Okay so today Me and my brother in law took apart the fuel bowl and saw what jet size i had in the ol' Holley 600 and i had 70 for a jet size we bumped it down to 66 it ran a bit better so we took it around for a drive. As we were driving my brother in law asked if my vacuum sec. were kicking open but go figure they only kick open around 2500 rpm which the truck is so low geared its never there so only the the primaries were kicking open.....sooooo my brother in law told me I could do one of two things I could change the spring for the vacuum secondaries or i could change to a Holley 500CFM 2 barrel which he said that could probably out perform the Holley 600 btw he has two Holley 500 to choose from.

Im sure what to do but... I wouldn't mind trying out a Holley 2bbl

 

The beauty of a vacuum secondary carb is that the secondaries only open when the engine is drawing sufficient air to pull them open. Opening them sooner won't improve performance and may actually make driveability worse. It doesn't sound like it's broke, so why fix it?

 

That's whats kinda drawing me from swapping the spring out. Tomorrow I might give the 2bbl a whirl see if i like it.

 

That's Holley's big 2-bbl, make sure the adapter you use has large enough bores.

You'll have to do something with the throttle cable/linkage too. The throttle lever on a 2-bbl is ~1" farther back (i.e. centered on the mounting flange) than a 4-bbl. With a Lokar bracket the stock cable wouldn't pull the throttle open more than maybe 1/3-1/2 way.

 

If I were you I would try to get an AFR gauge on the 600 and dial it in, tune the primary jets, the power valve, the acc.pump shot. Drive around with the gauge and a vacuum gauge on it and chart what it is doing when.

I'm certain that your brother-in-law is beyond reproach, but the fact that he just happens to have two Holley 500's for sale makes me suspicious of his reasoning and motive. With proper tuning you should be able to surpass your expectations with your 600 and save some bling$.

 

Haha I was thinking the same thing. funny thing I just bought a vacuum gauge today at harbor freight and I might be stopping the performance shop later today to see if I could get my hand on a secondary spring kit its only like 12 bucks i think.... my reason to changing the jets on the carb was because my spark plug get black and wet I smelled them and they don't seem to smell like fuel or oil but I do get a cloud of smoke that smells like maybe raw fuel or just fuel in general. I know I could get this thing running in tip top shape

Also I hooked up the vacuum gauge today after I got home and the engine is getting around 20 inches of vacuum which indicated normal motor

 

The great thing about Holley carbs is that just about everything is adjustable.

The worst thing about Holley carbs is that just about everything is adjustable.

If you think it's still running rich try a 4.5 power valve so you aren't stepping in it as much during daily driving. A smaller pump shot may help too.

You'd be better off getting the primary side cleaned up before you start fooling with the secondary spring.

 

"The great thing about Holley carbs is that just about everything is adjustable."

"The worst thing about Holley carbs is that just about everything is adjustable."

Truth has spoken.

 

Yeah I think thats what im gonna have to do I just took it for a spin this morning and when your driving normal its fine but when you have it in third or fourth gear and you hit the pedal she kinda hiccups and then picks up and goes.

 

It sounds like you may need a diff. acc.pump cam, one with a richer top end cycle. They are easy to change, but a bitch on a DP manifold. Let the engine cool and then lay cardboard under that side of the carb to catch the screw when it falls. Ck Holley site for graph of the various color cams.

If your secondaries are coming on around 2500 rpm that is about where you want them. They are the final added boost to each gear's rpm cycle. I would say to begin on the primary side. Wire shut the secondaries and worry about them latter. Tune your primary until your plugs are burning a nice walnut color. Read articles of how to tune a Holley. There are millions. Use a AFR gauge and a v.gauge to dial it in fine for peak performance and mpg. Drop down in your jets until you see performance suffer, then bump it back up. Once you get the primaries cracking, then open up the secondaries and do the same.

You mentioned your plugs were black and wet. I imagine you are extremely rich either on the primary or secondary side. I would PM AbandonedBronco about a good primary jet starting point when running a holley 600 on a 300.

Good luck.

 

Great thanks f250!