Carb size???? need some help

[1988broncoll]

I have a early 70's 302 in my 89 B2 It has a 670 cfm holly carb on it. It is a fairly stock motor with the exception of possibly having a small cam and it has a weind intake on it. other then that its stock right down to the points dizzy (will be changing that as soon as i get the extra cash) Anyway back to the topic I know this carb is over kill for this motor. What size carb do yous think would be best for it? I am going to be leaving the motor pretty much the way it is besides updating the dizzy once I get the money and that will pretty much be it.

 

[RangerFabWorks]

500 cfm is plenty, 600 would be good with a little more mods. 670 is way overkill.
i would go with an edelbrock. there easy to tune and are ready to run right outta the box.

 

[RangerFabWorks]

heres the edelbrock guide chart

http://www.jegs.com/pdfs/350carbchart.pdf

 

[baddad457]

The 670 is not overkill. It's only going to open the secondaries as far as the engine needs the flow. A 570 would give better throttle response, but the 670 is fine with your motor. Keep it unless you run across a really good deal on something smaller like a 570

 

[88mudder]

go with the Edelbrock 500cfm 4bbl, runs perfect out the box. I had a 650 on my 302 and it ran like horse shit, and no power. The 500 made a HUGE difference.

 

[Gotta_gofast]

The 670 is not overkill. It's only going to open the secondaries as far as the engine needs the flow. A 570 would give better throttle response, but the 670 is fine with your motor. Keep it unless you run across a really good deal on something smaller like a 570

Having a 4x4 B2, he's probably looking for good low-end throttle response. The engine will not draw enough vacuum for that large of a carb to meter fuel properly. Agreed, about the 570cfm Street Avenger from holley though. It is small enough that the near stock engine can draw enough air to meter fuel properly down low while giving him a little freedom to upgrade "go-fast" parts in the future without having to invest in yet another carb.


PS: The smaller carb will make tuning it WAY easier.

 

[baddad457]

Having a 4x4 B2, he's probably looking for good low-end throttle response. The engine will not draw enough vacuum for that large of a carb to meter fuel properly. Agreed, about the 570cfm Street Avenger from holley though. It is small enough that the near stock engine can draw enough air to meter fuel properly down low while giving him a little freedom to upgrade "go-fast" parts in the future without having to invest in yet another carb.


PS: The smaller carb will make tuning it WAY easier.

I ran a 3310 750 on a mild 302 and it was fine on the bottom end. Not optimum, but it was OK. The primary side of a 670 is 335 cfm, which is fine for a 302. And he can regulate the secondary side by a simple vaccum spring change, going to a heavier spring. That'll cost him about $10 for a Holley spring pack. Now if you're talking about a 650 DP carb that's a whole nother story.

 

[1988broncoll]

Im looking to replace the carb mainly because it has no choke and everything has been taken off of it for the choke and I am going to be using it as a DD. The truck right now with 3.73.s feels like trying to take off in a 2.9 until you get till about 30 then it really starts to move but one is the vaccum line for the trans isnt quite right and I want to get rid of the 70s points dizzy and go with a msd box and elec dizzy. I like holley products better then edelbroks personal opion

 

[Shran]

Fix the vacuum line first of all. Personally I'd also much rather go with a Duraspark distributor and module than aftermarket because you're not going to gain anything with a stock motor.

 

[1988broncoll]

ive never messed with the dura spark stuff. the vaccum line is ran into the back of the intake I think its the modulator on the trans. I can shift it manual good but on its own it is in 3rd gear by the time i hit 15mph and it doesnt down shift at all until i slow down to like 5 mph

 

[Shran]

Do you have the kickdown rod hooked up?

Duraspark is incredibly easy to set up...it's essentially a power wire and a ground for the module, and one other for the coil if I remember right. It is no harder than setting up an MSD system or whatever and you can find everything you need at a junkyard.

 

[baddad457]

Im looking to replace the carb mainly because it has no choke and everything has been taken off of it for the choke and I am going to be using it as a DD. The truck right now with 3.73.s feels like trying to take off in a 2.9 until you get till about 30 then it really starts to move but one is the vaccum line for the trans isnt quite right and I want to get rid of the 70s points dizzy and go with a msd box and elec dizzy. I like holley products better then edelbroks personal opion

Have you tried advancing the timing ? If it's set to factory specs (6*BTDC) there's one thing that's causing the poor bottom end. Advance it to 12-14* BTDC and that alone should wake it up. Replacing the points with a Pertronix unit (or any of the other drop in conversions) and adding a hotter coil will also help with cold starts. The 570 I have on my Ranger has no choke either. That was the first thing I removed. Cold starts and idles on it's own down to 25*F. If you still want a Holley choke, send me $10 and I'll mail one to you, I've got a box of em collecting dust in the shop.