1989 318 roller cam questions

[48chebbie]

hey folks,i am looking for a little info here and would appreciate some help. i have a 1989 318 roller cam motor out of a pickup and i am going to do a very mild rebuild to drop it into an 1989  dakota. what i am curious about is that the motor has a roller cam in it, and want to know does the engine have to keep a roller cam, or can i put a flat-tappet hydraulic cam and lifters in it? does the engine have a special reason for having the roller cam for the computer or some other goofy reason? i am planning on keeping the existing throttle body injection that is on the current 3.9 V-6 thats in the truck now,and would also like to know if anyone has added a larger cam to one of these engines and if the computer can handle it or totally freak out? now when i say larger,i mean like a comp-cams X268H extreme energy,nothing major. let me know please if anyone can help me. thanks in advance.

[Plumcrazy]

I'm pretty sure you can put flat lifters in a roller cam block.  The factory used rollers for fuel economy reasons.  If you plan on retaining the factory throttle body system then you had better also use the original camshaft.  That system uses the speed-density method of fuel control. Changing the camshaft will alter the engines vacuum(density) readings which will throw off the fuel mixture.

[r73mopar]

i have a 91 dodge ram w/318 put much larger cam in mine.i just changed the cam and used the existing roller lifters,if you put a flat tappet cam in you have to change the push rods also as they are different lengths. thhese motors also oil the heads different,so in my opinion i would change just the cam.