Compression leaking to valvetrain

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Alex "Berkowitz"

76 brazilian hardtop
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Hi!

My 318 was completelly rebuilt a little over 1400 miles ago.
Heads were completelly done (stock specs), compression ratio around 9:1 (Sealed Power 526ap pistons and Mr. GAskets 1121g head gaskets).

One day it started making some noise on the drivers side valve train, I took the cover off and found there was compression leaking upwards through cilinder's number 5 intake valve.

Curious part is that the leak occurs when this valve OPENS for admission, not while on compression (what could suggest the valve wasn't properly sealing to the seat)...so I guess the compression is coming from cilinder number 7, wich is under compression at the time.

First thought was burnt headgasket, but I took the head off and couldn't find anything wrong...

Any guesses?

Posting some pics, I have a video but not sure how to post it...
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I believe you either have a hole in a piston, badly broken ring, or a cracked piston. Compression is bleeding directly into the crankcase. That's just about the only way for that to happen.
 
By chance, could it be the other side? Run a compression test on the other bank, It may give you the sound like it's from the driver side but the blown head gasket is shootin from pass side.
 
OP, is the leakage coming up through the head by the pushrods? (That's what it looks like in the video.) If so, the compression is going into the crankcase (which this sounds like) and I agree with RRR... a ring/ringset is broken or ring lands busted out. And looking closely at the video, this pulsing of vapor does not maintain sync with #5 cylinder throughout the video, and so IMHO it can be coming from any cylinder.

Too late to run a compression test, which would have told us a lot; still could do the other side as suggested. IMHO, do that and get ready to pull the other head and look.

Was this a fresh re-bore or were the bores just honed? Broken rings/lands could happen due to detonation. Any hint of detonation sounds before this?
 
Pull all the plugs, then put only one in,then crank it.
Move plug to next cyl until you duplicate the problem.
Or too bad its all apart.
So pull push rods and hit the other 4 cyls with compressed air. I’m sure you will find it.
 
I’ll bet it pushed the head gasket into the valley. This doesn’t look great. I wonder if the heads were retorqued.

2D6E1D32-BE9A-4ACF-859C-262B241E0591.jpeg
 
Yup. Blowing by the gasket into the valley. Were the block or heads surfaced? That is a TON of oil on the piston tops for 1400 miles too...
 
One thing you could do, if you can't run it down, and won't cost you an arm, is to clean it up and get the heads / valve train back together, and run a compression check. You don't need exhaust, intake, or coolant. Just the heads, new gaskets, and the valve train. Hell you don't even need the valve train. Get/ buy / make yourself a leakdown tester (Do a search) and run a leakdown, and THAT test gives you the opportunity to listen for leakage......past intake / exhaust valves, and past the rings. Use a piece of fuel / vacuum hose to your ear, to probe and listen

This is the mods I did to a Horrible Freight leakdown, which essentially turns it into DIY. You can start from scratch about as easy, and if you have a compression tester with a quick disconnect hose, you can make one from out of it, and STILL have a compression tester

HF leakdown test is a Piece of Big Steenkeeng SHTUFF but here is

Search for DIY what you need is a .040 orifice. I actually found some on egag, some sort of carb jet I guess. I got lucky, the jet was a common thread, the tap is sticking out of the block. The HF tester is NOT "standard" that is, it does not use the common pressure setting, nor does it use the standard .040" orifice, here:

Leak-down tester - Wikipedia

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Replaced the other gauge with one from my HVAC days

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EVEN WITHOUT a leakdown tester, you can just hook your air hose to the plug hole, and probe around for air leakage, compare "the sound" with other cylinders. EASY!!

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I hate those gaskets, the thin ones, right?
Blew it into the valley.
I'd rather re use steel shims with with copper coat.
 
MOPAROFFICIAL said:
I hate those gaskets, the thin ones, right?
Blew it into the valley.
I'd rather re use steel shims with with copper coat.
Click to expand...
I don't care for those composition gaskets that peel apart like that. they make a helluva mess to clean up, and they're hard to "read" how they sealed when they separate like that.
Maybe you didn't properly torque the head bolts? maybe your torque wrench is out of whack.
 
check bolt length I have seen the bolts too long and bottom out because a hole was not drilled deep enough after deck and head milling and it will act like its torqued
 
Hey guys, sorry for disapearing!!

Hell of a hard few months!

So, I took the head that was off the car to the machine shop, and they showed me it had acctually "burned" in 2 spots, like furrystump mentioned.

They asked me about the gasket, said it was crap and advised to pull the other head off and change it too, I was so pissed I did just that, and guess what, that gasket had TWO giant holes in it, from cilinders 2 and 6 to the valley.

So, in the end, both headgaskets were shot.

Ran around 100 miles since the repair, and all is good except for a damn bad lifter knock that wasn´t there before taking the heads off.
Only thing changed were the gaskets, that now are the commom felpros and the heads were ressurfaced.

Thanks for all your help!!
 
Always nice to get updates on these things; tnx!. Sounds like the heads may have been tad warped and those thin head gaskets did not like it. Once they warp at all, sealing up gets pretty 'iffy'.

The standard Felpro's (8553PT) are somewhere around .050" thick, versus the .028" thick of the Mr Gasket 1121G. So there is a need for the lifters to take up the extra slack in the pushrods. The heads were milled but we don't know how much; assuming it was less than .022" (and it usually is well under .010" to just clean and true up the head surfaces), then you just might have a just-too-short pushrod right now. Or just a poor lifter.

I'd run the engine for a minute and then shut off ( to pump oil into all the lifters), take off the valve covers, and, for the lifters/rockers that are fully closed, see if there is any slack or softness in the lifter/pushrod side on each and every valve. You'll have to turn the engine over some to get all of the valves in the closed position, a few at a time.

While you are in there, re-torque the head bolts. I don't care if they are 'Permatorque' types.... it is good practice to do so.
 
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