Holley Jets

[milomilo]

I have a Holley 4bbl on my 390 and I am planning on reducing the jet sizes 2 sizes down based on my elevation of 4K ft. The numbers on the airhorn are:

80508-3
2048

I used my cheaters and still was confident I got the numbers right. If they do not makes sense, I will get out the magnifying glass and the cheaters and try again. I am looking to find out the stock jet sizes for my carb so I know what size jets to install. Can anyone tell me the stock jet sizes?

[Indy63]

Bookmark this:

http://www.holley.com/data/TechService/ ... isting.pdf

You're toward the bottom. Looks like 72s on the primary side and a 134-21 plate for the secondaries.

Has anything been done to the 390? That 750 is definitely on the big side, especially if it's mostly just a driver.

[milomilo]

Bookmark this:

http://www.holley.com/data/TechService/ ... isting.pdf

You're toward the bottom. Looks like 72s on the primary side and a 134-21 plate for the secondaries.

Has anything been done to the 390? That 750 is definitely on the big side, especially if it's mostly just a driver.

I got the truck forma guy who got the engine from a deceased person so no info on the carb work if any. Your right about the size of the carb. It is too large for me and it sucks a bit of fuel too. I know where I can trade the 72 jets for a pair of 70s. The hard part will be getting a secondary plate the right size. Are the secondary plates sized the same as the primary jets, i.e., 134-19 plate for two sizes down?

Thanks for the link.

[Indy63]

Check this out, especially post #9. You can drill and tap the metering plate to accept standard Holley jets.

http://www.hotrodders.com/forum/seconda ... 50145.html

Have you thought about trying to buy/ trade for a 600 cfm carb? Good working Holleys/ Edelbrocks go for about $100, and I'm sure you could find someone willing to trade for your 750.

[milomilo]

Check this out, especially post #9. You can drill and tap the metering plate to accept standard Holley jets.

http://www.hotrodders.com/forum/seconda ... 50145.html

Have you thought about trying to buy/ trade for a 600 cfm carb? Good working Holleys/ Edelbrocks go for about $100, and I'm sure you could find someone willing to trade for your 750.

Yes, I have thought about getting a 600 Holley with vacuum secondaries. Maybe someone here wants a trade??? Thanks for the link too. I still would like to know which metering plate would be two sizes down form mine if you know.