Firing order Stock 302 and Mass air efi

[rellimgneb]

I've tried and tried to find info on this, so I'm sorry if it has been covered and I'm rehashing old subjects.

I have a refurbished crate 302 with a 1972 vin. I'm putting the mass air efi from an 89-93 mustang on it. It's my understanding that the firing order was changed. If early, that firing order is 1-5-4-2-6-3-7-8. If late (HO), the firing order is 1-3-7-2-6-5-4-8.

Am I going to have trouble? Is my computer going to adjust? Is it not a concern?

I took a good 15 years off of my rebuild, but I'm back at it and getting a lot closer to firing it up. I just wanted to verify and see if I have to change my cam or anything.

If there is an article or thread you know of, and can point me towards, I'll happily read that instead of anybody having to type things out.

Thanks in advance.

 

[Broncobowsher]

What cam do you have?
The firing order is based on the cam. No way around that. The EFI will work, still puts the fuel in the right hole. Timing might be off a touch, but when you are on the throttle and the injector is open 70% anyway, its spraying on a closed valve and an open valve. At idle it still puts the right amount of fuel in the right hole, it still vaporizes and burns in the cylinder.

 

[yakelys69]

Do you have the code on the ECU like A9L or D3D ?

 

[rellimgneb]

Do you have the code on the ECU like A9L or D3D ?

I'm not there yet. I still have a little bit before I can fire anything up. I'm just trying to figure everything out now so I don't screw something up.

As far as my cam goes, I don't know what's in there. The crate motor came with the bronco when I bought it. I couldn't ever get the info from the previous owner, and it was like 15, 16 years ago.

 

[yakelys69]

Usually the ECU has a sticker on it with some numbers, that can help you know what you have.

 

[ared77]

I believe I'd start by trying the early firing order since you mentioned '72 on the crate engine.

 

[Jebus]

To figure out the firing order of the unknown cam installed, remove the valve covers and bar that engine to TDC on #1. Bar the engine a bit more clockwise while watching the valve train. Which other cylinder is up next to hit TDC? 5 or 3? Which is next after that? 4 or 7? You have to watch for the intake valve closing...

1-5-4-2-6-3-7-8

1-3-7-2-6-5-4-8

 

[wizard12]

If your crate has the distributor on, you should be able to tell the firing order by following the order of the wires as it goes around, starting with cylinder 1. If it doesn’t have the distributor, take off valve covers and rotate the crank slowly with a socket. Watch for the intake valves to close and see what order they happen. That should tell you the firing order the cam has.

 

[rellimgneb]

To figure out the firing order of the unknown cam installed, remove the valve covers and roll that engine to TDC on #1. Roll the engine a bit more while watching the valve train. Which other cylinder is up next to hit TDC? 5 or 3? Which is next after that? 4 or 7?

I know I just really don't want to do that, but I know I need to.

My main question is, if the order isn't 1-3-7-2-6-5-4-8 to match what the computer expects, do I need to change my cam, or is it going to be fine.

Does everyone who puts in the 89-93 mass air efi change their stock cam?

I want to do it right, it's been long enough, and I've put enough money into this that I'm not nickle and diming it now. It's just...do I really NEED to change the cam if it doesn't match? Am I going to regret it if I don't?

 

[Jebus]

I think that mustang mass air is sequential FI. I would think you could just rewire the fuel injector wiring to match the old firing order, but IIRC it will still run without doing that, although not as intended. Me, I would just change the cam to match the sequential fuel injection, if what I had was wrong.

Ford changed the firing order for a reason...

 

[rellimgneb]

Me, I would just change the cam to match the sequential fuel injection, if what I had was wrong.

Ford changed the firing order for a reason...

I agree. I'll check it this weekend and swap it out if necessary. It'll be a lot easier right now.

I just got my serpentine belt system all done, and my radiator and fan shroud mounted/fabricated, but the grill isn't on, and there's no hoses or water on/in the radiator yet. Now is the time to do it. Well a week ago, before the radiator was mounted, or a few years ago when I put the new water pump on were better times to do it. But now will work.

 

[Jebus]

The most likely scenario you have is the old firing order flat tappet engine.

IIRC an early 351 windsor cam is a quick way to change to the newer firing order.

Many aftermarket choices. Don't forget to change the lifters too...

 

[RVH]

This will sum it up for you ... link

 

[66horse]

Dont worry about. I ran mass air mustang efi on my old 70s block for years. I did not change the injector wiring. You don't even notice it.

If you want to change the cam, thats fine.

Now on to your next hurdle.

 

[Sporto]

Dont worry about. I ran mass air mustang efi on my old 70s block for years. I did not change the injector wiring. You don't even notice it.

If you want to change the cam, thats fine.

Now on to your next hurdle.

This^^^

Engine will run just fine with 302 firing order for all the reasons above. I run a Mustang mass air on mine with no problems at all. I do intend to change to a 351W cam in the future, but that is because of issues not related to the EFI.

Good luck!