What would be better for my new combo, 575 or 650cfm?

[Great68]

Hi Everyone,

I know I know, it's ANOTHER carb question....

Anyways, I've decided on a new speed demon vacuum secondary carb, but unsure as to which will give me better performance, a 575 or a 650.

My new combo is as follows:

289, 0.030" over

Performer RPM heads, 1.90" intake valve

Performer RPM Air Gap manifold

Cam (noticeably lumpy, I still don't know the specs)

Tri Y headers, 2.5" H pipe into flowmaster 40's

C4 automatic, 3.25:1 rear gear.

 

[347Fastback]

I think the smaller carb is going to give you more torque and performance.... I am going to use a 650 on my 347....

 

[Red66GT]

How's your performance now? and what carb do you currently have?

I'm asking b/c I plan on getting the Performer RPM heads, intake and cam on my 289. I'll also most likely be getting some tri-y headers like you have. I'll be using my Edelbrock 600cfm.

Anyway, just curious as to what I may be able to expect over the mostly stock set up I have now.

 

[Great68]

Well, my old combo I was using the stock 68 C code heads, Offenhauser dual port intake, and an old Holley 600 cfm 4160 carb. With the same bottom end and cam, I pulled 200hp at the wheels on the dyno. The old carb was tuned perfectly for regular driving, never bogged nor stumbled. It ran rich in the upper RPM's (5000+) Metering plates suck.

Can't comment on the performance now, because I'm putting the new heads on as we speak!