hemi head rework

#41
I had to widen pockets but did not deepen them. The valves are .180 longer hence the . 060 shims which gave me a .850 installed height. Stock hemi has shorter install height than regular head.
 

65ShelbyClone

Well-Known Member
#42
Dredging this up from almost three years ago...

Do you think a smaller cylinder would hurt the flow much? I just got a hemi head to experiment with on a GX140 because (I can't get the 60363 in CA and) the valve angle would allow larger valves to fit in the smaller cylinder (64mm) with less shrouding. I had already put a 28.5mm intake in the stock 140 head and it was really close to the cylinder wall, but there looks to be miles of space with the hemi.
 
#43
No idea but 212 is 70 mm so with a 64mm bore you would have a .140 lip under the head which may affect low lift flow but my guess would be not much. The other issue is the big chamber and small cc would have a low compression. If you mill the head you could close up the outer diameter of the head to 64mm to match the bore. May have to add valve notches if using a long duration or tight lsa cam.
 
#44
Ole,

I know this thread is three years old, but thank you for sharing all that information. I just got a serious education from you and a ton of practical information and tricks. If you don't mind me asking, what are you using for a flow bench? Is it a commercial unit or something you made yourself? I am asking as I have no doubt you have the skills to make one yourself
Ron.
 
#45
made it myself. It started out with plans from car craft approx. 1986. Since then have made many modifications but still use inclined manometer and motor box, and settling chamber. I would post a pic but since the upgrade I have not been able to post pictures.
 

65ShelbyClone

Well-Known Member
#46
No idea but 212 is 70 mm so with a 64mm bore you would have a .140 lip under the head which may affect low lift flow but my guess would be not much. The other issue is the big chamber and small cc would have a low compression. If you mill the head you could close up the outer diameter of the head to 64mm to match the bore. May have to add valve notches if using a long duration or tight lsa cam.
I'm not worried about the compression; it's going to be about right (6.8-7.0:1) for what I want to do. It would probably have to get milled down to the seats to get rid of the lip anyway.

I snapped this photo looking up through the cylinder if anyone was curious.



The stock head should be capable of 11-12hp in the high 6000/low 7000rpm range with 145cc and 8.5:1. It might be 10-11hp on gas with the low compression this one will have.
 
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