[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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