Let me first say that unless your intake is already matched to the 1233 then don’t bother!
A D port head can be reworked to flow 250 cfm before you need the added area of the 1233 gasket.
After you do the gasket match on the common wall side of the port then You can safely go to a with of 1.064” at the apex.
When grinding you want to try and keep the out bound side of the bulge a sharp edge / lip verticaly.
This will help to keep the fuel in the air mass atomized like it should be.
Opening up this pinch area depending on how much valve lift your running( and also if the rest of the intake runner) has been ported might only pick you up 2 to 5 cfm, but the main improvement will be your motors power band will be wider due to the air mass not having to contract and then expanded once again.
If you go to post #2 here and click on my second photo you can double expand it to see that I ground back right to the .030” wall 1/2” OD brass tube .
If your careful you should be able to come within .040” of that.
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I do stuff for reasons.
Last edited by 25stevem; 08-17-2022 at 02:18 PM.
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