Need to re-jet the Holley

[animal]

I am NOT a carburetor guy...period. They baffle me. But I need to re-jet the Holley in my Ford. When I bought the car, it had a worn-out 390 FE motor wit a brand-new Holley 600. I sold the FE, kept the Holley. It's on my box-stock roller-cam 5.0 small block now. The engine runs great, but rich. The car was jetted for a FE in San Antonio, and is now on a small block @ 7,600'.

Where do I start with jets as a ball-park size. I realize I'll need to play around a little to hit the optimum setup, but what sizes should I get to have on hand? I haven't looked to see what's in there yet, because I want to have jets in hand when I start.

 

[Old Iron]

It makes it impossible to suggest jetting, without knowing what jets are in the carb to start with.
You'll most likely have to change the power valve too.
At a guess, Holley usually ships the 600's with 64 to 68 jets front and 68 to 72 jets rear. Move the fronts to the rear and install something like 60 to 62's in the front.
Check the vacuum on the engine at idle and install a power valve that is one and a half to two numbers lower ie. (engine vacuum at idle 10 install a 8.5)
Remember, this is where I would start.
If the engine has ever coughed back through the carb then, the power valve is most likely blown causing the rich run.

 

[lowbudget50]

It makes it impossible to suggest jetting, without knowing what jets are in the carb to start with.
You'll most likely have to change the power valve too.
At a guess, Holley usually ships the 600's with 64 to 68 jets front and 68 to 72 jets rear. Move the fronts to the rear and install something like 60 to 62's in the front.
Check the vacuum on the engine at idle and install a power valve that is one and a half to two numbers lower ie. (engine vacuum at idle 10 install a 8.5)
Remember, this is where I would start.
If the engine has ever coughed back through the carb then, the power valve is most likely blown causing the rich run.

X2!

 

[sgtpontiac]

Not that Holley carbs are notorious about popping power valves or anything...LOL...
Pop off the float bowls and take a peek... see whats in there and and start dropping it down...As OI said, that power valve could be your issue...

 

[ssimpala]

These guys are probably smarter than I am, but a 600 sounds too small for even a 5.0 at that rpm. My Boss 302 performed well with a 780.

 

[Dr Crankenstein]

ssimpala: He's at 7000 feet elevation, not 7000 RPM. (With respect and admiration, I'm sure your 780 worked well on a screaming Boss 302! [cl)

Contrary to popular belief, "too much" carburetor is better than not enough, within reason, IF you know how to tune it.

animal: Find your list number. It should be stamped on the air horn...

When you have the number, look it up on this chart...

https://documents.holley.com/techlibrary_carb_numerical_listing.pdf

The chart will tell you which jet(s) it was built with... it'll also tell you if you have a 4150 model (metering blocks both primary and secondary) or 4160 model (metering block primary, metering plate secondary.)

If you have a 4160, the secondary metering plate has drilled (fixed) orifices for idle and jet size... if that's the case, you'd have to change the plate to change jet size... or, convert to 4150 with an expensive kit.

Otherwise, I agree with OI. Tune your primaries first as he described...


.

 

[ssimpala]

Dr. C, thank's for politely pointing that out to me....some of you guys know I'm officially "brain dead" or almost anyway, but I can't for the life of me figure out how I missed the altitude instead of rpm thing. Oh well, at least I'm here.

 

[sgtpontiac]

Maybe just fork out 1000 bucks and try one of those EFI set ups...
Then it will tune itself for ya... Dr. you are correct on the fixed jets.. not being a big Holley fan, I could stand to dive back into a few to re familiarize myself with them...

 

[animal]

A friend has offered to help. I may leave the carb as-is for the Dirt Drags if we find I need jets that none of my acquaintances have on hand. There is not one part store in my area that carries any. By the time we figure out what sizes we need and I wait to have them shipped, it may be too late to make the change.

The car runs great as is, so it won't be a huge deal. I just want to get it closer to where it needs to be before I drive it thousands of miles this summer.

Thanks to everyone for the suggestions, advice, and the nifty chart! I'm back to work for a month or so helping out a friend, so don't get much time to check in here. Thanks again.

 

[05snopro440]

I bought my carb used off a friend, and the jetting was all screwed up. I found the easiest was to put it back to what came in the carb from the factory and then tune it from there.