Proform HEI Distributor ?

High Speed Pursuit

High Speed Pursuit

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Anyone have any good or bad experiences with the Proform HEI Distributor for an LA engine? My engine is a balanced and blueprinted 340 with nothing stock inside or outside and will be used as a street engine in my Mirada...my engine builder recommends the Proform HEI distributor part# 66991, but I don't have any knowledge about their performance and reliability. Any comments are appreciated...
 
HEI is low-RPM garbage, not suited to an engine that's going to want to be shifted north of 6,000RPM. If you want it to perform well enough for your engine, you'll need to throw an MSD module in it, which will get it to spark well up that high. Of course, that adds another ~$120 to an already-expensive conversion, just to make it run as well as a stock Mopar electronic ignition. At that investment, you might as well have added an MSD, Mallory, or Summit 6AL-type box and actually gained some power.
Despite the wild popularity of the conversion, I've not seen any conclusive reason to swap to the inferior HEI setup. I know two guys that did it for economy and gained nothing, and another that did it for performance and it suffered. I've had extensive experience with both (I ran Pontiacs too) and much prefer the Mopar system.
It's also worth mentioning that while I don't necessarily condemn or avoid Proform, their quality control is sketchy. Typical Asian-market stuff. You've probably got a nice, well-made USA distributor already and are probably better off to use it.
 
X2 on the proform quality. I've used a proform vacumm advance dizzy before and had to completely recurve it and put a limiter plate in. The cap didn't even sit right on it. I ended up buying an auto parts store one and it fit just fine. I run a 4 pin hei module and a msd e core coil on my fifth ave and never had a problem. Easy to wire up and you get hotter spark than a chrysler electronic ignition. But like nocar340 said if your reving past 5500 rpm the chrysler ignition is a win win. Or the more expensive msd ignition. Those all in one hei module built in to the dizzy are all Chinese junk. I'd stay away.
 
I'm one with the so called "garbage HEI" setup, from Davis Unified Ignition. In MY case, it works just fine with absolutely zero problems. Of course to be honest, I don't go above 5,500 rpm so can't say what it would do above that. All depends on your intended usage. Pro-Form? No experience but I've been told, like mentioned already, the quality is hit and miss.
DSCF0001.JPG
 
The Davis system will run on a stock GM module, but the module included with it is much better than an OE GM unit (hence my comment about an MSD module earlier). Part of the reason the GM HEI sucks is because of the dwell arrangement. As mentioned, having run the HEI in the past, in stock form it falls on its face at about 4,500RPM in OE form. Once GM got into the 7-pin, small-cap HEI it was a better setup because they let a computer control the spark's timing and dwell and they used a much higher-capacity coil that was no longer mounted in the cap. Of course, that first appeared on V8s with Tuned Port Injection, which fell on its face at 5,000RPM anyhow due to the crappy intake design. No amount of spark trickery could help that, which is why there were so many aftermarket TPI manifolds available way back when.
Believe it or don't, the GM HEI was modeled after Chrysler's setup. It's the same basic circuit, right down to the VR pickup. GM's failure to use a ballast resistor is one reason the HEI system was a high-RPM loser; the lack of a big, hardy transistor was another. The circuitry available at the time simply didn't allow for the enormous dwell times the Chrysler setup could deliver. It didn't matter at the time, since GM didn't have any free-revving engines available by the time HEI was introduced anyhow. Conversely, the Mopar system debuted exclusively on the high-revving 426 Hemi and screaming 340 in '71. They were the only two engines to get it that first year, and in '72 it was standard only on high-performance engines and Imperials. It wasn't standardized until '73.
 
I agree, the Mopar system is excellent. One advantage (if you want to call it that) to the HEI style is fewer components and less wiring. Main reason I chose it. There's enough crap crammed under the hood of my car already without a ballast, external module, the added wiring, etc. :eek:
plug wires 1.JPG
 
Now add a pair of turbochargers, fuel rails, 8 injectors, two water-to-air intercoolers, boost control solenoids, distributorless ignition, charge-air and intercooler (liquid) plumbing, a pump and heat exchanger, sender and sensor wiring, water-meth injection and a partridge in a pear tree and you'll understand why I've been hesitant to pull the perfectly-good 318 out of the Imperial. I'm sticking with a small-block, thank God, but with the Challenger taking up most of the available garage space, the nightmare described is in a holding pattern.
 
NoCar340 said:
Now add a pair of turbochargers, fuel rails, 8 injectors, two water-to-air intercoolers, boost control solenoids, distributorless ignition, charge-air and intercooler (liquid) plumbing, a pump and heat exchanger, sender and sensor wiring, water-meth injection and a partridge in a pear tree and you'll understand why I've been hesitant to pull the perfectly-good 318 out of the Imperial. I'm sticking with a small-block, thank God, but with the Challenger taking up most of the available garage space, the nightmare described is in a holding pattern.
Click to expand...
Touche! lol
 
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