engine swap help

[mattp1788]

Ok so I have decided that I am going to keep my jeep jeep... It has a blown AMC 258 i6 / 4.2l and I want to replace it with something that is going to have more power(because trying to get that thing to do 60 on the highway was impossible), anyways this is a casual driver highway, street and maybe light trails. What motor would be best to swap in AMC 304 , 360, or 401? Remember I want something that will allow me to do say 70 on the roads, and nothing that is too expensive... The jeep has stock AMC20 and T-150 3 speed for reference, thanks for any info!

 

[BusaDave9]

A AMC 258 i6 / 4.2l should easily be able to go 70 or however fast you want to go. What tire size and gears do you have in the axles? Gearing may be holding you back.
If you want to go to a V8 I'd get a AMC 304 . That's what I have. You can go bigger if you want more power but if this is a daily driver it will suck gas.

 

[mattp1788]

I have 33's and not for sure the gears they are they stock ones still im guessing its a 79 model. When i try to get to 60 the rpms are maxed out and i have no more pedal left and its barely getting to 60... so either i guess my motor didnt have enough power or i need different gears not for sure.

 

[jasonmark1993]

I had a AMC 304 , 33s, and stock 3.73s that would run down the freeway at 75 real nice. I dont know what RPM I was at but it would go faster if I wanted to.

I've since pulled the engine and its for sale. But I'm all the way over in El Paso. Ran great when I pulled it but burnt a little oil. I pulled it over a year ago but I'd probably just rebuild it before putting it in.

 

[mattp1788]

Ok so I decided to stay with the AMC 258 i6 / 4.2l ... Now I want to get just a little performance out of it so if I do the 4.0 head, a cam, hei distributor, and maybe some fuel injection, is there anything else I can do to get some more performace out of this motor?

 

[mtnwhlr]

Gears, lower gears will make a engine feel like it has a lot more power. You take two Jeeps set up the same but one running 3.31 gears and the other running 4.10s the one with 4.10s will leave the other in its dust from a stop light every time.

 

[Jimbos76cj]

I'd save your money from doing the head swap and get a good set of 4:10's or 4:56 gears for it. A lot of cj's came stock with 2:72 gears. I'd swap gears first then look into adding power to the motor.

How do you you know your motor is blown? Is it smoking? Water in your oil? Honestly a bad clutch, realy high gears like 2:72, inproperly tuned engine, and about half a dozen other things will cause it to run like . Run a compression check on the motor and see how the cylinders end up.2:72 gears and 33's will make it feel like a huge dog.