Ollie8974

I just read the ChevyThunder post on the GM TPI, very informative reading. Gave me a lot of info for what I am trying to do, which is building an EFI system for a traditional Pontiac engine in a 1979 4 speed Trans Am. With a 400 ci test mule, later a built 455. Using the 1227727 ECM the new Edelbrock Victor Pontiac EFI manifold, an Accufab 4150 throttle body, right now collecting all the sensors and wire harness.

I have reread the TPI article several times, each time finding more info to help with the Pontiac EFI project.
I have several questions

1. What knock sensor should I use? Or is this going to be an experiment?

2. Speed sensor. Dakota Digital offers an 8 K pulse generator in several configurations, at a very reasonable price, is this I need for the speed senor?

3. EEPROM, I saw a new EPROM on EBay for the 350 TPI, can get it with the VATS and VSS disabled, is this a good place to start? I plan to learn reprogramming the chip with Tuner Pro RT.

4. I have been offered a wire harness for a LS1 engine at a very reasonable price. Would this be a good candidate to modify or should I continue looking for a harness from a 1227727 ECM?

bnoon

Sorry I can't help more, but for number 3, I would pass. Step into the DIYProm board and read the stickies at the top. Tons of factory 350 bins to start with in there. Buy your blank chips and adapters from http://www.moates.net and you're set. The burns sold on ebay have the most basic of changes that you can make in 5 minutes once you have the burning equipment.

A question: What do you use for a distributor for the ECU to read? Did Pontiac ever have an HEI electronic control dizzy???

Ollie8974

A question: What do you use for a distributor for the ECU to read? Did Pontiac ever have an HEI electronic control dizzy???

No GM never made a ECM controled distributor for the Pontiac motor, I modified one for my FEI set up using about $125.00 in over the counter parts. The modification is well documented with instructions and photos. I just tried to attach a photo with this but the file is too big, and I have to leave for work so I will have to play with making them smaller tomorrow.

Yes I have the TurnerPRO, and plan on doing the chip reprograming, I am just looking for a place to start sence there are no stock prom for the Poniac motor, and this is a stock memcal.

1981TTA

I've recently installed a TBI injection system on my 1981 Turbo Trans Am engine. So, I've probably run through some of the issues you're dealing with now....

This is incorrect. The 1981 Turbo Trans Am's timing is completely computer controlled (301 CI Pontiac engine) from the factory. I believe the distributors between all Pontiac V8s interchange as well...? You might have been able to get away with just swapping in the stock distributor in your application. I guess as long as you have a dependable solution, this really doesn't matter.

1. Knock frequencies have a strong relationship to cylinder bore size. If possible, you should get a knock sensor from a stock-EFI system with a similar bore size to what you have. From a quick search, it appears the bore sizes for 400 and 455 Pontiacs are 4.12" and 4.15", respectively. The closest Chevy engine would be the 400 small block. Unfortunately, I don't think these engines were ever outfitted with a computer controlled ignition system from the factory. So, you'll probably have to do some experimentation there. Remember, you'll also want to try a few different locations on the block to see what works best for detecting knock. On the 301's, they put the knock sensor right next to the distributor on the back of the block. Don't know if it would work for the 400/455. But, it's a point of information, anyway...

2. I don't know the details on the Dakota setup. So, it may be the best solution. The 1981 TA's came with an optical sensor mounted to the back of the speedo if you're looking for a more "stock" look. While I have that in my vehicle, I'm not sure whether or not it will work with my ECM (1227749). I'm sure you can find cheap '81 clusters on e-bay all day long to try this if you're inclined.

3. As you mentioned, there was never a "stock" prom for the Pontiac engines you're using. Given you're going to become very proficient in chip burning yourself, I wouldn't spend a dime on someone else's PROMs. I bought a stock 8 cylinder memcal and the associated burning equipment when I started my conversion. Trust me (and bnoon), you'll be more than knowledgeable enough to disable VATS once you get your engine up and running!! I'd also second the suggestion to check out Moates' site.

4. I don't think you're going to have much luck with the LS1 harness. The connectors to the ECM are very different. There would also be a lot of "extra" connectors (i.e. Coil-Near-Plug) and "missing" connectors (i.e. distributor). I think you'd be better off getting a harness that was set up for a 7727 ECM. At a minimum, you'd have the right ECM plugs to make life easier. To make your life a little easier (maybe), you could switch to the 7730 ECM instead. Both the 7727 and 7730 ECMs are identical "internally". (So, the same MEMCAL will work in both.) The difference being the 7727 is mounted underhood vs. the 7730 being mounted under the dash. There were a lot more 7730 equipped vehicles made in the day so finding parts will be easier. Not to mention, one of the few (only??) V8 applications of the 7727 was in late 80/early 90 Corvettes. I'm sure it's more difficult (and expensive) to acquire one of these harnesses compared to the equivalent 7730 F-body harness....?

One question to ask you since I'm working on this myself.... How are you modifying the fuel delivery system to support the EFI system? The first part of the problem entails routing a fuel return line back to the tank off the regulator at the engine. The second (and more involved) has to do with handing "fuel slosh" issues as the fuel level goes down in the tank. I'm planning on using Aeroquip line/fittings to run the supply/return lines. Also, I'm going to weld one of the Competition Engineering sumps to the stock gas tank to help alleviate any fuel starvation problems. (I know some people just never let the tank get below 1/2 full to get past this....)

If you're interested, here's a link to some details on my project.
http://www.transamcountry.com/forum/...ic.php?t=13356

Good luck with your project!!!

Ollie8974

Thanks for Your reply 1981TTA,

I was not aware that the turbo TA had a computer controled distributor, and of course try to find one in a wrecking yard let alone any Pontiac HEI. Do you have any photos of hte inside of your distributorwith out the rotor on ? I would like to see it

I have photos and documention showing what I did to modify the HEI that I will post on Monday. This modification uses about $125.00 in over the counter parts and anyone can do it.

The memcal I was talting about is stock for $75.00 sence I dont have one in the ECM I thought it would be a place to start. To at leaast get the car running.

The gas tank modification I plan is to use a kit that goes into the stock tank ckect out Chevythunder Lenord shows what He did to his 78 Camaro. Hopefully the stock fuel lines will work the fuel evaporative can also has a line running back to the fuel tank that I can use

92_ZED

Double check the evap line. Most of the time they have a restriction in them. Which means they can't be used as a return line (try to blow through the line, that will be the tell-tale).

Sounds like a fun project!

Al.

1981TTA

I've attached a picture of an '81 HEI dissy. Although they are around, I'm sure these aren't the most common item in any given junkyard. The main advantage to this is that you can generally get them dirt cheap when you do find them since there isn't a lot of demand for them!

Thanks for the pointer to the fuel pump modification. Fortunately, I haven't cut any holes in my tank for the sump, yet. I've been holding off in the hopes of thinking of something better. Your approach seems to be it. I know the sump will hang below the rear bumper cover so that the fuel lines can be seen from someone driving behind on the road. I really don't like that very much. With the fuel pump at that site, it appears all the lines are contained on the top of the tank out of sight. And, I don't have to think of a place to mount the external fuel pump. (Woohoo!!)

You'll want to be sure the return lines you want to use are big enough (and don't behave like 92_ZED describes) before you use them. The engine won't be happy if the unneeded fuel can't get back to the tank quickly.....

Ollie8974

1981TTA

This is a photo of my modifyed HEI

Ollie8974

Another Photo

Ollie8974

Try this again

1981TTA

That looks very nice! Was the general approach to remove all the "stuff" from a CC HEI Chevy dissy and swap it into the Pontiac version....?

bnoon

You do need both a memcal and eraseable proms. You will also need either a Moates.net memcal adapter, or modify the stock memcal to accept the new eeprom via a soldered in zif socket.

When you do your first burn, all you need are the blank eproms and a few bins to play with. Removing the VATS and VSS from the bin files are easy...

For 75 clams... Unless you're talking about a modified memcal that has a removable eprom in a zif socket already soldered to it, I would pass. Especially since it could be a source of sooooo many problems if it wasn't soldered carefully/correctly.