sbc heads and flow.

Tech Related Discussion

sbc heads and flow.

Postby mcdonnough bros » Thu Feb 28, 2013 10:23 pm

Ok. at what point will head flow not be your friend. I see some of the heads advertised to flow 420@.900 and then some of the sb2.2 claim 450 @???? With say 434 inches when would the intake flow numbers actually hurt the performance I guess my question is how much flow does a sbc need/use is a 434-440 inches ? Is this something that is based on say rpm or horsepower goals. Thanks just gatherin info for personal reasons.
mcdonnough bros
 
Posts: 1
Joined: Wed Jan 23, 2013 1:10 am

Re: sbc heads and flow.

Postby Chad Speier » Thu Feb 28, 2013 10:40 pm

mcdonnough bros wrote:Ok. at what point will head flow not be your friend. I see some of the heads advertised to flow 420@.900 and then some of the sb2.2 claim 450 @???? With say 434 inches when would the intake flow numbers actually hurt the performance I guess my question is how much flow does a sbc need/use is a 434-440 inches ? Is this something that is based on say rpm or horsepower goals. Thanks just gatherin info for personal reasons.


Every engine has a cfm demand. Too much cfm and that means the head is too big for the combo. I will post the formula tomorrow.
Chad Speier
Image
Chad Speier
 
Posts: 1846
Joined: Mon Nov 12, 2007 6:03 pm
Location: Hays, Kansas

Re: sbc heads and flow.

Postby jmarkaudio » Thu Feb 28, 2013 10:43 pm

below
Last edited by jmarkaudio on Thu Feb 28, 2013 10:53 pm, edited 1 time in total.
Mark Whitener
Image
____________

Good work isn't cheap, and cheap work can't be good.
jmarkaudio
 
Posts: 605
Joined: Thu Nov 29, 2007 9:58 pm
Location: Florida

Re: sbc heads and flow.

Postby jmarkaudio » Thu Feb 28, 2013 10:52 pm

On a 4" stroke plan to turn the SB2's 7000-8500. They will still work lower, just wouldn't be ideal. However, also look at the fact that the winning Engine masters engine was a 406 with SB2 heads and had to pull very low, the right cam can make a difference. I think they started around 4000 RPM, and the engine had a billet carb with a 2.400 throttle blade... :shock:
Mark Whitener
Image
____________

Good work isn't cheap, and cheap work can't be good.
jmarkaudio
 
Posts: 605
Joined: Thu Nov 29, 2007 9:58 pm
Location: Florida

Re: sbc heads and flow.

Postby upsidedown » Wed Mar 20, 2013 1:00 am

Chad Speir wrote:Every engine has a cfm demand. Too much cfm and that means the head is too big for the combo. I will post the formula tomorrow.


Hi Chad any chance of posting the formula. Thanks
upsidedown
 
Posts: 7
Joined: Tue Apr 27, 2010 3:52 am

Re: sbc heads and flow.

Postby Chad Speier » Wed Mar 20, 2013 7:12 am

CFM demand = cid x rpm x .0009785 / # of cylinders
Chad Speier
Image
Chad Speier
 
Posts: 1846
Joined: Mon Nov 12, 2007 6:03 pm
Location: Hays, Kansas

Re: sbc heads and flow.

Postby upsidedown » Thu Mar 21, 2013 10:55 pm

Chad Speier wrote:CFM demand = cid x rpm x .0009785 / # of cylinders

Thanks Chad so using that formula for a 350 @ 7000 rpm gives 300 cfm. I assume that this is what you would need from your head / manifold @ 28" at max flow?

I expect at that size for cfm it also gives the correct velocity?
upsidedown
 
Posts: 7
Joined: Tue Apr 27, 2010 3:52 am

Re: sbc heads and flow.

Postby JZEDBB6 » Mon Dec 12, 2016 5:43 pm

How do you then relate this formula to a boosted application :?:
JZEDBB6
 
Posts: 1
Joined: Mon Dec 12, 2016 3:05 am

Re: sbc heads and flow.

Postby Chad Speier » Mon Dec 12, 2016 5:52 pm

JZEDBB6 wrote:How do you then relate this formula to a boosted application :?:


It sure seems a boosted application likes a little bigger port. Exactly how much is trial and error I would assume. I had a customer build a 400" X275 car with a port that's 370cc. It hauls!
Chad Speier
Image
Chad Speier
 
Posts: 1846
Joined: Mon Nov 12, 2007 6:03 pm
Location: Hays, Kansas


Return to General Talk

Who is online

Users browsing this forum: No registered users and 1 guest