What's Your Opinion

[Hard Driver]

They will interchange, the 7427 and 8625 are nearly the same thing.

Anyone concur,will the memcals interchange and what's the difference between the 7427 / 8625 ?

[EagleMark]

He's the expert so I will concur. 7427 was the last year for that series of PCMs. 7427 will run any mask $0D, $0E, $31, $E6 or tranny, others may have issues with 4L80e, they will all run 4L60e, 700r4, non e auto or manual trans. Very versatile PCM.

[Hard Driver]

In the interest of learning,why is it better to start with a 4.3 memcal vs the 5.7 when tuning for a 3.4 engine,does it make tuning easier ? Please explain in layman's terms if possible.

[RobertISaar]

cylinder select on the 2 little chips that are under the knock filter would be my guess.

[Hard Driver]

OK,Thanks. It was suggested on another forum that when using the 7427 to use for a 3.4 engine get one from a 4.3,another suggestion was get one from a 305 because the cyl bore size was closer to the 3.4's bore.

[EagleMark]

You can tune a piano but you can't tunafish!

In other words you can tune the chip and you will have to tune the chip. But you can not tune the netres/limp home chip below knock sensor so it would be better to start with a six cylinder Memcal then an eight cylinder memcal. Or modify the memcal but no reason to when you can swap for one. Then when starting the bin use a six cylinder bin and make the cylinder volume, injector size etc... adjustments to get a close start for tuning.

Three parts in a memcal. Chip, limp home chip and knock module. Six cylinder memcal is way better starting point.

Knock module is also in memcal so that is going to be an experiment as the 4.3L knock sensor is a match for knock module, but a 3.4L knock sensor may work better? Have to look into that...

[Hard Driver]

Thanks,that makes things much clearer,gaining knowledge a post at a time !