Projects 318 engine Blow by and no compression

Well, I ***ume if it was related to the valve and not general engine wear, it would be more apparent on the bank with the damage. If it has damaged the guide and is pushing the products of combustion through the guide, it'll show predominately on the affected side in my opinion.

 

Anything that might get pushed past the valve guide will end up under the valve cover and eventually the crankcase, if the crankcase vent system doesn't get to it first. It will never see the exhaust manifold or tailpipe.

 

OK thanks

 

In his first post, the OP stated:

"Now it is in my car new carb and tune up and I noticed a lot of blow by. I then did a Compression Test. 7 cylinders were all around 120 psi. Cylinder #2 is zero."

I think there's been an unfortunate amount of confusion since this first post. Blow-by, by definition, only reveals itself in the crankcase. Though not stated I think what the OP was describing was something he was seeing in the exhaust output. Burning oil, an excessively rich fuel mixture or coolant that entered the combustion chamber, or moisture or condensation collected in the exhaust system and turned to steam by hot exhaust gases. He was not seeing blow-by at the tailpipe(s).

Actual excessive blow-by, seen from the crankcase breather or oil filler hole, means more expensive and complicated damage. Think damaged pistons, worn, stuck or broken rings, trashed cylinder walls. Upon your initial inspection none of this seems to be the case.

The following describes blow-by as accurately as possible, to my understanding.

"Blow-by occurs when the explosion that occurs in your engine’s combustion chamber causes fuel, air and moisture to be forced past the rings into the crankcase. Your engine’s rings must maintain an excellent fit in order to contain the pressure.

The causes of blow-by: wear, soot and deposits

As rings and cylinder liners wear away they are less capable of maintaining this seal. Consequently as a car ages the amount of blow-by that occurs can increase.
Soot and deposits left over from incomplete combustion that collect on the rings can also inhibit their seal worsening blow-by.

The effects of blow-by: loss of horsepower and oil contamination and dilution."

(Quoted from and more details available at the link below.)
https://bobistheoilguy.com/what-is-blow-by/

If the bent valve had put a hole in the piston, that would increase blow-by as well. But the results would show up in the crankcase, not in the exhaust system. Seemingly the piston is intact except for the witness mark left by contact with the (now bent) valve. And that explains the zero compression in that one cylinder and why adding a squirt of oil does nothing to improve the cranking compression. You already know what a leak down test is going to tell you.

I'd say the odds are that if you're working on a small budget you could likely get away with just pulling the head with the valve damage. Check the piston and cylinder walls for any other damage. While you're at it use your bore scope to check the other bank of cylinders as well. This may be as simple as replacing and grinding one valve and seat, maybe a guide, a valve spring and maybe a push rod. Or even install a good used or refurbished head. Throw in a few gaskets and ****on it back up. Seemingly you are not fighting a blow-by problem at all, especially if the engine truly does only have 46,000 miles on it and was reasonably maintained.

 

If you pull the 318 to put a 360 in, don't forget you need to have a 360 weighted torque converter or flywheel, other wise you will get an engine vibration.

If its a for real 40K mile 85 318, it should be a great motor to rebuild, even with a bent valve, broken spring, and a head that needs a valve guide replaced.