I had a series of cylinder heads made wherein they scrubbed the top of the
internal cores about 1/8" so that the stock machining gave a 12.5 to 1
compression ratio. Then with the cutting and grinding I would just mill a
little more more to get my 12.25 ( ideal) . This left the total thickness almost
stock therefore giving the material needed around the combustion cambers on the
squish area side. It could be one of those heads. The difference between the
late TR-3 early TR-4 head was at the inlet port side. The early inlet ports
had a ball mill inserted in the face about 1/4" and this made the face side
larger that the port bore by quite some fbit. It allowed for no interference
problems with the stock manifold when the head was produced this way. Later
heads were without this mill operation and were better in my opinion as the
reduced size gave a higher velocity of the fuel charge.
Bob Kramer wrote:
> Just in case anyone is wondering, and because I feel the need to tell
> someone who actually cares and knows what I'm talking about (my wife, my
> kids, and even my dogs just nod there heads at me), here's what I found
> inside the engine today. I was disappointed at not getting the close ratio
> gears, but happily, there is a set of Carillo (or at least Carillo style)
> rods. The crank looks normal (as in a casting), but has TR6 size flywheel
> bolts. I have only dealt with the TR3 cranks, were they upgraded to heavier
> studs for the TR4, or does this indicate some special treatment? The liners
> and pistons are near perfect, and the camshaft looks good too. The pistons
> look new, but I can't tell what brand they are because I'll have to buy a
> new socket for the ARP style rod bolts. The head surprised me, and again I
> have to wonder if its TR4 Vs TR3. The head is very thick on the spark plug
> side as opposed to my shaved TR3 head, but is actually thinner. The TR3 head
> is 3 6/16" while the TR4A is 3 3/16". There is no remaining evidence of the
> shrouded valve, no grind marks, nothing. In fact one of the chambers is a
> little off from square when compared to the others. The PO told me that the
> head was made from a special casting without a combustion chamber, could
> this true, or did the TR4A get an improved head, which in this case was
> skimmed past the shroud? In any case, its a ported and polished high
> compression head and looks to be in great shape. So all in all, I guess I'm
> lucky after all. That TR6 trade was looking worse every day, but not any
> more.
>
> Bob Kramer
> Hill Country Triumph Club
> Corinthians Vintage Auto Racing Club
> TR3A, TR6, TR4A
> rgk@flash.net
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