What size holley carb?

[mikemcvaney]

Thinking of buying a new carb car currently has 650 dbl pumper spreadbore repalcment holley. Want a regular base holley 600 or 650 dbl pump any suggestions? mike mcvaney motor is far from stock.

 

[turboc87gn]

Quick fuel 1050 :biggrin:

 

[WarWagon]

Quick fuel 1050 :biggrin:

NO NO NO

Mike this is the formula for carb cfm requirement:
Cubic in X MAX RPM / 3456 X VE VE=volumetric efficiency
for NA use .85
for high performance NA use 1.1
for boosted use 1.5

So 231X6000/3456X1.5 = 601.5
So a 600 cfm carb is just under the requirement and would IMHO would get the best mpg's, throttle response, kill oil less.
a 625 or 650 might net a high HP at the top but that's it.

 

[mikemcvaney]

NO NO NO

Mike this is the formula for carb cfm requirement:
Cubic in X MAX RPM / 3456 X VE VE=volumetric efficiency
for NA use .85
for high performance NA use 1.1
for boosted use 1.5

So 231X6000/3456X1.5 = 601.5
So a 600 cfm carb is just under the requirement and would IMHO would get the best mpg's, throttle response, kill oil less.
a 625 or 650 might net a high HP at the top but that's it.

Thats kinda what I was thinking now do you think a double pumper i or a vaccum secondary would work better . I was thinking a vac sec. with a rear metering block off of a 780 vac sec. this would give me better secondary metering but it does not have a power valve, so it does not need to be boost referanced on both sides only the primaries. what do you think Adam ? or should I just get a 600 double pumper. Mike

 

[mikemcvaney]

Quick fuel 1050 :biggrin:

I wish it was that easy need to buy a fuel injected car LOL Mike !

 

[dr_frankenstein]

your not going to like that regular base carb.

your spool wont be as even and linear.

but..... I run 750.... so 650 sounds about right.

A.j.

 

[charlief1]

Considering that the original Q-jet is rated at 800 CFM either one would work but I have to agree with Aj 100% on this. Use a spread bore carb.

 

[mikemcvaney]

Can you get adjustable float bowls for a spread bore holley? have never seen them

 

[charlief1]

Unless it's an econobastard then it's all the same.

 

[WarWagon]

All spread bore Holley's have side hung float bowls and are not externally adjustable.

 

[dr_frankenstein]

All spread bore Holley's have side hung float bowls and are not externally adjustable.

not entirely true good sir.

they do exsist..... I have a center float myself.

however the bowls are not interchangable...... so dont get any ideas about swapping goodies. Be patient.... and watch ebay... you will find a decent core with the centr hung bowls. its just a matter of time.

A.j.

 

[WarWagon]

ok then I've never seen 'em.

 

[WarWagon]

Not like I go looking for a bunch of spread bore Holley's anyways, lol

 

[mikemcvaney]

Freds olds ran a non spreadbore holley 3310 with the secondaries sat limited he has the fastest b4 black engins must not of hurt his car much. Mike

 

[charlief1]

True, But Fred stated that he couldn't open the back butterflies all the way without issues. It has to do with building boost and timing of the secondaries. A spread bore will reduce the issue to some degree.