High Altitude Head

Fri Mar 19, 2010 8:21 pm

My 53 Cub came with the high altitude option as indicated by the tractor serial number and engine serial number. Unfortunately the original head is no longer on the engine. I am in the process of rebuilding the engine and would like to put it back as close to original as I can. As I am sure that I will not find a replacement high altitude head, I am going to make one. I have read that the high altitude heads used the same casting as the regular head with more material removed to reduce the combustion chamber volume. I have calculated how much I need to deck the head to adjust the compression ratio. My question relates to the part number marking on the casting. I read in another post that the cast in part number for the regular head was machined or ground off and the high altitude part number stamped in. Does anyone have pictures of an original high altitude head so that I can see how the part number was changed? Was the original part number removed with and end mill and if so what width? What is the size of the stamp used to remark the head?

Thanks,
Chris

Re: High Altitude Head

Fri Mar 19, 2010 9:11 pm

Chris:

I am not really good on part numbers, but I just finished scanning a TC-37B Parts Catalog and it has a rather interesting few pages. One of them was the suffix list which included the High Altitude head. So I figured the High Altitude Head must be in the catalog, so I went looking on one of my harddrives.

The part numbers are:
  • 351 779 R1 Head, cylinder (high altitude)
  • 351 780 R91 Cylinder Head Attachment (high altitude)
    comprised of:
  • 1 Gasket 4 665 D
  • 1 Gasket 251 229 R1
  • ! Head 351 779 R1

I hope this is of some help.

Re: High Altitude Head

Sun Mar 21, 2010 7:57 pm

Rudi, Thank you for the reply.

How rare are the high altitude optioned Cubs? I am not sure how this one made it to the North Carolina Piedmont (elevation maybe 600-700 feet). I didn't figure I would get a quick exact response to my head marking question, but I figured that there would be some high altitude owners out there to maybe point me in the right direction. Maybe there aren't as many HA tractors out there as I figured. Unfortunately I have a Cub addiction problem and have read all the written tractor, parts, implement, and service manuals over several times and searched this forum and am still coming up short on an answer.

Re: High Altitude Head

Sun Mar 21, 2010 8:17 pm

I would suspect that not that many people are aware of this option. Probably don't even look at the part # when they do take off or replace a head. Unless there was something that made it stand out as different, it's probably be missed.

Bob

Re: High Altitude Head

Sun Mar 21, 2010 8:18 pm

Chris:

I really have no idea how rare they are... :!: The only thing that I know about them is that the option was available .. mostly because of the suffix codes. I happened to notice it when I was scanning the parts catalog.... :roll: .. I would think that Jim Becker would know a bit more ......

Re: High Altitude Head

Sun Mar 21, 2010 9:06 pm

I have no idea how many were built with the high altitute option. I remember seeing a picture of a head that was machined to high altitude, but don't recall ever seeing one first hand. As I recall, it appeared that the part number was ground off and restamped, not machined and restamped.

Re: High Altitude Head

Mon Mar 22, 2010 8:07 pm

Thank you for the replies. I guess I'll just grind off the part number and hand stamp the new number on (or maybe I should just leave it alone as no one will know but me).

Just an FYI here are a couple of pictures of the serial numbers indicating the high altitude option.
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Re: High Altitude Head

Mon Mar 22, 2010 9:06 pm

Chris:

Interesting pics. Thank you :!: :D Are you considering trying to find the proper head :?: I would check with Ralph, and JP as well as post wants on a number of tractor classifieds. You may actually find the correct head. I am not sure what the probability would be, but it could be worth a shot.

Re: High Altitude Head

Thu Mar 25, 2010 1:36 am

My '53 Cub also has the JL code on the serial tag. If I remember I'll look to see if any different numbers are stamped on the head. We've been busy using the Cub and forget to look until after dark.

Ed

Re: High Altitude Head

Sun Mar 28, 2010 2:40 pm

I finally remembered to check for numbers on my Cub and found no numbers stamped on the head, just the cast numbers on the top. I can't really see them without taking the hood off and I'm not going to do that, because you know what follows.

Anyone else got a Cub with a JL suffix on the serial number tag?

Ed