68 valve issue?
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Cruising
Joined: May 2017
Posts: 13
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68 valve issue?
I have a 68 with 327/350 that I bought as a project two years ago. Engine and heads were rebuilt by the guy I bought it from. Finally got to the point of first start-up and I hear this clanking noise from valve covers. Take them off only to discover that in his haste to sell me the car he never tightened the rocker arms. So after properly setting exhaust and intake valves, I was able to get her started. Sounds great at idle and revving in my garage. Once I take it out and put it under load I get this popping and backfiring sound coming from exhaust, it seems. It's not backfing that I'm familiar with through the carb. So here's the question. Is it possible that I bent a couple valves on that initial first start up? And if so, how do I figure out which ones without pulling the heads? Thanks! Randy
Le Mans Master
Joined: Aug 2017
Posts: 8,336
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From: Cool Northern Michigan
If you trust your skills on setting the valvelash properly you would not have suspected piston / valve contact. I really doubt that is an issue anyway unless a valve spring is getting lazy. Might be some wiped cam lobes though without knowing the history of oil changes involving zinc protection.
Most likely carb or ignition issues. But first, I would go back and double check the valvelash. Google which of the two procedures is comfortable for you: running or engine off. I bet a lot of the backfire goes away the second (adjustment) time around.
Hopefully its not dirty lifters that refuse to pump up. That would explain however, the loose valvelash from sitting.
Most likely carb or ignition issues. But first, I would go back and double check the valvelash. Google which of the two procedures is comfortable for you: running or engine off. I bet a lot of the backfire goes away the second (adjustment) time around.
Hopefully its not dirty lifters that refuse to pump up. That would explain however, the loose valvelash from sitting.
Le Mans Master
Joined: Oct 2006
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From: Gladstone MO
C3 of Year Finalist (appearance mods) 2019
It's really tough to get the valves and pistons to hit on a SBC. It can and has been done but it's not easy. I'd double check the firing order too.
