Technical '

Not my first time rebuilding a chevy engine. This engine runs, idles, and drives good. Here's the problem. The engine will go along good and then make a load clanking noise and it will drive the pushrod thru the valve lifter. It's done that three times. The first time was #6 exhaust, the second was #5 intake, I haven't pulled the valve cover yet for the third time. The first time I pulled the heads to make sure nothing was in the cylinders, nothing was. When I got the engine #3 was spun so I bought a new crank. The cam, pushrod, valves, lifters an everything looked good. I have tried adjusting the valves different ways thinking maybe that was it, nope. I don't know where to go now. HELP PLEASE!!!

 

Valve sticking in guides.......?



Ray

 

That's a good thought Ray. When I ***embled the heads everything seemed smooth. Thanks.....Jim

 

springs binding?

 

have the valve guides been replaced or liners installed?

 

Sounds like more cam lift than your valve spring travel can handle. In other words spring bind.
The Wizzard

 

I am pretty much with pist-n-broke, mechanical interference, probably above the valve seat, spring bind or guide/retainer contact, or end of the rocker slot hitting the stud or something along those lines. Piston/valve, or valve sticking in the guide it would have a bent valve/low compression in that cylinder.

 

It pokes a hole through the lifter? or the rocker arm?

 

If it does it after it gets hot, I'd say the valve stems are too tight in the guide and its gaulling them. Pull the offending valves and see if there are any signs of gaulling on the stems.

 

It is not easy to measure valve stem to guide clearance accurately, without a bore gauge.

 

Back off !! You are right Jim I did enter that wrong. Should be rocker arms. No wonder I can't fix it, I can't even enter it right. Sorry everyone, my mistake.....

 

I'm going to pull the heads right now and take them to the machine shop for a re-work. I think you guys might be right. Can't do everything on the cheap. Engine did run good and strong tho. If anything else comes to mind be sure to let me know.....Jim

 

Good luck and let us know.

 

If it were me, while the heads are off I would measure the Cam lift and give that info to your Head Guy along with rocker ratio so he can be sure you have enough valve travel without coil bind.
The Wizzard

 

I would probably also remove the lifters and inspect the bottoms of them.
The Wizzard

 

these and an outside mic. then you use the same mic to measure the stem.

 

yup, you can use that bore gauge, or the dial one...just make sure there's some clearance, at the center of the guide.

 

What valve seals are on this thing I have seen a bunch of sbc that came with o rings get a positive seal and it will hit

 

Okay, here's the story to end the story. Yesterday I pulled the heads but couldn't do anything because of the holiday. So today I head out for the machine shop but stopped by a friends house to ask a question. I explained to him about the machine shop and he said "let me see your heads". So we went to my truck and he then said "I'm gonna tell ya what the trouble is and I bet ya a hundred dollars i'm right". I didn't bet because I know him too well.
Think about this and you'll know he was right also.
When I put the valves back I wasn't really paying attention because I put the keepers on the second groove instead of the first. As a result the springs were so tight 'compacted' that it put way too much pressure on the pushrod and rocker arm. Stupid people do stupid things.
Thanks for all of your help and advice.....Jim

 

DOH!!! hey well at least you figured it out!

 

I bet we coulda figured it out, if you had included a couple pictures

(What did you do with the O rings?)

 

Thanks for the results and the humble admission

 

Jim; the o-rings are the ones that came with the rebuild gasket set. You know the kind with the little sholders that fit over the valve stem. I've used that type lots of times......Jim

 

yeah, you put the O ring in the lower groove, then put the keepers in the upper groove.... I'm just trying to imagine how you could have messed it up

Oh well, don't matter now, you figured it out

 

Easy enough...... After a huge headache!! LoL!
But at least it's an easy fix!!