OaklandChevy

Just found out my 350 engine has no compress on cylinder 8. What should I do as far as repair and does engine need to be dropped. Also switched from tbi to carb so does the electric fuel pump need to be removed or will getting a fuel regulator be fine? This is 91 camaro RS 305 swap to 350 1406 edlebrock carburetor.

sofakingdom

iTrader: (1)

Find out why it has no compression first. Step 1 is determining where it's going: intake manifold, exhaust manifold, crankcase, or what.

Depends on what you find wrong with it.

You can replace the electric pump with a carb style pickup but most people seem to use a regulator. Either way can work fine if done right.

I'm going to assume you're not going to be driving this on the street? Because you're sure as hell not going to be able to smog this and legally buy tags...

ULTM8Z

If you're failing the compression test, then run a leak down test to see where the failure is (like SofaK said).

Years ago, I was stuggling with an idle misfire for a long time until I ran leak down tests on all the cylinders and found the #7 cylinder had a much higher leakage rate than the others. I heard hissing coming out of the crank case which told me the issue was with the piston rings. As a last ditch, I bought some oil additive and after about ~50 or miles of driving, the misfire cleared up... my thinking is I had a stuck piston ring which freed itself up with the additive. That was ~10 years ago and still running strong.

In your case, if you have a bent valve or something, it'd only be a cylinder head swap/rebuild rather than a complete teardown/rebuild of the engine. The leak down test should be able to tell you where the problem is... valves, piston rings, head gasket (though that might produce other symptoms too).

ironwill

If that cylinder actually has ZERO compression, a likely cause would be a valve stuck open. Barring all the equipment required to do a leakdown, do an eyeball-inspection instead. Pull the valve cover on the dead cylinder's side of the engine, rotate the crank by hand and observe the valve train for the dead cylinder. A stuck-open valve should be easy to spot.

paulo57509

Where's the leakage? Grease Monkey Method:

Take your oiler () and squirt some engine oil (~tablespoon) in the cylinder through the spark plug hole. Then re-test.

Compression = poor ring/cylinder sealing
No/Some (~5psi) compression = leak at valve(s)