ok here is what i want. i have a 460 short block from an 85. i want to put it in my 90. i want to retain the speed density system due to financial reasons. what can i do along the lines of pistons? are the fuelie pistons different than the carb ones? i plan to run the efi friendly cam(i believe crane?). i am just looking to bump the compression up a bit. this is a plow truck that is going to pull trailers regularly. and the fuel pressure regulator? who sells one? HELP! i am tired of searching this board to find the wrong answers.

 

From what I have read, you can not use the fuelie heads on the carbed block. Hopefully Monsterbaby will chime in. He seems to know the 385 series engines really well.

 

As long as you have the heads and intake you can turn a carb'd engine into an EFI motor. Ok so you also should have the external bolt on parts since the distributor is different. The problem comes when people try to smack a carb intake on EFI heads or vice versa.

 

It will work if you use the fulie heads on the carb block. The only diffrences between 85 and 90 are the pistions and cam. You might run into valve to piston interfearence problems if you use a huge cam, but if its a RV style that dosent have alot of lift you will be fine.
Leadmic

 

the 85 and the 90 blocks are the same, teh cams are different the heads and intake are the difference. What you can't mix and match are the heads and intakes.

 

H mm, and what about the compression and speed density? I don't think that you will be fortunate enough to pick a match of cam/compression that will not upset the stock PCM.

I rebuilt a 351W in my 86 Crown Vic using cast flat top pistons, which were supposed to be near stock compression. With a mild Crane recommended cam, the computer controlled carburetor wouldn't run right.

The cam and compression are major items which speed density systems are tuned with. Changing either very much would require altered tables in the speed density PCM. That is why most people prefer mass air systems, they can handle more modifications before requiring special tuning.

I wish you well with the truck, I just believe that the PCM tune will be more trouble than the hardware. Regards,
Don