I have a 1983 Berlinetta that has a 350 TPI installed. This TPI unit originally ran a 1985 305 IROC. The cam is beefier, and 24 pound SVO injectors are doing the squirting. The engine runs OK, but tuning is needed to make the components work together.

I have been reading about chip-burning quite a bit, but it seems the 1985 setup is ignored- why? The PROM seems to come out just fine, and even though the ECM is much slower- it works fine. What equipment will be needed for multiple PROMS to be burned? Can I get an EEPROM that will work in a 1985 processor?

 

The 870 ECM used in 85 wasn't really ignored, its just that 1985 was the ONLY year that used that ECM, so demand for support just isn't there. GMEPRO does have support for it but the parameters that can be tuned are limited.

Go here for a DIY on swapping to the much better supported 165 ECM http://www.eecis.udel.edu/~davis/z28/ecm_swap/ Quite a simple swap, takes a few hours and the ECM is supported by several prom tuning programs.

 

To add further to Morley; when DIY Prom Burning began 3 years ago, the SD 7730 $8D calibration was very well documented and much was known (though still more is being found today).

The $6E 165 MAF used in 1989 became better known about 2 years ago, and that was the main reason many people went to that version. Later the $32B and $32 became known and less 165 users are swapping to the $6E now.

The 870 $1A (IIRC) is now fairly well documented and more ability to tune exists today. The concept of "tuning" the 870 has a lot of similarities to the other MAF systems, so the basics are the same. There is less reason to swap from the 870 today than say two years ago, and you should give it a try. If you go with TunerCat, and chose to swap to a 165 later, it will only cost $20 more for a new TDF - everything else will be the same.

But as Morley said, the limited number of cars with the 870 (85 MY only) and until recently, limited information has made the 870 an orphan until now. Go for it, you have little to loose.

Even between SD & MAF systems, there are many similarities when you start getting into tuning techniques - tuning is tuning and it all boils down to "fuel & spark" ultimately.

 

Glenn, that would make sense. I do not feel I would need to change much, mainly injector rating, spark knock, and fan temps. What is the main difference with 85 and later on the physical mounting of the PROM?

 

I am no expert on the 870. But it is a C3 type ECM which uses a removable eprom 2732 instead of a memcal like the P4 (7730 & 165s).

You should be able to use Craig Moates "stacker/adapter" with the 29C256 flash prom that will load multiple bins as the 29C256 is 32K big and the stock 2732 is only 4K big.

The 2732 is used by a lot of earlier GM ECMs and many of the TBI guys (and GN guys) can help you more in the specifics of working with C3 ECMs.

 

yeah...good question.

so it seems that the best thing to do for the 85 models would be to switch to the 86 ecm, as documented the tech. section, correct?

this is good to know, because i have my old 86 ecm sitting in my room, and i plan on putting in a 400sbc with lt1 intake this summer.

 

i did a post last fall titled Maf and why its such a pita. its an explanation of tables in the $3a code. the $1f is really similar. they tune about the same. so give it a good read. then ask more questons.

https://www.thirdgen.org/techbb2/sho...ts+such+a+pita

 

Right now I am grinding my way through Ben Watson's book, so I will tune it to what he says first, then worry about ECM work later in the fall.

My Pontiac needs some supension work, so that gets done now so she is ready for the summer.

 

dont even bother.get into the prom and start working on spark.

 

I disagree. You young' uns may like to dive right in, but I research my stuff first.

 

none of the stuff in that book is going to explian the ecm algorythms. however if your not familiar with tunning it might not be a bad idea.

 

The book did help. Currently the car is on reserve status- so when I finish work on my LeMans I will tune it according to Watson's book. Several things there caught my eye, namely fuel pressure/injector size ratio (I am running 24# SVO @ 50 psi) and idle air step motor issues. I will also check for vacuum leaks in the intake.