More CFM

[vht]

I built 2 1405 eddy carbs for my bbc 427. Street wise the car ran pretty good, it was low compression, 8.5 to 1, hyd roller 650 lift, square port gm cast heads. I'm upping the comp to 10.5 to 1 so just wondering if I went with 2, 1407 750's if it'd help performance. I want to make some passes on the strip with it this coming spring and would like it to make some decent ets. The 600's were the first time I had any experience with the eddy carbs, seems like you need to go bigger with them compared to a holley.

[F-BIRD'88]

Yes 2 1407 750 carbs will make more power at WOT than the 600's on a Tunnel Ram. You will need proper gearing to take advantage of the upper rpm power gain, to see a track ET reduction , mph increase in 1/4 mi. acceleration.

[Tuner]

Try your 600s before spending any money on 750s. The 750 uses the same booster casting as the 600 but the minor diameter of the venturi in the body is about 5/16" lower, so the bottom of the booster is above the minor diameter, however, it should be below the minor diameter in the "vena-contracta" where the highest velocity of the flow is located, so the metering signal that 'sucks' fuel through the main jet accurately responds to changes in air flow when throttle opening or RPM increases or decreases.

Cliff notes: 750 eddys cannot be tuned to give the correct A/F in all throttle positions and RPMs unless something is done to make the primary booster longer to locate the exit of the booster about 1/8" below the venturi.

[mag2555]

If your not running a tunnel ram already the don't bother going up in cfm as your Intake is the restriction.

[F-BIRD'88]

You cannot tell if the 750's allow a quicker ET nor higher MPH 1/4 mile VS 600's without actually testing them on track.
They will make more WOT power. The part throttle afrs are close enough. They drive fine. even if not perfect.
There are many carbs that do not make perfect afrs at various part throttke positions. In fact most do not.
Yoyr gearing (if under geared for 1/4 mi will be more of a limit.. The hyd roller cam has to be able to stay in the game at higher rpms too.
BBC hyd rollers are notorious for power/rpm limit for getting real max perf. These will be factors in track perf.

This is also trye in reguard to the Edelbrock Dual Quad RPM hi rise dual plane manifold. The bigger carbs make more WOT power.

2x 750 holleys will make even a bit more wot on a bbc tunnel ram.. But the eddy 750's more than get it done.
Wether to cost of this change 2x (600 to 750) is worth it is debatable.
Either carb setup will require correct on track tuning
To max the et mph perf.

[F-BIRD'88]

If yoyr bucks are up try a pair of the new recent 800 AVS2 eddy carbs.. The primary booster is all different design (annular discharge type) and the secondary side air door opening rate flow rate is fully adjustable. No they are not too big.

[F-BIRD'88]

Again.
, if you are not going to gear the car to use all the engine power and rpm in high gear in the 1/4 mile you will never
see the gain in track perf et/mph that the bigger carbs capacity allows... details matter.

[F-BIRD'88]

If a potential 2/10th ET and 2mph gain is not critical to you
then stay with the eddy carbs you have and track tune them
in correctly.

[vht]

Thanks for the replies.