Question about switching to a Mustang GT cam

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Question about switching to a Mustang GT cam

June 10, 2023, 09:46:24 PM

If I switch to a Mustang GT cam (from a 1992 in this case), does the firing order change? Do I also have to switch the crankshaft in this case?

EDIT: I just noticed that this section is for non-technical posts. Mods, would you be able to move this to the appropriate section?

Re: Question about switching to a Mustang GT cam

Reply #1 – June 11, 2023, 01:19:31 AM

Yes, the cam dictates firing order...and the SO 5.0 found in Tbirds/Cougars shares the truck 5.0 firing order.

The HO and 351w are the same.

Once the HO cam is in, re-route the plug wires accordingly. Depending on what year your engine is, you may need to swap the distributor. Some of the older cams require an iron dist driven gear, newer ones require steel.

If your engine is an '87, '88...you'll be fine with your stock dist an the HO cam. Otherwise, switch the plug wires around and go like hell.

Re: Question about switching to a Mustang GT cam

Reply #2 – June 11, 2023, 07:18:19 AM

I have an '87, so I'm guessing my distributor is fine? Question is, since the firing order changes, does the crankshaft also need to change?

Re: Question about switching to a Mustang GT cam

Reply #3 – June 11, 2023, 08:56:53 AM

Quote from: Quietleaf – on June 11, 2023, 07:18:19 AM

I have an '87, so I'm guessing my distributor is fine? Question is, since the firing order changes, does the crankshaft also need to change?

Nope

Re: Question about switching to a Mustang GT cam

Reply #4 – June 11, 2023, 01:11:24 PM

Thanks. The reason for these questions is because I've had the changes in my sig yet my engine sometimes runs very rich. I wonder if it's either from bad O2 sensors or because I'm still using my stock computer. I just double-checked my firing order for kicks and it's got the HO firing order, and with a Mustang GT cam it should be getting plenty of air. Has me scratching my head.

Re: Question about switching to a Mustang GT cam

Reply #5 – June 11, 2023, 03:05:36 PM

Are you running the stock Tbird EEC with an HO cam?

At best you'll need a Speed Density EEC from a Mustang....make sure to NOT get one for Mass Air. Or you could switch to mass air in which case an A9L would be what you'd need. IIRC, the SD (speed density) EEC is a DA-1.

The crank is the same between an HO and an SO engine, block too.

But yeah, if you've got an HO cam, you'll definitely need the corresponding EEC to run the show...

Did you start off with the SO 5.0 and upgrade it to HO specs?

I'd almost say you're going to want to go to Mass Air since you have the P heads and an Exploder intake on there...it'll run a good deal better with it.

Re: Question about switching to a Mustang GT cam

Reply #6 – June 11, 2023, 05:58:17 PM

That's exactly what I'm running, the T-Bird SO EEC, as I started with an SO 5.0 and upgraded it to HO specs. I had my mechanic friend try a mass-air conversion but he couldn't make it work; he said it ran better with the stock computer. I don't know if the pinout differences tripped him up or if it was something else. I wonder if I need to go to a speed shop. I think I need an expert, and I'm not it.

Question: will an A9L work for an auto trans? The one I'm seeing on ebay says it's for a manual trans.

EDIT: I found the answer. Looks like I need an A9P since I have an AOD.

Re: Question about switching to a Mustang GT cam

Reply #7 – June 11, 2023, 06:59:57 PM

Yeah, the A9P would be the one for AOD

Re: Question about switching to a Mustang GT cam

Reply #8 – June 13, 2023, 10:15:11 AM

I ordered a 1989 Mustang A9P and EVTM book so I can see what has to be done for a MAF swap. Hopefully comparing the Mustang EVTM with my T-Bird one will show all of the differences. I already have the Mustang split tube, but no mass air meter or barometric pressure sensor yet, but I'll get all my ducks in a row before attempting anything.

Re: Question about switching to a Mustang GT cam

Reply #9 – June 13, 2023, 05:50:32 PM

https://www.coolcats.net/modifying/

Scroll down to Mass air conversion for the HO engine (which you've converted to) for an in-depth guide to what you need to do
:)

Re: Question about switching to a Mustang GT cam

Reply #10 – June 15, 2023, 01:20:15 PM

Yup, I've been over that section. I got my 1989 Mustang EVTM today and it confirms that computer pins 3 and 6 go to the speed sensor and pin 19 goes to the fuel pump relay. Pin 6 is really just a ground though and can be grounded right at the computer. I can connect pin 3 to a wire coming off the speed control module. That only leaves the fuel pump relay; I have no idea where that is. The T-Bird EVTM says its above the right rear wheel well -- I guess I take out the back seat to get to it? I've never seen that relay.

Re: Question about switching to a Mustang GT cam

Reply #11 – June 15, 2023, 01:56:24 PM

It's in the trunk, attached to the rear seat bracing, passenger side. Might have to remove the trunk liner to get to it, but it's there, should be green in color.

Re: Question about switching to a Mustang GT cam

Reply #12 – June 15, 2023, 09:31:22 PM

Thanks. I went through both EVTM's and built an Excel spreadsheet with the differences in EEC pin allocations. It looks like I'll also have to connect pin 30 to the neutral safety switch. It looks like there's a spot near the fuse panel where I can tap it. I'd attach the spreadsheet here if I knew how.

Re: Question about switching to a Mustang GT cam

Reply #13 – June 18, 2023, 11:31:46 AM

I've made a harness that will simplify the wiring for the MAF conversion, but I have a simple question: how on earth do you get the computer out of there? Is there a way to do it without pulling the dash?

EDIT: I did some Googling and I found a video that shows pulling the blower motor box to get to it.

For what it's worth, here is a link to the spreadsheet I built based on the 1987 and 1989 EVTM's:

https://www.mediafire.com/file/cjuiieuvrxnp4n9/EEC_Differences.xls/file

Re: Question about switching to a Mustang GT cam

Reply #14 – June 19, 2023, 08:07:19 AM

I thought the EEC on Foxes was down behind the passenger side kick panel?