347...best carb question....

[synthartist69]

Hey guys,

I am having a 347 built and I wanted to get some opinions on what carb to run. I bought a new Holley 750CFM vac sec but am starting to question if it will be too much for this set up. Should I have went with a 650 vac sec instead. I plan on staying under 6,500 rpm.

This will be a street/highway racer....no dragstrip. Here is the set up...

1965 mustang GT350 tribute

347 block
Ford Racing F303 Cam
Hipo manifolds...for now (headers later)
Pro Comp castings
2.02 exhaust 1.90 intake
Performer Rpm intake
3.00 rear end
T5Z 5 speed

Thanks in advance!

 

[blown65]

650 would probably be better suited I'd think.

 

[synthartist69]

650 would probably be better suited I'd think.

Thanks for the opinion!

 

[woodsnake]

Have you got any plans for a rear end gear change, to match the cam? In regards to the carb question, I agree, smaller usually is better. If you can return the 750 and try to get the 650, I'd say try that.

 

[synthartist69]

Hey Woodsnake,

I am doing a t5z conversion with this 347 right now. It will have a higher 5th gear (.63) than the normal T5 (.68). Therefore this will give me a little room to go with a lower rear gear at some point. At the same time I want to keep my RPMS at 70 under 2300. Right now with the 4 speed and 3.00 they are 2600 at 70mph.

 

[S-Car-Go]

2600 rpms (at 70) x .63 = 1638 rpms with the new trans.

I'd go 3.55 or 3.40 at minimum

 

[robbz28]

I agree with everyone else, 650 would be better.....but I would like to throw in there that a step to a double pumper would just be oh so fun with that 5 speed

 

[jcode68]

When I got my 347 I asked e engine builder to suggest a carb and they (Coast High Performance) recommended the Holley Street Avenger 670 cfm, which is what I went with. I haven't dyno tuned the car yet, but runs very strong and the vac secondaries don't need much fussing. You will love the T5 also, best upgrade to date!

 

[woodsnake]

in my 68 I have a 3.50 geared rear end, and the car feels like it needs more gear. I'm planning the upgrade to a 3.73 here in the next month or two. The lower highway RPM's are a good idea, until you have to kick into 4th every time you need to get around somebody. With that motor and trans, you might be happier with a slightly taller gear....

 

[synthartist69]

670 street avenger?

What about a 670 street avenger for my set up? Pros and cons....

 

[robbz28]

Thats a good carb....why the oddball CFM who knows, but its a good carb, and you get a quick change secondary spring kit and its less (in many cases) than a standard 650 carb. I had one in my camaro with a 400 horse 350 in it, worked great streeting around...but I stand by my original post, a double pumper is more fun

 

[NMEMJCM]

I have a 347 with overdrive in my car too. I have a eddy 650 carb with 370 end gears. Perfect for freeways, and the car will still get out of its own way if need be. I have no problem goung to 6500. I prefer it over the 750 for street driving (the 750 is a bit much for the street, the car seems to run better with the 650). If your going to the track more than the street, bump er up to a 750 fwiw.

 

[synthartist69]

I have a 347 with overdrive in my car too. I have a eddy 650 carb with 370 end gears. Perfect for freeways, and the car will still get out of its own way if need be. I have no problem goung to 6500. I prefer it over the 750 for street driving (the 750 is a bit much for the street, the car seems to run better with the 650). If your going to the track more than the street, bump er up to a 750 fwiw.

I have never given an Edelbrock much thought, but you now have me looking at the 650. This may be the way to go...

 

[blown65]

I really don't think with his setup a 750 would be faster at the strip anyways.