[TR] Advice on high compression head

[Cliff Hansen]

I appreciate all the advice. This is why I have subscribed to this list for 24 years.

I had measured the head height on the car and that figure was not accurate, or my eyeball didn’t read the scale correctly.

Off the car now and on the bench the head measures 3.180” which means it has had 0.150” cut away.  This is the limit which Kastner describes. The chambers have had some radiusing, not as much as is described in Kastner’s book.

Since I’m not building a race car, and prioritize reliability over performance, I think I will look for a different head.

If anyone knows someone looking for a usable head for a race car, perhaps I have what they need.

Oh, and the pushrods are 257mm in length, which is the shorter set sold by Revington TR (stock is 260mm).

Cliff


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From: Cliff Hansen<mailto:cliff_hansen at outlook.com>
Sent: Wednesday, April 7, 2021 3:24 PM
To: list Triumph<mailto:triumphs at autox.team.net>
Subject: [TR] Advice on high compression head

The telenovela “What’s going on with this 4A cylinder head” has developed a new plot twist.

The head, after cleanup, measures 3.21” from bottom to the surface for the valve cover gasket. Stock is 3.330 (if I got the number correctly). Some PO cut 0.11 off, because only 0.010” was removed in this round of clean up. Now I can see an explanation for the persistent pinging I’ve dealt with over the last few years (head has been milled so compression is high, material near intake valves has been thinned, increasing likelihood of hot spots – I’m getting this from Kastner’s preparation book), which I had thought was due to leaking intakes, carb shafts, or operating at higher altitude.

As is, I can’t use this head because there is not enough slack in the valve train to give 0.010” clearance on several valves. I didn’t notice before, but now that I am looking, all the valve adjusters were nearly backed out all the way.

Looking for advice from the list: is there any reasonable way to use this head?
- I’d prefer to reduce compression but don’t see any reasonable way to accomplish that. I called GasketWorks and he gently discouraged me from getting a custom thick head gasket, saying instead I’d be better off finding a head which had not been milled so much.
 - Shimming the rocker pedestals to get valve clearance feels like a bandaid which certainly won’t address the pinging (assuming that the pinging is a result of the shortened head).

Would appreciate any advice on the way forward.

Cliff

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