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Discussion Starter · #1 ·
Greetings Everyone, I looking for recommendations for a good street performance electronic distributor. My car currently has the GM HEI ignition (probably from the ‘70s) and I’m rebating trying to recurve the mechanical advance or buy a new one from DUI where they say they will curve it to suit my engine. Currently mechanical advance seems to be all in around 2000-2200 rpm at 36* BTDC. I’ve tried some different spring rates with no noticeable difference so far. So I going to try heavier springs to get full advance up to around 2800-3000. I’m not sure how tunable the HEI is, am I better off to go with DUI or MSD or Pertronix? Or, perhaps the original type distributor with a Pertronix kit? I have to say I’ve gotten some really great expert advice on this forum. Thanks!
 

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If you have an HEI Petronix conversion is not necessary although Petronix sells their own distributors. You can buy MSD or DUI or any brand but it won’t make your car run better than a stock HEI. The HEI is very tunable.

just get a GM HEI curve kit....try one light and one medium spring to start.

my favorite vac can is the Standard Motor Parts (SMP) VC 302 Rock auto has em

o’Reilly calls it a BWD V482;...Napa calls it a VC 1703...all the same. Hook one of those to full manifold vac. It will give you 10 degrees. Your goal at 36 is good. Change springs and for $25 bucks, you can have perfect timing.

there are fancier ways to get there, and more claims of better, but if the spark is strong at the right moment, that is all you need.

all in by 200 is too low.
 

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Discussion Starter · #3 ·
Thanks for the info. I just purchased an advance spring kit/ Mr Gasket 928G and a Duralast DV1838 vacuum advance control. The vac can is supposed to give me 12* BTDC. For the springs I thought I’d try a med and a heavy, with the lighter springs the mech advance seems to come in too quick and is all in around 2000 rpm.
 

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Discussion Starter · #6 ·
To follow up on my previous posts, I tried several different spring combinations trying to delay mechanical advance until 2800-3000 rpm as recommended. Nothing seemed to make much difference. Every combination seemed to yield the same results, all in by 2000 rpm. So I wound up using 2 medium weight springs, initial timing set at 16* BTDC at 900 rpm, mechanical advance all in by 2000 rpm at 32*. Reconnected vac advance to manifold port and checked timing again which yielded 25* @ 900 rpm, 41* @ 1900 rpm. So... 16* initial, vacuum advance 9* and mechanical @ 16* for total of 41*. Backed idle down to 700 rpm which gave me 21* w/vac advance or 12* w/o vac advance. Not sure what made the most difference, the springs, new vac advance cannister, vac from manifold or timing adjustments but... it is now running like a scaled dog and definitely puts a smile on my face! Thanks for all the advice!
 

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To follow up on my previous posts, I tried several different spring combinations trying to delay mechanical advance until 2800-3000 rpm as recommended. Nothing seemed to make much difference. Every combination seemed to yield the same results, all in by 2000 rpm. So I wound up using 2 medium weight springs, initial timing set at 16* BTDC at 900 rpm, mechanical advance all in by 2000 rpm at 32*. Reconnected vac advance to manifold port and checked timing again which yielded 25* @ 900 rpm, 41* @ 1900 rpm. So... 16* initial, vacuum advance 9* and mechanical @ 16* for total of 41*. Backed idle down to 700 rpm which gave me 21* w/vac advance or 12* w/o vac advance. Not sure what made the most difference, the springs, new vac advance cannister, vac from manifold or timing adjustments but... it is now running like a scaled dog and definitely puts a smile on my face! Thanks for all the advice!

Hmmm. I am tired, but numbers not adding up quite right. At 700 idle - 12degrees. You have 16 degrees coming from the distributor mechanical advance. 12 + 16 = 28 total mechanical advance. Plus 9 degrees from the vacuum advance means 28 + 9 = 37 Total with no throttle/light throttle cruising down the road.

The 16 degrees Initial at 900 RPM's most likely indicates that the vacuum can was advancing the timing at that RPM and why it dropped to 9 degrees at 700 RPM's and gave you the 9 + 16 = 21.

Bottom line - if it works and you don't have any detonation, or engine is running hot, then go for it.
 

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Discussion Starter · #8 ·
To add to my original post… The problem I’ve been having is occurring is when I wind-out 2nd gear above 4000 rpm… I start having a kind of stall situation where I have to let off and shift to 3rd. I’ve had the same problem with 3 different carburetors, I thought is was a fuel starvation issue but then decided it must be the old GM HEI ignition system. DUI advertises they will curve distributor to my engine spec’s. I‘ve had 3 back surgeries since 2017 and can’t do prolonged bending to reach the distributor anymore and… I’m tried of trying to fix it to no avail. So i want a plug and play electronic distributor that I can drop-in and get this baby to wind-out like a Pontiac should. I have been stranded by the road with points so I’m not interesting to going back to old tech. Any recommendations so i can stop tinkering and start enjoying my ride? Thanks!
 

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Have you called DUI and spoke to them about your situation? I dont know them, but it looks to be custom to your needs. Not to say the others would no work with you. I have only heard good things about Davis. Also asked about the turn around time so its not showing up in February.
 
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