[TR] Advice on high compression head

David P frogeye at porterscustom.com
Wed Apr 7 17:24:12 MDT 2021


Have a thick gasket made.. Lubbock Gasket and Supply 806-763 2801

On 4/7/2021 4:39 PM, Greg Lemon wrote:
> If you want to save the head you may be able to lower the compression 
> ratio a bit by reshaping the combustion chamber.  This is 
> theoretically, I don't know how much can be removed, Kastner book 
> would be a starting point, but you would probably want to take out 
> more than that, measure combustion chamber size, etc.
>
> On Wed, Apr 7, 2021, 5:23 PM Dave Connitt <dconnitt at fuse.net 
> <mailto:dconnitt at fuse.net>> wrote:
>
>     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
>>     <mailto: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
>>     <mailto:cliff_hansen at outlook.com>>
>>     To: list Triumph <triumphs at autox.team.net
>>     <mailto: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 <https://go.microsoft.com/fwlink/?LinkId=550986>
>>     for Windows 10
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