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Triumph TR3 - Cylinder head steel shim gasket

Hello TR3 afficianadoes I'm trying to increase the HP on my 3 engine. I've gone with a mild street cam,Tr4 intake manifold and an exhaust header. My intent is to increase the power for the street and possibly race at a local track occasionally. I'm trying to increase the compression on my 59TR3A 87mm engine by installing a steel shim headgasket and possibly milling a few thou off the head. Does anyone know how much to mill? I have heard that .020 will yield 10.5:1 but I have also heard that milling .125 will yield 10.5:1? I realize that after doing this I will have to use high octane or octane boost but I'm OK with that. Anybody have experience with this or know of a link?
karl

karl,
before you do any milling on your tr head,you might want to check on these books.
"triumph preparation handbook" by kas kastner
r.w.kastner
1611-a south melrose drive #281
vista,ca.92081
$34.50 + 3.85 shipping
"how to restore tr2-3-3a" by roger williams
"how to improve triumph tr2-4a" by roger williams

if to much of the head is milled,the head will interfere with the water pump housing.
on page 20 of the "triumph preparation handbook it says "interference is most apt if you have milled more than .125" from the cylender head".
on page 43 it says "to achieve the 11.7c.r. mill .150"
from the stock cylender head face,use the 87mm cyl. &
piston kit and a steel shim head gasket".
you should check and make sure someone before you has not done some milling on the head.
i have these figures ,but i can't recall were i got them.the original head thickness 3.325"-3.330".
never mill below 3.170"
hope this might be of help,
payne
payne

Hey Payne Thanks for the info....most helpfull. Karl
karl

Check with Mordy Dunst, the owner of The Gasket Works. As well as making gaskets like this, he races a very fast TR4.

http://www.headgasket.com/

Dobn Elliott, 1958 TR3A
Don Elliott

Agree with Payne and Don; but suggest you have the machine shop cc the head before you decide how much to mill.
This is the best way to find out if the head has already been skimmed. I would suggest 10.5 is too high a ratio for street use, even with 94 octane you will most likely have to retard the ignition so far you will lose much of the benefit.
If you skim off too much it is possible to open up the volume of the combustion chamber slightly by a combination of grinding away some of the metal shrouding the inlet valve, and some from the squish zone. Kas Kastner and David Vizard explain how this should be done in their books, and it is something you will want to do ti improve performance anyway.
After the head is skimmed and the valve unshrouded, the chambers should be cc'd again to match so you have equal ratio in all cylinders.
Remember, measure twice, machine once; it's difficult to add material back if you go too far!
Simon.
Simon

This thread was discussed between 06/03/2005 and 01/04/2005

Triumph TR3 index

This thread is from the archive. The Live Triumph TR3 BBS is active now.