QuicheLorraine

Errr,. .... ahhh almost an update:

Pulled the plug wires & ignition system out completely. No prob. Yanked out the spark plugs and all looked great except for oil fouling (mild) on #4 right under that A6 compressor

So I pulled the pump back & removed the valve cover. No problem. Pulled the drivers side valve cover next. No problems. No broken parts, all springs intact. Pushrods in place/none broken or bent.

Next comes a compression check ... will post more later this wk when I get to it. Now I gotta get to work so I can pay for this project

OMF

Oh man.....I was sure it was a valve spring

midyearvette

next.check for a wiped lobe..sorry it wasn't a pushrod.....

QuicheLorraine

This one I doubt 'cause it's a Crane cam and was properly broken in. And it's got several years & 25K miles on it. Guess anything is possible though.

OTOH, it really is curious otherwise. If I floated the valves & put a hole in a piston there's no way it would have still run on the ride home and not shown signs of crankcase pressure: I.E. dipstick pushed out or breathers showing something like oil pushed past them all over the valve covers.

When I took it apart, the engine looked just fine and as I said yesterday in the original post, there was:

• No water in the oil
• No water out the tailpipe
• No moisture in the breathers
• No unusual internal noises

I'm thinkin' of just yanking the heads and then again, I really do need to cap off the fuel line and crank it over to watch the rocker geometry before doing so.

Right now it's 85* outside and there's 40* cold beer in the fridge. I'm thinkin' that the beer's going to win, over pulling working on the car. I have three other sets of wheels when I need to go anywhere.

THE PROBLEM IS THAT IT'S SPRING TIME IN SAN DIEGO AND I WANNA CRUISE WITH THE TOPS OFF THE CAR :o

Stroker-427

If the cam is an hydraulic one..... I would check the lifters.

Sometime is enough a small debris inside and the lifter start to pump like a hell.

dstaley

My last Crane cam lasted 30 miles. That was in a BBC though, in 1996, and we all know how hard those are on FT cams. I haven't bought a Crane Cam since. By the look of things, it might be my last.

63mako

Bet you wiped a lobe. Don't matter who made it, it is a fast ramp rate flat tappet cam. You did well to get 25,000 miles out of it. Hope it didn't take anything else out with it. Good luck on getting it fixed soon.

QuicheLorraine

Compression check: 150PSI all the way around except for that #4 mentioned above; the only plug that had any oil fouling at all on it. Zero compression on that one.

I'll be pulling the head for a better look next.

Who knows what I'd need to put Vortec heads on her? I know the intake is different and that I'd not be able to use my Crane roller rockers. Will my headers work?

dstaley

If you aren't sure you want to dive in that quick, you could cut open your oil filter and have a look-sie. If there are no metal particles, your cam might be fine.

I wouldn't bet on it though.

You could also try to observe how much lift you have on both rockers on that cylinder. If it's the cam, it's usually obvious. One or both of the rockers on that cylinder will be loose if the cam has gone South on ya.

QuicheLorraine

Good advice for sure - but it doesn't apply. Flat cam cannot cause zero compression.

dstaley

Actually, it can. If the intake valve doesn't open, there's little to nothing drawn into the cylinder to compress. It happened to me.

CA-Legal-Vette

You'd have to completely wipe the intake and exhaust lobe for this to happen. Seems unlikely if the rest are ok.

dstaley

It does seem unlikely that the rest would be OK, good point. In my case I found a bent pushrod on the intake and the exhaust was damaged but still moving a little bit.

150PSI seems low in any case, but if they're consistent this is a little less clear cut.

Broken ring maybe? Lots of things to think about...

OMF

My new guess.......chipped or broken valve head

DRIVESHAFT

Oh no.
Zero compression is never good.
If you have an air compressor, pump some air into #4 with the rockers backed off and see where it blows out.
That way you know if it is valve related or piston related.

QuicheLorraine

Ack I'm just gonna yank the head(s). You are correct I could do that, but I'd wind up doing teardown anyway. All I can pray for is that the piston & block are OK - just a head issue. One of the reasons for using an all forged bottom end was that forged pistons are more forgiving under the stress of a ping. I figured cast iron heads and California 91 octane would be a ping problem - but it turned out to be very minor.

I'm bracing for it to be a head issue not requiring a teardown of that great bottom end. I can get the Vortec heads locally for a song. Great price indeed, being a member of the local Vette club that's sponsored by the biggest Vette dealer in the city of SD.

But I'm hesitant to use iron heads again as she's prone to minor ping when the AC is on. And the small chambers would raise my comp ratio beyond 10:1 thereby giving it even MORE of a propensity to ping. So that makes aluminum a better choice obviously but at twice the cost of the Vortecs.

Ahh it's all conjecture at this point anyway. I have to pull the top end off that motor & take a peek at the damage. For all I know, I may just wind up spending my tax return on a ZZ383.

Thmprr

Zero compression usually means a holed piston or a badly bent or burnt valve, I hope not but be prepared.

pauldana

I have 10.5:1, Iron heads and no ping unless hot hot summer on a hard pull.... but I am also going to be running an aluminum duel fan radiator that keeps it nice and cool...This should get rid of that ping as well. 150 psi? maybe 9:1

QuicheLorraine

Well I pulled the head today and it had a bad spring after all. I looked hard at 'em when I pulled the cover off a couple days ago and didn't see anything wrong. Even after the compression test told me which cylinder it was, I didn't see it and the valve spring felt tight to the touch...I didn't think that was it.

Today I was pulling head bolts out, armwrestling with the header on that side, and then I saw it: With the lifter off I could see the spring didn't look right. This time it was loose and perfectly obvious.

I already had half the head bolts off by that time so I figured I'd pull the head & look inside. Everything is fine. But I took the head to the place that assembled them in the first place & told 'em to look at it & verify that it's good.

I'm half hoping the head is bad - for whatever reason - to give me the excuse to pull the other one & replace them with newer technology. I am SOOOOO glad that bottom end is good! I put a lot of thought into it and it would have been a shame to screw it up by sucking a valve or something.

63mako

I would replace all the springs. Fatigue causes broken springs and if you broke one under 6000 RPM it is time for a new set or you will be into it again. Glad for you that it was minor.