460 weak performance
#1
Join Date: Nov 2009
Location: starship enterprise
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460 weak performance
as I have previously mentioned, my 460 is VERY, VERY sick. The cause isn't found yet, might be pistons, might be cam might be ? However, the engine loses vaccum as the RPM increases, like it has a plugged exhaust. Noone seems to have ever seen these symptoms before and We can't pinpoint the cause. Any suggestions?
#3
The best mechanic in town replaced an engine just to have the new one do the same thing. I was walking behind the car, while the owner was watching the mechanic try to figure out the problem, and noticed the exhaust crammed with red clay mud. Pointed it out, and the mechanic unplugged the exhaust, and the car ran fine.
#5
#6
Join Date: Nov 2009
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The engine does this with the exhaust un corked at the manifolds, so I doubt that the exhaust is plugged. Same symptoms with the exhaust hooked up as with it unhooked. As for the spark advance, this occurs with the timing light going all the way to over 40* at about 2500 rpm with the Mr gasket dizzy recurve kit. Thanks for the input so far this seems to be a never ending battle so far. This is the third time that i've asked about opinions on the problem, and am still looking but with perseverence and peoples input from similar problems, I will find it eventually. The builder is thinking that it might be a bad camshaft, we have verified cam timing, tried different distributors, and so on. I will try some L&L headers and fool with the carb a bit, but I think the engine is going to have to come out and be tore down this winter. Thanks guys, I will keep looking for the problem.
#7
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#10
Bobby look were he lives. He is at high altitude. 18 is about as high as you can get at 5000ft.
Have the engine builder check with a dial indicator the ACTUAL valve lift at the exhaust valves (all of them) He could be right in a bad cam and have some of the exhaust valves not opening far enough which would cause similar symptoms as a plugged exhaust.
Have the engine builder check with a dial indicator the ACTUAL valve lift at the exhaust valves (all of them) He could be right in a bad cam and have some of the exhaust valves not opening far enough which would cause similar symptoms as a plugged exhaust.
#11
I don't know about setting up for high altitude, but 40 degrees at 2500 sounds a bit high for me. Have you tried backing the timing off a little to see if it makes a difference? I know back in the 70s we used to set up small block Chevy engines to run 38-42 degrees at around 3000, small block Fords we used 36-40 degrees at 3000.
I second the thought of checking all the exhaust valves for lift, heck, at that point, I would check all the valves and valve timing on each cylinder.
I second the thought of checking all the exhaust valves for lift, heck, at that point, I would check all the valves and valve timing on each cylinder.
#12
Bobby look were he lives. He is at high altitude. 18 is about as high as you can get at 5000ft.
Have the engine builder check with a dial indicator the ACTUAL valve lift at the exhaust valves (all of them) He could be right in a bad cam and have some of the exhaust valves not opening far enough which would cause similar symptoms as a plugged exhaust.
Have the engine builder check with a dial indicator the ACTUAL valve lift at the exhaust valves (all of them) He could be right in a bad cam and have some of the exhaust valves not opening far enough which would cause similar symptoms as a plugged exhaust.
#15