Rear Main Seal

[Bobby]

Hello all! I’ve been working my 1972 Mach 1 since purchased in April 2018. Recently, I had an engine built earlier this year. It’s has 1972 CJ 351 block and is stroked to 393 with an eagle rotating assembly and trickflow 2V aluminum heads, etc, etc. I had it machined and assembled at a local machine shop and then had it dyno’d. During the dyno the rear main seal blew out. I returned the engine to the machine shop to have the seal replaced. I provided a new fel-pro rear main seal for installation. The machinist dug the bad seal out of the trash and showed it to me. It appeared to be heat fatigued and brittle. I figured that it was the result of the high rpm’s of the dyno and the initial break-in. After dealing with rough idle issues and shifting problems with the new rebuilt AOD transmission now the rear main is leaking again! What gives? Any ideas or fixes?

 

[boilermaster]

Bobby,
Let's just get this out of the way first.
Was your block align/ line bored ?
If YES was the rear main seal groove in the block and rear cap also machined ? .
Are the CORRECT harmonic balancer and flywheel/ flexplate being used for your engine balance ?.
Rechecked cam core plug and lifter gallery fittings ?

 

[Bobby]

Bobby,
Let's just get this out of the way first.
Was your block align/ line bored ?
If YES was the rear main seal groove in the block and rear cap also machined ? .
Are the CORRECT harmonic balancer and flywheel/ flexplate being used for your engine balance ?.
Rechecked cam core plug and lifter gallery fittings ?

I doubt that it was aligned and lined. I ended up going to three machine shops to eventually get my engine built. Two of the shops did little of what I requested. Some of my requests were very specific but mostly it was blanket request. I also eventually found a much tallied machine shop that was recommended to me by a friend when I was looking for a dyno. The correct balancer and flexplate are installed. I do not know if the cam core plug and lifter galleries were checked. The block was inspected and I specifically asked for a magnaflux/sonic check that were not performed. I dont get it but the first two shops just didn't perform up to my expectations. The block was in excellent shape when checked. The bores were excellent and it was rebored 30 over for the new rotating assembly. After the first botched attempt to get my build complete, I changed shops but they were little better. I specifically told both shops to re-deck the block. Both resisted for whatever saying that the surfaces were close to perfect and it was unnecessary. The second shop eventually caved and performed the re-deck and then told me that it actually did make a better surface for the heads. I've been shaking my head over all of this since the get go.

 

[MAD IRISHMAN]

Very tough to find quality engine shops these days. Many have gone by the wayside. We have lost our share around Cincinnati but luckily still have a few competent shops to get work done. Sounds like your not that fortunate.

 

[boilermaster]

Bobby,
Suggest that before you fire this engine again that you remove your oil filter, cut it open and inspect for debris, you should only have microscopic particles from the honing process and the piston rings seating to the honing process.
If the rear main seal shows signs of heat damage, you should be concerned as to heat damage of the main bearings as well.
my next would be some engine oil dye and a black light.
you 100% ,need to know if the rear main is the issue or something else is the cause of your leak.
cam plug, lifter galley plugs, intake rear leak, rocker gasket leak, oil pan gasket leak, porous engine block and also the little pin that fits in the rear main cap to hold the OEM rope rear seal in place.
There are lots of leaks that can look like a main seal leak that actually come from other sources.
Boilermaster

 

[Bobby]

Very tough to find quality engine shops these days. Many have gone by the wayside. We have lost our share around Cincinnati but luckily still have a few competent shops to get work done. Sounds like your not that fortunate.

With all the sophisticated cars out now, nobody has the basic skills to work on a car. Buy an extended warranty and let someone else deal with it. Given that, fathers have not been able to pass down basic automotive skills to their kids and few people build and service their own hot rods. I still perform my own maintenance on all my vehicles. However, when you try to trade in a vehicle, if you don’t have official maintenance records, the dealers happily degrade your trade in and offer you much less for it. I told one dealer that I self perform 90% of my maintenance. they could care less. If it doesn’t show up on carfax, it didn’t happen.

 

[Bobby]

Bobby,
Suggest that before you fire this engine again that you remove your oil filter, cut it open and inspect for debris, you should only have microscopic particles from the honing process and the piston rings seating to the honing process.
If the rear main seal shows signs of heat damage, you should be concerned as to heat damage of the main bearings as well.
my next would be some engine oil dye and a black light.
you 100% ,need to know if the rear main is the issue or something else is the cause of your leak.
cam plug, lifter galley plugs, intake rear leak, rocker gasket leak, oil pan gasket leak, porous engine block and also the little pin that fits in the rear main cap to hold the OEM rope rear seal in place.
There are lots of leaks that can look like a main seal leak that actually come from other sources.
Boilermaster

I already took it to a speed shop that I was unaware existed.....under my nose. Literally around the corner from the first machine shop with a more professional building and setup. I had noticed very fine metal shavings on the dip stick and I did cut the oil filter open. Problem was that this filter must have been made with armor plate as it was extremely difficult to cut open and although I didnt see any shavings in it per-se, I did contaminate it with bits of metal from the filter casing while cutting it open. At the shop they drained the oil and inspected it closely and determined that there were no shavings. There is a bit of a rough idle but they could not determine why. The second machine shop did find the pin that secures the old style rope seal on the main cap....obviously overlooked by the first shop. The dyno guy also found that there was another leak at the rear of the intake manifold and the pan gasket as well as the rear main. Again clearly quality control issues at the shops. The second shop "fixed" the leaks. The transmission shop found and fixed another leak. The tranny shop had noticed that the starter was misaligned with the flexplate and there was damage to both. I ordered his recommended flexplate and he replaced the starter with one for an earlier model Mustang. All is well there.

 

[boilermaster]

Glad to hear that things are turning around for you Bobby.
Were the dyno numbers close to what you expected ?.

 

[DAverkamp]

I already took it to a speed shop that I was unaware existed.....under my nose. Literally around the corner from the first machine shop with a more professional building and setup. I had noticed very fine metal shavings on the dip stick and I did cut the oil filter open. Problem was that this filter must have been made with armor plate as it was extremely difficult to cut open and although I didnt see any shavings in it per-se, I did contaminate it with bits of metal from the filter casing while cutting it open. At the shop they drained the oil and inspected it closely and determined that there were no shavings. There is a bit of a rough idle but they could not determine why. The second machine shop did find the pin that secures the old style rope seal on the main cap....obviously overlooked by the first shop. The dyno guy also found that there was another leak at the rear of the intake manifold and the pan gasket as well as the rear main. Again clearly quality control issues at the shops. The second shop "fixed" the leaks. The transmission shop found and fixed another leak. The tranny shop had noticed that the starter was misaligned with the flexplate and there was damage to both. I ordered his recommended flexplate and he replaced the starter with one for an earlier model Mustang. All is well there.

I will chime in now that you found out the hard-way and eliminated the rope seal index pin which should have been a no brainer to the builder unless you wanted to stay totally original which you obviously didn’t. Unless you machined the crank journals for some reason all the other theories are like hearsay to me and the only way to ensure the fel-pro two piece was installed correctly is to be there witnessing the install if not doing it yourself. They need to be “slid” into a clean journal and indexed correctly without being deformed and trimmed to spec and then sealed correctly with a dab of RTV and allowed to cure. Lastly, the main bearing cap is torqued down per spec. That’s the simple part of installing the seal but oil overfilling, extreme oil pressures, etc., will keep you on the wild duck chase IMO.

 

[boilermaster]

DAverkamp,
Never heard of using RTV on rear main seal ends or main cap flanges.
Always used an ANEROBIC sealant, such as Loctite 516 that does not require the presence of air to cure.
Boilermaster

 

[DAverkamp]

Permatex Ultra Black - flexible & oil resistant.

 

[boilermaster]

Bobby,
A couple of items that have not been discussed as of yet, are you running a pcv valve and pcv return hose ?
What oil pan are you using ?
Be aware that some of the aftermarket OEM ( look alike ) pans have issues sealing at the front and rear where they meet the rear main cap and timing cover.
Excessive crankcase pressure could have caused the leaks that you have already discovered.
Boilermaster.

 

[Bobby]

Bobby,
A couple of items that have not been discussed as of yet, are you running a pcv valve and pcv return hose ?
What oil pan are you using ?
Be aware that some of the aftermarket OEM ( look alike ) pans have issues sealing at the front and rear where they meet the rear main cap and timing cover.
Excessive crankcase pressure could have caused the leaks that you have already discovered.
Boilermaster.

Yes, I do have a fully functional PCV system. The oil pan is a Canton Racing expanded capacity flat bottom at the sump. Capacity is 6 quarts. Currently have 6 quarts of Comp Cams 10W-40 break-in oil and a K&N filter.

 

[Bobby]

Glad to hear that things are turning around for you Bobby.
Were the dyno numbers close to what you expected ?.

The dyno results were 475 HP at 4500 RPM and torque 476 ft/lbs at 5800 RPM. The sweet spot is at 5200 RPM. It actually exceeded my expectations. One of the very few things that went right!

 

[Bobby]

Very tough to find quality engine shops these days. Many have gone by the wayside. We have lost our share around Cincinnati but luckily still have a few competent shops to get work done. Sounds like your not that fortunate.

There are more shops around but again what quality of work can I expect? The dyno guy could have performed the build but it would have taken many months to complete. I can rebuild an engine and bring it back to spec but building a hot rod engine with performance parts is not my forte. I do not have the expertise nor the equipment for that. I tried to finish the build myself after the botched attempt from the first machine shop but I had hell with the rotating assembly as the balancer/crank pulley would not line up with the water pump pulley and I was looking for spacers for the crank pulley. I threw up my hands and took it to the second machine shop. they immediately notified me that there was a 3/8 in spacer that was supposed to be installed at the back end of the crankshaft that wasn't! Since it wasn't installed the crank was jacked back and put the timing chain in a bind and would not let the crank be rotated so I could position number 1 piston at top dead center...... In addition to that, one of the cylinders was not bored out to the 30 over spec and required additional honing. The machinist mentioned that it was a tight fit for the rings and piston at that time.

 

[DAverkamp]

Not to break up the HP party but did you guys figure out the rear main seal issue?

 

[Bobby]

Not to break up the HP party but did you guys figure out the rear main seal issue?

Nope! I could still use any possible cause.....I have a functioning PCV system. The crank is part of an Eagle/Mahle system. The oil is accumulating at the bottom of the bell housing. It appears that the oil pan is NOT leaking......

 

[DAverkamp]

I would offer that the E/M company (not familiar with) should be held accountable for your seal issue if they have altered the geometry of your block. Beautiful car but not a fan of the “jacked up” air shock (or look) especially if you want launch from light to light from the torque you have.

 

[Bobby]

I would offer that the E/M company (not familiar with) should be held accountable for your seal issue if they have altered the geometry of your block. Beautiful car but not a fan of the “jacked up” air shock (or look) especially if you want launch from light to light from the torque you have.

I wanted a little more pep for my pony. This stang did not have the performance suspension as it is an H code as built. I dont plan on going to the strip nor do I plan on losing control, totaling my babe and getting myself killed. The HP is there if I need it but I want to go balls to the wall it will be for a few seconds and not trying to get a 12 second quarter mile. Way back when.....all the muscle cars that were customized had the jacked up rear....it was cool and still is for me!

 

[clevelandcoupe]

Bobby,
I didn't see this mentioned but, a note from a previous post stated that the flywheel bolts should have sealer applied when an aftermarket crankshaft is used in a build.
Thanks, Jay