I have read several posts here lately that mention jet size and air quality in the same sentence. I know nothing about this. I will be mounting a Holly 850 dbl pmpr w/ mechanical secondaries on my 454 for racing here in Houston. Our air here is like soup in the summertime. It literally feels like a sauna during the summer with very high humidity. Will I need to re-jet my new carb for this tropical air ? I do not know off hand what size the stock jets are. This is something I can be doing while waiting to do other things. Thanks for any advice graemlins/waving.gif

High humidity means less available oxygen per unit of air. Water vapor doesn't burn but it occupies space. Less oxygen to burn means you need to lean out the carb.

John, in the past with my old 355 I would have to jet down 3-4 sizes (front and back) during the summer time. Jet changes are about as quick and painless as they come, I'd just run it box stock first then tune from there.

Texas70, let me suggest taking your car over to T&T Motor Sports and put it on their chasis dyno before taking it to the track. It is much easier and quicker to dial in your motor there first. They are the people in Houston that does the "hop ups" for the Vipers.

SS540 (Wayne) and I took my goat over there to dial in my roller motor and in an hours time we jetted and found the correct timing. Very quick and easy. Your final tuning should be done at the track as the chasis dyno will get you in the ball park.