Learning Curve 2.0 - ughh

**trlrider** · 05-14-2021

Originally Posted by dave w

It appears my copy of BDJY is $E6, see attached.

BDJY has been superseded to BLCP, with a release date of 04/26/94

dave w

Okay, good! Thanks for the slap upside the head. Now I am somewhat back on track.
Somewhere I crossed the BDJY to a OD mask in my files. Deleted that and save yours.
Will re-read mine tonight and see what happens. It is in a '7427, to if it was superceeded by the BLCP, which is the original file in my '1993 K1500 in a '8625, then at some point the PCM was replaced and upgraded. It does show a different tag then my other salvage yard units.
So back to the thousand dollar question!

Isn't learning fun?

Thanks DaveW again.

**trlrider** · 05-14-2021

Originally Posted by dave w

BDJY has been superseded to BLCP, with a release date of 04/26/94

dave w

DaveW, or anyone,
So what is the preferred PCM, the '7427 with the $E6 or $OD mask?
, or the '8625 which appears newer?
Or is there not enough difference between them to be concerned about for a basic reliable unit, with a possibility of add-ons later such as cam and Vortec heads.
Right now just learning to make the truck reliable and have a learning platform.

Thanks,

Louis

**trlrider** · 06-02-2021

So update on this journey!

- after much searching, tinkering, agonizing and soul searching I found the following.
- the big cap HEI that was modified to work with the PCM was out of phase (retarded) approximately 10 to 12 degree's. Thus it was firing to early for full spark. This could possibly explain the knock retard both the stock .bin and the modified .bin was experiencing.

- so, this past weekend I pulled the modified distributor, rebuilt the original small cap HEI and dropped it in. Mounted the coil to the firewall, with extra grounding to both the head and the frame.

- with the stock .bin it would still spit and sputter but minimal knock retard.
- the .bin file with the vortec timing table, a little better but still spitting an sputtering.
- found a timing table post on one of the Camaro forums (will post the source when I remember where it was) for a Iron Head LT1. Hmm, my cam and heads are very close to identical to the old LT1's! Created a modified .bin with that timing table and burned a chip.
- and, we have a drive-able truck again.
- so far with 5 short mild trips on it and nothing adverse is showing up, except the BLM's are in the 112 - 116 range at steady mph's in various increments.

At least I can drive it now to start working on fine tuning to this heavy vehicle.

Learned:
-how to find the correct .xdf and .adx files for my .bins
-to keep notes and backup files of what works, and send what doesn't work to the trash.
-that my understanding of setting up distributors for computer control still lacks. Although I still want a big cap HEI. But the current setup will work.
-that no matter how prepared I though I was for this swap, I was severely lacking.

But first and foremost of importance: There are some really great and very experienced folks on this forum always willing to nudge you in the correct direction, if you just ask the correct questions!

Thanks to all those that have helped this far.

Louis

**dave w** · 06-02-2021

The 1985 - 1991 TPI Corvette used the Large Cap HEI's from the factory. Likely a factory EFI Large Cap HEI will be correctly phased.

Often, adjusting the injector so some of the BLM's are Rich and some of the BLM's are lean is a good plan before adjusting the VE tables.

dave w

**trlrider** · 06-02-2021

Originally Posted by dave w

The 1985 - 1991 TPI Corvette used the Large Cap HEI's from the factory. Likely a factory EFI Large Cap HEI will be correctly phased.

Often, adjusting the injector so some of the BLM's are Rich and some of the BLM's are lean is a good plan before adjusting the VE tables.

dave w

Afternoon Dave W!
I don't believe the late '80's TPI Corvettes/Camaro Large Cap HEI's had centrifugal advance. There were locked at the factory. That is where my problem started is when I did the lock. Apperently when I pulled the weights and locked the centrifugal advance I went to far and misaligned the rotor with the stator.
We were supposed to have a couple of those Corvette/Camaro HEI's here at the shop, but I be dipped if we can find them.

Anyway, went back and made the small cap work and found a place for the coil which did not have a home on the aftermarket intake with the fuel lines and new throttle bracket in the way. All is good there now.
If I do find a Corvette HEI I may put it in when I do the head swap this fall.

Thanks!

**dave w** · 06-02-2021

The Corvette distributor is an option. The Corvette distributor uses screws to hold down the distributor cap, not fairly priced. Many of the early 80's SBC's were equipped with an "Electronic" carburetor combined with a "without" vacuum advance distributors having the common spring loaded "J" hook to hold down the distributor cap. Most of the early 80's distributors "without" vacuum advance have the same 7 pin ignition module used in the TPI Corvette distributor.

dave w