Bent or burnt valves, how do you tell without a leakdown test? - Hot Rod Forum : Hotrodders Bulletin Board
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Old 03-29-2009, 06:32 PM
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Bent or burnt valves, how do you tell without a leakdown test?

I have an engine miss I've been trying to get fixed. It seems I've checked everything but the valves. I'm trying to rule everything else out before I start yanking heads.
I did a compression check and I got over 200lbs in each cylinder. My engine is an 11-1cr SBC 406. All of the cylinders were within 5% of each other. Could you still get excellent results with bad valves? I don't have a leakdown tester and I don't know anybody with one. I have already spent enough money and I don't really want to buy one if I don't have to. It would actually be cheaper to yank the heads and check them. Of course I don't want to if I don't have to.

I guess what I'm looking for is signs your valves are bad. I've heard backfiring and flames out of the carb are potential signs. I don't have either issue.
Thanks for your time

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Old 03-29-2009, 10:55 PM
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I'm no expert, but if you've got good compression, I don't think you have burnt or bent valves. If you've checked everything else, it might be a bad cam, lifters, rocker? I would re-check again though. What do the plugs look like?
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Old 03-29-2009, 11:45 PM
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maybe a valve adjusted too tight?
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Old 03-30-2009, 12:12 AM
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Nothing wrong with the valves. Keep looking.
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Old 03-30-2009, 12:21 AM
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Thanks for the replies. My spark plugs have soot on them, I do know its running rich. I have been tuning my Holley and I've even swapped carbs with no luck.
I did install a new cam last year. I've always heard if it goes bad you will hear alot of noise from the excess clearances. I don't hear any pecking or ticking. I'm pretty sure its ok.
I'm going to swap in another distributor today and see what that does.

Thanks for your time and replies
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Old 03-30-2009, 12:49 AM
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Drop your fuel pressure to 5 psi at the carb.
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