Different year engine swap

[70worm]

I have a 77 cj5 and I need a new motor. The early 70's stock motors have alot more power, so how old can I go and still bolt up to a 1977 trans? Is there a website with a chart? 69-71 Have the most power

 

[superj]

Is it a 6? If so, I think any of the 6 and AMC (not dodge) v8s bolt to the trans. That is what my reading has led me to believe because I have the same engine as you and I wondering about drop in v8 swaps

 

[kingmega]

If u have not found anything out yet try carls car restoration 2198722737 vivtrunk@yahoo.com this guy only deals with amc and amx and really knows his shit real nice guy helped me out alot with my cj5 build he mostly deals with amc/amx cars but seems to know alot bout thr old amc jeeps

 

[flatie46]

The reason the older engines have more power is they gradually dropped compression over the years. I wouldn't want to go no higher than 9 to 1 if you plan on driving it everyday. What engine are you wanting to bolt to what trans?

 

[Jester32]

The reason the older engines have more power is they gradually dropped compression over the years. I wouldn't want to go no higher than 9 to 1 if you plan on driving it everyday. What engine are you wanting to bolt to what trans?

And the camshafts got considerably milder with less overlap and duration.

 

[69jeepcj]

Your jeep is AMC, any AMC motor, 6, or 8 will bolt right up to your drivetrain. Not sure what year AMC bought the kaiser corp but the motors in the kaisers are not AMC engines. My 69 is a kiaser built jeep. If you have a 6 now, and go v8 you will need to change one motor mount, and reroute you gas line up the other frame rail. (from driverside to passenger or visa versa) You can do a google search and find out what year AMC bought kiaser, and go from there.

 

[Saddle Tramp]

1972 is the first year CJs used the AMC I6 & V8 engines and is also the year 3” was added to the engine compartment to accommodate them. The engines to bell housing bolt pattern on all CJ & YJs are the same regardless of I6 or V8. I’m not sure when but at some point in the TJ run I have heard of some problems with bolt up continuity.

 

[69jeepcj]

didnt mean to post, my mistake.

 

[70worm]

Thanks for the info! I was thinking about putting in a 401 but with government regulations the specs (HP & torque) on the late 70's motor are horrible. I mean who really wants a 401 with 150hp at 12 miles to the gallon! If I get engine that big I want at least 250+ hp. I have a 360 now that's blown and I'm getting a new engine this summer and I havnt decided if I want to put a built up 258 in it or keep it v8. I dont know if 6 vs v8 weight difference is big enough to matter?

 

[69jeepcj]

I think it would be easier to get 250+hp form a v8 then it would the 258.

 

[superj]

A few people have 200+ horsepower 6 cylinders on here and jeep forums. It's not that hard, same amount of work as a v8

 

[69jeepcj]

cool, I just thought it might be more work, or more parts I should say.

 

[carnuck]

The reason the older engines have more power is they gradually dropped compression over the years. I wouldn't want to go no higher than 9 to 1 if you plan on driving it everyday. What engine are you wanting to bolt to what trans?

In spite of all you hear, this is not true. The way engines were rated changed in 1971 from BHP (bulk horse power) to net HP which means with all accessories attached.

 

[superj]

yup. net is about, what 20 or 30 percent less? they did change how they rated them to standardize the way the hp was derived so the numbers could be fairly judged when people were out buying cars.


but, original poster, don;t compare them by gas mileage. my 4.5 gets 9-11mpg and is the 6. for that kind of gas mileage, i would rather have a v8 so at least i could sound badass, ha ha ha.

i jest about the sound, my i6 sounds like a monster, and from 800-2000 rpms, it is. it will pull anything without thinking about. with the proper fuel delivery system, it rides right upto 100mph, like nothing. i am having some vacuum leak issues right now or it would probably do it right now though