So for the second time I popped the front and back seal on my intake. The first time I thought that I hadn't put down a sufficient amount of RTV, so I pulled the intake a couple weeks back to have a look. I had plenty of RTV but what is happening is that at high RPM apparently there is too much crankcase pressure and it is pushing oil out the front and back of the manifold.

I do have a pcv in the drivers side cover and a breather in the passengers side cover.

I did a leak down test about a month ago and all cylinders tested out good, but you can hear air getting past the rings. I changed the valve springs out a week or so ago and aired up the cylinders and there is enough air getting past the rings where you can feel it coming out of the breather and pcv holes....but no different than when I did the leak down test.

So...I can't have my motor pushing oil out the front and back seals of the intake, not gonna work for me. Unless I can improve my pcv somehow I think that I'm going to have to yank the motor and install some new rings. If memory serves me correctly we used KB hyper pistons with standard rings. I'll have to talk to my buddy and see if he remembers any better than I do.

The specs on my motor are:

-350 4 bolt block bored 30 over
-steel crank
-stock 5.7 rods
-KB hyper flat top pistons
-The rotating assembly was balanced and the block was clearanced and zero decked

Assuming that everything is good in there what kind of rings would I want to go with? I'd like to run something proven that will have less blowby than the current standard rings....some kind of file to fit rings?


Anywho, the rest of the specs on my engine are:

-Edelbrock performer RPM heads 70cc
-Crower solid flat cam .242/.248 .482/.504 114/110
-1.6 rockers
-Holley Stealth Ram intake
-58mm TB
-30 lb injectors
-C950 ECU
-GM CC small body distributor
-Thorley tri-y headers
-2.5 x-pipe and 2.5 exhaust

On a side note, I made my first 12 second pass the other night....12.77@107.99.

I would expect your leak-down test to have shown something if you're getting that much blow-by. What were your leakage numbers for each cylinder?

First thing that comes to my mind is a broken ring or two....

Were the leak downs consistant?

What kind of pressure were you using on the leak-down test? And did you try putting some oil in the cylinders to see if that made a difference in ring sealing?

No insult intended here Paul, but are you sure you did the leakdown test correct and read it correct? There are at least 3 different style testers I am aware of, and the gauges are the main diff. Enough ring leakage to feel leakdown test air flowing out the breather is significant is what I want to say but that is probably subjective. Kinda would need to hear and feel it to say that for sure. If it leaks it has to go somewhere huh:)

There's more than 1 orifice size PCV available.

PCV won't really pull on the crankcase at WOT. It will equalize pressure though if there is a differential(that's all it's doing anyway), and if the orifice is large enough to permit equalization.

If I had an engine I thought was good, but blowing out manifold endseals, I would lose the silicone and go down to O'reilly and buy a $15 cheesewhiz tube of The Right Stuff. 1/4" bead of The Right Stuff on the ends and up onto the intake gasket a little, let it skim a minute or less, set the intake straight (some do this with the use of dowels but I usually just decide to see how good I am:)), start the bolts but leave them just snug about 15 minutes, then barely tight about 15 minutes, then put the **** to them. The Right Stuff is like silicone on steroids. You really don't even need to let it skim or do the stages of tight but I usually do just so I'm sure I get some crush on the solidified poop.

If I thought I needed rings I would also need honed at the least. That means complete disassembly to me cuz hone crap is nasty crap and you can't get it out of the cyls without powerwashing and brushing. And yes, file fit rings always but they get double money for them. Especially with KB hypers, you don't want too little gap with them. Lots of good rings available. I have expensive tastes on engine guts so I won't recommend you a set of rings that costs more than your pistons:). If I was in your shoes I think I would see how much gap I had with a set of .030's, might work out perfect and save you 50 bucks or so.

I kind of doubt blowby pressure is pushing out the manifold seals. If you had that much crankcase pressure you would have smoke coming out of the breather and you would be able to see and smell the blowby while driving around.

I suspect you have a problem with the way the intake manifold fits on the engine. Did you have the heads shaved or the block decked? Could the manifold be warped? How big is the gap you are filling with the silicone?

I'm with Steve on this one, I think.

My old 327 had both compression rings broken on #2. On the highway, she'd blow a quart out the breather in 4 hours. Real messy stuff. Ventilation was same as yours, pcv on one side breather on the other.

She never blew a gasket out.

I think either...
Your manifold isn't sealing properly for reasons yet to be found, or...
Your crankcase ventilation is suspect. Are you sure the air can flow out that breather? Maybe the darned thing is clogged? Or snapping down right on top of the baffle so it gets plugged up that way? This could be happening on the pcv side too, depending on the valve covers and baffles.

I would expect your leak-down test to have shown something if you're getting that much blow-by. What were your leakage numbers for each cylinder?

The were all in the "set" area or like 10%...like this picture (except not 20% plus like the picture).

http://www.carcraft.com/techarticles/116_0406_cylinder_leakdown_tester/photo_09.html


First thing that comes to my mind is a broken ring or two....

Were the leak downs consistant?

Yes


What kind of pressure were you using on the leak-down test? And did you try putting some oil in the cylinders to see if that made a difference in ring sealing?

Whatever the instructions said....was it like 90 or 100 PSI and no oil added? I could do it again for grins, it my buddys tester and I could grab it from him.


No insult intended here Paul, but are you sure you did the leakdown test correct and read it correct?

Oh no, I could never ever make a mistake, LOL!


PCV won't really pull on the crankcase at WOT. It will equalize pressure though if there is a differential(that's all it's doing anyway), and if the orifice is large enough to permit equalization.

If I had an engine I thought was good, but blowing out manifold endseals, I would lose the silicone and go down to O'reilly and buy a $15 cheesewhiz tube of The Right Stuff. 1/4" bead of The Right Stuff on the ends and up onto the intake gasket a little, let it skim a minute or less, set the intake straight (some do this with the use of dowels but I usually just decide to see how good I am:)), start the bolts but leave them just snug about 15 minutes, then barely tight about 15 minutes, then put the **** to them. The Right Stuff is like silicone on steroids. You really don't even need to let it skim or do the stages of tight but I usually do just so I'm sure I get some crush on the solidified poop.

If I thought I needed rings I would also need honed at the least. That means complete disassembly to me cuz hone crap is nasty crap and you can't get it out of the cyls without powerwashing and brushing. And yes, file fit rings always but they get double money for them. Especially with KB hypers, you don't want too little gap with them. Lots of good rings available. I have expensive tastes on engine guts so I won't recommend you a set of rings that costs more than your pistons:). If I was in your shoes I think I would see how much gap I had with a set of .030's, might work out perfect and save you 50 bucks or so.

Good input, thanks!


I kind of doubt blowby pressure is pushing out the manifold seals. If you had that much crankcase pressure you would have smoke coming out of the breather and you would be able to see and smell the blowby while driving around.

I suspect you have a problem with the way the intake manifold fits on the engine. Did you have the heads shaved or the block decked? Could the manifold be warped? How big is the gap you are filling with the silicone?

Could be warped I guess. Heads were not shaved, I put the intake gaskets on dry, put a couple of flashlights in the lifter valley and set the intake on....Didn't see any light coming out, except from the dist hole. No burning oil driving around...just oil out the breathers at WOT, high RPM once on the dyno.


I'm with Steve on this one, I think.

My old 327 had both compression rings broken on #2. On the highway, she'd blow a quart out the breather in 4 hours. Real messy stuff. Ventilation was same as yours, pcv on one side breather on the other.

She never blew a gasket out.

I think either...
Your manifold isn't sealing properly for reasons yet to be found, or...
Your crankcase ventilation is suspect. Are you sure the air can flow out that breather? Maybe the darned thing is clogged? Or snapping down right on top of the baffle so it gets plugged up that way? This could be happening on the pcv side too, depending on the valve covers and baffles.

Could be clogged I guess...



Bottom line is that my motor has more blowby than my buddies who used "file to fit" rings. You can hear the difference although the leakdown doesn't show much difference.

Yer just looking for an excuse to go thru 'er, ain't ya Paul?

Well just do it then, yank 'er outa there and check 'er out. Nuttin to lose but time and money, lots to gain. And it's always so much fun.

Yer just looking for an excuse to go thru 'er, ain't ya Paul?

Well just do it then, yank 'er outa there and check 'er out. Nuttin to lose but time and money, lots to gain. And it's always so much fun.

Well....I am definitely not opposed to pulling it out and going through it but it would be good to know why I am popping end seals on the intake BEFORE I pull it out. I mean at least have a good theory before getting crazy.

So, so far theories are....

1. Error doing leakdown and there IS a problem.
--Do test again to double check.

2. Bad seal on intake due to warpage or ???
--No way to check this without disassembly but everything looked okay when I resealed a couple of weeks ago.

3. Bad PCV setup.
--I'll check it out....this would be an easy fix huh?


I have learned a bunch over the past few years, but I don't have any clue about picking rings. So what do I need to know about my pistons inorder to determine what my options are on rings? What are good rings for street/strip?

If I do pull it apart I want to change the timing chain too. I have a double chain that had 3-4 degrees of slack when I checked when I changed to the crower solid flat cam. What is a better chain that won't stretch? I read about a Cloyes true roller? Is that a better option?

Keep in mind that the KB hyper's use a considerably larger ring gap than a standard cast piston...if your doing your leakdown/air pressure test with a cold engine I would certainly expect you to feel or hear more air bypassing the rings.
You might try simply disconnecting the PCV system and either run an open hole or some sort of breather where the PCV valve normally resides. This will give full ventilation on both sides of the engine, then you can see if the problem remains.

I've had excellent luck with the speed-pro plasma-moly ring sets, and they aren't that expensive. Just pay close attention to your rind end gap as the KB's are special that way.

if your doing your leakdown/air pressure test with a cold engine I would certainly expect you to feel or hear more air bypassing the rings.

That's true the engine was cold when I swapped the springs.


You might try simply disconnecting the PCV system and either run an open hole or some sort of breather where the PCV valve normally resides. This will give full ventilation on both sides of the engine, then you can see if the problem remains.

OK...It can't hurt to try! I've never not run a PCV...will no PCV hurt the motor at all or was it simply an emissions thing?


I've had excellent luck with the speed-pro plasma-moly ring sets, and they aren't that expensive. Just pay close attention to your rind end gap as the KB's are special that way.

Well, my buddy says that he doesn't remember KB pistons. He said that he remembers TRW hyper pistons...:clonk:



I did some fine tuning yesterday for idle and off idle. The motor is running so sweet that I hate to pull it out just yet. I suppose I can live with a couple of drops of oil out the front and back of the intake until I confirm that there is a "real" problem.

With the engine fully warmed up, if there is any blowby you will see it with the PCV valce removed and an open PCV hole in the valve cover. I certainly wouldn't leave it open, but it won't hurt anything to drive it for a while with the hole open. Heck, I've seen people do it for years!
The only reason I mentioned the thing about the ring gaps is because KB's hyper pistons definately use a wider than normal ring gap than any other piston out there, including speed-pro/trw hypers. Once the engine is warmed up, the larger ring gap with the KB's closes down to normal.

With the engine fully warmed up, if there is any blowby you will see it with the PCV valve removed and an open PCV hole in the valve cover.

Yup, there is definitely blowby! Thanks for the simple test!

Yup, there is definitely blowby! Thanks for the simple test!

Well that sucks :( Congrats on getting well into the 12's though, FWIW :thumbsup:

Well that sucks :( Congrats on getting well into the 12's though, FWIW :thumbsup:

Thanks, I'm not overly worried about the motor....I mean I did multiple cranking pressure tests with different gauges and all eight are very close together, in fact each bank (pass & drivers) match almost exactly and the two banks are within five PSI of each other. That just makes me feel better that there isn't a broken ring or something really bad. I'm thinking there is a ring issue but it's not catastrophic......I hope! So, maybe some racing this weekend and then yank it out...we'll see.

If I can get my car to hook a little better maybe I can get deeper into the 12's...It will be a whole new learning experience as chassis tuning is not something that I know sh*t about, LOL!

You might add a can of EOS to let it help seal the combustion chamber to reduce blow-by, unless you're sure of the cause.

Reducing blow-by is on the older cans of EOS.

You might add a can of EOS to let it help seal the combustion chamber to reduce blow-by, unless you're sure of the cause.

Reducing blow-by is on the older cans of EOS.

I won't be sure of the cause until I tear it down, so it can't hurt to try some EOS.