Standard combat head?

I no longer have my 1970 Commando roadster so thought I should sort through some of the spares I have. I found this Combat head which I have had cleaned up. It looks in great condition but also looks very different from my earlier 750 head. Is this what a standard Combat head should look like or does it appear to have been modified? Thanks for any information, pictures are attached
http://s1156.photobucket.com/user/peril ... i.jpg.html

Easiest way to tell is to compare two heads side-by-side. The most obvious difference should be at the head gasket surface. A combat (or modified) head's gasket mating surface should be closer to the bottom fin (milled down for higher compression). The valve seats may have been replaced, but that may have been maintenance rather than modification.

As Danno pointed out, the standard iron seats have definitely been replaced with bronze seats. The seats also appear to be significantly larger than stock. Have you measured the valve size? It may be that the head has been modified for a larger intake valve. It looks to me like the combustion chamber has been re-sphered a bit to allow a larger intake valve. The squish bands are much narrower than stock. It also has bronze guides installed in place of the stock iron ones. Does it have had the larger 850 guides installed, or are those the smaller 750 guides? I can't really tell for sure. If so, you might have a head that has had the intake guide re-angled to allow a larger valve. If so, you would expect to see a 1.625 " intake valve instead of the stock 1.490", Lots of possibilities here. Dunstall, Mick Hemmings, Steve Maney, the factory race shop, and quite a few others have done the big valve mod over the years.

The stock combat head is just a standard 750 head with something like .040" (might be .036") milled off the surface, but no other changes.

In any case, it is clearly not an un-modified combat head. Looks good though.

Ken

perilouspierre

http://atlanticgreen.com/nhth.htm

Your pix does not show enough detail to tell what your head is, except bronze seat modified.

Std combat heads are not very favorable IMO. At least for a street bike.
I'd take a 68-70 head over a combat head any day...

lcrken said:

The stock combat head is just a standard 750 head with something like .040" (might be .036") milled off the surface, but no other changes.
Ken

Click to expand...

A minor point, but in 1972 weren't the Combat heads the first 750's with factory 32mm intake ports? And for comparison, this photo should be a stock Combat head, just one guide replaced.
Bill