Jarrid, I agree with you on swept vol, unswept vol, and published stock CR.
I "burretted" a similar near virgin AM3 head 6 yrs ago at 39.2. I used a 60 cc medical Syringe that I calibrated at 40 cc using a precision scale and water at 1 gm per cc. Furthermore using the factory stated 9.2 CR, and resulltant unswept volume of 52.6 cc here's a calculation
deck height 0.018" = 2.4 cc deck height volume
gasket thickness 0.025' and gasket diameter = 3.4" ( slightly larger than bore)= 3.7 cc
Piston dish volume = 7.2 cc (mean beyween 6.9 and 7.5 factory spec)
52.6-2.4-3.7-7.2= 39.3 cc
So I have confidence in my "burrett" measurements. And I used the same measurment method after adding the mod and measured 41.4 cc. After I had the head repaired and valves ground I found the vol was 42.4, except that the repaired cyl (re-welding some burned/ corroded area and shaving was 43.5 cc so I had to remove a lot more material from the other 3 chambers to make them even. I suspect that the Vizard mod done on your head may have been done more aggressively and with curved walls more like the stock walls, but not matching the profile in the Vizard dwg. In addition I suspect you had some valve work done which may have set the valves further recessed into the head- as was done on mine. I estimate/ calculate about 1.4 cc added due to the valve work on mine.
In Nathan's case, assuming my estimate of 2.2cc increase from the Vizard mod and loss of 1 cc due to previous and new head (not deck) shaving, that's a net increase of 1.2 cc over stock. resulting in 9.0 CR.
Tom
I "burretted" a similar near virgin AM3 head 6 yrs ago at 39.2. I used a 60 cc medical Syringe that I calibrated at 40 cc using a precision scale and water at 1 gm per cc. Furthermore using the factory stated 9.2 CR, and resulltant unswept volume of 52.6 cc here's a calculation
deck height 0.018" = 2.4 cc deck height volume
gasket thickness 0.025' and gasket diameter = 3.4" ( slightly larger than bore)= 3.7 cc
Piston dish volume = 7.2 cc (mean beyween 6.9 and 7.5 factory spec)
52.6-2.4-3.7-7.2= 39.3 cc
So I have confidence in my "burrett" measurements. And I used the same measurment method after adding the mod and measured 41.4 cc. After I had the head repaired and valves ground I found the vol was 42.4, except that the repaired cyl (re-welding some burned/ corroded area and shaving was 43.5 cc so I had to remove a lot more material from the other 3 chambers to make them even. I suspect that the Vizard mod done on your head may have been done more aggressively and with curved walls more like the stock walls, but not matching the profile in the Vizard dwg. In addition I suspect you had some valve work done which may have set the valves further recessed into the head- as was done on mine. I estimate/ calculate about 1.4 cc added due to the valve work on mine.
In Nathan's case, assuming my estimate of 2.2cc increase from the Vizard mod and loss of 1 cc due to previous and new head (not deck) shaving, that's a net increase of 1.2 cc over stock. resulting in 9.0 CR.
Tom
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