Changing cam..firing order question..techy.

[oldiron]

So I've decided that in the interest of being thorough, I'm going to change my standard 302 firing order cam to the 302HO/351 firing order cam. (EFI swap). After much debating and reading I've decided that simply swapping the pins at the ecu will cause problems that I don't want, and leaving it as it is will cause a slightly rough idle quality, which I also don't want.
Question is.... why did the ford engineers change the firing order for the HO motors in the first place? Did it give a power or torque increase? More effecient? My little 302 runs great (daily driver) and I want to keep it that way. Any ideas?
Greg

 

[needabronco]

Don't worry about the firing order! Your engine WILL idle better even with a mismatched cam.

Do the efi swap and see what you think. If you don't like the way it runs, then do the cam swap. You'll only be out a set of intake gaskets.

 

[broncnaz]

My understanding of why they changed the fring order is to revise the loading on the main bearings and increased crankshaft reliability.. with the old firing order 1,5 fire consecutivily and load that from main bearing a lot. along with added stress on the crank.
Keep in mind this was probably only done due to findings in high RPM racing more than likely no real effect on normal use engines.

 

[broncobran68]

What problems does swapping injector pins cause? I've been running that way for a while. Only problem I see is the O2 sensor is reading the wrong cylinders, but from what I've read that really isn't a problem. Not trying to change your mind, just curious.

 

[hdmc]

i did the cam swap when i did mine fedral mogal cam with .498 lift and .288 duration it runs a whole lot better

 

[broncnaz]

The O2 sensor doesnt read cylinders it only reads whats in the exhuast it doesnt care where it comes from or even know.
A cam swap generally seems like it runs better because you probably saw a power increase as well as rougher idle that you wanted. If you did a cam swap that only had firing order differances you'd see no change.

 

[oldiron]

What problems does swapping injector pins cause? I've been running that way for a while. Only problem I see is the O2 sensor is reading the wrong cylinders, but from what I've read that really isn't a problem. Not trying to change your mind, just curious.

Ryan posted on the rjm website that repinning the injectors can cause one bank to run 15% lean and the other 15% rich.
I tried to find the link but can't locate it at the moment.
Greg

 

[broncobran68]

The O2 sensor doesnt read cylinders it only reads whats in the exhuast it doesnt care where it comes from or even know.
A cam swap generally seems like it runs better because you probably saw a power increase as well as rougher idle that you wanted. If you did a cam swap that only had firing order differances you'd see no change.

There are two O2 sensors on a 5.0 H.O. One for the left one for the right. Change the injector wiring and it reads the wrong cylinders and then adjusts the wrong cylinders... Or at least you'd think it would. Maybe that's not actually the case.

 

[Pedestrian]

Cams are cheap, just replace it while you have the intake off.

 

[Viperwolf1]

What problems does swapping injector pins cause? I've been running that way for a while. Only problem I see is the O2 sensor is reading the wrong cylinders, but from what I've read that really isn't a problem. Not trying to change your mind, just curious.

By swapping the injector wiring to match the 15426378 order the computer thinks that half (4 of 8) the injectors it's firing are on the opposite side of the motor. Now if one of the O2 sensors see a rich or lean condition the computer will try to adjust the fuel trim on that side (what it thinks is that side). In reality it adjusts 2 injectors on one side and 2 on the opposite side which causes the other O2 sensor to see a problem. Then it all snowballs downhill quickly.

 

[fungus]

i did the cam swap when i did mine fedral mogal cam with .498 lift and .288 duration it runs a whole lot better

hdmc, care to share any more of your cam specs or number? I'm looking to swap mine out as well when I do the EFI conversion. It'll be going on/ in my '69 302 and I'll have the topend torn down anyhow as I've got a fresh set of GT-40 heads going on with my Exploder EFI stuff. Figured I'd swap to a better cam w/ the right firing order while I was already in the motor that far anyhow. I'm guessin I'm looking for a 351W flat tappet cam and would like to get as much low end torque out of it as possible. Powerband from idle up to say 4500 would be ideal.

If anyone else has any flat tappet cams they'd recommend for this I'm all ears!

Thanks,
Fungus

 

[broncnaz]

There are two O2 sensors on a 5.0 H.O. One for the left one for the right. Change the injector wiring and it reads the wrong cylinders and then adjusts the wrong cylinders... Or at least you'd think it would. Maybe that's not actually the case.

The O2 sensor can only read whats coming out the exhuast in that bank. A injector may fire on that side of the engine but if the valve doesnt open it doesnt send fuel through that cylinder so it doesnt burn it gets pulled to another cylinder even if the O2 reads a rich condition due to injectors being pinned wrong it will just lean the fuel by the correct amount. But if your swapping the injector wiring then the O2 sensor should read correctly because you have the injector firing at the correct timing.
Now yes if a problem develops in the system then the 02 will not be adjusting corectly but the other O2 will also adjust due to that problem so in the end everything evens out. Unless the problem is just to large to adjust for.

Granted the wrong injector wiring is probably not the best from a performance stand point. but were not really talking about the wrong wiring were just talking about making sure the correct injector fires for the cylinder that is going to fire. As opposed to leaving the injector firing in a cylinder that doesnt need it and trying to pull that fuel through the manifold to the cylinder that is going to fire next. You end up with lean cylinders and the system will try and richen everything up.


Fungus I wouldnt use a cam with 288 duration unless you plan on lots of high speed stuff. or have very low gearing and can use that much cam. the larger the duration the more lowend suffers. Id stay around the 270 duration and lower for power from idle to 4500. You might try calling a few cam companies see what they recommend. with all your other parts EFI, 69 bock gt40 heads ect.
One persons concept of running good is not everyone else's concept. You have to look at the complete setup and useage. but generally speaking cams with 280 or more duration are better suited in lightweight cars with low gearing for high RPM use. not heavy cars used at lower RPM's.

 

[oldiron]

This is the link I was referring to.
http://fordfuelinjection.com/index.php?p=92

 

[hdmc]

hdmc, care to share any more of your cam specs or number? I'm looking to swap mine out as well when I do the EFI conversion. It'll be going on/ in my '69 302 and I'll have the topend torn down anyhow as I've got a fresh set of GT-40 heads going on with my Exploder EFI stuff. Figured I'd swap to a better cam w/ the right firing order while I was already in the motor that far anyhow. I'm guessin I'm looking for a 351W flat tappet cam and would like to get as much low end torque out of it as possible. Powerband from idle up to say 4500 would be ideal.

If anyone else has any flat tappet cams they'd recommend for this I'm all ears!

Thanks,
Fungus

i'l get you a part number and specs later this afternoon

 

[00gyrhed]

OMG still!!!! What numbscull is it on th einternet that still thinks this firing difference is a problem??????

It will idle better than any carbed engine.

You can fix it by changing pins but its not as easy as swaping the pins side to side. Rt side injectors and left side injectors have to stay on the same side of the enfine. You swap #1 for #4 and # 2 for #3. Same on the other side #5 for #8 and #6 for # 7. They will then be 90ndeg out of sinc with the ignition but in the right order. You v=can run it there or move the sparek plug wires 90 deg arround the dist. Now everything is in order and the computer things #1 cylinder(#4Injector) is # 1.

I have run it each way proper cam, wrong cam, wired wrong, rewired per above and belive me none of it is worth the trouble. Unless you need to change cams just leave the old one in and run it.

Chevy batch fires their injectors so most of them are out of syn all the time. There are a lot of idle issues that get blamed on this cam thing and a lot of people buy cams to fine they still have the problem.

If you arte getting advice from a website and they are telling you to changge cams, GO FIND ANOTHER WEBSITE. They do not know what they are doing.

 

[1970mule]

ok please excuse me if i am waaay off on this but i thought the problem lay in the computer. If you have a regular 1-5-4 firing order, then you use a non H.O firing order ECC. if you have the 1-3-7 firing order then you need the H.O compatable computer. Like the A9L,A9P,A9S or the like of such. this can affect the performance of the car.

also i grounded pin 30 on my computer but i have the manual transmission eec so that is why i did that. for the auto ecc you would not do that. i should say the auto or manual harness. if you ground pin 30 on the auto style harness then you will fry your computer.

 

[Viperwolf1]

ok please excuse me if i am waaay off on this but i thought the problem lay in the computer. If you have a regular 1-5-4 firing order, then you use a non H.O firing order ECC. if you have the 1-3-7 firing order then you need the H.O compatable computer. Like the A9L,A9P,A9S or the like of such. this can affect the performance of the car.

A non-HO EEC will require different (smaller) injectors, possibly some harness changes too. You could pull everthing from the same donor car if it has the same firing order as your motor but you lose the extra power of the HO. I'd rather live with the injector firing order miss-match.

 

[broncnaz]

ok please excuse me if i am waaay off on this but i thought the problem lay in the computer. If you have a regular 1-5-4 firing order, then you use a non H.O firing order ECC. if you have the 1-3-7 firing order then you need the H.O compatable computer. Like the A9L,A9P,A9S or the like of such. this can affect the performance of the car.

also i grounded pin 30 on my computer but i have the manual transmission eec so that is why i did that. for the auto ecc you would not do that. i should say the auto or manual harness. if you ground pin 30 on the auto style harness then you will fry your computer.

Kinda dependent on what you consider a problem. but basically either computer will run either firing order. So is the cam your problem or the ECM? or is there really even a problem? in most cases there's no problem now maybe if your trying to squeeze every last bit of power out of the engine then all the HO stuff would be the way to go.
There are other differances in the Non HO engines that reduce the power besides the injectors. Mostly the throttle bodies tend to be small 55mm I believe, heads dont flow as good, cam is a little tamer, exhuast is more restrictive. I believe the compression is slightly lower as well. All this coupled together help reduce the power compared to the HO engines.

Mostly people want the HO setups because the ECM will adjust for a lot of engine mods before needing extra programing. The Non HO ECM's can only handle small mods before they cant handle it.

 

[1970mule]

A non-HO EEC will require different (smaller) injectors, possibly some harness changes too. You could pull everthing from the same donor car if it has the same firing order as your motor but you lose the extra power of the HO. I'd rather live with the injector firing order miss-match.

you mean smaller than the 19lb injectors?

 

[fungus]

you mean smaller than the 19lb injectors?

All the non-HO motors I've seen came w/ grey 14#ers.