Comp Cam 1

Hi all I purchased a Billy Mitchell 415 World product motor. The motor has given myself and mechanic fits (replaced the rear main twice now)! The problem we think is blowby making the rear main seal leakas well as through the pan bolts like crazy! After a few google searchs I have found others have had the same problem with the motors as well. Can anyone shed some light on the subject to help me understand if there is a fix for something like this overpressurized lower end problem? Thanks (I am afraid of the answer) but can take it.

SledgeHammer 2.0

That's a lot of blowby...

Okay, to have that much crankcase pressure you got to have something really wrong. Do you have an adequate ventilation system for the engine?

Frankie the Fink

Does it have a PCV system....and/or a vented oil filler cap ?
You don't want those corrosive (and explosive) combustion byproducts in your crankcase...

Comp Cam 1

Thats what we added to the engine to try and relieve the pressure. Thanks Frankie.

paulywannafly

Yes he does I installed it PCV on one VC and a breather on other This motor is giving mark and I fits !! there is so much internal pressure it spits out op gaskets intake gaskets and even pushes oil out the oil pan bolts I have installed no less than 3 rear main seals of every brand . This motor has issues

Comp Cam 1

Thanks Paul for seeing the post!

midyearvette

hey, you are not by chance running the rubber baffles for grommets in your valve covers??.....they can be a problem from moroso to mr gasket!...

paulywannafly

no just plain grommets and sheet metal baffles under covers they are clear as you can add engine oil through them Never seen a motor create so much pressure unless it was super charged

relics6067

Guys:

It looks to me with that much blowby (causing your crankcase pressure problems) your only real options are relief of some kind from the seller (are there any warranties?) or tear it down, see what is wrong, and fix it (if possible).

You have already spent lots of time messin' with it, looks like it's time to find out what's really wrong with it.........................

That's my $0.02, and it costs exactly what you paid for it!

HTH

Comp Cam 1

I bought this engine a few years back and have always had some sort of issue with oil leaks! In all honesty I would probably go with a 383 crate motor and use this thing as a boat anchor! Billy Mitchell (world products) has no answers at this point to even guide us in the right direction. Thanks

relics6067

Sounds like they won't be much help.

I wonder if they put the pistons in upside down?

That would do it!

SledgeHammer 2.0

If you do have adequate ventilation, which it sounds like, The next thing I would do is get a boost gauge (or maybe even a fuel pressure gauge) and hook it into the VC and see what pressure it is building. You can remove the PVC valve and hook it into that valve cover and make a pass on the motor.

The gauge will tell you what you have.

and if it does have too much and that is the issue, Then you know what you have to do...

vetrod62

Do a leak down test. Listen where the air comes out.

Westlotorn

I worked with engine shops for 12 years, my largest did 50 engines per day and I had many that did 10 to 150 per month. Most of these shops did production engines but many also did performance engines. With that type feedback I never saw blowby like you have.
The leak down will identify a piston ring issue. Maybe someone put Std rings in a 30 over bore? Or the wrong size ring.
What brand of rings were used and what size, 5/64, 1/16, 3mm.
Are you sure they match the piston.
How much tension on the oil ring, Std, low or light?
What finish on the cylinder bore?
A wrong set of rings MIGHT give you this much blow by.
A terrible cross hatch might.
Non torque plate honed block could give you an out of round cylinder, this makes the rings rotate to the large part of the bore and stop, when they stop the ring gaps are lined up causing large blow by. Could be one cylinder.
Have you loaded the engine yet? Rings won't take a complete set till the pressure of a load makes them seat to the cylinder wall.
Drive the car up a medium slope hill at 50%-75% throttle. 2,000-3,500 RPM. See if your blow by improves. The type ring makes this fast or slower. Chrome faced and cast faced are slower. Moly faced seal pretty quick.
I see Moly rings on good finish seal up before the second pull on a dyno test.
Any chance you have a head gasket issue allowing combustion to escape? You would see the leak path on tear down with careful study.
Whatever it is it is big to create this much pressure.
I like both the leak down and the pressure gauge ideas, they might identify where the leak is and how much pressure you are seeing.
I bet you have more than 10 pounds pressure.

DZAUTO

Something that so far has NOT been mentioned yet (although it's almost been mentioned) is where is the blowby coming from?
Do any of you guys know where blowby comes from?????????? Venting is NOT what needs to be addressed. It's the CAUSE that needs to be addressed!!!!! Blowby comes from combustion pressure that gets past the piston rings. That's where the pressure comes from! On a fresh engine, or even a not so fresh engine, there should only be MINIMAL pressure getting past the rings. But if LOTS of pressure is going past the rings--------------------SOMETHING'S WRONG! Broken rings, prematurely worn rings, WRONG rings, busted piston(s), etc, etc. That's what needs to be addressed and diagnosed.
Pressure INSIDE the engine ONLY comes from the combustion chamber, nowhere else. If pressure is building up in the crankcase, it can only be escaping down between the pistons and cylinder wall. Find out why.

Tom Parsons

Westlotorn

I did see one block using MLS ( multi layer steel ) Head gaskets and AFR heads that did this. The rivet that held the MLS gasket layers in place hit on the inside of the block and did not allow the cyl head to clamp the gasket to the block. It was hard to find but easy to fix. Cut the rivet off and re torqued the head. The rivets only function is to keep the multiple layers of the head gasket in place for assembly, if one is in the way, remove it. The rivets are larger than the gasket so they can't be between the head and block. The Fel Pro MLS head gaskets cleared the OEM block and heads but hit on the aftermarket head and block. Non MLS gaskets do not use rivets and could not do this.

midyearvette

nailed it.....

Comp Cam 1

Again Many thanks to all! Would I see smoke blowing out of the car with that much blowby? Not blowing a thing out of the exhaust? Will still do a leak down. Also feeling no loss of power. Bare with me if the questions seem dumb.

Westlotorn

Not necessarily but the blow by might smell of exhaust

SledgeHammer 2.0

That's correct, but first you need to find out if you really have that much blowby.

My last engine "mistake" was almost the same thing. I had a race motor built that was already .060 over. After I got it back together, it leaked from the rear seal. Shop told me the block was to far gone and I never should have re run it. It had two much blow by and was pushing the oil out passed the seal.

Like a dumbass I believed them and ordered a new Dart block and pistons for a fresh build. When I pulled it down, the rear cam bearing was leaking from an incorrect installation.

You need to find out if you really have that much blow-by and then decide where to go. A leak down test or some sort of crankcase pressure gauge will get you to your next decision.