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#1
H75 Head 'Low compression head, bigger combustion chamber' True or False?
clyons8
Posted on: 2010/6/5 3:25
I finally got around to cc'ing my H75 head to see if it is in fact of larger capacity than the H89.
So it turns out it the combustion chambers are larger than a H89, but only by 2cc (that is assuming the H89 29cc measure is in fact correct). So in reality it isn't THAT much of a lower compression ratio head. People go to the effort to source these head specifically for forced induction suitability. Is the 2cc really worth the hassle? I have a H89 here that I can check but it appears it may have been milled at some point in time. I did the test using a CD case cover with a vent and feed hole drilled into it (which I should have drilled further apart!). I put grease around the edge of the chamber to get a decent seal and I pressed the case down hard onto the face of the head, I used a 10cc syringe to feed the oil. It was a little crude but it works (I've lost my acrylic cc disc). Does anyone see any errors with this method? The only variables I can see are spark plug and valve face. Chris Attach file:  10cc.JPG (169.05 KB) 20cc.JPG (172.65 KB) 30cc.JPG (186.14 KB)  
#2
Re: H75 Head 'Low compression head, bigger combustion chamber' True or False?
bige
Posted on: 2010/6/5 5:55
no thats fine chris, but kero is better then oil (thinner)just make sure valves are sealing good,put springs on. cheers ernie
#3
Re: H75 Head 'Low compression head, bigger combustion chamber' True or False?
ddgonzal
Posted on: 2010/6/5 6:10
So what was the measurement?
#4
Re: H75 Head 'Low compression head, bigger combustion chamber' True or False?
clyons8
Posted on: 2010/6/5 6:43
Hey Guys,
Yeah the oil was a little annoying as I had to tilt the head all over the place to try and chase the air bubble out. Kerosene would work better, cheers! Sorry the final measure was 31cc with stock/factory A14 valves. I'll do a second test later on just to confirm (& I'll put some springs on too).
#5
Re: H75 Head 'Low compression head, bigger combustion chamber' True or False?
ddgonzal
Posted on: 2010/6/5 7:42
I use water, easy to use with the syringe, and if the valves hold it overnight, you know they have a good seal.
Thanks for posting the CCs and the great photos previously.
#6
Re: H75 Head 'Low compression head, bigger combustion chamber' True or False?
clyons8
Posted on: 2010/6/5 9:44
No worries, if you want to use them then do so. I have the part number label on the box as well if you want some pics taken of that.
Chris
#7
Re: H75 Head 'Low compression head, bigger combustion chamber' True or False?
ddgonzal
Posted on: 2010/6/5 16:58
Yes please. I have updated the tech section: http://datsun1200.com/modules/mediawi ... series_Cylinder_Heads#H75
#8
Re: H75 Head 'Low compression head, bigger combustion chamber' True or False?
dattoman_1000
Posted on: 2010/6/6 3:13
I'm going to have to recheck mine now
My engine builder told me I had 24cc (H89) But I have larger valves
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