I am building a new motor for my 68 ss.I have an edelbrock dual quad intake(low rise)and I don't know if I should run the edelbrock 500 or 600 cfm carbs.The motor will be a 496 with a set of the old L88 aluminum heads.The car has a 4-speed and 3.73 gears.Thanks Bill

ttt

Years back,a good friend of mine was running a pair of Carter 625's on a low rise Offy with his 455 Olds..motor was pretty mild,and it certainly ran very well.
With that in mind,I think a 496 with square port heads can handle 1200 cfm

Not to get into a big off issue discussion, but the adavatange to dual quads is velocity through the smaller diamter Venturi. A motor will still only consume just so much air. It is futile to assume a 350 motor with dual 500CFM carbs will actually see 1000CFM. A 496 motor also, will probably not use the entire 1000CFM. The 496 though will produce a very strong signal through those smaller throttle openings, that (and the KOOL :cool: factor) is what makes it work.

Bill,

I emailed you about this (because I checked my email before checking TC)...

I think Edelbrock recommends the 600s for the 454, and thats what I run on the 396, with no problems...

Tony,

The dual quad setup looks nice. I assume this actually sits a little lower than the high rise manifolds like an RPM or RPM Air Gap because you don't seem to have any clearance issues with the hood. I couldnot see in the picture real well, does only one carb have a choke? How hard was this to set up and tune?

I'm gonna throw something out here..... Something to dwell uppon...

Next time you have a typical Dual Plane 1X4 intake around take a look at it... look inside the plenum..
and how the plenum merges with the runners.... Then imagine the actual flowpath of A/F at various throttle openings.... from idle to WOT.... going through the entire fireing order....

Now do the same with the typical dual plane low rise inline 2X4 intake..... from idle... to part throttle on the primary carb... to opening the primary on the front carb ( progressive linkage )...then WOT with all 8 bbls opening.....

Then add in the effects of reversion ( especially on big cams )....

... Just something to think about.... graemlins/beers.gif

You could also use the holley 9776 @ 450cfm. It is a mechanical secondary, but with no secondary accelerator pumps. They are meant for tunnel ram and dual quad intakes. They are $190 ea from summit.

Thanks for your input guys.I have always wanted to try a 2X4 setup I know that a single 4 would work better but I wanted my motor to look old school like that 68 dick harrell chevelle that was in musclecar review a few years back.It had a 427 with 2X4 intake and it really looked cool.I don't think the holley carbs will work on an edelbrock intake the carbs are set really close together and the bowels on the holleys will hit.Thanks again Bill.

Does anybody think (2) 500cfm AFB type carb's would be better??

AND yes, old school COOL, imho......

pdq67

Here's something interesting...

Just got done working on my bud's T-bucket w/350 (as some of you know). And it has a tunnel ram w/2 Holley vac sec's on there. The #'s on the carbs were 4548, which translates into 450cfm vac sec. I though it would be kinda sluggish (tunnel ram, 2 carbs, etc). But I got her fired-up today and couldn't belive the throttle response. I didn't drive it though, but this thing sounded awesome. No chokes, just hit the throttle a couple of times, and start her up. The secondary vaccum pods were liked together via vaccum hose.

Wish my 454 was as crisp as that!

I got to park next to the Dickey Harrel car at my first Chevelleabration. Very cool.

Hmmm, I'n wondering if you could use side-hung bowls on the Holleys. Won't two Holley 600 cfms, or is it another bolt pattern?

650 DP Holleys work great on my little 427 with tunnel ram and L-72 heads. I'd think with Rectangle heads and 3.73 gears you'll be moving a bit of air, I'd go with at least 600's. I'd be more concerned with the top end flattening out too soon than loosing a few low end foot-pounds with that 496, it all depends on what your after.

Good Luck