engine problem

[ks147j111928]

Hey guys, I normally post in the 67-72 area but this is for my project truck. It's a 1980 K10 I got for $600 with a blown engine. I rebuilt a donor engine from a former parts truck that ran well. The engine is a mystery, it was injected (no fuel pump rod hole in block) but I got it with a 2-bbl on top. The casting # is 14082508 (if I remember right) It has been totally resealed and is running. The problem is this: it backfires through the carb on the driver's side intermittently but not erratically. It's a steady pop, like something hitting inside the carb. I have double checked everything I can think of: plug gap, wiring, firing order, timing, TDC, jets, needle/seats but it still pops. It's noticeable at idle but gets real bad under load/higher idle. I am at my wit's end here, this is the only thing holding me up from getting it on the road. More info: I redid the heads (factory iron) with new valve seats and seals, 3 angle job and decked it .010. Also the pop didn't show up until after I had the engine running for a day or two, not longer than @ 15 minutes at a time. Either that or I didn't notice it. I also had to switch to points-type dizzy to clear the old school Edelbrock intake (C4B) I put on. Points gap and dwell angle are within factory specs (Haynes manual specs anyway...) and I get good spark at the coil and all wires too. I am out of ideas here!

Thanks,
Dan

[ks147j111928]

okay so here's what I did: I took off the valve covers and saw the #3 intake rocker was OFF the pushrod! Checking the rest of them revealed a few other loose rockers... what did I do??? So I tightened them and now it's running as it should, no popping. Dang, how could this happen? I was being so careful to double check my work every step of the way!

Dan

[Boog]

Easy mistake to make. Now what I would do is to warm the engine up and idle it down low, remove the valve cover and readjust them all while it is running. If you aren't familiar with this method loosen one rocker at at time until it starts to peck then tighten it down until it stops pecking then tighten an additional 1/2 to 3/4 turn for preload. Do each one and she ought to run right and quiet. Yeah, it's a bit messy but you get a good adjustment doing it this way.

[ed3196499]

I would definatly check the pushrod if the rocker was OFF at some point and make sure its still straight and not fouled. I had a valve spring break and it bent the pushrod just a little in the process. Just out of curiosity did you soak the lifters before you put them in?

[ks147j111928]

When I had the engine apart for the reseal I kept the lifters in a tub of oil. I did check the loose push rod for damage and it looked good. I may not know much about building engines but I know a few important things, except the whole rocker adjustment thing apparently... dammit. It's running great and has good power through the rpms, can't wait to sell it!

Thanks again,
Dan