Anyone know how to increase the CFM on Edelbrock Carbs?

[SUPERSTOCKRACER]

Well it seems that I have run out of carb on my 588 wedge and hemi and need to figure out how to increase CFM to get more out of them otherwise I'm going to have to go in a different direction, carb wise.
Same carbs on 3 different motors and going quite a bit bigger netted the same ET and mph. Almost to the .00
So I need to improve the flow of the Edelbrock carbs.
Any information and tricks are greatly appreciated.

 

[bobtile]

.

 

[SUPERSTOCKRACER]

.

Don't you have black bear to catch?

 

[Longroof]

No first hand experience, but what about milling off the choke horn for starters and maybe some epoxy on the top to help shape the entry... kind of like a race demon??

Not many people mod the AFB to where you want it to get to... Do you have to run the AFB for NSS rules?

 

[lewtot184]

i think about all you can do is play with the venturi sizes. you might be able to pick up .060"-.090" but thats probably it and i doubt there's a big flow gain. maybe it's time for some hilborn stacks sticking thru the hood?

 

[SUPERSTOCKRACER]

No first hand experience, but what about milling off the choke horn for starters and maybe some epoxy on the top to help shape the entry... kind of like a race demon??

Not many people mod the AFB to where you want it to get to... Do you have to run the AFB for NSS rules?

I have 2 pairs with the choke horns milled off and did not net any gains. yes I need them for some NSS rules plus i'm trying to keep the car nostalgic to some degree
I'm on a mission to keep the car in the 8's in the heat.

- - - Updated - - -

i think about all you can do is play with the venturi sizes. you might be able to pick up .060"-.090" but thats probably it and i doubt there's a big flow gain. maybe it's time for some hilborn stacks sticking thru the hood?

How much gain if any with the bigger venturi's is the question. Are these available through summit or jeg's. I might be worth a try.

 

[lewtot184]

the venturi enlargement will need to be done by you. i assume your using 800's. take the primary clusters out and take a good look at the venturi pinch point in the main body. sometimes there's some roughness from the casting that can be blended and an increase in size can be picked, but nothing great. be sure to keep the venturi smaller than the throttle bore size on the primaries to keep velocity up at the booster. maybe go out 1.56". the venturi for the secondaries is part of the cluster. i wouldn't be afraid to blend that close to the same as the throttle bore size, 1.75"; of course keeping the air valve in place. ever thought about working the intake for flow or having it flowed? carbs won't work any better than the intake.

 

[khryslerkid]

Put one of these under them

 

[lewtot184]

Put one of these under them

yep, strap one of these big boys on and forget about cfm; cubic yards!

 

[rumblefish360]

The problem with Venturi sizing, going larger is the butterfly plate needs to be reangled. This may not be a big factor in racing @ WOT.

SSR, I know not the rules so here is a dumb question. Does the carb have be a 4bbl.? Or can it "Look like" a 4bbl.?

You did already take a dremel to the boosters and make them narrower?
Debur, make smooth & Polish the the walls?
Make/install thinner blades? (butterflies)
Cut down the shaft on which the butterflies attach to?

 

[lewtot184]

the venturi (smallest cross section of the bore) is well above the throttle plate. the throttle plate plays no part in what i'm referring to. or, maybe folks don't understand what a venturi is?

 

[cdr]

find 2 of these 3 barrel carbs

The 950 rating was assigned to only one AFB, the so-called “trapdoor” or three-barrel 3636s used on the Pontiac NASCAR 421 super duty engines.

 

[SUPERSTOCKRACER]

the venturi (smallest cross section of the bore) is well above the throttle plate. the throttle plate plays no part in what i'm referring to. or, maybe folks don't understand what a venturi is?

Going to open a pair up tomorrow to see inside, isn't venture the top pieces held in with the 2 torx screws? Primary and secondary on top in the middle
http://www.edelbrock.com/automotive/misc/tech-center/dl/carb-owners-manual.pdf

 

[lewtot184]

Going to open a pair up tomorrow to see inside, isn't venture the top pieces held in with the 2 torx screws? Primary and secondary on top in the middle
http://www.edelbrock.com/automotive/misc/tech-center/dl/carb-owners-manual.pdf

the pieces your referring to are the clusters. the secondary cluster has the venture built in. turn it upside down and notice how the i.d. of the top is smaller than the bottom. the small i.d. is the venturii. the primary cluster is the booster, idle jet, and some air bleeds but not the venturii. the primary venturi is cast into the body. it's the narrowest point in the bore. primary venturii may have some casting flash that can be cleaned up. modifying venturiis isn't nothing new. there are holley hp carbs with modified venturiis out there.

 

[SUPERSTOCKRACER]

the pieces your referring to are the clusters. the secondary cluster has the venture built in. turn it upside down and notice how the i.d. of the top is smaller than the bottom. the small i.d. is the venturii. the primary cluster is the booster, idle jet, and some air bleeds but not the venturii. the primary venturi is cast into the body. it's the narrowest point in the bore. primary venturii may have some casting flash that can be cleaned up. modifying venturiis isn't nothing new. there are holley hp carbs with modified venturiis out there.

This might be a dumb question but can one of these carbs be made to flow 1050 cfm?

 

[DennisH]

Isn't Damon Kuhn supposed to know a thing or two about these carbs?

Dennis

 

[rumblefish360]

the venturi (smallest cross section of the bore) is well above the throttle plate. the throttle plate plays no part in what i'm referring to. or, maybe folks don't understand what a venturi is?

It is the whole shape, as I remember it, not the narrowest point. But hey, I could be wrong.
But to carry on, the butterfly needs to be enlarged if the bore size increases. That I think you understood, correct?

CDR is reading my mind with the 3 bbl. idea, but if he has to stay with the stock carb, that would be an AFB right? I do know they made a 3bbl. AFB, all 3 are hard to find.

SSR, what size carbs do you run now?

 

[SUPERSTOCKRACER]

SSR, what size carbs do you run now?

Edelbrocks 1412 800's AFB and I have a pair of edelbrock 800 thunder series 1812 AVS That i'm running now

 

[lewtot184]

It is the whole shape, as I remember it, not the narrowest point. But hey, I could be wrong.
But to carry on, the butterfly needs to be enlarged if the bore size increases. That I think you understood, correct?

CDR is reading my mind with the 3 bbl. idea, but if he has to stay with the stock carb, that would be an AFB right? I do know they made a 3bbl. AFB, all 3 are hard to find.

SSR, what size carbs do you run now?

the measured venturii is the narrowest point in the bore. it is there purposely to speed up the air flow around the discharge nozzle. it is at this point that the carb has the strongest air flow signal to draw fuel from the main well.

 

[SUPERSTOCKRACER]

the measured venturii is the narrowest point in the bore. it is there purposely to speed up the air flow around the discharge nozzle. it is at this point that the carb has the strongest air flow signal to draw fuel from the main well.

Do you think there's any chance you could get these to flow over 1000 cfm? I need more power and fast w/o going to dominators

- - - Updated - - -

here's my setup now