My friend has a 68 coupe with a 302 out of a 72 Maverick. His uncle told him is jets were too big for the engine. He has a 4v holley with 350 main jets. Are those too big? I'm trying to help him.

 

hows it running? if its rich the jets may be to big. what are 350 main jets?

 

take it for a good beat run, then pull a plug, dark=rich, tan=perfect, white=lean. and go from there. this is assuming that the accelerator pump and power valve are correct and working properly.

 

Rich where? Idle, part throttle cruise, part throttle acceleration, WOT? And there are no 350 jets.

 

Last time I looked his jets were in the 300s size wise. His uncle told him those were too big for his car.

 

Holleys don't have jets that big. The biggest alcohol jet they make is a .200. Maybe it's an old numbering system they don't use any more.

 

I have a mild 289 with a 4bbl holley and I have number (main) 64 jets and they are just a touch on the rich side. number 62s are just a touch on the lean side. bet you can guess what jets I'm putting in next. 64s are a good place to start as they come on most out of the box street holleys but tend to be a little bit rich. I have no idea what a 350 jet is, but I know Holly jets corrrepond roughly to the drill size. i.e. a 64 jet is .064" in diameter. this doesn't always hold true because they are actually numbered based on flow not diameter. for a stock to mild 302 the jetting should be VERY close to what I have. to fine tune the jetting at cruse you can use a vacuum guage fixed in the car with you. adjust jets fr highest vacuume. then put fresh sparkplugs in the car, cruse for a mile or so then shut the car off while crusing. coast to a stop and check the color of the porcelen. it should be a light grey to tan. darker is to rich. white is too lean andbad fr your engine!!! hope this info helps.