Well my motor was running great and then all of a sudden I noticed a small light knocking and some misfire backfires. The back fires sound like a cyl not firing consistantly.

Checked all the fluids, the timing all the sparkplug wires and everything seems to be good.

If this motor is toast I swear I'm never buying another chev motor. This is the thirdsbc in the truck this year. And this one is a lightly built 94 Goodwrench crate motor.

Any ideas?

@ 500rpm it runs perfect you would never know theres an issue at all. But when the revs are held around 800-1000rpm you can hear both the sputtering and the knocking easily.

Well it sounds like it might be either a bearing or a wrist pin BUT That wouldn't explain the misfiring.

do a compreshion test. you could have fried the rings in one or more holes. that could be the miss and if its bad enuff than that could be the knock.

Trust me I would love to have a compression tester here, I hate living 45min from my garage but a 10min comute to work is great.

I have narrowed the misfire down to the pass side of the motor. The knock can be heard through the oil pan, both headers and the intake but not through the valve covers.

collapsed lifter?

collapsed lifter?
Thats what I'm hoping at this point. I pulled the valve cover and the #8 exhaust valve doesn't show much movement. I pulled hte push rod and it was fine so it's either the lifter or the cam lobe.

I'm a neewbie to sbc admitedly, what can I say the toy motor wasn't enough balls for me. I have a Haynes manual but it doesn't give me info on lifters at all. I'm guessing pull the intake and then I can get to the lifter or do I have to pull the head to?

I have a few friends that can do this for me with out a problem but i would rather do it myself. Just need to be pointed in the right direction to start from.

Thanks.

Pull the intake and you can get to the lifters, oh the joys.....

Hows the oil pressure. sounds like the pump might be giving out causing wear on the cam and lifters. knock could be bearings. rev it up and pressure will increase.

Oil pressure is good holds around 20 at idle and 40-50 when driving. I always keep an eye on my oil pressure and my temp gauges. She runs hot easily, I need a better fan set up so always watching the gauges. The first 350 I swapped in went because of low oil pressure, lost the line to the gauge.

Well I guess I know what I'm doing tomorrow if it's not raining too hard. I'm guessing I can go into the stealership or any performance shop and buy a lifter?! If I only lost one should I replace them all? The motor was fully rebuilt not too long ago.

It's up to you, but I'd only replace the offending lifter. After you pull it, look with a light down the lifter galley for a galled lobe while rotating the engine. More than likely it's just a bad lifter, but if it's flat tappet it could be the cam. May the luck of the SBC be with you!
Scott
Oil pressure is good holds around 20 at idle and 40-50 when driving. I always keep an eye on my oil pressure and my temp gauges. She runs hot easily, I need a better fan set up so always watching the gauges. The first 350 I swapped in went because of low oil pressure, lost the line to the gauge.

Well I guess I know what I'm doing tomorrow if it's not raining too hard. I'm guessing I can go into the stealership or any performance shop and buy a lifter?! If I only lost one should I replace them all? The motor was fully rebuilt not too long ago.

Thanks for the help and the hope pf good luck with the sbc's. So far I haven't had the best of luck with them. This is the third one in the truck and it's only been on the road since december.

Head out to the parking lot now to tear into it. Wish I had my toolbox here. Hell even my socket set I loaned out in an emergency that wasn't returned would be great right now. Combination wrenches it is.

I'll update when I know whats happening.

Well it sure looks like it's the cam. Pulled both the intake and the exhaust lifters jammed a screwdriver on top of the cam and theres not much lift on the exhaust side. Can you guess which lifter is from which side?

http://www.imagestation.com/picture/sraid208/p2672593defa7befcbf8f7a598d4810a2/ee6bb56b.jpg

So much for a mild cam. Looks like i might have to jam a stock cam in for now.