I recently watched part of the Engine Masters competition on HotRod TV. Two engines ran on the dyno in about the same rpm range. Each was using valve cover breathers (no PCV) mounted on, what looked like, 4"/6" stand-offs.

One pulled to redline as clean as a whistle; the other blew smoke out of the breather like one of those old coal burning locomotives.

Seems that one guy had figured it out and the other hadn't.

Jake

 

I wouldn't put teflon seals on those heads. They leak at the "forked" spot on the body spring. I like the viton/full metal bodied ones. You're on the right path with the pushrods.

 

I suppose that engine may have interference issues from
larger primaries?

My Canton and Armando's RR pans both went in and out relatively
easily with 1-5/8" StainlessWorks headers (and I have the OEM
oil cooler coolant tube under the pan ahead of the sump that is
almost certainly not in place on the subject car.)

.

 

In this link:
http://www.grandsportregistry.com/lt1vslt4.htm#RINGS

This statement speaks volumes:
"High-speed durability tests of the engine revealed that ring flutter became a serious problem above 5,500 rpm, and the result was excessive blow-by."

GM obviously has a lot more capability to research this problem than I do. So, assuming that statement is fact, that tells me any LT1 engine going past 5500 will have "serious blow-by" problems without doing something about it.

As I have stated before, my '92 LT1 has AFR heads with the same drain-backs as others and I have never had a problem in 40K miles. But, I have stock short-block and an A4 that shifts at about 5500 so I don't get into the RPM range that GM says is a problem.

My belief is that anyone building a higher reving engine should look into decreasing blow-by to attack the source of the problem.
It seems to me, that looking at valve seals, lower-volume oil pumps, etc., is attacking the symptoms instead of the problem.
Unfortunately, after an engine is already built, it is much more time consuming and expensive to attack blow-by problems.
If I were building a new engine from scratch, I would be looking at things that decrease blow-by.
In particular, I would question using forged pistons with excess clearances, and I would be looking at rings designed in particular for that -- I would be looking at ways to decrease clearances and keeping blow-by to a minimum. A certain amount of clearance and blow-by may be acceptible in Grandmas barge, but if she puts heads and a cam in it and revs it to 7K, those same clearances may become fatal.

If you build an engine and have to add breathers to the valve covers etc., to me, you have confirmed you have a serious crankcase pressure/blow-by problem that needs to be addressed.

In the late '50s and very early '60s, vehicles had "road draft" tubes that vented directly from the crankcase (usually with some type of oil separater) to the atmosphere instead of only through the valve covers. But, "closed" Positive Crankcase Ventilation did away with that.


Tom Piper

 

Wow! This thread REALLY has me wondering now. Ever since I had my 396 built 6 years ago it has burned shiploads of oil. I too have a set of AFR 195's. My plugs also look good and the motor runs fantastic. I have changed valve springs twice and currently run viton seals. I had big problems with valve cover leaks but solved the problem by using a double thick cork gasket that is glued to the valve cover. I also have a hi volume oil pump. I never take this car out without rippin it up. The harder I run it, the more oil it uses. I did the filter in the PCV line thing but did not discover a lot of oil. What I do get is white smoke during WOT runs and do not notice smoke during hi-speed decels which I always thought valve seals meant smoking on decels.

I burn about a quart a tank or so or a little more. Unless my oil pan is completely full, I can watch my oil pressure dive during hard acceleration. I'm also running a stock oil pump with no windage pan under the crank. BTW, I do not have oil that leaks out of the head when I remove the valve cover for what it is worth.

 

If we're talking right flutter as a contributing cause to blow-by, that's been long known. Once the rings go into flutter, they no longer seal against the cylinder wall. So not only does power drop off due to the lack of ring seal, but compression pressure leaks by the rings and into the oil pan, creating higher pressure. Something, then, has to be done or the pressure will continue to increase.

I believe it was Smokey that ran some tests many years ago and actually saw the oil pan balloon from the increased blow-by.

Engines designed to high RPM should always have thinner - hence lighter -ring packages. There are pros and cons to each though.

5/64th rings seal better at the RPMs the engine is designed for and will normally see, but once the R's climb to above 5500 or so, engines will generally need 1/16th or even thinner rings. Has to due with ring inertia as the piston changes direction from up to down.

There are several other ways to address ring flutter including changing the traditional ring gap recommendations. A few years back, Speed Pro and others changed their recommendation on the top and second ring gaps to address the issue.

Some of the newer design pistons incorporate a groove in the piston below the top ring land to address, I believe, blow-by and flutter.

I called Speed Pro as I was assembling the 415 engine to go in my 86 and learned about the results of their most recents tests on ring gaps. I became convinced and used their new recommendation when I gapped my +.005 plasma molys.

Even with all those changes, flutter and blow-by can still be a problem; hence the move to vacuum pumps to better control blow-by. Some of you guys who have actually had to resort to that measure can comment on it's effectiveness, but I believe just about all of the top Pro Stock guys, and other professional racers run one.

All those wondrous "R's" come at a price.

Jake

 

If it smokes on decel, I would think that is because, with the throttle blades closed, the vacuum is sucking it past the valve seals.
If it smokes on WOT, there is very little vacuum in the intake and runners -- so, I believe it is because the crankcase pressure is blowing it past the valve seals.

Tom Piper

 

My 396 uses 1/16 on the top two rings(, low tension, gap .018) and 3/16 for the oil rings, by JE (J10008). I am starting a run now to monitor how much oil I use, I think its quite a bit, and I have SRP pistons that are tighter than the J/E pistons. I guess well see, as my engine is broke in with about 4 thousand miles + -.

 

FWIW which probably is not much, I run a stock LT1(280 RWHP) on track events. Constant redlining, I never shift to fifth gear, so often times I overrun the engine in fourth down the straights. It is definitely in the over 5500 RPM ring flutter zone. I too experienced reasonably high oil consumption and very high oil temps(above 300 F.) Against all the expert advice, I switched from a 10W-30 to a 10W-40(Redline Oil in both cases) and experienced a decrease in oil consumption and temperature(10 deg under similar conditions.) My BS theory is that the increased viscosity dampened and reduced the ring flutter. In the absence of a known design flaw(the AFR head design) the piston ring interface is going to to be crucial. All these unusual piston, ring manufacturer combinations can contribute to hard to diagnoise ring flutter issues. Is anyone using a factory engineered Mahle Powerpak piston ring combo with their design tolerances?

 

Steve, who told you to use low tension rings? That's one of the causes of oil consumption, right there.

 

I have to whole-heartedly agree on that one. I believe in standard tension oil rings in any engine that'll be street driven.

Low tension oil ring sets free up a few HP in certain RACE engines, but they don't perform well in street driven engines.

I don't recall the exact percentages, but I've read test results that show the greatest power loss results from piston ring friction against the cylinder walls. Of the three, the oil ring set causes the greatest loss by far and is the biggest offender. That's the thinking behind low tension oil rings sets; less friction more HP.

When I was building quarter-mile BB Chevy engines that were intended to go a full season without a re-build and were expected to run extremely consistent ETs, I INSISTED on standard tension oil rings.

Jake

 

I do not run AFR heads on the Corvette...yet, but figured I would add my 2 cents.

My owner built 11.9 to 1, 381 runs Plasma Moly rings I customed gapped-tight with the SRP pistons (with standard tension, but narrow rings-std spec for SRPs) and it burns next to no oil.

I shift at 7000 rpm and ran 7000 miles of One Lap using maybe 2 to 2.5 quarts.

5W30 Mobil 1 always with the Canton road race pan and 300 degree temps were common (coolant of 230 at times too!).

Even locally when I do a 100 miles on the road course...the oil quantity drops only marginally...

I would like to say I'm the cause of the oil tightness, but it is more pure luck! I don't even want to take it apart again, but more hp is required...

 

Its on my build sheet from MorePerformance. I will upload it later.

 

Steve, see JAKE's comments above. When I was forced to shop for pistons and rings (plasma-moly), I was explicitly told not to purchase low-tension rings, that I would suffer from excessive oil consumption. UNless the engine would be dedicated to all-out racing and racing only (where teardowns are done constantly) I would be very unhappy with low-tension. I was steered directly to standard tension rings, and was told there was a big difference in the area of oil use between the two.

You may wish to consult again with your builder and press him as to exactly why he thought you'd be happy with low-tension. Maybe you told him from the beginning it would be used more for drag racing than anything else? If this is true, thats explains it. It also explains why you're consuming so much oil, for street use.

Just my .02, hope its useful in some way. Please understand I'm not an expert from experience, just going by what I've been told. I wish you best luck

 

What's weird is they used SRP pistons instead of the JE pistons which are tighter clearance piston and don't expand as much as the JE. No worries, the oil consumption isn't going to kill me. But now I know.
I am concerned of the oil blow by though that TJ is working on here. I am going to look into a better breather system than the one I have, and to fix my crimped hose for my PCV valve on the drivers side of the manifold.
Heres the data on these pistons, they are plasma moly coated.
http://www.jegs.com/webapp/wcs/store...20537_-1_10221

 

One other thought on oil ring sets:

Speed Pro's SS50U oil ring set is the ABSOLUTE BEST oil ring set on the market. Has been for a long, long time.

For me, there's no other way to go.

Jake