I got a set of GT40p heads from a 2000 explorer the other day. I plan on a cam swap when i put the heads on my engine. I am runming a 500 cfm Holley 2 barrel carb right now on my stock 77 intake. Would i gain anything by changing to a four barrel intake and using an adapter to keep my carb. I'm already running full length headers. I haven't decided on a cam yet, I figure I can pick what cam I want from the other fifty millon posts about what cam to use with gt40p heads.

 

If you want to go through the trouble of replacing the intake with a 4bbl, you should also replace the carb with a 4bbl to realize any benefits. You can get better gas mileage as well as more power that way. Otherwise, leave it all 2bbl.

 

I agree. Go whole hog or don't go at all.

 

There will be very little benefit to the 4V swap unless you are modding the cam etc.....

 

The 500 cfm Holley 2 bbl is exactly half of a 750 cfm double pumper Holley 4 bbl. As for whether or not to swap to a 4 bbl intake, that depends on what 4 bbl intake you're talking about. If you swap to an Weiand Action Plus or an Edelbrock Performer, then you may as well keep the stock 2 bbl intake. I would go futher and swap to any of the following intakes: Ford A321, Edelbrock F4B, SHelby "Cobra" (these are all basically the same intakes) or Weiand Stealth, Edelbrock Performer RPM, or Air Gap RPM. You could then keep the 500 2 bbl and later swap to a 4 bbl carb, but keep to nothing larger than a 600 cfm carb. The smaller a carb's cfm rating, the better throttle response you'll get on the street. A bigger cfm only nets you more power on the top end, at the detriment of the bottom end.

 

In my original post i stated that I am upgrading the heads and cam.

I like my two barrel carb and its only a few years old so i'd like to keep it for now. I just didnt want my stock 77 intake to keep the engine from breathing after the upgrades.

 

Yes, but what are the specs......

The above poster is absolutely right on the mark with regards to intakes, etc......
That particular 2v carb is an excellent one....50cc pump, etc....the same as the 4V carbs and 2V's have been used in racing application (road) for many, many years....with the choke horn milled off, the 500 will flow 550+ cfm....a very common practice in the 60's/70's....and Holley even built a 650 cfm 2v (#6425)...
My own Mustang has been in the family since new had many oem mods (done at Shelby's shop) prior to delivery......without going into detail, the engine was rated at 306 hp (whether is really was or not none of us know for sure as this was one of the "standard" rating numbers that was "thrown" on special orders if you had part X, y & z)....and my father (who was a well known engine builder) had several friends who worked at the shop...and one of them did the assembly of the engine......because he & my mom wanted a little mpg out of the car, he called his friend, got the specific order number and ordered the car with a 2V carb....which we still have....it is an autolite that has been heavily modded with venturis big enough to sail a steamship through...but with my mom as the primary driver (hot rodder herself) she would consistantly get 21 mpg...of course that's back in the days od leaded gas & 105 octane. When I purchased the car from them a did a ground up rebuild, at the time, the rebuild kit for the carb was overly expensive...I bagged the carb and it is still on the shelf...I bought the 500 cfm V2, did some comparison calcs taking into consideration the design differences of the 2 carbs, rejetted with some other changes and the car runs plenty strong with an excellent idle...as close as one can get to the autolite that was on it...After the rebuld, my mom (before her passing while she was still full of vigor) drove the car for about a month....in Lake Arrowhead (mountains)...when I got the car back I asked her what she thought......her reply...
"It runs just like it did when it was new.....BTW did you put wider tires on it?"

I replied yes....but never asked why she inquired...

Anyway, IMHO, that carb (with tuning) can easily handle a cam duration (hydraulic assuming) of up to 290 and a lift up to 590 or so for street use application....so its a really good solid carb that will serve you....even with most street type mods.

 

4V not required for big power, but you might get a better manifold:

Ford 289 Engine Buildup - La Carrera Panamericana - Hot Rod Magazine

Short version: 352 HP, 316 TQ.

 

Beechkid, that was a pretty interesting post you wrote about your 2V engine (I assume a 289 hipo that was "Shelby-ized").

One cheap and cheerful possibility for JSutton: How about scrounging up a stock later 302-2V aluminum intake? I think they switched in 1978 or 79. You should be able to get one for little more than scrap price.
I don't know how the ports compare to the earlier iron pieces, but I assume are pretty similar. But you will save weight.
I did compare a 351W-2V iron vs aluminum intake some years ago and recall they were more or less the same in regards to ports.

Is your engine a 302 or is it a 351W?

 

I'm currently running heavily worked '69/'70 302 heads with a '69 16 bolt 4 barrel intake that was ported with a Holley 650 4bbl with vacuum secondaries. With the port job and gasket matching, and a rather large spacer and a RV cam, I picked up about 45 horsepower or so over the 2 barrel and the RV cam gave me some more bottom end. The '69 cast 4 barrel intake we put on the flow bench an it flowed similar numbers to that of the Edelbrock performer intake. The motor started as a '75 2 barrel 351 Windsor out of ranchero. I have a lot more done to it but that the intake setup I have. Flows a decent amount for what I need. With everything else done to it, it was dynoed at 310 horse at the crank.

 

get some dual quads on that bad boy! might as well put them on tunnel ram intake too!

 

Are you talking to the OP or me lol??

 

im talking to everyone with a gas engine!

 

I'd consider it if I was using it to race again lol

 

Two carbs ? I've got three on mine