I got out of the office early today and decided to do that compression test on my engine.

As some may know, I STILL have an oil consumption problem. About 1 quart every 3 hour drive. What stumps me is the car does not smoke a heavy blue cloud... however, it does emit a light cloud of oil.

Other than the consumption and apparent oil on the plugs, the engine runs VERY strong. Warms up easy, no miss and crisp off of the line and when driving (no stumbles or weak performance).

I've warmed up the engine and taken readings on #1-#7:

# 1 150psi - Oil stained/caked with oil on electrode/insulator
# 3 150psi - Oil/lighter caking of oil electrode/insulator
# 5 150psi - oil/practically clean; light tan color on insulator
# 7 165psi - Comparable to #3 but a bit lighter oil.

I don't have 1K miles on this rebuild.

Since reassembly, I checked all rocker threads for potential that they may extend into combustion chambers and introduce oil. ALL (#1-#7) rocker holes were dry and no oil. I took the precaution of applying thread sealer to all four rocker studs and retorqued.

Is my $700 valve job leaking? Could my DART heads have porosity issues? Perhaps intake gaskets sucking oil? No surfaces were decked or machined.

I'm about to pull the rockers and springs to see if the shop truly DID install new guides. They apparently installed the nice seals and new Comp parts from my kit as I had stripped the old springs, keepers, locks and seals from the valves when I took the heads in.

Heading to #2-#8 for testing. I wonder if the 150 165psi variance from 1-3-5 compared to 7 is telling? I will re-test 1-3-5 and advise.

 

Your $700 valve job might not be the problem but your valve seals might be. Try changing them out or at least have a look before you rip everything apart. I have 150 across the board on my 69 427 but the valve seals were garbage.

 

Beat me to it. I got busy watching Youtube videos on how to change out valve stem seals. Do a search there and you'll see that it's relatively minor work. That's what I'd look at first. Good luck.

 

I took another round of readings on 1-7:

#1 - 160psi
#3 - 165psi
#5 - 165psi
#7 - 165psi

I have about 35k on my Hastings Moly Rings and Federal Mogul Hypereutectic (H345NP) pistons) from my 1999 build.

The engine may have cooled a tad but I don't think I was giving it enough revolutions.

Ah, I see what you mean. The guides could be fine but if the fancy seals aren't washing the oil away, the oil WILL make its way down the valves into the chambers.

ok. I am going to take a close look at #1 first as that plug looks the worst. The teflon positive stop valve seals are from the Comp Retro-Roller cam kit. They are the fancier ones that fit inside the Comp dual springs. The heads once had the black one-piece umbrella seals that fit in the single valve springs (with damper). Here's a picture of the seals from my kit:

http://www.jegs.com/i/Comp+Cams/249/...FUcV7Aod0moAFQ

 

ok. Pulled the left valve cover. No valve seal debris. I really can't see the seals for the dual valve springs.

Looks like I will be pulling #1 rocker and spring pack. Going to plug all oil return holes in the cylinder head and pressurize the cylinder with my compressor.

Will advise what I find on #1... It is the worst-appearing so it should indicate issues if there are any.

 

The stem seals on my SBC looked good....but were very hard/apparently not wiping the stems...I replaced them/oil consumption dropped to 1/2 quart every 3,000!

Let's hope seals cure your problem.

 

#1 exhaust PC valve seal is securely positioned over the head of the bronze DART valve guide. Is it supposed to ride on the valve where the old-style rubber valve seal was?

I checked and the PC seal is secure over the valve guide. No movement.

I will reinstall the springs, locks and keepers on #1 exhaust and proceed to the #1 intake valve seal inspection.

 

Usually valve steam seals cause start up smoke and rarely cause an oily haze with the engine warmed up and to burn 1 quart every 3 hours is a ton of oil. If it is valve related your guides have to be totally worn out and the seals have to be shot.

 

As long as you have #1 springs, etc. Off, why don't you stick on the old style umbrella seals. Then after you go a couple hundred miles , see how the #1 spark plug compares to how it looks now. That way you'll know if it's the PC seals. You can't tell if the seals are bad just by looking. Good luck.
Duane

 

Both #1 I & E PC seals are securely in place over the tops of the valve guides. The valves don't wobble at all with the springs removed.

So, my next thoughts are... it IS ingesting oil:

1. Can I have a bad intake gasket and have good, steady performance? There is no stumble, not erratic and has strong performance.
2. Perhaps bad fit (warpage) of intake to heads/block? I run the Fel-Pro 1204's per recommendation of DART for the Iron Eagles.
3. Could I have a porous Edelbrock performer intake manifold?
4. Can I have bad head gaskets?
5. Can I be sucking oil vapor through the PCV?
6. Porous cylinder head castings?

If #1 seals look this good and #1 has the worst oil buildup on the plug, do I not bother with checking seals on the rest? I'm thinking the positive locking seals are fine like on #1 I & E.

I can try a push in breather in place of the PCV to see if that helps.... that seems like the easiest change without pulling intake manifold, gaskets or the cylinder heads.

 

The old umbrella seals won't clear the inner spring and were hardened and brittle. I do have those small rubber seals that come with rebuild kits.

 

Mine is an old original 69 427. It doesn't smoke but I had to take the intake manifold off to inspect the lifters. There was a build up on the intake valves so I pulled the springs and found four broken seals. You can't see them unless you look for it. Here is a pic. The original owner replaced all the valve seals except one... Please don't ask as I have no idea.... The one on the right is original 1969 but the others were the problem.


I would check this first before ripping into your motor and finding out it was a ten dollar problem.

 

The umbrella seals do clear the inner spring. All of these cars, big or small block, came with them from the factory.

 

#1 Do you have a PCV valve in your induction system, and is there a baffle in that valve cover below it? (so that any oil splash CANNOT be sucked up by the PCV valve)

If you do not have a PCV system and/or no other way oil could be sucked into the intake, you may have some intake manifold gasket problem, where some oil run-off is being drawn into the intake somewhere. From your data, it would not be into just one cylinder, but to the whole intake (or to just one bank, if all the right bank plugs are clean).

I don't think you have a valve seal or ring problem, or, at least, I think that is unlikely.

 

Actually, with the double springs required for the roller cam, the umbrella seal will not work with the inner spring. It has outer spring, damper and inner spring.

The umbrella seals only cleared the inner damper spring on the single 1.25" springs I had before the retro roller conversion.

One other thing which may be telling... I have had oil on the intake near #1 intake port... a small puddle. Not recently. It was shortly after I got the engine back together and had the engine running for a while. No puddle since then. But, I also put better hoses between the PCV and the carb.

Question: I still run an L48 PCV. I note that the L48 and L82 part numbers differ for PCV.

I have quite a bit more HP and TQ. Do I need the PCV for a healthier engine?

This is an interesting thread. I may see about getting an LT1 PCV or big block, solid lifter PCV:

http://www.chevytalk.org/fusionbb/sh...hp?tid/222851/

Considering this PCV valve for '70 396-427: AC CV736C

I've had oil consumption issues since I reached 224rwhp. Got worse as my valve guides/seals failed on the DARTs (blue CLOUDS at startup).

 

Maybe if you had mentioned the roller cam and Dart heads we could have figured this out.

 

Intake gasket. My guess it is sucking oil from the valley, did you cut the heads at all? I like the Mr. Gasket ultra seal gaskets.

 

They are in my signature...

 

I've not had the heads, block or intake cut. When I had the block refreshed with the 1999 buildup, I just had the cylinders torque plate bored/honed, block hot tanked and cleaned, new cam bearings, and block plugs pressed in. When the heads were refreshed in 2013, I just had the heads resurfaced; not cut.

However, it is possible the heads and intake are not matching up perfectly. Wouldn't they be bleeding vacuum if that were the issue? I remember when I mistakenly installed 1205 gaskets. The gasket port was so tall, it protruded above the the intake casting and sounded like a broken rocker... I installed the 1204's after I realized the 1205's were incorrect application.

I've ordered the 396/427 PCV that should compensate for lower than stock vacuum. It may explain why I had oil on the intake above #1 intake runner... that is where the PCV hose passes on way to the carb inlet.

If the HiPo PCV doesn't solve it, the intake gaskets will be next. I read a write-up in one of the motor mags about big block that kept blowing intake gaskets... block, heads or intake had been milled. They found the machining differences by putting shot lead in gaskets and torquing. The shot was in about 8 different places. The different clearances were identified by how much the shot was smashed across the different spots. The machine shop did the measurements and machining to fix.

perhaps I could install double 1204 fel-pro's or just a thicker intake gasket. Do fel-pro or Mr Gasket offer a slightly thicker 1204-style intake gasket?

Will advise once I try the HiPo PCV from the big block.

 

Sorry. Just read you post and not your sig.
I don't think your intake is the problem. If it is sucking oil, it's either from the top or the bottom end. Try the top first as it is cheap and easy. Intakes don't suck oil.