BLKMGK Posted September 30, 2001 Share Posted September 30, 2001 Okay, I had noticed that my car seemed to sputter in the 2K-4K range at light throttle. I thought that perhaps it was the ignition and installed an Accel 300+ ignition and a HUGE monster E-coil. Well, problem still persists! I'm starting to wonder if perhaps at part throttle the silly ignition timing is too far advanced - would that make sense? Accel says their distributor's mechanical advance is 24degrees "all in" by 3K. The vaccum advance is an additional 10degrees. Base is close to 15. Adding it all up (?) is sounds like maybe high vaccum low throttle conditions may be advancing quite a bit - am I on the right track I'm considering unplugging the advance tomrrow to see if that helps at all. I'd hoped that this ignition would clean up the idle a little and fix this problem but it hasn't seemed to help much. I've NOT tried playing with initial advance too much but at WOT it sure seems to run pretty well. Will try for a dyno run this week, I suspect my A/F is WAY off on the rich side too P.S. When I get a chance I'll try to post something in regards to the two ignitions I've recently tried to work with - Crane HI-6 and Accel 300+. Somem noticable differences... Quote Link to comment Share on other sites More sharing options...
Modern Motorsports Ltd Posted September 30, 2001 Share Posted September 30, 2001 Jim, is it present at 1500 when stepping into the throttle transition? You mention you haven't played with initial timing much......why not??? I know I rec'd it as a solution to a prior q you had a while back......sbc's like lots of initial...it can seem find, add a couple degrees and it'll scream more Here's my more recent..fine to bump it up to see if it makes a difference, just DON'T go WOT higher rpm's until you're sure your max timing is in a safe realm....fine to do low rpm transition 'tests' though. Good luck http://www.hybridz.org/cgi-bin/ultimatebb.cgi?ubb=get_topic&f=1&t=001183 Quote Link to comment Share on other sites More sharing options...
BLKMGK Posted September 30, 2001 Author Share Posted September 30, 2001 I've moved the timing around some to clean up the idle. However it seems to want a TON of initial advance and that just seems "wrong" to me especially since I know this is bumping my total advance ever higher. How high is too high? I don't think it's detonating but with the loud exhaust it's darned tough to tell! Just seems to sort of miss a little at part throttle, 1500rpm seems okay if I remember right and I can pull 6th from 1K to 2K on the highway fine. If it were "missing" in that range then I'd certainly expect to feel it in 6th! My calcs seems to say that in the 2K-3K range with high vacuum I may be seeing as much as 48degrees. That's 10 from the can, 24 from the mechanical, and 14 initial. That seems super high to me! My carb is probably rich too but until I get a dyno run I won't know for sure. I'll tinker with it some today but a dyno run is looking like a must have to get A/F if nothing else. Need to wire up my A/F gauge too but it won't be today Quote Link to comment Share on other sites More sharing options...
BLKMGK Posted September 30, 2001 Author Share Posted September 30, 2001 Hrm, I was right. Removing the vac advance allows the motor to pull cleanly at part throttle Now what? Obviously part throttle advance under cruise is hosed but this isn't EFI where I can simply plug in a number to fix it (soon!). Heh, I'm beginning to appreciate the Holley programmable ignition setups now Shoudl I simply leave it disconnected? Seems "wrong" to me. I can adjust it for less advance easily enough and that would add some advance at idle at least? I don't want to monkey with mecahnical advance if I can help it - getting to it requires a ton of work and resetting the mag trigger when I'm done. I think I'll watch my MPG this time around as well as get a dyno pull to help figure this out... Quote Link to comment Share on other sites More sharing options...
Modern Motorsports Ltd Posted September 30, 2001 Share Posted September 30, 2001 Do you know for sure how much vaccuum that can was adding? I had a crane adjustable can once and quickly found out it was adding in 20+ degrees and wouldn't adjust low enough without putting limiting plates in my dizzy etc. Yanked it and put a normal GM 10 degree can in ($5 or 6 bucks at any auto chaing/Neihoff lists by inches of vaccuum) and that helped. I had tooo much advance at part throttle so it would knock.....sounds like what you're experiencing. 48 total including vaccuum at cruise is not alarming....you just need to ensure it drops off fast enough when you load it up or it'll knock/stumble as perhaps you experienced. WOT total I keep at or below 38 typically and rest as high as possible without stumbles or knocks. FWIW, 16/17 initial is where mine really wakes up off idle. An initial timing change a few years back is what got my first 2-3 rear end stepout at WOT w/ the ole 327......made a surprising overall difference/I was v. green tuning at the time and having my car jump a 1/2 lane sideways at 50mph was a 10 on the pucker factor.. good luck nailing it down. Quote Link to comment Share on other sites More sharing options...
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