Correct motor and transmission mount set up

[Cgoldhill]

Just looking for confirmation on the correct mounting set up for my '72 Chevy C10 long bed as I'm trying to diagnose a potential bad rear main seal. I swapped a Muncie in over a year ago and at time of install there was no rear transmission crossmember so I purchased a new one and installed it with a new rear mount. The truck was originally equipped with a Saginaw that used the bellhousing mounts. My question is should both the rear transmission crossmember mount and the bellhousing mounts be used or just the rear mount along with the 2 engine mounts? Can using the both sets of mounts for the transmission cause any driveline angle issues?

At the moment I have the rear transmission mount, the bellhousing mounts and engine mounts all attached. I'm having a serious oil leak issue coming from the rear that looks like a rear main. My thought is by having both the transmission rear mount and bellhousing mounts attached its pulling the transmission down at enough of an angle to create a gap in the rear main. The bellhousing mounts themselves are in pretty bad shape and very squeeshy. The rear main was replaced about a year ago, not at the same time as the Muncie, but was performed by a shop and had no leaking issues for some time. A few months ago I noticed the bellhousing mount bolts were pretty loose so I tightened them up. It seems like not too long after I developed this leaking issue. At first I thought it was a bad oil pan gasket as I know the shop had replaced the main ( or so they told me). Replaced both the pan and gasket with a one piece fel pro, made sure I had the right thick gasket, etc. RTV in the corners, torqued properly, waited 24 hours for rtv to dry beforing filling and running. Pan bolted up nicely but the leak actually seems worse now after start up. It won't actively leak at idle, only when giving it the business. When I say leak, I mean its pretty prominent. After a good full throttle run oil quickly collects around the starter and backside of motor and drips on the passenger side. I've also replaced the valve cover gaskets and distributor gasket in the past.

This is a supercharged 350 with about 100k miles on the rings. Considering the motor still runs great and don't have issues with performance, I don't think the rings have gone so bad that I'm pressurizing the crankcase at full boost. I get alittle smoke on initial start up from probably leaky valve stems but no smoke while driving or under boost. It also has a breather on one valve cover, and pcv valve properly routed to a catch can and a good vacuum source on the other side.

[68bbc/20]

i wouldn't see where the 2 mounts would cause a problem. it would be hard to bend the input shaft to enough to cause the rear seal to leak when trans is held in line with the bellhouse and pilot bushing. i'd look at the oil pressure line under the distributor and see if that' where it's coming from, simple to check and eliminate before you start digging deeper for the problem. do you have any noise from the transmission indicating the from bearing may be going bad?

[Cgoldhill]

Good to hear. I was afraid someone was going to respond with "you ruined your crank idiot!" or something like that. Is the extra set of mounts redundant though? If they're unnecessary, I'd rather just run the rear trans mount and pop out the middle crossmember for better under engine access for repairs.

I just checked that area you suggested and see there was some oil build up from the base of that oil port and what looked like a nice sheen of fresh oil leading to the clutch lever hole. I have an in cab oil pressure gauge and theres an adapter fitting at that port to a hard line. The inside of the bellhousing also gets covered in oil but i always found it odd that the flywheel has no oil on it at all. I'm thinking oil leaking from the port flowed down the bellhousing into the clutch lever hole and the rotation motion of the clutch assembly is whipping the oil around to then collect at the starter. Im not experiencing any clutch slip which I'd think I'd notice immediately if the clutch was getting soaked in oil. Fitting didnt feel loose but I backed it off 1/8 turn and retightened it another 1/4 turn. Ran the motor and revved and not seeing anything coming out. Also checked the rtv between the backside of the intake manifold and lifter valley and didnt see any blow outs. Again though, this only seemed to happen at high load so it may not even be possible to recreate the issue in my driveway.

I have permadry plus valve cover gaskets and may have torqued them too tight previously. I'm going to pop the covers off, make sure they are straight and properly torque them instead of good and snug.

Once I've eliminated all of these potential causes, I'll go for another test ride and if it still leaks, I may put in a new rear seal. Should I do decide to dive into the rear main, I'm fairly sure there is currently a Fel-Pro 2900 rear main installed if thats what comes in the gasket sets. It could also be the regular BSXXXX standard main. Is the 2912 a large improvement over the 2900?

As for the trans, I don't hear anything out of the ordinary but this is my first Muncie and between the oil school Weiand 142 gear chatter at idle, dolphin noises when it revs and the gear noises the Muncie makes normally, I'm not exactly confident I know its all good. The throwout bearing makes some noises as it changes when I push the clutch in and out. I know the oil leaking out is definitely fresh new motor oil, not stinky gear oil from the Muncie but where the oil tends to collect on the trans side in the bellhousing and not the flywheel side is what is confusing and makes me think its not a rear main.

Any more info is greatly appreciated! I'm actively working on the truck now and will check this post periodically. Thanks!

[HO455]

Have you checked your bell housing for run out? Here is a link to a primer on the process.
You can also put dye in the engine oil to help determine where the leak is coming from. (2nd link)


https://www.bowlertransmissions.com/...install-guide/

https://www.amazon.com/Tracer-Produc.../dp/B000JFHNTM

[Ironangel]

There is a 3/'8-16 threaded hole in the front of the block directly in front of the fuel pump. A 3/4" long 3/8-16 bolt should be in that hole, sometimes they're missing and oil can escape and travel to the bell housing oiling the lower right side of the motor including the fuel pump and starter. That hole is provided to lock/hold the fuel pump push rod in place when the pump is removed. Just a thought...

[Cgoldhill]

Originally Posted by Ironangel

There is a 3/'8-16 threaded hole in the front of the block directly in front of the fuel pump. A 3/4" long 3/8-16 bolt should be in that hole, sometimes they're missing and oil can escape and travel to the bell housing oiling the lower right side of the motor including the fuel pump and starter. That hole is provided to lock/hold the fuel pump push rod in place when the pump is removed. Just a thought...

I will definitely check it. I’m fairly sure there’s a bolt there but not sure how secure it is. I also resealed the fuel pump block off plate as I had a paper gasket in there before but still leaking heavily. I take it I should be using thread sealer on this bolt, correct?

Anything else like these suggestions? This is exactly the kind of stuff I was looking for. All of this info seems to be scattered through out the forum. Searching turns up some stuff but it’s a lot of randomness that doesn’t always apply to my circumstances.

Anyone have any suggestions for the lifter valley gaskets in a forced induction application? Everyone says to use straight permatex black or the right stuff. Are there any lifter valley gaskets out there that stand up to added pressures for some extra insurance? With boost, I’d think a sealer dressed physical gasket would hold up better than squished rtv.
I’d love to hear from someone who is boosted and what they have had good experience with.

This is somewhat off topic and I may need to post this somewhere else.
I have a set of felpro 1205 intake gaskets new in the garage which has the heat crossover blocked. The weiand blower manifold has no crossover at all but I do have original heads. Will the 1205 gasket burn out or be ok since there is no void in the intake manifold? Even if it did burn out, would it matter? I just don’t want the exhaust to damage the gasket enough to affect the seal around a nearby intake or coolant port.
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