[TR] Advice on high compression head
Paul Tegler
ptegler at verizon.net
Wed Apr 7 18:35:41 MDT 2021
ditto. Validate the issue with minimal work
ptegler
On 4/7/2021 7:24 PM, David P wrote:
>
> 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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