It's time to replace my tired engine (it only has about 250000 miles on it). I have a 1990 F250 351w 5 speed ZF. I'm thinking of just buying either a short block and building it myself from there with a cam and aluminum heads to start, and doing the intake and exhaust later, or picking up a junkyard motor and building the whole thing. Can anyone tell me how new an engine I can use that will be pretty much bolt in? What I mean is, I understand the 1996 FI is not compatible so I'd have to stay 1995 and under. Is that correct? EEC4 vs EEC5? I should stay EEC4? This thing needs to pass smog. I'm not going to do any mods to the FI system except a size or two larger injectors if I have to. I would (of course) like more power and I think 300 to maybe 350 hp is a good goal to shoot for. So what's the newest year motor that I can put in there without changing my EFI (except maybe the injectors if need be)? Is the roller really that much better? I heard it has problems (something about the lifter valley). Thankye!

 

If you're not making any changes to the EFI system you won't be able to use larger injectors and therefore won't be getting more than about 300hp. The proven combo is GT40 heads with the Crane 444232 camshaft and longtube headers, this will run much like stock but with much better power and will pass emissions if there is a cat in the exhaust. You can use any year engine for this but the '94+ roller motors are better and it doesn't matter what EFI system(computer and wiring) is on the donor truck because you won't be using any of it. If you do use a roller motor alternate cams include the comp 35-512-8 or the 5.0HO cam with 1.7 rockers.

 

OH! I thought any changes like what you mentioned (headers, GT40s) would require larger injectors. Maybe I need to consider changed to my EFI. I just don't want to foul my emissions test. Do you think I can get away with any EFI changes and still pass the test? Thanks for your help!

 

No.. stock injectors can support 300hp give or take and the computer is capable of adjusting to the reltively mild airflow increases that result from bolting these parts on an otherwise stock motor.

Just about any engine combo can pass emissions tests and there is no reason a fairly well built motor couldn't do it as well.. but the computer will have to be tuned for the larger injectors and MAF meter and the cam will have to be milder(more EFI friendly) than what you would use for a max power build.