anyone know what the procedure was for fitting valves 44 in 38 ex as the factory used back in the day,did they have to adjust the angle,and was there a great advantage over 41/36 as on the 750,s.Just curious as to the work involved.

Well, I have a VERY limited knowledge of these. But from what I have seen they were used on very big bores, such as 92mm. I say that because they also widen the chamber to about 104mm from the 100mm used for the 88 and 90mm pistons. I tested the valve angle with a cardboard cutout, and they are still same as all Pantahs, 60 degrees I believe. I see no evidence of moving the valve guides. But they used very short guides. It looks like they just ''hogged out" the ports the old-fashioned way back in the day, and went for volume, rather than velocity. Obviously, they used really big Malossis. Here are some photos of two sets I have had in my possession. MikeV

PS: I remember Pat Slinn said that the Rutter TTs ran best on a 42/37 combo, and J Precision now uses 42/36 on the heads they modify.

Very interesting,thank you,love hearing how they done things back in the day. If only there were sufficient motors about nowadays for us to play about with,but the rareness perhaps makes them more unique.Just how far we stretch them today is a little tricky as finding replacements can render a bike useless.But its all good fun.

No wonder it doesn't rev

Yes, I noticed on your other post that you have VERY big pistons, and small valves. But trying to get those heads reworked in two weeks seems impossible. Good luck. MikeV

PS: I think there was a misprint in the article when it stated that the valves were 42/44! Never heard of that kind of valve setup.

Mike V,

I am guessing that in order to have proper valve to valve clearance on the heads pictured, the valves had to be sunk into the heads. Was material removed from the combustion chamber to keep the valves from being shrouded? I know that in the more modern bathtub style heads the combustion chamber is much deeper than the early stock pantah heads, which requires the use of the shorter valves and guides that you mentioned. Just wondering if the early hemi style chamber heads with big valves had a deeper chamber as well.

Dave

Yes, Dave, they mill them longer, wider, and deeper after welding up the plug hole. They are not true hemi, nor bathtub, but something in between --- elliptical? If you look you can see the milling marks on one head. MikeV