Hey guys!

I've got a bit of a decision on my hands here.

I've got a mild 355 in my 3/4 ton 4x4 truck, with a stock TPI intake on it. Its got a 165 ECM right now, and a custom chip for my engine in it. However, my MAF doesn't appear to be working correctly, so I'm trying to decide if I should get an aftermarket MAF, or if I should get myself a 730 ECM, and go speed density.

I've done some basic prom work for my TBI truck, but I'm trying to decide if I'd even be able to get my truck to run at all on the stock speed density prom, lol

 

Depends how fast you need the car back. If you have time to shop around then you can convert to SD for dirt cheap. I have an extra chip for my 305 to change from MAF to SD if you need one (just change the fuel tables and you're ready to rock). If you want to change to SD down the road, get a used MAF and sell it for what you paid for it. Everyone is going to tell you how this subject has been beaten to death so do a quick search and you'll find alot of threads with pinouts of the ECM and conversion tables.

Also, a stock 730 chip for a 350 in your truck will not work in your car that came with a 165 ecm. The VSS input is different (atleast it changed in the F-bodies, I assume all the 165 and 730 ECMs work the same).

 

Ah, thats right... I dunno how I'd change the VSS out. I'm running an SM465 in my truck, other than one of those costly inline VSS, I'm not sure how else I'd go about providing a speed input. At the moment, its getting it's 2k ppm signal from the back of the speedometer.

I'm in no rush to get the truck running at the moment, cause I am still in the midst of building it, lol

 

If you can do the PROM stuff, then it's pretty easy. Just use the existing VSS setup you have now and change the flag from magnetic to optical, then the SD will run off the 2000 PPM input.

I'm using a converted SD in my IROC, and have and MAF harness that I am converting now to go in the K10 next spring.

I have a few '730 ECMs that I have grabbed for cheap.. look on ebay for ones from non F body cars and you can find deals. Or even local people parting out Corsicas or Berettas.. anything with the '730 will work.
Aside from that, you'll have to either wire in a resistor or replace the knock sensor, and add in the MAP stuff.

 

Have you got a spare 5.7 ECM lying around I could possibly buy from you? Also, are all MAP sensors the same between TPI and TBI?

I can infact do some mild PROM burning (getting BLMs right by adjusting the volumetric efficiency tables, and spark curve etc) so I'm glad to hear I can adjust the newer ECM to run off the 2k ppm signal

What resistance is needed to use the MAF knock sensor with the 730? I just laid down over 100 bucks Canadian on a brand new AC Delco 5.7 knock sensor, and I'd hate to have to get a new one, lol

So far, from what I've learned in here, I do believe I am going to do the speed density conversion. It sounds far cheaper than buying a new aftermarket MAF, and would eliminate the headache of trying to figure out the air box ducting, just put a good ol' paper cone filter on the throttle body (I don't believe in K&N filters, let way too much stuff through, esspecially if you don't remember to maintain them religiously)

One last question -- I am putting Hydro boost into my truck, so I no longer need the big vac line for the old vac booster. What size / thread pattern is that nipple so I can buy a plug for it instead?

 

Also, cavalier's had the 730 ECM for a while as well. 91-93 or something around those years.

 

taken from - http://www.eecis.udel.edu/~davis/z28/ecm_swap_730/

as for spare ECM, they are one of those thing i tend to not like parting with
They are easy enough to find though. You only need the right PROM, any 730 ECM will work. It's basically the early 90s V6 GM cars with MPI, I know the on in my IROC is from a Buick something or other.

The other thing you would have to change is the VATS flag, that will need to be turned off.

As for the MAP sensor, I am not sure. I seem to recall reading on here that they do interchange both being 1 BAR, but I can't say for sure.

As for the nipple, just pull it out and head to the local hardware / plumbing supply store to compare.

 

Correct. All GM 1 BAR MAP sensors have the same output scale.

 

Just to play "devil's advocate", other than the MAF, was there anything else wrong? If not, then you may wish to stay with the MAF system. You have to admit the "fix" for the MAF system is simple enough.

 

I dunno if there is anything else wrong with it, very well could be. As I think I mentioned, this truck is still in the re-construction stage, and I have not driven it.

I am fairly confident that the MAF is no good, but that is not the only reason for wanting to swap.

First and foremost is that I do not want to have to make some sort of cheesy looking, or restrictive air ducting for the MAF, I'd far rather run a paper cone filter on the throttle body.

Second is that I can eliminate a few relays by going to speed density. I have all of my TPI's wiring out of the truck at the moment, and plan on totally rebuilding the power / relay harness, so that I've got all of my modules, relays, and other components that used to be under the firewall behind my glove box on my airbox. Also, gives me an opportunity to eliminate a lot of extra wiring that would otherwise go into the engine compartment, and replace the relays with modern bosch style relays to match up with the rest of the truck.

Third, of course, is the expense of a new MAF.

 

That alone is a huge debate. 3" diameter ducting is hardly restrictive, and a cone filter taking in cool air is going to give better results than one sucking in hot air from the engine bay.

 

i have seen the firebird ducting used, flipped upside down. I am not sure what I am going to do for my setup yet since I had planned on using dual batteries.

 

Exactly what I mean

I can have a nice looking ducting from a firebird, but I am told its real restrictive ducting. Or, I can use some cheesy looking air ducting.

Really, as far as I am concerned, the amount of power gained by a cold air intake is really isn't worth it for a truck that isn't built for racing