Can a caveman do DIY EFI? Nothing ventured, nothing gained...

[STINEY]

In the spirit of learning something new, I'm diving in deaf, dumb, and blind.

Santa brought a Megasquirt MS-230K, I've acquired a throttle body from a 7.2 Chevy truck, and will be slowly gathering the rest of the parts needed to inject a '74 500 Cadillac that we swapped into a '86 Mustang, that also will be getting an older Doug Nash Overdrive unit commonly used in RVs of the time.

I also plan on getting a common 350 EFI distributor, and slicing and dicing it to work with the Cadillac distributor. They are extremely similar, but the cadillac one has a different dimension to the block flange where the clamp holds.

My wife has arranged for a pair of older functional laptops to come into my possession for this project as well. I haven't seen them yet, but she's onboard! Found a 9-pin serial connector in the ancient computer parts here at work.

I've been printing out the Mega manual (easier to read in my "office") Holy cow... I thought it was called the Megamanual as a play on words due to "MegaSquirt", I didn't realize it was a descriptive term due to the size of the thing.

This is about 1/2 printed out.



Here is the TBI unit. I need to source some pigtails for the injectors, TPS, and IAC, and a couple of stubs for the fuel feed and return would be a good idea as well. Note this is the larger 2" 900 cfm unit, the 350 version has smaller venturies and flows in the 390 cfm range. The calculations show the 500 Cadillac will want approximately 1150 cfms at 5500 rpm, so this is a close compromise for this stage. MPI will come much, much later, if things go well at this stage.



What is missing here? The notch where an air cleaner assembly would sit, what went there originally?





The mustang. Nothing special, just a '86 LXGT. Bought as a roller from some guy who wanted the drivetrain.



Dual pass aluminum radiator, 500 installed, HHR electric fan setup. (Thanks BBR!)






I'll be adding to this thread as things progress. Wanted to get it started as personal motivation. Goals for this is at this point is a decent driver with a lot of freak factor. Joining Drag Week '12 would be an extra bonus, especially as it seems like a few guys semi-local are planning to attend.

[dieselgeek]

just a guess, but is that notch maybe for an Intake Air Temp sensor?

Everything else about this thread screams WIN! to me.

[TheSilverBuick]

I can't see the pictures through the firewall here at work so I'll look again when I get home but I to printed out the assembly instructions (twice!) but used 11x17 paper in portrait layout. Worked really good. I have a clean copy filed away incase the internet dies or something.

On the distributor. What are your plans for ignition? If you are running an aftermarket ignition box I'd recommend just using a stock Caddy HEI and just run a single wire from the pickup coil. I'm told you could use a set of points contacts and it'll work just as well, but I haven't tried it, yet (first try with points will be on the OHC Pontiac six). I did run a 7-pin briefly using a 4-pin HEI gutted with a 7-pin module and pickup coil installed. I got the 7-pin stuff from a mid-80's chevy.

[STINEY]

I can't see the pictures through the firewall here at work so I'll look again when I get home but I to printed out the assembly instructions (twice!) but used 11x17 paper in portrait layout. Worked really good. I have a clean copy filed away incase the internet dies or something.

On the distributor. What are your plans for ignition? If you are running an aftermarket ignition box I'd recommend just using a stock Caddy HEI and just run a single wire from the pickup coil. I'm told you could use a set of points contacts and it'll work just as well, but I haven't tried it, yet (first try with points will be on the OHC Pontiac six). I did run a 7-pin briefly using a 4-pin HEI gutted with a 7-pin module and pickup coil installed. I got the 7-pin stuff from a mid-80's chevy.

I'm kind of up in the air on ignition at this point. I have a few extra cadillac HEIs, I was thinking of converting an HEI8 distributor to work on the 500. Is there any advantage to that approach over using the standard HEI pickup to fire a MSD box? Wouldn't I need to lock the mechanical timing advance in this scenario? Then the HEI pickup is just a cam position sensor that reports to the computer, and then the computer tells the MSD when to fire?


edit: oh, and I've triggered a MSD with points in a pinch before, it works but you still have the dwell adjustment to contend with.

[dieselgeek]

I'm kind of up in the air on ignition at this point. I have a few extra cadillac HEIs, I was thinking of converting an HEI8 distributor to work on the 500. Is there any advantage to that approach over using the standard HEI pickup to fire a MSD box? Wouldn't I need to lock the mechanical timing advance in this scenario? Then the HEI pickup is just a cam position sensor that reports to the computer, and then the computer tells the MSD when to fire?

Correct.

ALthough it may be wise to lock the timing, or let it run it's own advance and feed an MSD box, so that the MS is NOT controlling timing when you first run the engine. I like this step because then you only have to worry about fuel, which is easy. Then once you have the engine running decently, you can make the 2-wire change to put the Megasquirt in control of timing. I highly recommend this extra step for the guy who is new to electronic engine management.

[TheSilverBuick]

Then the HEI pickup is just a cam position sensor that reports to the computer, and then the computer tells the MSD when to fire?

^^This is exactly how I ran my Skylark up until October when I went to a crank trigger. And even then I just moved the wire from the pick up coil in the HEI to the pickup sensor at the crank.

When I ran the 4-pin and 7-pin HEI's I ran the tach signal for the MS straight from the Tach port on the distributor cap (then the spark output wire from the MS to one of the pins on the HEI for the 7-pin).

**Oh yeah, when I used the 4-pin HEI with 7-pin guts I did remove the vacuum advance and drill and pin the mechanical advance. Did this a couple years ago and it's still in the car today.

[STINEY]

Correct.

ALthough it may be wise to lock the timing, or let it run it's own advance and feed an MSD box, so that the MS is NOT controlling timing when you first run the engine. I like this step because then you only have to worry about fuel, which is easy. Then once you have the engine running decently, you can make the 2-wire change to put the Megasquirt in control of timing. I highly recommend this extra step for the guy who is new to electronic engine management.

Gotcha. That is my plan - baby steps, baby steps. These big cadillacs like to break the starters off if they kick back, so that's an extra reason to be super cautious with the initial timing. I'll probably just let a completely stock HEI do the job until I'm ready to let the computer do it. I'm not chasing every last HP, although I'm excited to see just how much is on the table and can be gained by taking over ignition. Mechanical advance is extremely crude stuff.

[OldMachinist]

Here comes the first hijack, hope you don't mind. What are the dimensions of the HHR fan shroud? And the picture looks like dual fans is that correct? Thanks.

[STINEY]

Thanks DieselGeek. Its collected dust long enough, time to do something.

That is my guess too, IAT sensor. Wonder if the 350 version was the same part? Knowing GM, probably.

Strictly a guess on my part though..... I've spent the last 26 years ignoring EFI stuff for the most part. Not snubbing it but strictly hands off. Stuck to what I knew if you get my meaning. 3 years ago I brought a '89 EEC-V van back from the dead, lots of codes at first but got rid of them all. That and reading the EFI book is just about it, so I've plenty of questions.

[A/Fuel]

The wires to the injectors go in that notch, there is a rubber groment that fits there as well.
There is usually a ring with a pcv hose that attaches to the valve cover that that fits over that before the air cleaner too.