Re: Just fired my Hemi... what total ignition do they like?
[Re: mickm]
#1708947
12/10/14 10:10 PM
12/10/14 10:10 PM
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Joined: Mar 2010
Posts: 984 Tennessee
Hemi ragtop
super stock
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super stock
Joined: Mar 2010
Posts: 984
Tennessee
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As has already been mentioned, it takes time but is worth it! There is absolutely no reason to even break out a timing light until you KNOW exactly where top dead #1 is in relation to the timing tab on your damper and timing chain cover. If you didn't measure this yourself, check it with a piston stop! NEVER TRUST YOUR ENGINE BUILDER TO DO THIS! Ask me how I know. I have seen as much as 18 degrees off! (I once pulled the vacuum advance line to check timing and the engine died, (what's this?) The owner couldn't understand the "lazy acceleration) On the dyno, my engine made more power at 32 degrees as well, or so said the sheet. Problem was, the timing marks didn't match top dead center when I checked with a piston stop (the builder hinted that it "might be off a degree or two"?) Three degrees, (out of 360) may not sound like a lot, but when you are actually at 32 vs. 35, you can FEEL the difference! I am also a believer in vacuum advance. Look at it this way, if it wasn't needed the factory would have NEVER added the cost. Once you get the mechanical figured out, then TUNE the vacuum. It pays off big time in part throttle "tip in" response, HAS to be good for the engine, (burning fuel that would otherwise contaminate the oil and wash the rings down) and improve mileage. My engine shows over 200lb cranking pressure, is 10.75 to 1 measured with aluminum heads and runs great it 100 degree weather with 93 octane and over 40 degrees with vacuum advance, (adjusted to come in slow of course). All of this takes time and experimentation, all a part of a sweet running, powerful STREET car. One more comment and I will shut up, no two cars, engines, gear/converter combos will be the same, the ONLY way to tune your car, it to take the time as was said earlier. My car weighs 4,175lb, 3.54 gear (2.76 in OD) and has a "small cam", 11" converter and etc. A lighter car with more gear, different cam/converter would be totally different. So you have to experiment with YOUR combo. Still, starting at 32 degrees total is safe, but not absolutely right for YOUR combination.
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Re: Just fired my Hemi... what total ignition do they like?
[Re: WarEagle1]
#1708950
12/12/14 11:37 AM
12/12/14 11:37 AM
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Joined: Jan 2003
Posts: 13,345 Marion, South Carolina [><]
an8sec70cuda
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 13,345
Marion, South Carolina [><]
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30-35° will be fine.
FWIW...the timing that makes the most power on the dyno doesn't necessarily run the fastest at the track. My 572" pump gas hemi likes 34-35°.
CHIP '70 hemicuda, 575" Hemi, 727, Dana 60 '69 road runner, 440-6, 18 spline 4 speed, Dana 60 '71 Demon, 340, low gear 904, 8.75 '73 Chrysler New Yorker, 440, 727, 8.75 '90 Chevy 454SS Silverado, 476" BBC, TH400, 14 bolt '06 GMC 2500HD LBZ Duramax
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Re: Just fired my Hemi... what total ignition do they like?
[Re: an8sec70cuda]
#1708951
12/12/14 04:50 PM
12/12/14 04:50 PM
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Joined: Jan 2003
Posts: 964 Odessa, Fl
blowndart
super stock
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super stock
Joined: Jan 2003
Posts: 964
Odessa, Fl
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I assume he's using the FAST system to control ignition, so reference to vacuum advance don't apply. My Iron headed, 10.5:1, FAST EFI 477 hemi likes 33 FWIW. My solid roller is similar to your hyd roller.
Last edited by blowndart; 12/12/14 04:52 PM.
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