Exaust valve trouble

[blasterD]

I'm working on a friend's 69 K5. It has a 350/350/205. It sat for about a year while he was deployed to Afghanistan. He parked it at another friend's house. While he was gone, his friend's son decided to "help daddy work on the truck" and filled the fuel tank using the garden hose. It then sat that way for six months. We replaced the entire fuel system, including the tank, lines, pump and carb. We finally got it running. It idles fairly well, but when you accelerate there is a loud popping noise from the carb. I thought it might be a timing issue, but after triple checking the timing and plugs, I could find no problem. I started pulling one plug wire at a time to see if I could isolate the cyllender. It turned out to be #4. I pulled the valve cover and had my wife crank the engine. The #4 exaust valve did not appear to be opening. It only moves about 1/8 of an inch. I think it might just be a collapsed lifter. I am going to switch the intake and exaust lifters to see if it makes a difference. If It doesn't, it may have a flat cam lobe. What do you think the chances are of it just being the collapsed lifter? Or, am I totally off track here? Thanks.

 

[dyeager535]

When you pull the lifter, you'll know if the cam or the lifter is the culprit, if its not a bent pushrod.

All lifters I've seen from a wiped cam lobe were extremely worn at the "foot".

When a lifter is not "pumping up" they typically make noise.

 

[diesel4me]

Typical small block!

I'd wager its a cam lobe!--90% of all the chevy small blocks I owned needed a cam(and a few 454's too! )--for some reason chevys seem to eat cams,until they finally put roller lifters in them...

But before going that far,you might want to see if the rocker arm stud has pulled out of the head some--I had a 307 motor I yanked out of a 69 chevelle,I gave it to a friend to use as a "dummy" motor to set up small block chevy motor mounts in his 33 ford coupe that had a 302 previously-

-I told him it needed a cam,the #1 exhaust valve barely opened last time I looked with the valve covers off..a few weeks later he drove in my driveway with it,with the 307 in it!--it was running sweet!--I asked him what he put in for a new cam,he said "none!"--I just beat the rocker arm studs back in with a hammer and drilled the bosses they go into and put pins in them!--I guess a few others were pulling out as well--but the lifters "pumped up" enough to keep everything quiet--but lost enough "travel" so the valve(s) couldn't open very far....

First time for me to see that!--but I looked at a few other small blocks in my friends shop in for a cam swap,and we found studs pulling out on them too--AND flat cam lobes! Thats why they have screw in studs on hi-performance heads I guess---..

 

[79chevyk10]

Yep, seen it before....99.9% sure it's a cam lobe.

 

[blasterD]

I put a new lifter on the #4 exaust and it didn't fix the problem. The pushrod was not bent, and the rocker stud did not appear to have pulled out. It looks like the cam will need to be replaced. I am going to do a compression check this afternoon to see if the engine is even worth the work. I can get a used 454 for a pretty good price, so I may just end up doing an engine swap. Thanks for all the advice