how much cfm in a carb should I be looking for?

[67mopr]

408 stroker 2800 243 HP and 458 LBS Torque..4200 RPM 406 HP 510 Torque. 5700. 492 HP and 442 LBS Torque. And I'm running a Holley 670 street avenger per engine builder. There's times I think about a bigger carb. But except for some idle adjustment I think it does pretty good.

 

[T-N-T]

408 stroker 2800 243 HP and 458 LBS Torque..4200 RPM 406 HP 510 Torque. 5700. 492 HP and 442 LBS Torque. And I'm running a Holley 670 street avenger per engine builder. There's times I think about a bigger carb. But except for some idle adjustment I think it does pretty good.

If you don't mind me asking, I was wondering if I could get some details on your engine? cam, heads compression and such. That sounds like what I need power wise.

 

[winstoninwisc]

so rev it to its potential = if your going to run 7ooo rpm, then tune it from top of stall
buzz it to 7k rpm kill ignition at flat 7 k read your plugs . more air + more fuel = chit if it cant expel the combustion a lean 650 will blow the fat 750 if it cant burn the fuel
and get it out out quick enough to reload the cylinders . A dyno read on an engine can be way different than a read at the end of your exhaust system at wheels. air and gas =
what the flow will handle not just the engine . just my1 cent worth

 

[midnight340]

so rev it to its potential = if your going to run 7ooo rpm, then tune it from top of stall
buzz it to 7k rpm kill ignition at flat 7 k read your plugs . more air + more fuel = chit if it cant expel the combustion a lean 650 will blow the fat 750 if it cant burn the fuel
and get it out out quick enough to reload the cylinders . A dyno read on an engine can be way different than a read at the end of your exhaust system at wheels. air and gas =
what the flow will handle not just the engine . just my1 cent worth

Now this just makes sense to me!!!!

 

[RogerRamRod]

Mind Blown.
All that information in just 3 sentences.

 

[273]

Answering another post I think I may have figured out our problem of formulas, rule of thumb and running 1050 carbs.

One we're going by stock flow numbers which are rated by a vacuum of 1.5 but at vacuums above and below that will actually change the carb cfm.

So say the formula is right and say the cfm needed is a 750 but that's not necessarily the carb sizes but what engine will consume at peak power.
(These numbers are not meant to be mathematically correct) So you have a 500/750/1050 carb to try on our imaginary dyno. So we first try the formula recommend 750 carb and it has a vacuum of 1.5 at full throttle and makes a peak 500 hp. Now we try the 500 carb and we lose a bit of power 475 hp and vacuum goes up to 3 cause it's more restrictive. Next we try the 1050 carb and now make.525 hp and vacuum goes down to .5 cause it's now less restrictive.

So if you take out the variable of pumping lose or gain of hp cause of the carb restrictiveness. I bet all three carbs would move about the same amount of air since 500 hp within a small range needs a certain amount of fuel and air. So basically any carb you put on will flow the 750 the engines requires I think the trick here is how big (less restrictive ) of a carb you can go before it can't do its job properly.
Just thinking out loud here


P.S. some drunk tried to rip me off while driving cab and smashed my car door off my leg as I wrote this waiting for the cops cause he was too drunk to pay lol

 

[autoxcuda]

Ok , lets use your own formula.....he said 360 stroker so probably 4 inch arm so say 408 cu in.....say max RPM he wants is 7000 / 3456 = 826.39 Seems to me 850 is right on the money...not too big even using your own formula...and you say add 25% for race application is another 206 cfm is 1026CFM for a 408 stroker whats up with that? So a 1050 Dominator you are saying should be OK for his 408 twisting 7000 RPM in a race application and wait, he only has 450 horsepower? You said it was too much for a 525 HP engine

A 450 hp 408 stroker wont see 7000 unless it's completely over rev'd.

Peak is going to be somewhere between 5800 and 6200.