Head thickness

porsskar wrote:

I have two heads with

-script Willys and JEEP WITH A THICKNESS 53,20 mm =appr. 2,095 in

-and a SUPERSONIC KAISER head with a thickness of 53,50 mm =appr. 2.106 in

Questions:

1 What nominal thickness should the heads have?

2 Restoring a 1947 cj2a which of the two heads would make sense to use?

The engine is donauts shape casting at freezing plugs. serial 3531348 at cooling water pump area. This is a originally red painted engine.

Addtional info:

Numbers in castings

Jeep Head Casting nr

W5

6.48

800376

Supersonic Head Casting nr

6 18 C

741422

Sten from Finland
1947 CJ2A serial 94118
1949 8NAN Ford tractor
1965 Mahoghany Snipe FIN 14018

1 Must I conclude the 800376 cannot sit on a cj2a.

2 Would the Supersonic be a better alternative for a cj2a? ( was it not sold as a high performance head at the time?) or have I understood this incorrectly?

Sten from Finland
1947 CJ2A serial 94118
1949 8NAN Ford tractor
1965 Mahoghany Snipe FIN 14018

Either head should work. The supersonic head allegedly has a slightly higher compression ratio.

Nowhere on the web does there seem to be a specification as to the machinability limit on a 134 head.

If you go to G503.com and to the MB/GPW forum, you can do a search for "cylinder head machining"...and you will find a post that talks about head thickness...

If you haven't checked out the tech FAQ section, go to:
http://www.thecj2apage.com/forums/tech-faq_forum57.html
for a lot of great stuff you need to know!!

800376 head thickness = 2-9/64 = 6.48 compression ratio

640035 head thickness = 2-7/64 = 7.0:1 compression ratio

Both made from the same casting

Where exactly on the head do you measure this? Is there a spec difference between the smooth early head and the late ribbed head?

I did a pretty extensive search for this info over on the G 503..never found anything specific, so I am glad someone found something!!

If you haven't checked out the tech FAQ section, go to:
http://www.thecj2apage.com/forums/tech-faq_forum57.html
for a lot of great stuff you need to know!!

Are you measuring the depth to the flat roof of the combustion chamber. To get an accurate measurement of the compression ratio, you need to measure the deck clearance (block deck to piston top), actual cylinder bore and then using a cover plate and burette measure the volume of the combustion chamber. This is assuming you know the stroke already.

A 0.040 overbore has more compression than a stock bore, for instance. I suspect for most heads that have been cleaned up from minor warps and pits, planing them will not affect the compression enough to change fuels, for instance. Given what I have heard, however about L134 sensitivity to timing and overheating, increasing the compression even a little might require backing off the advance a little bit.

My head has had 0.012 taken off to clean it up because of water jacket leaks and associated pitting. I'll find out about timing when I get it together enough to drive it, I suppose.

My opinion only, not backed up with experience, in this case.

BTW, my wife thinks my head is sufficiently thick between the ears, perhaps because of Jeepmania.

John

Edited by jwitt - 03 Dec. 2010 at 4:12pm

Free men are not equal, equal men are not free -- Jerry Pournelle

48 CJ2A

Yes Fred, that is a good thing for a guy that lives at high altitude to know.

I agree with the comments on combustion chamber volume, but in this case, I just read it from a spec sheet... I didn't calculate it. (being thick headed myself)

Dimensions are from the top of the rib to the machined mating (gasket) surface

I'll have to get back to you Bill. It may be for the late non ribbed head but probably not for the early one.

On my 46cj2a I am machining my head and would like to know what is the minimum thickness. To the best I can tell the casting number is 340161. The first digit is the only one I am not sure of, all the rest are easy to read.

Does anybody have any specs for this casting number?

48 CJ2A,225 v-6
46 CJ2A L134
50ish CJ3A L134
98 TJ,1 tons w/detroit lockers,Cummins 4bt,TH475,NP205,38.5" tires