440 w/TorqStorm SC - Boost Getting Into Crankcase?? Valley Pan BULGE

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table30

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My engine builder says he's stumped how boost ended up pressurizing the crankcase at our dyno session. This is a freshly built built 440 (1974 RB Block). The first run went fine, generating ~600 horsepower at 5200rpm. On the second run, the engine fell on it's face at around 4000rpm.

The dyno technician noticed that oil had sprayed out of the breather, and that the valley pan had bulged completely outward! I've never seen anything like this. There was no smoke in the exhaust. My builder tore down the engine and reported that the ring seal was excellent on every cylinder. The intake gaskets were fine. The head gaskets were perfect.

My only concern with this build is that he went with 10:1 pistons to begin with? I don't know if that could be a factor. I thought older engines needed lower compression for boost (9:1 or 8:1).

This is a mystery. Hopefully someone has some insight on how boost could enter the crankcase with good ring seal and good intake gaskets. Any ideas would be helpful. I can include some pics of the set-up.

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Getting Past the rings makes the most sense. Breather, pvc?
table30 said:
My engine builder says he's stumped how boost ended up pressurizing the crankcase at our dyno session. This is a freshly built built 440 (1974 RB Block). The first run went fine, generating ~600 horsepower at 5200rpm. On the second run, the engine fell on it's face at around 4000rpm.

The dyno technician noticed that oil had sprayed out of the breather, and that the valley pan had bulged completely outward! I've never seen anything like this. There was no smoke in the exhaust. My builder tore down the engine and reported that the ring seal was excellent on every cylinder. The intake gaskets were fine. The head gaskets were perfect.

My only concern with this build is that he went with 10:1 pistons to begin with? I don't know if that could be a factor. I thought older engines needed lower compression for boost (9:1 or 8:1).

This is a mystery. Hopefully someone has some insight on how boost could enter the crankcase with good ring seal and good intake gaskets. Any ideas would be helpful. I can include some pics of the set-up.

View attachment 1715756514

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I don't see much of any breathers on the engine photos.
I had this happen with a 451 NA engine while I was drag racing it. The only thing we came up with is the PCV valve stuck and the crank case could not breath and built pressure. Changed nothing popped the valley back down and ran it for the rest of the season. Never happened again. Maybe ?
 
Darter6 said:
I don't see much of any breathers on the engine photos.
I had this happen with a 451 NA engine while I was drag racing it. The only thing we came up with is the PCV valve stuck and the crank case could not breath and built pressure. Changed nothing popped the valley back down and ran it for the rest of the season. Never happened again. Maybe ?
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By the time we ran the engine, we had a breather and PCV.
 
You will always have some pressure leaking past the rings in to the crankcase. Especially so with boost. You just have to make sure it can get out. Get rid of the pcv valve and put breathers in both valve covers. Making a pcv valve work with boost is not an easy task. All kinds of check valves and gizmos are required to separate vacuum and boost and standard pcv valves can’t do it. Btw just because you have 10:1 pistons does not mean you have 10:1 compression. There are way too many factors at play besides pistons. He could have used 10:1 pistons with a big chamber and thick gaskets and got you down to 9:1. Or even 8:1. It’s all in the combo of parts.
 
Did yall break the rings in, or just warm it up and start pullin?
 
TT5.9mag said:
You will always have some pressure leaking past the rings in to the crankcase. Especially so with boost. You just have to make sure it can get out. Get rid of the pcv valve and put breathers in both valve covers. Making a pcv valve work with boost is not an easy task. All kinds of check valves and gizmos are required to separate vacuum and boost and standard pcv valves can’t do it. Btw just because you have 10:1 pistons does not mean you have 10:1 compression. There are way too many factors at play besides pistons. He could have used 10:1 pistons with a big chamber and thick gaskets and got you down to 9:1. Or even 8:1. It’s all in the combo of parts.
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I've heard good things about this Wagner tunable dual flow PCV system. Little pricey, but might improve things?

Dual Flow Adjustable PCV Valve – M/E Wagner Performance Products
 
TT5.9mag said:
You will always have some pressure leaking past the rings in to the crankcase. Especially so with boost. You just have to make sure it can get out. Get rid of the pcv valve and put breathers in both valve covers. Making a pcv valve work with boost is not an easy task. All kinds of check valves and gizmos are required to separate vacuum and boost and standard pcv valves can’t do it. Btw just because you have 10:1 pistons does not mean you have 10:1 compression. There are way too many factors at play besides pistons. He could have used 10:1 pistons with a big chamber and thick gaskets and got you down to 9:1. Or even 8:1. It’s all in the combo of parts.
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My mistake, we actually DID have two open breathers by the time we ran the engine...and it still bulged the valley pan and sprayed oil out of the breather.

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table30 said:
Right....but what are you asking here? It was a dyno session with a freshly rebuilt motor.
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It's plain as damn day what I'm asking. You've already answered. The rings aren't broken in yet. Rings don't break in in a couple hours. Especially moly rings. Sometimes they can take a while. Like 1000-2500 miles worth. ...and here you are blowing the crap out of that motor and wondering why it's trying to blow the valley pan off.
 
Yea if the the breathers are up to the task the only way it can get in is the rings or head gaskets. Are you using a stamped steel valley pan? Maybe once it bowed there was no sealing it.
 
TT5.9mag said:
Yea if the the breathers are up to the task the only way it can get in is the rings or head gaskets. Are you using a stamped steel valley pan? Maybe once it bowed there was no sealing it.
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The head gaskets were fine. The ring seal was excellent. Leak down was 3%. Maybe a different style of breather would help? Open element breathers?
 
RustyRatRod said:
RINGS. Rings can take 1000 miles or more.
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Not today it shouldn’t. If it takes more than 2, maybe 3 pulls on the dyno before the rings are seated it’s junk.

There is an incredible amount of information out there on bore geometry, surface finish and all that. We are well past the long mileage for ring break in.
 
table30 said:
The head gaskets were fine. The ring seal was excellent. Leak down was 3%. Maybe a different style of breather would help? Open element breathers?
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So after it had an issue you leaked the engine and it was 3% or less? BTW, I don’t think there is anyone here who advocates for higher than orthodox compression ratios on pump gas than me (its probably not even close) and there is no way in hell I’d build a boosted pump gas engine at 10:1 ever. Especially with a blow through application.

Maybe, and by MAYBE I mean if you were using a very capable EFI set up and maybe and I mean MAYBE if I thought you had the tuning ability to deal with a compression ratio that high (no offense but I’ve seen a lot of “tuners” who are full of crapola...not saying you are I’m just point out WWYRD) and IF I know for a fact you had your cooling system up to snuff and you had a big water pump and a great thermostat and all that was scienced out then maybe I would consider that compression ratio.

You are a point and a half higher than I would have used. Under boost pump gas does weird stuff. If you can’t control the timing curve and the fuel map, plus keep the coolant at ALL TIMES no more than 160 you are going to be in for a tuning nightmare.
 
I guess I'm just confused as to why it had enough pressure to bulge a valley pan but not blow the dip stick out.

I'm with RRR, just because an engine can break in asap doesn't mean this one did. Plenty of machinists out there just run a dingo ball hone through the bore after they cut some metal out and call it good. Plenty of engines out there don't get broke in. You breaking in on really good synthetic oil?

If boost is a factor, I'd run the overlapping rings (can't remember the name), or the ones with the little holes in the pistons or whatever the hell else it is that blower people use. If you got that much pressure getting past rings, something is up.

You sure you ain't got a hose plumbed wrong, like from the vacuum port on the carb to a breather, or something like that?
 
The LS engine guys running turbos all usually use crank case vents plumbed to puke tanks on their racing engines. I think it is pretty common to have some positive pressure in the crank case when hammering on a boosted engine. Those guys have a lot of aftermarket support made for dealing with this kind of application - maybe poke around on their forums to see if you can pick up some info.
 
yellow rose said:
Not today it shouldn’t. If it takes more than 2, maybe 3 pulls on the dyno before the rings are seated it’s junk.

There is an incredible amount of information out there on bore geometry, surface finish and all that. We are well past the long mileage for ring break in.
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Yeah, but how do any of us here KNOW what level of machine work he had done? If it was honed with a torque plate, the rings are pretty much broken in as soon as it warms up. If not.......it'll take a "bit". ...and that doesn't mean anything is "junk" either.
 
RustyRatRod said:
Yeah, but how do any of us here KNOW what level of machine work he had done? If it was honed with a torque plate, the rings are pretty much broken in as soon as it warms up. If not.......it'll take a "bit". ...and that doesn't mean anything is "junk" either.
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That’s true...we have no way of knowing what level of machining was done. I always hope that the machinist keeps up with current technology. It’s moving so fast right now (ring tech, oil tech and even piston skirt finish) that what was top of the mark 5 years ago is just passable today.

The other thing I forgot to mention is the high compression with no way to cool the inlet air is a recipe for serious detonation. The OP could be running into enough detonation it’s upsetting ring seal and that’s where the combustion pressure is coming from.

You know as well as I do how critical engine temp and inlet air temp is when running higher than orthodox compression ratios on pump gas.

The tune up window gets substantially smaller as the CR goes up. And what would be a small tuning error with a lower CR becomes a huge error with that CR and boost.
 
@yellow rose the blow through in this application will be the best case scenario. The latent heat of vaporization will give him an intercooling effect. It will be significant up to the point that the blower becomes inefficient. Which, with a torquestorm on 440 inches is a small window. I would say he’s pretty safe up to about 8lbs of boost. And it should have a rising boost curve through peak torque so he may only see 3-4 psi at that point. Anything more than that IMO this thing will stop making boost and become a giant heat pump and all the things you’re talking about will ring true. We need much more info from the op on machine work and set up. And what it took to get to his power level. We have no idea if he’s at 10:1.
 
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