[TR] Advice on high compression head

[Dave Connitt]

Hi Cliff,
A lot of racers have milled the heads of wet liner engines to increase compression. In Kas Kastner’s TR4/TR4A competition preparation manual, he goes into much detail about how to reshape the combustion chambers in the head to reduce/eliminate “hot spots”. This may be the cause of your pre-ignition. Yoy may want to get that book and read over his cylinder head chapter. Regarding the push rod length, the length reduction is directly related to how much material is removed from the head so just buying shortened pushrods won’t get you the best results. I think you should figure out how much material was removed from the “stock” head and shorten the pushrods accordingly. 
I think you can certainly save the head but you will need to do some homework reading over Kas’s competition prep manual and find a good automotive machinist for the pushrods.
Dave Connitt 

Sent from my iPhone

> On Apr 7, 2021, at 5:41 PM, DAVID MASSEY <dave1massey at cs.com> wrote:
> 
> 
> I went the band-aid route on my TR3 for the same reason.  But the right way is to get a machinist to shorten the pushrods.  BPNW sells short rods for the TR6/SC engine but at that time they didn't have any for the wet-sleeve engine.
> 
> Dave 
> 
> 
> 
> -----Original Message-----
> From: Cliff Hansen <cliff_hansen at outlook.com>
> To: list Triumph <triumphs at autox.team.net>
> Sent: Wed, Apr 7, 2021 4:23 pm
> 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
>  
> Sent from Mail for Windows 10
>  
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