Kristian Jonsson
Donation Time
Are there any differences between the two kind of al-heads. I mean the inlet and exhaust channels. They appears to be the same.
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Enjoy.
The very late heads have single springs and no sparking plug tubes and the slightly larger chambers ( like a super subtle vizard profile)
The earlier heads have the double valve springs and for the SI the slightly smaller valves
Inlet ports are same size execpt for holbay heads which are a different animal all together
Important annotationThe very late head's valve springs are shorter in height, but the coils are stronger. I tried to install the taller, early springs, but there is a risk of coil binding with these later heads.
Jan
FWIW, in looking for info on my Holbay cam, I came across the Holbay H120 head spring specs. I thought I'd add it here:
Two springs
Free length: 1.584" inner; 1.694" outer
Length fit: 1.280" inner; 1.400" outer
Load fitted: 28.3 lb inner; 52 lb outer
Same two sources for the cam info I posted on another thread. The WSM.149 - Rapier H-120 supplement, and the Holbay company data sheet.Could we ask what your source was?