92offroadf150

Hey guys so I have an interesting question. I just rebuilt my 5.8l that I just converted to MAF and I am now puzzled. Fired up, timed to 10* and idles. The problem is that I have different cylinder exhaust temps 1) ~500* 2) ~500* 3) ~250* 4) ~250* 5) ~250* 6) ~500* 7) ~250* 8) ~500*.
The cylinders that are ~500* have carbon soot and the ones that are ~250* have excess fuel. I have checked spark on all the plugs and they look good

Currently the modifications to the engine are EGR delete, MAF conversion, Cam, intake and exhaust.

There is no check engine lite on. Has anyone experienced this?

Matthew Burr

what did you have done to the heads? complete rebuilt, new?

92offroadf150

So i have found the fix.... The person that did the machine work to the engine decided to use a 302 cam in lieu of the 351.... I have been told that this is not an issue besides firing order. So i switched the firing order to the 302 and it started right up and purred like a kitten.

I am considering replacing the cam to 351 just to make it "right"... but is this necessary? Has anyone had any issues with this?

Matthew Burr

well it runs... so cant be too far off... besides firing order your going to deal with possible differences with lift and duration, which obviously isnt making the piston heads strike the valves at this point in time, so unless it feels way underpowered id imagine your getting enough fuel into the cylinders. check the plugs if they are new and see if they are burning too rich or too lean and or check the cam spec differences between the two engines

PerryB

Most aftermarket small block Ford cams are ground to the older 15426378 firing order, and require swapping wires at the cap. My guess is the builder installed something other than Ford manufactured part. I think changing out the cam would be a complete waste of time.

Chris_1

iTrader: (1)

What computer did you use ? Just wondering about injector firing order if you switched from speed density bank fire to maf. Maybe it's not an issue, but it doesn't seem right to have a 351 or ho maf setup with a standard 302 firing order. But as Mathew said it runs.

1RobW

New to the site, not to the 302HO 351W. That said, it's been over a decade since I built these and I don't know everything or wanna step in unwelcome. Glad to know it's fixed, but... seems odd to me, that a firing order(FO) change to the wires fixed the problem, unless they'd initially been done wrong on the rebuild. The 302HO and 351W share the same, 1-3-7-2-6-5-4-8 FO

1-5-4-2-6-3-7-8 should be used on the pre 1982 5L and the truck 5L, but not the 351W in any application. If that FO is working now... something just isn't right.

Since you switched to MAF(Mass Air Flow), you should be using a 302HO "with Mass Airflow" camshaft to benefit in the HP and TQ department and hopefully fuel economy too(not notably in your truck). Either will technically work, but you will be limitless on cam choices w/ MAF in comparison.

FO is dictated only by the camshaft, not the ECM, but the ECM can indeed matter in other areas, including(on some vehicles) whether or not the cruise control works and other areas. That said, on that specific pickup, w/ that specific swap... I'd go w/ the A9L ECM if I could find it, even if it has a manual transmission.

Side note: BUMP THAT TIMING! It should run @ 14* w/ no trouble and 12, at a minimum. 10 is an unbelievably safe factory tune and unless you're using nitrous or something, no need.

PerryB

Rob, in his original post he lists the cam as one of the mods.to the engine. I am assuming (yeah, I know what happens there) its an aftermarket cam. Since the 302 and 351W cams have the same physical dimensions (for a given grind) most manufacturers grind them to the older 15426378 pattern and advise the installer that the 351W will require re-ordering. Obviously if this was a distributorless/COP engine the cam would have to match the programming of the ECM. The part about having to rewire a 351W with an aftermarket cam is as old as the engine itself, literally.
FWIW, When the W motor was developed, the engineers decided it ran smoother with the revised order. All they did was took two groups of two cylinders (5-4 and 3-7) and moved them to opposite sides of the firing order. The crank is the same but intake strokes became power strokes and exhaust strokes became compression strokes. This also carried over to the 351M and 400. I think it was a change for the sake of appearances. You have to make it look like you're doing SOMETHING. The official answer was reduced torsional stress on the crank/improved harmonics. I think it was a solution in search of a problem.
As far as the injection system is concerned, I don't think it really matters does it? If my understanding is correct this is a non-sequential system so I don't think the revision would have any effect on mixture distribution quality. Oh well, maybe I'm way off base. I'll quit rambling.

92offroadf150

THanks for the help! I will bump that timing up which will probably help out the idle.

92offroadf150

I have done some additional research and it does not matter. THe thing is running like a rapped ape. Because the engine fires on each bank and not each cylinder, it runs right.... Super not normal but hey it runs. Thanks for your input on this!!!