Ive got a question, I have a TPI setup from an 87 Vette which is a MAF system.

Ive got a 727 ECM from a newer style Vette, with the intentions of swapping to a speed density system. Is this a fairly straight forward swap, and will the connections on the 87 TPI harness hook into the 727 ECM?

I know Ive got to repin the harness, but Im not sure if the harness will physically connect to the 727 ECM..

The reason I ask is because I am still waiting for the TPI setup to show up in the mail, so I cant give it a try.

Anyone have experience with this conversion? Is it the same as going from a 165 to a 730?

 

Haven't personally used a '727, but I'm pretty familiar with the F-body 165-730 conversion.

The 727 itself should work, but unless you've also got the ECM connectors from a SD 'vette harness, you may have a bit of a challenge with the connectors. The '727 connectors I've seen in junkyards didn't seem like they could be repinned so easily. And the V6 connectors, which are readily available on Luminas, etc., don't have the right pins for a V8 application.

But, if you've already got a '165 harness, why not just keep things simple, and use a '730 instead of the '727? There'd be a couple of minor wiring differences if you plan to use the Y-body wiring setup, vs. the F-body (oil temp sensor, secondary fan, etc.) but those shouldn't be any big deal.

Is this being installed in an F-body, or a Y-body? (or something else?)

 

I think I read something about the 727 plug problems on EFI-tuning.org a while back, and IIRC, you can modify the non-V8 plugs with extra pin locations to fix the problem.

The other thing you could do is to use $5d code or $12 code on the '165 for a speed density swap without an ECM swap. See the sticky at the top of this board.

John

 

Well, its actually going into my 81 Monte Carlo. The reason Id like to go with the 727 Vette ECM is due to the fact that I can just mount the ECM in the engine compartment, and not have to worry about routing the harness into the cab of the car.

I do have the connectors for the 727 too... Would I be able to just remove the connectors off the old harness, and solder these connectors on?

If not, I guess its time to start lookin for a 730..

 

If you've got the connectors, I'd think you're set.

What I'd suggest is cracking open the respective wiring diagrams, and doing a pin-by-pin comparison, to see what needs to go where.

IMO, it'd be worth taking a little time to probe the donor harness with a continuity meter, and verify the function of each wire. You'll need to make a few changes to the '87 harness anyway, for the MAP wiring, and knock sensor, at a minimum...I won't speculate as to what else GM might have changed between '87 and '90, but I wouldn't assume anything.

 

Might be sure to carry a spare. The 727s can be hard to find at times. If anyone want to search for the posting, Ludis posted at the DIY-EFI list some years ago the part nos for new blank ecm connectors for the 727.

With as hot as underhood temps can get, and wet, I feel safer with ecm indoors. It's weather resistant, not weather proof.

 

Well, thats very true about the weather thing. Hrmmm...Ive got some wiring diagrams I guess Ill wait till I get the harness and just see what I have, and go from there.

If its going to be difficult, I guess ill just go with 730, and call it good.

Thanks for the info.

 

Heres another thought... Ive been planning on doing a twin turbo setup on my car once I get the chance to, but would I be able to program and run my car off of a 749 ECU, so I could later use it for my forced induction setup? From what Ive seen, the connectors are the same on the 165 harness, as they are on the 749 ECU.

If so, whats a good location for the 749 bin, and ecu etc.?

 

In that case, go ahead Wire it up for a '730, and the '749 will fit right on. There's a few wires that need to get relocated, but not many.

The 749 bin you'd probably want to start with is BBZB (Sy/Ty). Continue to use your 730 memcal, since there aren't any OEM 749 V8 apps.

Others are more qualified than me to explain what needs to be changed in the bin besides the cylinder select.

 

The 727 connnectors foro the V-6 lumina's and so on, will work for you, I did a conversion to 64 IMPALA using a 727, there are ALTERNATE PIN LOCATIONS for certain sensors, and you will be able to use all necessary sensors wanted. Make sure that you get some extra connectors, or take apart some extras in the junk yard, so you can extract some spare blank plugs. Also, some 89 3.1L PONTIAC GRAND PRIX, came with a turbo, and they used the 727 ECM as well. So you could use it for your turbo setup as well. I've been running a HOWELL EFI 90-92 SD harness with my TPI setup since 1997. They claim it is for the G-BODY's, but it is really univeral for multiple platforms. I in my 88 6-speed Monte SS, and I'm building a custom harness with a 727 ECM, since it will fit to my specific car. The reason for this is to add custom circuits that I want. HTH's

 

Very interesting 88SS6Speed...Would you happen to know where I could come by additional information about the 727 computer? Ive started doing a swap of the wires on the 165 harness over to the connectors on the 727 harness...Ive got most of the wiring figured out, but Im still unsure about a few things..

If I could come across other info, it would help me out a great deal.

Thanks for sharing your knowledge with me!