Dead Cylinder?

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cudafan

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Hi Guys, I know there's a lot of good mechanics here at FABO and I need a little help. My 318 is fairly fresh from the rebuild a '78 model w/stock 340 cam in it dual exhaust small Holley carb stock ignition etc. I have now a dead cylinder, it's getting fire and fuel and the valve train seems to be working like it should, I havent tried a compression check yet. What could my problem be? Burnt valve?
Thanks!
 
Try a compression test and report back.
 
i just tore my slant down for the same issue. good cyl pressure (140psi) untill #6 @ 90psi..

had a broken top ring
 
Very first thing--I guess you did--look at the valve action,

second is a compression test and maybe a leakdown

Not having a leakdown, you CAN just rig a fitting to an air hose and pressurize the cylinder, then listen for bad leakage at the carb throat and exhaust.

Is it using oil? Any possibility it has some broken rings, or someone LEFT OUT the top ring?

Are you sure it's not a plug? (Don't just go by the looks) Swap a known good plug, known good wire, make sure.

Know how to do a simple "cylinder balance" test? Just pull up the boots on the dist, then use a probe to ground out each wire. You'll quickly discover which cylinder(s) is not firing
 
Thanks for the help guys! I just have got a chance to work on it with a buddy and looks like the cams worn! My friend (whose a mechanic for a living) said my oil might have caused it, Castrol 10w30, & I'd need something w/zinc additive?
I'll update later!
Thanks again
 
cudafan said:
.......... My 318 is fairly fresh from the rebuild
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cudafan said:
............. looks like the cams worn!
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Adding these two together, sounds like this occurred fairly quickly. You need to SERIOUSLY consider pulling the engine, tearing down the bottom end and inspecting the bearings, pump, oil galleries, etc, for filings and metal debri, and flushing it out
 
Happy Thanksgiving guys! No its not the cam but lifters two are collapsed & 1 stuck,w/broken valve spring. In process of new cam/lifters, I'll keep you updated. I really appreciate all the replies! Any thoughts about oil in our older Mopars?
Have a great weekend!
 
cudafan said:
Happy Thanksgiving guys! No its not the cam but lifters two are collapsed & 1 stuck,w/broken valve spring. In process of new cam/lifters, I'll keep you updated. I really appreciate all the replies! Any thoughts about oil in our older Mopars?
Have a great weekend!
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I run Valvoline Racing oil 20w50 (the bottle has to say "For race use only" or something like that) and a bottle of ZDDPLUS

http://www.yearone.com/serverfiles/fbshopmain2.asp?input=zinc+oil+additive&SM=1&SC=

It is a costly frickn oil change believe me but we want the best for our motors. Not saying that is the best but I don't know everything. lol
 
The final virdict, a broken valve spring on # 3 cylinder, exhaust valve. This drove me crazy! I didn't feel good all winter and just now had the time & energy to work on it. It was keeping #2 cylinder from firiing also, (pulling vacuum from it?) anyway I just wanted to post this in case it might help someone else.
 
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