What cc are stock banshee domes? Does anyone know how much they are if shaved 10 or 20 thousandths? My stock head is shaved 20 thou, and I just got a cool head and trying to use equivelent domes, or maybe slightly smaller for more compression.

 

i believe 20 or 22cc is arond stock! i used to run 18's on race gas and methanol!

 

I am pretty sure 20cc isnt stock, but 22 could be

 

I think 22cc is as close to stock as you can get.

 

I milled .040 ( Yes 40 thousandths ) off my head. That equaled 150 psi of compression. I have 19 cc domes on my vortech head 175-psi compression. I think stock is about 24 cc domes.

 

Here is the chart for dome sizes and compression, 22cc=stock


Approximate Cranking Compression

These pressures are estimates based on fresh stock bore, piston, porting, and deck height.

It is recommended to check your compression after installation.

Sea Level 1000' 2000' 3000' 4000' 5000'
18cc 197 178 171 170 165 145
19cc 183 167 160 158 152 137
20cc 169 156 149 146 140 129
21cc 156 145 138 134 128 121
stock 130 125 118 112 106 100

 

At one time, I remember measuring the stock chambers and I am pretty sure they were 23.5 cc's. If you shave 0.040" you get a 20cc chamber, which is good for pump gas. I had mine shaved 0.040 and my compression at 2000 feet was 145 psi.

BTW - if you're shaving off the head, you can calculate the amount of decrease in chamber size by using this formula.

CC reduction = bore in mm^2 X milled amount in inches X 0.02

the 0.02 is a conversion factor

for the Banshee if you shaved 0.040" (40 thousandths): 64^2 X 0.040 X 0.02 = 3.2770cc's

Shaving 20 thou gives you 64^2 X 0.020 X 0.02 = 1.638 cc's

I personally would not shave more than 0.040 off the Banshee head. You will start to impact the squish band in a bad way and beyond 0.040, I don't know exactly how far beyond, you could have piston contact with the head = bad, very bad. The guy I took it to locally (Screwie Lewie) wouldn't do it at first. He is an idiot. He recommended only 10 thou off - which is pointless. I told him that I would accept all responsibility if it did not work and I got it done for 20 bucks (I think). I made sure I measured the head thickness BEFORE and after sending it to him to verify that I got 40 thou off. It came back at 39 - no big deal. It's an inexpensive and worthwhile mod. Anyone saying you will overheat the motor is full of it. Run 290 - 300 mains in the dunes and you'll be fine. The 22 cc number is from ProDesign and it is not correct. If you look at their compression chart, it drops about 13 - 14 psi for every cc at sea level, then there is a 26 psi jump below 21 cc chambers. If you extrapolate the data, you'd reach a chamber of about 23 cc's. Like I said, I actually measured the chambers, and got 23.5 which corresponds to the 110 psi compression I had when stock.