sticking or floating valves

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flathead5173

flathead5173

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I recently bought a 73 duster with a 318. It had sat for a while and had old gas in it but it started and I drove it home. It has a edelbrock intake and carb. When You nail the gas it don't really do much. It kinda moans and accelerates slowly. It does gear down. I decided to install a mild cam. When I took it apart I found two bent pushrods. I replaced them and the cam and lifters but did not replace the springs. After breaking in the cam I took it for a test drive and still have the same problem. I replaced all the ignition parts except the distributor. I also replaced the carb. It will cruise along ok but when I nail it doesn't have any power and sometimes backfires thur the carb. I took the sparks plug out which I had just replaced and found one bent and two with the ceramic part broke. Done a compression check all were in the 115 to 130 range. Anybody know whats going on here?



















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If your carb is good and your distributor is in good working order then I would check the valve springs
 
How did the push rods bend--chances are a few valve steams are bent, put new plugs in and see what happens but it might need for the heads to be re done--slap some milled 360 heads on it if your pulling the heads, IMO
 
If the valve stems were bent would he have low numbers on a compression test or is it possible that the valves still seat good?
 
The bent pushrods would definitely have me wondering. They're usually not the first thing to go, bent pushrods usually mean bent or stuck valves.

But, if it really does run fine as long as you're not "punching it" and the compression numbers are good, I'd say that its either a carb tuning problem or an ignition issue (just because its new doesn't mean its working right).

What size cam? What size carb?

Even Edelbrocks aren't perfect out of the box, you typically have to adjust something. If it runs fine the rest of the time, but bogs on acceleration, check out the step-up springs and see what's in there. You may also have to change the size of the step on the primary rods.

As far as the sparkplugs, there's really only a couple of possibilities. Either you got a bad batch, or you're detonating. I've actually had a batch of spark plugs (all out of the same box) where the ceramic broke on several plugs during installation to the specified torques, just some kind of manufacturing flaw. But if the electrodes are bent and they weren't that way during the install, you could be having detonation issues too. Which would actually go right along with a carb tuning problem.
 
Backfire through the carb? Lean and/or the pump shot needs to be adjusted. Not enuff pump shot.
Stock compression? That is a problem. A lack of squeeze can hurt the power out put and give slow acceleration. If it is a stock ratio, your probably in the high 7's-1. You could use 9-1+ even for mild performance cams.
 
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