Is the Combat Wombat head and the Super Combat head the same? The difference in the part numbers is 952501 vs. 972501.
Can a Combat Wombat head be used with the Super Combat cylinder and piston, or is there a difference in squish sizes? Are the Two heads the same or is it like the Ace & Super Rat differences?
A friend was offered a Super Combat cylinder and wants to put it on his Combat Wombat motor. I told him we need to find out if the CW head is compatible with a Super Combat cylinder & piston combination.
In terms of "bolting on", the two heads in question are interchangeable . . . HOWEVER, in terms of function they are not interchangeable.
The Combat Wombat head's combustion cavity is sized to provide approximately 150psi compression with a compression stroke of 28mm. (it is 28mm from the head gasket surface down to the top of the exhaust port in the Combat Wombat cylinder)
The Super Combat head's combustion cavity is sized to provide approximately 150psi compression with a compression stroke of 26mm (it is 26mm from the head gasket surface down to the top of the exhaust port in the Super Combat cylinder)
Soooo . . . a Combat Wombat head on a Super Combat cylinder will result in low compression . . . and a Super Combat head on a Combat Wombat cylinder will result in excessively high compression.
Ed is correct in that a super combat head on anything but a Super combat will result in too much compression,unless the exhaust port is raised to compensate. However a 95 or 03 head on a 97 can work quite well. I sometimes use an 03 head on my cylinders that have 97 exhaust port timing . I do run a 10 thou copper head gasket that compensates a bit but it’s still lower compression than a stock
97 by about 10psi . I find the lower compression let’s the engine rev better although there is a bit less bottom to mid , at least that’s how it feels.
So you won’t do any harm using a 95 head on a 97 cylinder however I would advise using the thinner head gasket. Stock is 20 thou. See how you go.
Third. Thanks for the “practical experience enlightenment!” I’ll let my friend know. And recommend a thinner head gasket. Where can they be obtained? Victor
I had an interesting discussion with Danny Cooke about cylinder heads! He told me the Road Toad heads were the same stock as the later 125 heads! The only difference is the squish area was milled out smaller for the 100 cylinder. But, the good news is the Toad head has the same bolt pattern and can be machined out to use on a 125 cylinder. There’s enough metal there in the head to machine it out!!! He gave me the name of a company who can do the machining but I didn’t write it down. I’ll have to contact him and get their name again! Victor
Victor