i recently pulled the engine out of m y 1992 ford f 150 truck it is a 5 litre installed new crank rod 40 over pistions the local auto store spec a cam for me i asked him to get me something that would be good for towing are race car trailer around the country he spec a series 35 cam from comp cams which changes my orginal firing order truck does run like **** my questio n or any opinions anyone has would be greatly appreciated. is the c omputer still firing the injectors to the old firing order and what do i have to do to correct the problem . w hen i called comp cams they told me this cam would work iam starting to wonder anyways before i tear back into this engine i want to make sure i have elminated alll other issues it could have

thx

 

Yikes! Hopefully the new firing order involves only swapping pairs of cylinders that are at least at top-dead-center at the same time?

For example, if the old firing order was 1-8-4-3-6-5-7-2 then the new one swaps 1 with 6, 8 with 5, etc....

Right?

 

Next time you do a cam for anything, NEVER ask the moron at the auto parts store. This ranks right at the absolute bottom of what you need. It'll sound mean but it's not going to do what you think. Operating range of this cam is 2600-6000 RPMs. I doubt you'll be pulling down the road at that rpm range. Did he tell you to do the head work like screw in studs? If you are running an auto behind it, did he tell you about the 2500 stall converter? I hope you didn't use stock valve springs or retainers. If you did, tear it apart or it won't live long. And you'll need to be pulling something around 3.73-3.90 gears depending on tire size. The bigger the tire, the lower the gear ratio. It is what it is. Here's the correct firing order for this cam. Note, this is the same firing order as the HO series of engines.1-3-7-2-6-5-4-8
Hope this works out for you but next time start with a phone call to the people that make the parts, not some minimum wage twit behind the sales counter.

 

...or just put the stock cam back in. It might surprise you how well a bone-stock engine can run if it's ONLY properly maintained.

My engine sat in a JY for a few years after being wrecked hard enough to shatter all the brackets on the front, rip it off the engine mounts, & crush the Y-pipe against the crossmember. I replaced everything with undamaged JY parts, installed it, and DROVE IT. That was ~15 years ago. In that time, I've replace the coil, the plugs, the oil pan gasket, and 1 exhaust manifold. It'll do 115mph on cruise (GPS confirmed). And this is a little 4.9L in a fullsize Bronco with BIG bumpers, a 4-sp stick, 33" tires, and stock 3.08 gears that get severely abused on- & off-road.

 

well turns out series 35 comp cam does work distributer tells the pcm when to fire the injectors i had a broke rocker arm which has also bent a vALVE and the fella behind the counter at the auto store has actually rebuilt many motors
have nice day

 

If he actually knew what he was doing he would have put you into a cam which matched your application. You're driving a 5000# truck with 29" tires not a 3000# Mustang with 26" tires.