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ChadS
08-07-2007 09:49:08
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Re: Venturi size in reply to Frank Y., 08-03-2007 21:58:08
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The venturi sits in the middle of the carb bowl, hour glass shaped on the inside. They have a 2 digit code casted into the very bottom of the venturi. Example is #27 thats measured in 27/32 of an inch. #29 is 29/32 and so on and so on. To find ou the actual size, divide the 27 into the 32 and that comes out to the bore size of the venturi. Cyl pressure,,, higher is best, but here is what you can see by taking a compression test. Remove the spark plugs, open up the throttle all the way, install the guage into the spark plug hole, and crank the starter. Should have full reading after 5-7 cranks. Average is 100-135 psi Good is 140-165 psi, great is 165 to 200 psi, and over 200 psi is considered excellent for making power. If your 298ci motor is 160 psi or better, would be 70 hp prety easy on a pto dyno. You did not mention before you were turning it at 3000rpm,,,, no way to measure it at 3000 rpm on a pto dyno. I still say a 27 wit the big bore carb you have should make a difference,,, but think of a cam grind if its still the stock M cam. A cam spec with a rpm target in mind, tried tested and true would be the next step. 450 cam would be good up to 2300rpm. Chad
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