Holley help

[Z06killinSBF]

So I've got a 750 Holley 4150 that was pieced together. After I got it installed and started, it wont run lower than 2500 rpm. When I mean lower, I cant hold the throttle shut enough to get it to idle down. The idle screw is backed out and the bleed screws are where they are supposed to be. The choke is wired open aswell. I suppose there is an air leak somewhere. I didnt build this carb and it was free. Motor sounds really strong with this carb so I would like to use it. It just jumps straight to 2500 upon start up. All vac ports are plugged. Ideas? TIA

[ZZ430]

The secondary throttle blades could be cracked open too far.

You could take the carb off, turn it upside down and adjust the stop screw.

A starting point would be to just close the blades, and then turn the screw in 1 turn.

[Z06killinSBF]

Ok, I'll try that.

[70bird]

Probably a dumb suggestion, but is the throttle cable adjusted properly and not holding the throttle open?

[Z06killinSBF]

Turns out the fast idle cam was catching on the carb base and was keeping the blades cracked open. So I took that off and it works great. Now I just need to adjust it as it's a bit rich.

[705.0Merc]

Is that on you 289? It will be way too big. I think you'll make more power and torque with the 600 holley. I ran an Avenger 670 holley on my n/a'd 302 and had to jet it way down, it was still way to rich. You could easily tweak the 600 for more power.

[Z06killinSBF]

I has smaller jets and smaller different parts. I'm not sure what all was done to it. I had a 600 Edelbrock that ran like crap from the get go. This actually seems faster this way. I'll have to save for a smaller Holley unless some one wants to trade.

[hotrodf1]

I has smaller jets and smaller different parts. I'm not sure what all was done to it. I had a 600 Edelbrock that ran like crap from the get go. This actually seems faster this way. I'll have to save for a smaller Holley unless some one wants to trade.

You can find decent used smaller carbs on eBay for little $. Everyone ones wants a 750 double pumper, so if you look for a 600 or 650, vac. sec., or double pump., you can probably find a decent deal, if you are willing to rebuild and fork out cost of a rebuild kit. One of the better carbs I have was given to me, I rebuilt it, removed the choke tower with a hacksaw and some carbides, and she works fantastic.

[Z06killinSBF]

I ended up pulling it off as it had an internal leak from somewhere leaking gas into the motor as it ran. Kinda added up to HORRIBLE gas mileage and rough running. I put the Edelbrock 600 back on it.

[Shaker455]

I can set up your carb and if you want swap for a 650 mainbody I can do that as well.

PM or email me

Jeff