hey guys,

i have a 89 f250 with the zf 5 speed and was going to rebuild the engine in it. Thing is i found another engine that is in a 91 bronco that was rebuilt about 6 years ago and has 10,000 miles on it.

now i asked him to do a compression check just to verify the engine health he told me across all cylinders its 150-155, so it sounds pretty good to me.

i was digging around in my specifactions book for 1989 trucks and noticed that my truck is supposed to have a 8.8 ratio and a bronco(A/T) should have a 8.3 ratio. that applies to the 89 model year idk about his bronco for sure. i would like to know if i were to buy his engine and get it in my truck would i have a problem powerwise?

ill be talking to him in the morning again, but if his bronco is automatic would that be a big problem for my truck(i assume not but not sure)? i just don't want to buy something and regret it after i get it home.

another thing that comes to mind also is that if he has done anything to the motor as far as upgrades for power or something. when i put it in my truck would i have computer issues or the like? i also know ill have to put my smog pump on his engine as his didn't come with one he said.

if he has done any modifying to the engine it throws just about everything i said here out the window, but i don't think he has but havn't asked.


thanks in advance for any info you guys can give me.

 

Those motors are identical so you won't have a problem swapping it in.

I'm not sure what you mean about 8.8 and 8.3 ratio, are you referring to the rear axle? If so your F250 has a 10.25 sterling axle and the Bronco has an 8.8.

 

according to my book it says nominal compression ratio is 8.8 for the bronco and for my f250 8.3

i assume its should/could also be written as 8:3:1??? that would be my guess.

i know it seems strangely written in the book as it lists the 7.3L as 21.5:1 compression and the rest are written as i posted at the top there.

 

That difference in compression would be unnoticeable under everyday conditions. I'm with Conanski this would be an easy swap.

 

you also dont have to put your smog pump on the new motor

 

Your reference is mistaken, both of these motors are literally identical and have the same nominal compression ratio of 8.8:1.