4 barell CFM range

#1
Good day.
I have a 3.5 v8 150hp engine. I plan on a new 4 barell set up. Not decided on holley or edlebrock yet. Although the holley sniper is looking good.
Does anyone know what the requored CFM would be for a carb for this engi.e?

Thanks
 
#3
I've had trouble finding a Holley 390 - I have a Holley 450. Having the metering block as opposed to a plate (as on the 450) would be more tuneable I think. Sniper would be cool, too!
 

quattro

Administrator
Staff member
#4
I have a 4L in my car and did have the edelbrock 500, on a twin port JWR Offenhauser inlet manifold. I never did quite get it set up right though, and it is my opinion that the 500CFM carb is a little too large for the 4L, let alone a 3.5.

I know there are a few people on here who have it running well, but I couldn't get it spot on so I eventually removed it.
 

corazon

Well-Known Member
#5
Yes I agree, on paper 500cfm is too much for anything below the 4.6 really, but some people seem to be able to tune a compromise from them on the smaller capacities.
A lot of people use 500cfm on Ford 302s (5 litres) as another guide to sizing.
There are theoretical equations for working out correct CFM but real world results depend on so many factors as always.
Jim
 
#6
I done the maths. Cubic centimetes x max revs x 80 ÷ 3456 = apparently i need a 300 cfm carb. The 80 is based on 80% of something. Based on a standard set up engine.
I have looked atthe sniper and it learns your driving style and self tunes. This may be the option. I will do some homework.ework on it.
 

corazon

Well-Known Member
#7
The 80% is volumetric efficiency.
Ah yes the Sniper is EFI, could be interesting to see results. There are cheaper versions from FI tech and iirc Summit Racing have their own 4 barrel style throttle body efi setup too.
Apart from the reliability and ease of tuning, performance is unlikely to exceed a carb. You’d need a proper multi point injection system to make a real difference I think.
Still I have also thought about using one on my build. I have an edelbrock 500 for my 4.6 along with mappable digital coilpack ignition which I felt was a ‘best of both’ for my budget- time will tell!
 
#8
I used a 450 because the primaries are smaller than on a 350, so until you open the secondaires it's a smaller carb. I've yet to do a proper tune of the secondaries circuit but it runs just fine. I used to run a 600 on a 253 which was also fine once tuned. There's more to it than just internet maths.
 

ghce

Well-Known Member
#9
I have the Weber 500 on mine and it works very well. It was my understanding the way the 500 is built the full flow is not used until the secondaries are wide open giving you a more appropriate sized carb for the 3500.

Graeme
 

cobraboy

Well-Known Member
#11
On the front of the air horn is a list number. Once you have that simply google the list number to find out the carb details.
This will tell you how it started out from Holley.
You can visually see if someone has added a secondary metering block, which is the only likely major change from the list No.
Of course owners may have changed jets, power valve, secondary spring, etc, etc along the way.
 
#12
On the front of the air horn is a list number. Once you have that simply google the list number to find out the carb details.
This will tell you how it started out from Holley.
You can visually see if someone has added a secondary metering block, which is the only likely major change from the list No.
Of course owners may have changed jets, power valve, secondary spring, etc, etc along the way.
Mant thanks. And that will tell me the CFM also, yes?
 
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