Hi Mark,
One thing that strikes me is the possibility that the previous assembly
might have been with a thicker than standard head gasket. Did it look like
a standard style? I know you can get various thicknesses if you go to solid
copper.
I have a brand new uncompressed head gasket here, and it measures .072". I
checked it all over the place and the thickness is very consistent.
The old one is .048" at the top of the sleeve, so in my case there was
0.024" of gasket compression. Even worse news I guess.
Also - how big are your pistons? I don't think mine at 87.2 mm would have
quite fit through the hole in the gasket (87mm?).
Depending on piston diameter you are likely to have quite a higher
compression ratio too. Just moving from the old 83 mm to the 87.2 is
putting mine at about 9.3, with the pistons exactly at the top of the sleeves.
One thing you might consider is to double the figure 8 gaskets. They are
about 0.017" thick. Of course then you would probably have to get a custom
thickness of head gasket to compensate.
I think there was also a plate available at one time as an option to lower
compression for countries that could only get low octane gas. The plate
went between the head gasket and the block, so it might be just the thing
for your situation. I don't know how thick they were though, or what they
were made of. They must have been somewhat compressible to deal with the
sleeves standing proud of the deck.
Are the liners still out of the block? If so and you have a means to
measure them send me the height between the seating surface and the top,
and I'll let you know what mine are (I still have the old ones around).
Then we would at least know whether they have been reduced - who knows,
maybe you have the wrong pistons in there! There's another thing we could
try - if you measure from the top of the wrist pin hole to the top of the
piston I can give you that measurement on my old ones too.
Regards,
Jim Wallace
++++++++++++++++++++++++
>In putting the pistons back into my early -4 engine, I noted they were
>about .030" above the tops of the liners at TDC. The block evidently had
>been decked some time in the past, the head had been milled .093". I'm
>using the same crank, pistons, rods & head (std bearings, too upon
>rebuild) as were in the engine in the as received condition so I'm
>supposing it ran this way. The head gasket I have is .070" thick. Allowing
>for .020" compression of the gasket upon installation (wild ass guess),
>I'm anticipating .070-.020-.030-.004 (liner protrusion above the block)
>equaling .016". Wow! Is .016" comfort zone before metal to metal contact
>acceptable?
>.......
>Mark Meany
>Keene, NH
>TR4A CTC 62486
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