TR4/4A Head Gasket Issue

Recently I've been losing water from the rad; pulled the valve cover off and around #1 I/E valve springs noticed the familiar white mix.
Have taken the head off and it seems to be fine. Straight edged the heck out off it and all ok.
Have used a copper head gasket & cannot detect issues with it. Maybe I missed something so will re-check it am.
Block looks good after cleaning it up a bit. Planning on draining the pan to check for water. Nothing on the dipstick.
So I'm thinking it's something in the top end.
I have the 89mm set and am wondering about going with a Cometic Head Gasket. They only come in the 88mm.
size. Would that be usable?
Thanks Everyone,
Harry

Was your copper gasket solid or sandwich? Solid can be a real problem. Check that your head studs are all good. Are the number one and two sleeves protruding the correct height (in thousandths) above the block? Don't know about the 88-89 issue, but I seem to recall the Moss catalogue or BPNW site saying that gasket size works. But I'm just not sure--sorry.

Harry,
How long ago did you build this engine? Another thing to look at would be the stud holes in the block...sometimes you need to chamfer them to make sure the head and head gasket fit all the way down on the block. You should be able to measure them with a straight edge across the holes.
Rut

I remember when I rebuilt my 4a engine with 87mm pistons and used a standard, 86mm gasket. It didn't seem to cause any problems and the engine ran very well for many years. I don't know that I would recommend it if a proper sized gasket was available, but it seemed to work.

Think I know the problem after listening to a buddy who was using a straight edge on the block & head.
The liners aren't protruding from the block enough. Will know tomorrow when I can take a look at the car.
Thanks,
Harry