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TR4/4A TR3/4 head thickness

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Marvin Gruber

Marvin Gruber

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Pulled out an old TR3/4 head today to take to machine shop. I bead blasted it, no obvious cracks but there was low place rusted in the head gasket area. Checked my TR4 shop manual to see what the deck height was std. Could not find info anywhere in the book on deck height. I've found it in the TR 6 shop book easy enough but its not listed that I can find in the TR3/4 book. Anybody got the std deck height. Mine measures 3.330. Hope its std so I can have the head surfaced out. Don't want to take out any more than I have to but how far can I go without pushing limit?
Marv
 
TeriAnn has it posted on her web site as 3.330".
https://www.tr3a.info/FAQ_heads.htm

Found it: I've got an old post from Ken Gillanders that says 3.325" to 3.330"

On a street engine, the main limitation seems to be having the CR too high for available fuel. I ran one for awhile that had a bit more than 0.100" taken off, and it held up fine. Just had to add a healthy dose of MMT to every tank.
 
MMT? Some kind of anti-knock or octane booster-I googled and got Modern Monetary Theory, I am guessing that was not the direction you were going.
 
I've run .090 off 3.30 for maybe 40 years. Recent head gasket failure has me at .103 off. We shall see how that works out. At .090 93 octane worked fine. May need to retard timing some for current head. Lots of friends have run for years at .070 with no problems.
 
I've skimmed 0.085" from the head and have 87mm liners (which will also increase compression), and run with 93 octane and no problems.
 
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