Upgrading HEI On the L69

[Papa_Wheelie]

I just found out today that the HEI that comes factory installed on the year 1986 Chevrolet Monte Carlo SS is a special unit with computer controlled module. After browsing thru catalogs and online, I was assured that many HEI performance products would replace my stock unit. They were wrong! and they should warn customers that they aren't compatible. I realized that all of them have a 4 pin ignition control module, and my car has a 7 pin, so it will not run correctly. Looks like my only choice is a reman. unit.

Does anyone know of a way to bypass the computer and get a Mallory or MSD, etc. HEI to work on the L69?

 

[Evan11]

My understanding is that the only way that you can run a older style 4 pin HEI successfully is if you run a non computer controlled carb. I believe the 7 pin computer controlled HEI & carb work together. Back in high school, there were always people around town that would throw an edelbrock, Holley carb on & leave the 7 pin HEI in & wonder why it won't run right. Of course, they never listen to my advise & would park the car I may not be 100% on this, but this is what I've always thought to be true.

 

[Clone TIE Pilot]

The two work together. It is best to go with AC Delco since some aftermarket modules lack a dwell circut to cut costs.

 

[tetomas]

You cant just change the module, you have to change the whole dist. The OEM one does not have a vacuum advance on it. Get a dist. and carb from a non-computer control engine this is the only way you will get it to run right.

 

[badlad]

That's funny my 86 monte ran fine with the factory carb and dizzy I ripped out the computer ditched the wiring going to the carb and dizzy access wiring crap thats not needed plus its ugly. Turned the dizzy into a oil pump primer when i put in my crate motor bought a complete dizzy through summit for $90.

 

[Clone TIE Pilot]

You cant just change the module, you have to change the whole dist. The OEM one does not have a vacuum advance on it. Get a dist. and carb from a non-computer control engine this is the only way you will get it to run right.

I was telling him to keep the CCC Qjet and get a AC Delco replacement computer advance dist. CCC Qjets beat all the aftermarket junk carbs. Why people are so bent on removing the computer for no good reason is beyond me. Going to non CCC is a downgrade, not an upgrade, worse MPGs with no gain in performance and sometimes a drop in it plus the cost of the conversion. Money would be better spent on better heads, or a better cam and headers. My car runs excellently with the CCC, very easy to work on system and simple, read my sig. GM 7-pin modules have a higher current limit & use adaptive dwell from the ECM unlike the older 4 pin modules.

Also badlad, your carb would have gone into full rich, cylinder washing mode with zero spark advance, must have been a real fun to drive . Most likely you had a bad vacuum leak leaning out your mixture, with the CCC disabled and the carb defaulted to full rich, it would mask the lean problem, not really fixing it.

Papa, if you really must have a performance dist, here is a list of computer advance versions. http://www.summitracing.com/search?keyword=HEI Distributor computer advance&dds=1 You can advance the base timing some, but you can't change the advance curve without burning a new PROM chip or using the rare Crane Cams aftermarket adjustable ECM. All US cars 1981 and newer are computer controlled, 1980 was the last year you could buy a non computer car in this country except CA, they were already all computer in 80.

 

[81Regal]

I was telling him to keep the CCC Qjet and get a AC Delco replacement computer advance dist. CCC Qjets beat all the aftermarket junk carbs. Why people are so bent on removing the computer for no good reason is beyond me.

Its because many people still don't and never will understand how the computer command system works. Just look at all the posts on this site that ask what they need to do to keep the gauges, A/C, cruise, ect, ect.... working after the computer is ripped out.

 

[81Regal]

Papa_Wheelie, there is no Special High Performance dizzy for 86, that is when GM changed from the large cap HEI to small cap HEI used for several years after that in many GM cars and trucks.
Like was mentioned use Delco replacement parts, those tend to be much better quality than the aftermarket pieces from places such as Standard, Mr Gasket, and so on.

 

[badlad]

My setup was just a temp setup till I got the dough for something better there bud! And yea it ran like a champ would light the 255/65/r15s up with the 2.41 rear gears and there was no lean or rich condition I can read plugs so yea your gd right it was real fun to drive! The only computer i need is the one im on now that i built 2 years ago and it runs strong also. And as for gauges aftermarkets the way to go on that too! Better accuracy and so on.