how do I identify my engine

[hotrod]

516000

I have a 1979 jeep CJ 5 with what I assumed was a 304 V8, unfortunately I have found the heads at least are not from this engine. I found this out when I went to fix an exhaust leak, and the manifolds had these “dog ears” in them. I am told that this is factory for this truck, however the heads do not have the same “dog ears”. How can I identify the engine block for make model and year, and also the heads for make model and year? The heads have rectangle ports for the exhaust and I am told they are probably from an AMC car such as a Javelin. I need to find out all pertinent info on this engine so I can fix it. Can anyone help?
O.K. I looked at the engine to see what I could find for information that could identify it and on both sides there was the number 390 on the block. I am not an AMC guy, but is this the engine size, I've been told this is a 390 out of a Javalin, any other suggestions?

[This message has been edited by hotrod (edited May 18, 2001).]

 

[hotrod]

517000

Originally posted by hotrod:
I have a 1979 jeep CJ 5 with what I assumed was a 304 V8, unfortunately I have found the heads at least are not from this engine. I found this out when I went to fix an exhaust leak, and the manifolds had these “dog ears” in them. I am told that this is factory for this truck, however the heads do not have the same “dog ears”. How can I identify the engine block for make model and year, and also the heads for make model and year? The heads have rectangle ports for the exhaust and I am told they are probably from an AMC car such as a Javelin. I need to find out all pertinent info on this engine so I can fix it. Can anyone help?
O.K. I looked at the engine to see what I could find for information that could identify it and on both sides there was the number 390 on the block. I am not an AMC guy, but is this the engine size, I've been told this is a 390 out of a Javalin, any other suggestions?

[This message has been edited by hotrod (edited May 18, 2001).]

Since it seems everyone out there is pretty stupid when it comes to thier jeep, and after exhausting research I will use the information I gathered to answer my own questions, that way if any of you retards decides to investigate you will have the answers.
This is from a guy who I emailed individually. He writes.
Easy answers.
The engine is a 390. The numbers on the side of the block make it easy,
once you learn how to position yourself to see them.

The 390 from 67 through 69 uses the rectangular port heads you describe.
This is probably what you have. The 70 390 uses dog leg heads that would
match the exhaust manifolds. Your manifolds are most likely for the 304,
and original for the Jeep. If you need to know for sure if the engine is a
67 to 69, check the diameter of the head bolts. 7/16 bolts make it a 67 to
69, if it has 1/2 inch head bolts, then it is the 70 390.

I don't know whether headers are available for a Jeep with rectangular
ports. I show a listing in an old JC Whitney catalog for a 72 to 80 Jeep
with 290 to 401 V8. 290 has rectangular ports, 401 has dog leg, so the
application is not technically accurate.

I think you can get the dog leg headers, and that eventually they will work
just fine on the old rectangular heads. In my experience, the dog leg in
the headers doesn't match the dog leg port very well. The smaller
rectangular port going into the bigger dog leg header port won't affect
performance, and will probably seal just fine. Use the stock type metal
reinforced gaskets, the gasket kits usually have gaskets for both the
rectangular and the dog leg style.

The 304 manifolds should be an improvement over the stock log style early
390 manifolds. I would recommend that you use them and forget about
headers.

The 390 is not only a good AMC engine, it is superior to most engines
period. If you are not getting enough performance, it is not because of the
lack of headers. Most likely it is because the timing has been retarded so
you can run on cheap gas, or the carb is not set up correctly.

With a 750 or 780 Holley, optimized timing, and a good set of performance
mufflers (or even just one!) this Jeep should have enough power to be scary,
more than any 350 Chevy.

There is one more option. The late model heads, from any 360 or 401 from 72
up, will have a larger combustion chamber and reduce compression from 10.2
to 9.5 which is a little better suited to the alleged gas available today.
If you need to re-do the heads, these would provide improved flow, moderate
compression, and match the manifolds you have. You will have to slot the
two center bolt holes on the intake manifold to bolt the early manifold to
the late heads, or mill a late model manifold to fit. By the way, what
intake manifold do you have? The late ma

 

[Guest]

518000

 

[willys]

519000

wow, you did it! it's not really that hard or exhaustive, we have computors now! good for you, now if all the lazy people out there who keep asking the same stupid questions, did what you did........

[This message has been edited by willys (edited May 26, 2001).]

 

[sillsmack]

520000

HOTROD<
Sound great, except.....304 heads on a 390 ?

Does the 304 heads have large enough valves & ports for the 390 breath like it should ?


My 304 is a boat anchor @ 11mpg highway & 4.5mpg 4X lowrange.

I've been thinking of a GM 350...

My wife's '98 Chickaree with 4.0L blows my doors off as she takes the kids to soccer practice...Dang embarassing...

 

[hotrod]

521000

Yup, I ain't so stupid after all!!!! Great reply, however I thought that was what this forum was for wise guy. If you knew the answers you could have solved the dilemma several days earlier. If I had known where to go for the answers I wouldn’t have been looking here. Granted with the computer age it made it easier to find the answer, however with a little help from those willing to hand out some free info, life is easier. Instead chuckle heads like you seem to feel they should keep the information to themselves, way to go man. Keep everything to yourself, including your opinion, we’ll all rest easier knowing you didn’t help out.

 

[hotrod]

522000

to sillsmack, they are 390 heads on a 390 engine.

 

[willys]

523000

i didnt have the answers to keep all to myself, but ill be damned if i was to find them for you! you should be proud that you did it on your own, and about saving a couple days, slow down, don't be in such a big hurry to get to the end of your life!!

 

[hotrod]

524000

To all who may be interested, no one makes a header for a Jeep with an AMC engine transplanted in it. I have contacted all major header manufactureres and they don't exist for rectangle port engines. You can get them all day long for dogleg port engines, but for this application they don't have anything.