Josh B

Ok - got my head back from the machine shop with all of the intake valves replaced. I bolted it back onto the block and before attaching the cam tower or intake did a leak down test. I am getting 80% leakage on all four cylinders and it is all coming out of the crank case! Cylinder walls look fine - what could I be doing wrong? I guess the head could be warped although I don't think I over heated. I didn't get it surfaced because it is o-ringed. Other than that I am at a loss....

theedge

The engine needs to be warmed up for an effective leak down test.

You could put a bit of oil in the cylinders if youre wanting to leakdown test the cylinder head... That should help.

Tom M'Guinn

How was it running before you pulled the head? Burning any oil out the exhaust? Are you sure you are using/reading the tester correctly? Are you sure it's not 80% not leaking? That would be tolerable on a cold motor. Piston under test should be a tdc -- rotate the engine to locate the piston, so that the rings seat normally. If its coming out the crankcase, that would point to rings, but I'd think you would have known if they were that bad before pulling it apart. You can still check for flatness of the deck and head with a precision straight edge, you just need to work around the o-rings. Sorry it's not cooperating. Good luck.

Josh B

I know it isn't the gauge as this is the same one that I got great leak down numbers on the same motor about 6 months ago.

For the heck of it I bolted this head onto a spare short block I have in the garage and got much better readings. I really don't know what to think at this point.

Josh B

Hmm - maybe I should just bolt on the cam and intake and see if she will start?

brad-cam

I rebuilt a spare motor using a good block, new rings and did a leakdown test on the engine stand and also got some pretty poor numbers, a little like yours. I've chocked it up to rings not seated and a cold engine
so will just wait until I put it in the car and break it in. I would recommend that you put it all back together and start it up and do the tests on a warm engine.

And yes, I still have the spare motor. The one I rebuilt that is in the car is still running strong!

CarbonRevo

Josh- Not to be off topic as I'm sorry for your troubles, but what engine harness is that? I love how clean they look. Is this Lindsey racing harness pieces?

Josh B

It is the Lindsey racing stuff but I made a bigger project out of it than needed I completely disassembled my old harness - removed anything I wasn't using like the diagnostic plug and top dead center sensor, and then put it all back together through the original firewall rubber hose. It took about 2 months working on it on and off.

m73m95

You have a lot of new parts that aren't broken in, to be doing a leak down test.

The engine needs to be warm (as said above), and ideally, each cylinder should be at TDC.

As long as you assembled everything correctly, you're worrying over nothing.

Run it, drive it for a few thousand miles, THEN do a leak down test.

CarbonRevo

Damn...I really want to replace the majority of mine. Update the engine bay some to compliment my headlight delete and oil cooled turbo. Looks very clean though.

ilikemy944

Guys - I think we might be thinking too hard.

There isn't that much new stuff - this short block didn't get touched, rings/pistons/etc are the same as they were before.

The car wouldn't start and we were getting spark and fuel so we did a compression test and got 50psi.
Then 80-85% leakdown.

Only 'new' engine parts are in the head.

ilikemy944

BTW - the 50 psi compression test bumped to 52 psi after adding some oil.
80-85% leakdown was with oil in the cylinders as well.

95ONE

Hoping not to insult, but no way around it.. You're sure you're using the tool correctly?

Van

If you have a nice straight edge, you can check the flatness of both the head and the engine deck. Use a piece of package cellophane (like from a cigarette pack) to slide under your straight edge.

Out of curiosity, how much do your o-rings "stick out" (proud above the surface)?

ilikemy944

Yes - been used to test several motors prior.