Need help picking a carb!


New Member
Aug 19, 2009
Lansing, IL
So heres my first post. I was referred to the site by stripped88hatch or something along the lines of that. I cant remember his name on here to save my life.

So heres my question. I need a new carb for my car and im not sure what to go with. The carb on my mustang is a holley 650dp with mechanical secondaries and no choke. The base plate is cracked and some jackass jbwelded it and i just now noticed it.

Im not sure what kinda carb to go with but heres my setup

Holley 650dp
Weiand Stealth Single Plane Intake
GT40P's decked 30thousandths and ported and polished
Roller Rockers. Not sure of the ratio as i bought it like this.
Full length longtubes
Mac pro chamber
Flowmasters to dumps
Aluminum Driveshaft
FRPP wires
MSD Blaster coil

I was told a 650 is to much for the car and go with a 600. I was looking at holleys but theres alot of them with vacum secondaries and i dont want to mess with the electronic choke deal. I was also looking at proform carbs as well. I need something that would be ok for daily driving but can do its job at the track which is very often.

Can someone chime in and help me out here? I dont know anything about tuning carbs either!
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New Member
Apr 2, 2005
Oakwood, GA
a good street-friendly carb? :p

my vote is for a 670 street avenger.

it has vacuum secondaries but still works great on a built up 302.

I had one on a motor I built with ported windsor jrs and a camshaft innovations cam and it made just over 300rwhp . . . a/f was perfect out of the box.


New Member
Mar 8, 2009
North Coast
650 should be fine.
Are you haveing problems with it now? (besides the crack)
You can down jet most holley's if needed and adjust just about every aspect of them if needed.
Some you can even just get a new body for them, and transfer the parts from your old one. (easier to get a new one)
I never noticed much difference between the 600's and the 650's myself.
One car did need to be backed off on the 650 because it was flooding, but after a few adjustments and a rebuild kit, it was fine.
I cant say forsure which to get, the 600 will save gas, but you may need the 650 for track use.
If i had to say, get the 650 and some smaller jets to change for daily use.

Tuning them is pretty easy once you learn what the parts do, and what can be done with them. Holley prints several books you can get, and im sure there is PILES of stuff on the net.


Apr 19, 2006
Okeechobee, Florida
I used a Barry Grant Speed Demon 575cfm on my 302, it has many of the same mods you have probably with a touch more. I used to have a Holley 650 and found it to be a bit large for street driving. Also as a rule of thumb mechanical secondaries are generally used on stickshift cars or auto trans cars with larger stall converters, vac secondary carbs are used on street automatics.


New Member
Aug 19, 2009
Lansing, IL
man thanks for the awesome responses. Some of the other sites im on i get some really stupid answers. You guys are really helpful.

With the car as it is now i do have problems. When i got to get on it, it spits, kicks and bucks. Then it clears out and starts to pull. I pulled cylinder's 1 &2 plugs and there dead white. The cars running really lean!

So i guess im going to stick with a 650 and im looking for something with mechanical secondaries. My cars a stick so i figure it help out. Its nice to be able to get on it and not have any hesitation.

what do you guys this of proform carbs? Im looking at a 650. Its a holley base with there own base plate and metering blocks.

im also looking at holleys hp series carbs.

Is a barry grant a pretty good carb?


New Member
Jun 15, 2004
Puerto Rico
650/750 Holley DP will work fine, my 302 junk has worked for the past 16 years with a 700 Holley DP that also required the jets size to be increased by 3. Another great option you could also check is Pro-Systems, provide Patrick with your setup info, and he'll build you the correct carburetor based on your needs/expectations..... just a thought.