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Triumph TR6 - Diamond W

There is a TR6 head on ebaY that the seller lists as being a very rare "diamond W" casting. Anybody know what makes this casting so "rare"?


Rick O.
Rick Orthen

Never heard of it, but rare is the most overused word on ebay
R. Algie

My best guess is that it is related to emmission controls. I seem to recall that the EGR valve was mounted to the cylinder head toward the aft end above an exhaust port. I haven't looked at a late TR6 in so long that I just flat do not remember for sure. Perhaps one of you guys with a late USA spec car can verify this. If you are really feeling sporty, anyone with a wide intake port head (any PI car and late CC/all CF carb cars) can pull the rocker cover and look at the left hand rear corner and see what casting stamp is there and report back.

I believe that the diamond w casting refers to the specific foundry that the head was cast in...and that this foundry produced the best the upper and lower halves of the casting are in better alignment than any other...this provides the possibility for better porting and polishing
Chip Collingwood


I have 2 '74 heads in my garage, both have the 'Diamond W', so I guess I must be pretty lucky. Since your head is off, is it on yours as well? I agree with Ron, rare is overdone a bit! Maybe it was just medium rare!?! (Goosed again!)

Rod Nichols

if looking for a head, the article at may be of interest - (sorry can't help with the diamond 'w' - not to be confused with the VW !)
Roger H

I've accumulated 3 heads and all of them have the diamond-enscribed W. Go figure. Since I'm always learining trivia about our cars, thought maybe I was on to something meaningful; apparently, it is just a seller tactic in this case.

Rick O.
Rick Orthen

I was checking back through my notes last night and found the proper article on came from grassroots motorsports mag is an article written by John Hagerman titled PartIV Selection and initial building of our IT TR-6 engine...I am sure that you can get archive reprints from well according to the article I was is the script "B" casting that is preffered
Chip Collingwood

The "B" head was specifically mentioned by Kas Kastner in the TR250/TR6 prep books from long ago. As far as I know from a NA market standpoint, it was limited to the early carb TR250 and TR6 with the closer spaced intake ports.

As for the reports from people having the Diamond W heads, does your head have the EGR valve fitting or not?

Just had a look at a spare head in the workshop off a 1975 ex USA car, it has the EGR fitting and the diamond W. As I said earlier 'rare' is the most overused word on ebay
R. Algie

My diamond W's have the EGR port.
Rick Orthen

I have a spare head that has the cast #s of 308351. What is this? i.e. year ect?
Gene Holtzclaw

There were three castings. A circle B which has the best port geometry and more meat in the casting if you shave it down for over 16:1 compression. the diamond W is the next best for shaving though not rare! The least desireable is a round castin with no mark on it.
Mike Munson

I should have read the other posts before I spoke up. Hi Chip I didn't know you were on here. Steve I have circle B in both the early and late heads. Matter of fact I am looking for someone to trade a late model circle B for an early head I have.
Mike Munson

Long time, no see Mike. I had contemplated shooting an e-mail your way to see if you could shed some light on this. I was unaware of a late circle B head as I have only seen early ones. It would appear then, that the casting mark would have nothing to do with whether of not the head is a close port, wide port or wide port with EGR provision. Does this match up with your experience? I will be heading over to the shop tonight and had planned on looking at the heads that I have for casting numbers and to verify casting marks. The only things that I can tell you with certainty right now is that I have no heads with an EGR fitting and that the engine that we will be sticking in my six this spring has a close port B head.

Funny, both of my installed heads have a W on them
but in my case that stands for "Winsor"
Christopher Trace

I looked at five heads and found the following on three:

Circle B head for fresh engine:
Stamped on flat at #1 cylinder - 516323
Cast in above ports at #2 cylinder - 188 12
Cast in above ports at #3 cylinder - 307837
Cast in above ports at #4 cylinder - 1703
Cast in above inlet port at #6 cylinder - V3069

Circle B is cast at front corner of head on manifold side under valve cover, cast in at rear of head on manifold side under valve cover was a 1 with a D below it. Also noted above the cylinders #1&2 inlet ports and the cylinders 3&4 inlet ports evidence of cast in information that had been ground down. If you looked closely at all the cast in information except the circle B and the 1D, it looked like the information was from a plate screwed to the mold. These screw head marks were common to all of the heads. This head also had a cast in boss above #5 exhaust port such as that used for EGR fitting. This was the only one out of five heads that had this boss. Perhaps a replacement head made from a common base casting mold? Any insight on this out there in TR land?

Circle B head on TR250:
Stamped on flat at #1 cylinder - 516323, only smaller than on other head and upside down
Cast in above inlet ports at # 1& 2 cylinders - 307837
Cast in above inlet ports at # 3 & cylinders - STANPART logo
Cast in above inlet ports at # 5& 6 cylinders - V3069
Cast in above ports at #2 cylinder - 100010 (had been partially ground, so 0s may have been some other number at one time
Cast in above ports at #4 cylinder - 1703
Cast in above inlet port at #6 cylinder - V3069

Circle B cast in at some location as other circle B head, head also had cast in "1" at rear, but no "D."

Diamond W head on tired engine:
Stamped on flat at #1 cylinder - 218227
Cast in above ports at #3 cylinder - 312388
Cast in above ports at #4 cylinder - X08 looked to be upside down based on uppper and lower loops of the "8."
Cast in above ports at #5 cylinder - STANPART logo
Cast in above inlet port at #6 cylinder - V3267

Diamond W was cast in at rear on manifold side, a 2 was cast in at the fron of the head under the valve cover.

There were a couple of other heads there, one that was Circle B and one Diamond W, I think both are close port head. They were rather crusty and cleaning them would have taken a while. Had other things to do and did not clean them off to get the cast in or stamped information from them.


The casting mark identifies what foundry the head was cast in thats all. the circle B foundry had the best molds.

BTW I am a member but I can't find any place to sign in.

Mike Munson

Mike--We'd love to have another member registered. Go here:

Rick O.
72 TR6 (w/'rare' Diamond W's)
Rick Orthen

I was registered but just forgot how to sign in. I think the ghost of Mr. Lucas must have invaided my brain!

MGM Munson

This thread was discussed between 02/02/2004 and 07/02/2004

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