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Topic: Your idle rpm with MP cam? (Read 375 times)
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Duster440
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I was talking to Don at FBO today (always an "interesting" experience) about the distributor he curved for me. He thought I should have my idle set at 850 rpm rather than the 700 I have it at currently - citing more cam cooling via oil splash. I've got an MP 280/.474 (238 @ .050).
Where do guys run your idle rpms for .474, .484, or even .509 cams?
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NYrr496
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I ran the old 509 cam with 906 heads, Performer RPM and a 750 Holley. It idled at 700 RPM with Roads lifters and 800 RPM with regular Comp hydraulic lifters. Everyone that saw my combo said it wouldn't work, but it worked well.
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Logged
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It takes a Mopar to catch a Mopar.
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bOb shingler
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750 is a good number to shoot for unless it's a really long duration cam.
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"bOb Built" (no matter how many times it takes)  |
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cristoir
Newbie
 Offline
Posts: 1
BigBlockDart.Com
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I'm running the 509 in my 383 (431) low deck stroker edelbrock performer rpm, 750 speed demon and 1 3/4 headers. compression is about 10.25 with pocket ported 906's with Ross flattops .040 down in the cylinder. The idle vacuum sucks (excuse the pun), only about 7 inches and 850 rpm and in neutral. Needless to say, it drops even further when put in gear... So I fiddle around a bit, but it seems to like 1000 rpm a bit better. This cam shows a lot of reversion at idle speeds. But from 3000 to 6000, grab your butt!
Cristoir
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satellite65
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I ran that exact cam in my 440 (280/.474). Mine was a LOOOOW compression (8.2:1) engine. This cam has a lot of overlap for such a small cam. It's an old design. I was able to pull about 13-14" @ 750-800 RPM on a good day. I'm at sea level, your altitude may affect it (I don't know where you are). Although it idled pretty smooth, due to 60* overlap it always smelled like unburned fuel at idle. My problems only got worse when I removed the headers and used stock exhaust manifolds - 10-11" hg max. It also likes a lot of ignition lead and a CD ign system (MSD) might help. Don't expect too much more out of it. It was a good cam 20 years ago but there are much better sticks for that RPM range nowadays.
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farmington
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when you get that nasty exhaust smell from your car with a performance cam, the problem is the carburetor. you're idling on the main circuit. you need to either crack the secondaries open a little (holley or demon) or go with the old drill the hole in the primary butterflies. works wonders.
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Logged
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When in doubt, Whip it out!
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satellite65
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Ordinarily I would tend to agree. However, my idle adj. screw was backed out all the way at the time. Definitely not on the mains. I had to crank my timing up to about 35* initial. At that point it was running really good but wouldn't re-start after shutting down (no surprize). Exhaust still brought tears to your eyes. Remember, this motor had very low compression (8.2:1). That probably had a lot to do with it.
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Winter
Jr. Member
Offline
Posts: 64
BigBlockDart.Com
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Open the secondary' s with an allen wrench ground flat on the short side, for a right angle screw driver, in order not to remove the Holley carb. Look down into the top to see if they are evenly set.
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Duster440
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I can get it to idle as low as 650, 700 no problem, but I settled on 800. Tuning isn't a problem. 4 corner idle screws ended up 1 to 1.5 turns out. Turning one all the way in will kill it. I've got 7.5" to 8" of vacuum in gear, 9-10" in neutral. 16* initial. I'm happy.
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