351 to 302 swap

[djmikel]

hello i have a 1990 gt

i installed a 351 w crate engine in my car back in 1998 after destroying the stock 302 so i went with a 351 the cam went in the 351 so i put in a bigger cam for that nice sound but the car has never run consistent some days it runs great no problems then it runs like @#$% so my question should i just go back to a 302 or should i try and figure out the right size solution like mass air meter throttle body and i still have the stock computer, and no oxy sensors which the car does not have. the car does run but it has been sitting since june of this year i started it up so it just needs to be taking on the road and ran all day but then after all the gunk is run out the idle is up and down which has been the problem
the idle is bad ,up and down so guys what the best bet to get this car back in tip top shape ? the car has stock mass air and stock throttle body
with gt 40 upper and lower intake
and no 0xy sensors. or just do the swap and move on and where can i swap a great running race ready 351 w with a big cam for a good 302

[86nu]

check the idle air control valve for the idle problem. You might need a bigger maf, Not sure on those, ive delt mostly in carbs.

[QWKSNKE]

you need the 02 sensors installed, at least a 70mm t/b, a 80mm MAF, and some type of EEC tuner to fine tune everything. After that it should run like a sewing machine

[04 Mach1]

I Agree YOU NEED THE O2

[banditmwp]

:agree:

[EHardy1971]

x3 on the O2's.I also agree you definately need a bigger TB like QWKSNKE stated. The stockers are only 60mm,and the GT40 upper already has a 70mm opening.

[militarymustang88gt]

what size inj are you running?

[Italian LX]

I agree with the comments above. How many miles have you put on the motor?

I'm curious... you've had this set-up for ten year, so why did you wait this long to finally try to get it running right? :think: