Jets to use?

[Richard050]

We are currently running a 408 Mopar stroker motor on 3/8 mile and 1/2 mile dirt tracks in a modified chassis. The carb has been a 750 Barry Grant sportsman with 98 jets in all 4 corners. We want to try a 825 Demon Carb which uses different jets. The Demon carb came with 161 jets in it but wonder if anybody has had any experience with this. The cam has 250 duration @ 050 and we typically run around 7000 rpm. We use alchohol for fuel. We would rather be on the fat side because we already know how to burn pistons.

Thanks for the help!!

[340king]

Typically, a methanol modified carb uses a set of holes in the metering block located just above the jets to augment the fuel supply to the venturii. This hole varies in equivalent jet size from manufacturer to manufacturer. They seem to range in the 70-90 range. I don't have any idea how to actually measure this, because the hole size is all you have to go by. Holley jets can be differing sizes and have the same hole size, because of shape induced flow. You should however be able to get in the ball park by measuring the holes in the older carb and comparing the measurement to a Holley Jet Size Chart. A super good indexed set of drill bits might do the measurement trick. Then you could add that number to the old jet size to see if it makes sense. If you are close, I would fatten up and be safe.