Oil control problems on 6, diagnostics on 8, oy bey!

[The Blue Pig]

I just gave a guy 500 bucks for a 71 2 wheel drive half ton lwb. He said the straight 6 in it runs, but oil is blowing into the air breather assembly from the pcv valve, which I guess could be a couple of things. I have not got it yet, so I am not sure. But, the main thing is my girlfriends truck. 350, edelbrock 650 manual and intake, headers and the rest of the engine is supposedly stock. I put new spark plugs in it, and set the timing back to 12 degrees initial. Ran like a raped ape for a couple days, then it starts pinging and running like complete crap. Oil still black, so I guess it aint a head gasket. Compression tests a week or two ago revealed all 8 cylinders @ 130#'s + or - 2 lbs overall. Ohmed out the plug wires, they seem to be good. It pings and rattles under acceleration, and it has lost a lot of power. I double checked the timing today, still at 12. But the way the truck lopes and slop's around, especially when you put it in gear, I think it has a dead cylinder. I put a ratchet on the crank pulley and turned it and watched the rotor, didnt have too awful much play in the timing chain. I will pull out the plugs again, and see if they tell me anything. Anyone have any suggestions? I am running out of ideas, unless the distributor gear or something like that went to crap on me.

[GMCPaul]

Pull each individual plug wire and replace 1 at a time while motor running. If RPM's drop when you pull wire good cylinder if no drop in RPM then cylinders dead and not firing. Pinging followed by running like crap afterwards normally a sign of detonation and detonation will blow a hole through the top of a piston and break rings leading to running like crap, I would check the compression again. Throw at vacuum gauge on it and check the readings. To determine what the readings on vac gauge means visit our tech tips page
http://www.gmcpauls.com/Tech%20Tips1.htm
GMCPaul

[The Blue Pig]

I tried doing the spark plug thing, and I was 2 for 4 (times getting an intense wake up call). I tried insulating myself and the channel locks well, but I still got zapped. One guy told me to (since it's an HEI) to stab through the top of the terminal boots on the cap with a test light and ground it and it would give the same effect, but sometimes, it leaves a hole big enough to get ya when you go to advance or retard timing. I will, however, pull the plugs today and see what they tell me and do another comp test.

[Patrick Sullivan]

I've been shocked so many times that I've stopped pulling plug wires while the truck's running.

I second the vacuum gauge idea, it's a great way to tell what's going on in the engine.. they're cheap, too.

[GMCPaul]

For around $3 at Ace Hardware you can pick up a fuse cartridge puller tool designed to pull the tubular fuse cartridges from electrical boxes, these are made of fiberglass and are designed to allow you pull fuses without electrical shock they work great for pulling & reinstalling plug wires while motor is running to prevent getting shocked.
Before starting engine though pull each spark plug boot free of plug and reinstall so all are easily removed when you start motor.
GMCPaul

[slam33]

check the vacume advance can on the distributor