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Can you get shorter push rods to make up for the thinner head?
Alex Thomson
From: Triumphs [mailto:triumphs-bounces@autox.team.net] On Behalf Of Cliff
Hansen
Sent: Wednesday, April 07, 2021 5:24 PM
To: list Triumph
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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class=3DWordSection1><p class=3DMsoNormal><span =
style=3D'font-size:12.0pt;color:#1F497D'>Can you get shorter push rods =
to make up for the thinner head?<o:p></o:p></span></p><p =
class=3DMsoNormal><span =
style=3D'font-size:12.0pt;color:#1F497D'><o:p> </o:p></span></p><p =
class=3DMsoNormal><span style=3D'font-size:12.0pt;color:#1F497D'>Alex =
Thomson<o:p></o:p></span></p><p class=3DMsoNormal><span =
style=3D'font-size:12.0pt;color:#1F497D'><o:p> </o:p></span></p><div=
><div style=3D'border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt =
0in 0in 0in'><p class=3DMsoNormal><b><span =
style=3D'font-size:10.0pt;font-family:"Tahoma","sans-serif"'>From:</span>=
</b><span style=3D'font-size:10.0pt;font-family:"Tahoma","sans-serif"'> =
Triumphs [mailto:triumphs-bounces@autox.team.net] <b>On Behalf Of =
</b>Cliff Hansen<br><b>Sent:</b> Wednesday, April 07, 2021 5:24 =
PM<br><b>To:</b> list Triumph<br><b>Subject:</b> [TR] Advice on high =
compression head<o:p></o:p></span></p></div></div><p =
class=3DMsoNormal><o:p> </o:p></p><p class=3DMsoNormal>The =
telenovela “What’s going on with this 4A cylinder =
head” has developed a new plot twist.<o:p></o:p></p><p =
class=3DMsoNormal><o:p> </o:p></p><p class=3DMsoNormal>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.<o:p></o:p></p><p class=3DMsoNormal><o:p> </o:p></p><p =
class=3DMsoNormal>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.<o:p></o:p></p><p class=3DMsoNormal><o:p> </o:p></p><p =
class=3DMsoNormal>Looking for advice from the list: is there any =
reasonable way to use this head?<o:p></o:p></p><p class=3DMsoNormal>- =
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. <o:p></o:p></p><p class=3DMsoNormal> - 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).<o:p></o:p></p><p =
class=3DMsoNormal><o:p> </o:p></p><p class=3DMsoNormal>Would =
appreciate any advice on the way forward.<o:p></o:p></p><p =
class=3DMsoNormal><o:p> </o:p></p><p =
class=3DMsoNormal>Cliff<o:p></o:p></p><p =
class=3DMsoNormal><o:p> </o:p></p><p class=3DMsoNormal>Sent from <a =
href=3D"https://go.microsoft.com/fwlink/?LinkId=3D550986";>Mail</a> for =
Windows 10<o:p></o:p></p><p =
class=3DMsoNormal><o:p> </o:p></p></div></body></html>
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