305 TPI Speed Density swap to 350 TPI Speed Density ... 1990-1992

I'm not talking about the EPROM. I'm talking about the MEMCAL, complete with limp-home and ESC circuitry. Do you need a freakin' 350 memcal for this swap or not??????!!!!!!

I'm about to pull my hair out searching for the answer. Some say yes, some say no. Obviously there are some differences. Is the enough difference in the ESC circuitry to make my car (just swapped out 305 to 350 a couple weeks ago) miss at idle and have a "searching" tach when I come to a stop?

Before I tackle the IAC (which I cleaned 2 years ago), TPS, check for vacuum leaks, etc. I want to know a definitive answer.

So ... again ... ONCE AND FOR ALL ... can you use a 305 SD memcal in your 350 swap?

Thanks.

 

Yes, you can. People do it all the time. You may get some false knock, or get knock that doesn't get spark retarded by the ecm, but thats about it other than the limp mode maybe being a bit worse than normal.

The memcal isn't the cause of your idle issues. Before you clean out the IAC, you should try unplugging the vaccum scource from the EGR valve. When the springs get weak, they can get opened a little during high vacuum and cause a hunting idle and stalling on decelleration.

 

GMgod ... you're the man. Thanks for such fast responses to my newb-like posts. I can rip an Fbody interior apart or put one together in about 2 hours flat, but when it comes to under the hood, I'll admit that I'm a newb.

Be cautious, you may be receiving many PMs from me in days to come! LOL!

But what do you mean "knock that doesn't get spark retarded by the ecm"?

And even though you say you can interchange the MEMCAL's, would the car still run better with the 350 memcal? (and by that I mean >$200 good lol).

 

I'd keep the 305 memcal and just swap the knock sensor. The sensor itself is supposedly tuned to the bore size. I've gone crazy trying to find answers to these questions as well especially since the 350 memcals are discontinued now and carrying an obscene price tag.

 

Bumping this post up for a similar question.

Have a '92 Z28 with a 350 TPI in it. Planning to swap in a '91 305 TPI stock motor, and was told I need to find a 305 memcal chip for the computer.

1) Do I really need a new chip for the swap? This will be a "track car", no emissions, no cats, etc. What happens if I use the chip that's in it now?

2) Is the VATS disable and emissions disable programmed in to the memcal? I.e. if I do need to get a new chip burned, can I get it programmed for all that?

 

Can you just trade wik someone who has what you need? 305 to 350 swaps are pretty common around here.

 

I posted a WTB thread for one, but no response yet.
https://www.thirdgen.org/forums/engi...hip-305-a.html