How long would it have taken you to figure out this problem?

[ForceFed70]

This happened to me shortly after purchaseing my mustang. The previous owner had recently done a "performance rebuild" on the 351W, and the car seemed healthy and powerful.

I decided to give the car a tune up even though it was running pretty good. Gave her a complete fluid change and Replaced cap, rotor, points, plugs and wires.

After the tune up, I fired up the car to do the timing but was greated with a horrible miss and backfireing.

Here's the troubleshooting steps I took:
1) Double checked firing order, and ensured it was correct.
2) Replaced plug wires, double and triple checked connections.
3) Put old cap and rotor back on.
4) Tried a different ignition coil. Eventually even swapped in a different distributor.
5) Tried new plugs.
6) Swapped old points back in.
7) At this point I was confused as hell. Did a compression test, everything was fine.
8) Pulled off valve covers to check valve train, turned engine over by hand, Everything appeared fine.


I spent days trying to figure this one out. I was confused as hell as to why the car was missing and backfireing. It would barely idle. Even had a few friends who were good with engines come over to see if they could figure it out. They were as confused as I was.

Anyone want to hazard a guess as to what my problem was?

 

[Max Power]

302 cam with different firing order.

 

[foghorn67]

rotor faced the wrong way?

 

[66 BLAKE 96]

302 cam with different firing order.

That's my guess too, but I would have tried everything you listed before coming to that conclusion. Are we right?

 

[TobyGaff]

I have seen that with a bad vacuum advance unit before, but swapping the distributor should have taken care of that.

 

[DarkBuddha]

I'm going with the 302 cam thing, or your spec book may have been wrong... my other guess, but I don't think you're this, uh, dim... it's a 351C instead of a 351W.

 

[ForceFed70]

302 cam with different firing order.

Lol.. Damn you guys are good!

I won't make that mistake again. Back then I didn't even know you could put a 302 cam in a 351W OR that the engines had a different firing order.

 

[Max Power]

Yup. 302 cams are a lot more common. Woulda been nice if the PO had bothered to tell you.

Or if you had replaced the wires one at a time rather than tearing the whole set off!

 

[1320stang]

One of my buddy's dad put a late model roller 302 (although I didn't know it at the time) in his '68 fastback. He went through the engine, but it was basically stock, put a early 80's aluminum 4bbl intake on it even. He was showing me the car, and said he had a problem. He got it to run, no backfires, but it still sounded like crap, had no power, he could even drive it and get it to idle, but something just wasn't right. We messed with the carb and the timing, but all we did was make it worse, even checked for vacuum leaks. I started asking him about the motor, he said it was a 302 out of an 80's model Mustang, he had changed the cam out, it still didn't register. He said it had EFI on it originally, but he bought the long block and put this Ford aluminum intake on it. I asked him where he got the cam, he said the parts store, I said did you get a cam for a '68 Mustang or a cam for the year engine it was? He said it was a hydraulic roller cam (light comes on!!!) I start cracking up "lets try rearrangeing the plug wires and try it again". Fires right up and purrs like a kitten. Then I give them the lowdown on the 351w firing order Ford changed to. He had the thing so tuned for the wrong firing order, it was in perfect tune for the correct one, I couldn't believe he had gotten it to run so well. He's an old time car guy and has restored '57 Chevys before and he knows his P's & Q's, but he wasn't aware of the firing order change, so you can teach an old dog new tricks. Oh, BTW, it took about 30 minutes to figure it out. It really ran well on 4 cylinders, so I didn't figure it was the firing order, although we did check it for the early 302 order.

 

[mfp4073]

LOL, I had a old school style cobra intake on for a while. Of course the firing order was for a 289. But mine was not! every once in a while someone would say....heeeyyyy you got your firing order wrong! I wrote it in sharpie marker under the top of the aircleaner so I could remember it. Just unscrew and turn it upside down for my cheat.

 

[12sec67]

lookin' at your sig.... what do you run for times with that 150 shot, what type of pistons are you running, and also did the guy who built that 351w use ARP bolts?

 

[bnickel]

302 cam in a 351. did i guess right? i just skipped down to the quick reply and posted without looking at the other posts. mainly just to see if i was right

 

[66 BLAKE 96]

302 cam in a 351. did i guess right? i just skipped down to the quick reply and posted without looking at the other posts. mainly just to see if i was right

Nope, sorry man. You were way off. ;-)

 

[TT670]

Once youve heard a ford run with the wrong firing order its easy to diagnose, I can see where someone whos not a ford guy would be pulling out their hair. You gave it away with the performance rebuild statement. I think the 351/5.0 HO cams and firing order run better..

 

[ForceFed70]

lookin' at your sig.... what do you run for times with that 150 shot, what type of pistons are you running, and also did the guy who built that 351w use ARP bolts?

Unfortunately there is not a track anywhere close to where I live, so I have no times.

There are cast pistons in there! My original plan was to run the cast pistons until they melt then swap over to some forged slugs. That was 4 years and many a nitrous refills ago. I still have excellent compression and use no oil. I credit it all to a conservative tune.

I've had the engine apart and I believe them to just be factory replacement type bolts. The plan is to replace them also..if this cast stuff ever dies on me.

 

[bnickel]

Nope, sorry man. You were way off. ;-)

damn, i hate it when that happens

 

[Swede958]

I had a similar problem when I did a tune up on my '70. Got a new cap, rotor, wires, plugs, coil, etc. Put everything on (even did the wires one at a time, just brainfarted somehow). Started it up and it ran, but it had a misfire about every 3 seconds or so. Ok... plugs are wired wrong, went back through the manual and got the order, tried again and it was worse. Tried the late model order, no go either. Needless to say, after many trials and tribulations my dad and I cracked the valve cover open and found TDC (no pointer) and viola...

One of the previous POs had installed the distributer with the rotor pointing two positions left of where number 1 normally is... Rewired it, and it fired up beautifully.
Some POs just need to be shot...

THe Swede