Need some carb selection advice

[sniper]

Hey guys, I am wondering if any of you could assist me. I don't know a whole lot about carbs and how to select the correct size.

Here is the deal, the motor is in a 66' F100.
It has a built 460 with 11.5:1 comp.
The motor is set up to run upwards of a 500 shot. But plan to maybe do 250 possibly two stageing it.
It currently has a 750cfm edelbrock. The guy wanted it to just run out of the box, so that is what he purchased. And it did what he wanted it too.
I believe these are the cam specs;
-Basic Operating RPM Range: 2,000-6,000
-Intake Duration at 050 inch Lift: 230
-Exhaust Duration at 050 inch Lift: 230
-Duration at 050 inch Lift: 230 int./230 exh.
-Advertised Intake Duration: 280
-Advertised Exhaust Duration: 280
-Advertised Duration: 280 int./280 exh.
-Intake Valve Lift with Factory Rocker Arm Ratio: 0.530 in.
-Exhaust Valve Lift with Factory Rocker Arm Ratio: 0.530 in.
-Valve Lift with Factory Rocker Arm Ratio: 0.530 int./0.530 exh. lift
-Lobe Separation (degrees):

On the Dyno it made around 470 ft lbs at 4200 but only 298 HP and then the HP nose dives. And goes rich, If I remember getting to 12.1:1 or so on the wideband right where the drop off occurs.

If all that makes sense here is the question. I suggested that he go with a 950cfm carb, in either a proform, or holley. But I am not exactly sure (again not a carb guy) if that is too much cfm or if something else, smaller in the 850 range, would be better. Maybe a good quality, flowing 850 would be plenty, compared to the current low buckl 740 that is on there.

I hope that is enough make informed advice easier.

Preciate it, Mark.

[Teetoe_Jones]

Call these guys- Best carbs money can buy, and they will set it up to your engine:

http://www.pro-system.com/

Tyler

[Stang's Bane]

good lord that thing needs more cam. That is a baby!!!

What kind of heads are on there???

[sniper]

good lord that thing needs more cam. That is a baby!!!

What kind of heads are on there???

Is it? Guess that is why I don't build engines for a living. I think the heads are either the stock iron heads with a little work done to the chambers or they are 428 cobra jet heads. He has a 390 as well, so I am not sure which heads went on which motor.

BTW, he ordered an 850 from AED performance. They are supposed to have done a few things to it to make it flow better and what not. We shall see, soon.

[Stang's Bane]

If the HP is diving after 4200 rpm, it needs more cam and probably more head also. It is running alot of compression for that size cam. I would love to see a dyno sheet from it.

I wouldn't suggest putting the bottle on it until it breathes up top a little better. You are right about it neding more carb also. What intake is it running?? Single or Dual plane??

[Shaker455]

Sniper,
How did you make out with the AED carb?

I build custom carbs and I have tested and modified many AED units.

If you have any issues and they are not helpful let me know and I can advise you.
Jeff

[sniper]

Well, I cannot say for certain if the carb fixed the issue, we haven't had it back on the dyno yet. But, it dropped .4 at the track, similar conditions. Not sure about mph though which I would think would be a better indicator of how it ran down track. It ran consisent 7.61-7.62 all night at 87-88 mph. By the MPH I don't think it picked up much power up top that seems to be good for about 325 HP.

On the street the hesitation is gone in the 3500 to 4000 range, and runs good al around. The only noticeable thing now seems to be it loading up on fuel after coming out of a burnout.

I appreciate your guys help, even more so that it's for someone elses truck. Thanks!

[Shaker455]

Sniper,
There's alot of aspects to tuning not covered here and also how the carb is set up on the truck...

Float level and basic power tuning as well as technique can affect his performance in the box.