Too much air pressure on valve cover breathers

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drugster

drugster

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Hi:
I'm just finished the rebuild on my stroker small block, but in the first passes, after proper break in, when I rev up it blows a lot of air and oil thru the valve cover breathers ( real mess) ; Obviously something's wrong,
Everything was new, my builder says he cut the first ring to. 024 and the second to. 028, flat top forged Icon pistons, Hellfire rings.
Any toughs?
Thanks in advance
 
Well that sucks, er, blows.
If the exhaust is free-flowing, and the rings truly are "broken in", Then somebody may get to do a, do-over.

I suggest a leak-down test. Both a normal TDC one, and a low-pressure sweeping test from BDC compression to TDC compression. The first will give an indication of the ring seal. The second will reveal a gouged cylinder wall.
The sweep test is tricky, and cannot usually be done with more than 30 to 40 psi.I turn the air on and bring the piston up to the point where the intake closes, then reposition the Johnson bar, so I can do a step test. I crank the bar over, about 1/8 to 1/12 turn and stop/hold and listen for escaping air as well as checking the gauge. Then continue, another step, and so on. To reposition the bar, I shut the air off first.Its good to have a helper. If cylinder wall is damaged, it will show up real quick.
You dont really need a L/D apparatus for the sweep test, but you do need a regulator. And a point-of-use shut-off valve is real handy, too.
 
I have a newly rebuilt stroker and had a similar problem.I run a pcv valve on left side.A breather on the right side and a breather that is connected to the air cleaner also on right side.This took care of it after i put some miles on it and let the rings seat better.It was dynoed and thought that would be enough to break the rings in but it was not
 
At WOT there is little to no manifold vacuum, so the PCV is not pulling any blowby. The connector pipe will be dumping the blow-by into the air cleaner housing. If its oil-laden, it can/will ruin a paper filter.
The cure is to go to the source. Find out whats causing it, and fix it. Different types of rings need different cylinder wall finishes, and/or different break-in procedures, and/or break-in times.
 
Not a surprise at all for a stroker engine to have a fair amount of blow by. You have just increased the amount of volume of air that is being pushed around in the crankcase and unless you give it somewhere to go it is going to build up pressure. A big oil pan can help but the best bet is to go with a remote breather setup. Run a couple of lines from the valve covers over to a puke tank with a breather on it. You can also run a remote PCV valve if you want. Moroso builds remote tanks as do a bunch of other guys. Very common problem that has been around for years.
 
drugster said:
Hi:
I'm just finished the rebuild on my stroker small block, but in the first passes, after proper break in, when I rev up it blows a lot of air and oil thru the valve cover breathers ( real mess) ; Obviously something's wrong,
Everything was new, my builder says he cut the first ring to. 024 and the second to. 028, flat top forged Icon pistons, Hellfire rings.
Any toughs?
Thanks in advance
Click to expand...

You didn't state which rings you were using, but the old rule of thumb was for every inch of bore, the ring gap would be .004". A four inch bore would be .016" ring gap. A .024" ring gap would work for a six inch bore engine "back in the day". Just throwing this out there, food for thought.

Edit: I don't know the Hellfire brand, but I know Total Seals are different.

Russ.
 
I was thinking the ring gap was a little excessive too...if starting out fresh.

Most stock compression, OE setups run .016" top ring..... .019-.20" second.

Even if Forced Induction were an option on the table.....I think I would have ended up more around .020" top ring.....022" second ring.

I eliminated my pcv valve...and put a breather filter valve cover on both sides....no more oil leaks!!!!
 
drugster said:
Hi: I'm just finished the rebuild on my stroker small block, but in the first passes, after proper break in, when I rev up it blows a lot of air and oil thru the valve cover breathers ( real mess) ; Obviously something's wrong, Everything was new, my builder says he cut the first ring to. 024 and the second to. 028, flat top forged Icon pistons, Hellfire rings. Any toughs? Thanks in advance
Click to expand...

I've been through this problem. Try PCV, baffle your breathers. If that doesn't work then get a vac pump from GZ. Problem solved and HP gained with vac pump.
 
way too much ring gaps. those belong with KB hyper pistons not ICONS. also wall finish enters into picture. are rings cast or moly or chrome??
 
I agree that the ring gaps are incorrect. However, here is a proper PCV diagram. You should have a PCV system very similar.
 

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drugster said:
Everything was new, my builder says he cut the first ring to. 024 and the second to. 028, flat top forged Icon pistons, Hellfire rings.
Click to expand...
A quick google look-up shows .004 to .005" per inch of bore for all the possible uses, street tot nitrous drag racing. Bore clearances for these pistons are pretty large so some extra blow by with pistons rocking and ring seal variations is not totally unexpected.
See here for ring gap and bore clearance:
[ame]https://www.uempistons.com/installation_instructions/icon_installation.pdf[/ame]

Read up on Hellfire rings; they are not standard cast iron. That makes me question what hone finish was used, break-in procedures, and which version of Hellfires was used. (There are references to reverse twist rings, which effect oil control.) Why did you or the builder choose these particular rings, and which Hellfire ring material is being used? Is this a race only engine? Nitrous? (Which is FME's key application for these rings.)
See here:
[ame]http://www.fme-cat.com/docs/1110.pdf[/ame]

The OP also need to tell us what break-in procedure has been used.
 
The rings are sealed power hellfire, ductile iron, we use the chart in the pistón ring instructions, the engine is for street strip, planning in a 150-200 hp shot nitrous
 
The rings are sealed power hellfire, ductile iron, we use the chart in the pistón ring instructions, the engine is for street strip, planning in a 150-200 hp shot nitrous
 
OK. Hone finish? Break-in procedure? Is this happening with the nitrous being used or not?

I looked up the ring gaps for Hellfires with nitrous for drag and the numbers you cite look to be on the money. But, those large gaps are done for the heat on the rings and the expansion when under nitrous. When not into the nitrous, they're just going to be unusually large gaps. With the large bore clearance of the forged pistons, then the actual exposed gap is going to be many times larger than a 'normal' ring gap and a tighter piston.

[ame]http://www.dssracing.com/v/vspfiles/assets/images/ring%20instructions.pdf[/ame]
 
Is this your first NOS engine? Did you break it in on a dyno? Did you use a blow by meter while on the dyno?

I'm not so sure that you have a problem, my guess is that is just how it is going to be. First of all it is a stroker so you have a lot more air pumping around. Secondly you have it set up loose for NOS. Do what other people do. Either a vacuum pump or run remote puke tanks.
 
Still wouldn't hurt to run a leak down test if you think it is really excessive. Iron rings do take a while to seat. Hopefully the rings are staggered properly.
 
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