is to heat it up with a torch with low heat and use the brass punch and hammer, working evenly around the edge.
"To put a new one on, put the flywheel in the freezer, overnight if possible. Then, heat the ring gear in the oven on the top shelf at about 300 degrees or so. Use a piece of plywood as a worktop. Plop the flywheel down, grab the ring gear with oven mitts or thick insulated leather gloves and it should fit right on. If not, use a hammer and a soft punch. Work quickly. If it still doesn’t go on, reheat/refreeze and try again with quicker action. Oh, and make sure the wife is gone for the afternoon!"
Rick recommended: "Thirty percent worn is not that bad; it probably will last 20 more years. Leave it unless you already have flywheel out anyway."
Steve: "I think I need to install a new ring gear on my flywheel while I have my engine apart. After seeing what a new one looks like I can see it was very worn. The starter bendix would slip out of gear while starting frequently. I have the service manual: it states to heat the gear up to 750 degrees F and install it. Can I cook it in my oven broiler or can I use a torch to heat it? Can anyone give me any tips or should I take to a machine shop and have it done?"
Ernie: "When I changed my ring gear it was easy. With the flywheel off the engine, and sitting on top of a welding table, I warmed the old gear up with the torch and it fell off. I set the new one on the flywheel and warmed it up evenly, then before it cooled I tapped it lightly with a small hammer until it was seated. If you aren't quick you may have to apply heat a second time."
Bob: "Heat the new ring in the oven at 500 degrees for about 10 minutes. Put the flywheel in the freezer about a half hour before you start. It should slip together. Use a 2x4 and hammer if it needs a little help."
Larry: "I have replaced several ring gears by putting the ring gear in the oven for over 20 minutes, the flywheel in the freeze for the same time, and they just fall together. Fact is, you will think the gear is too large! However after all return to room temperature, it fits perfectly. Oh, on an F-134 engine, I have found you can reverse the ring gear when the teeth are bad on one side. So check this out before you buy the new gear."
Will Peltier discovered that his pilot bushing did not fit properly upon installation: "The pilot bushing fits on the end shaft of the transmission before I install it into the flywheel, but when I install it into the flywheel it will not fit over the end shaft. Where can the installation/brandishing tool be found that is shown in the universal manual? Any tips are appreciated."
Reed replied: "The amount of interference that you write of is very small indeed; perhaps less than .001 of an inch. The service manual does not offer the running clearance specs, but I would guess that it is no more than .001 of an inch. This means that you might well only need to remove .002 of an inch of material. This could be accomplished with the proper reamer, but I would think that you could hand-hone it out with some fine crocus cloth wrapped around a dowel, stopping every now and then to check your fit."
Bob Christy agreed: "This is a common problem and I used the same fix; I wrapped emery cloth around a dowel rod and used it to make the bushing fit correctly. It only took about two minutes."
Evan asked: "I thought that I'd query all the great minds out there to get your tips on how best to start up an engine after rebuilding it. I'm sure that there are some ‘make sure you...’s from your own experiences."
HWooldridge had some advice: "I can tell you what not to do: make sure no mud daubers have built a nest in the air cleaner or hose; they tend to get pulled into the engine and screw up your nice freshly honed cylinder walls. This happened to me and is apparently not that uncommon. They can find open holes in a day or so.
"Assuming that you don't have that problem, check twice and then check again to make sure that all fluids are to the right levels and everything is plumbed correctly. Fire it up and idle for 15 minutes then shut it off and check everything. If all is new inside, the engine will smoke like a chimney until the oil rings seat. Start it again and let idle for 30 minutes, but periodically raise the RPMs with the throttle and hold for 5 to 10 minutes and then let it return to idle. Shut it off and let cool overnight and then tighten all of the head bolts and you should be good to go on a test drive. I used 10W-30 oil and changed it and the filter at 500 miles."
Bob said: "After I started my engine and brought it up to temperature for about 15 minutes, I shut it down and changed the oil. This gets all of the special rebuilding lubes out of your oil system. Change the oil again after a few hundred miles. Upon initial startup, it's also a good idea to have a timing light handy to set the timing and a screwdriver to adjust the fuel/air and idle settings."
Bert added: "The most important thing to do when starting a new engine is to make sure that it has oil pressure. I advise turning the engine over without any spark plugs in it until you have oil pressure on the gauge. Then put in the plugs and fire it up."
Thanks to Tech Editor Doug Hoffman and all the contributors. -- Derek Redmond
See Eric Lawson's F-head Engine Rebuild Guide on CJ3B.info.
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