Hi! i have a transam GTA 88 TPI 305 manual, looking to put new seals, some says i need the 0.341 and other says i need 0.344, anyone know for sure wich one i really needs?

 

The valves are 11/32" diameter when new... that's .34375". Might be a bit smaller now that they've got some wear on them.

That said, the .003" difference is about the thickness of a sheet of thin paper. Isn't going to make much difference to a piece of stretchy rubber-like material. Either is fine.

 

I just replaced mine with a new set of umbrella seals and o rings.
Intake and exaust valves used different sizes.
One set was black and the other had blue stripes on them to show
the different sizes.

Cured hot starting oil puffs and minor smoke at idle.
Uses no oil between changes now even with 180k miles.
Best $40 bucks I spent on this car.

Bought a name brand set off rock auto..........

 

yeah thats summit racing that made me question myself, i bought the good felpro kit SS72527 wich are .344, then if you check for the 88 transam on summit, they give you the part MV1888 wich is .341 and description for ss72527 is for 90 to 92, dont know if i can trust what they saying because they even sent me the wrong distributor kit heh, i already bought ss72527 for stem pos and ss72526 for the exhaust

 

I just went to my local machine shop and got 16 from seals from their head guy. I got the silicone "rider" style seals rather than the stationary ones that attempt to clamp to the head at the base of the stem. No o-rings under the keepers and no exhaust rotators.... zero oil consumption. I would say these new style seals work great. Should last a long time being silicone.

There are a LOT of different seal styles that can be used successfully. I went with most common sense and best/newest material construction for longevity. Things have improved since 1988.

GD