I was wondering if you guys could give some input on your favorite carb for a 1970 302. I am putting on an edelbrock preformer 302 intake so input on four or two barrels is great!!

Can a 4 bbl get the same mileage as a 2bb?

Are there any advantages to having a 2bbl?

What size carb would you put on?

Any and all input appreciated!

Scott

ps. How many psi compression should this thing have? (1970 F100 totally stock 302)

 

Yes A 4 barrel can get you the same mileage or if you can keep your foot out of it even better than a 2 barrel, a holley 450 or 470 would be good or for fuel economy get an adapter and put on a rochester quadrajet from a 305 or 350. My bones stock f100 with a 302 has between 143 and 145 psi in each hole with 100000 miles on it.
Steve

 

Another carb to consider is a Carter 500.

----Patrick

 

In a lot of cases, you can actually get better gas milage when you use a 4-bbl. Let me explain.... Most V-8 2-bbls are about 500cfm, and most 4bbls are around 600cfm. The 2bbl is pumping out 500cfm all the time, but the 4bbl only pumps half what it is capable of most of the time, 300cfm. When you need the power, the vacuum secondaries kick-in and give you full 600cfm.

Personally, I love the Classic 600cfm Holleys. I buy them any time I see one at a swap meet cheap.
These have to be the most popular carbs on hotrods, and you can still get new ones for under $300...

Lots of aftermarket parts to fix them up with too!

 

would you use vacuum or mechanical secondaries?

Which is the most common?

Can i get one of these carbs new?

What do you guys think of the 575 Holley Street avenger?

 

Scott, what have you OR are you going to be doing to the engine?
An over carb'd engine will run poorly.

----Patrick

 

A spread-bore 4bbl will typically give the same or better mileage than a similarly sized 2bbl. Vacuum secondaries are better for mileage. The Rochester Quadrajet is the best carb ever devised by man IMO.

 

currently i have done nothing. It is completly stock. I plan on an edelbrock performer 302 intake, headers, dual exhaust. Depending on how all that works out i may have the heads rebuilt and ported exhaust side, larger valves exhaust side.

 

If you're doing all of that, then I would believe that a Street Avenger would work pretty good.
Are you also going to change the cam?

----Patrick

 

You will only want mech secondaries if you are running circle track. On the street if you floor it, it will just bog down if you don't have enough rpm's. you will also use more gas. Just installed Holley 600 on my 390, and was able to dial it in with a spring change on the secondary vacuum valve when it opens to full throttle. If you go that route, make sure you order the quick change kit for that carb. If you have to change springs with the carb on truck, you will be glad you spent the $7.00 for it. Don't know why they didn't put it on there in the first place. Carb with kits (both spring kit and quick change kit) was around $260 at jegs.com