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Author Topic:   Volumetric Efficiency
Dubz
Gearhead

Posts: 443
From: Manitoba Canada
Registered: Oct 2002

posted 01-16-2003 12:19 AM     Click Here to See the Profile for Dubz   Click Here to Email Dubz     Edit/Delete Message   Reply w/Quote
When calculating carb size, you are to take the cfm of the engine into account, as well as the max rpm of the engine as well as volumetric efficiency. It is to my understanding that VE is higher for race bred cars than stockers. Now my question is, do race cars that have the same max rpm and displacement require a larger carb?? shouldn't it be that if they don't have a high VE they need a bigger carb to make up for not being 100% efficient.

------------------
1974 Gran Torino, 351W
1970 Mustang Grande, 289

Just a young buck

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Fastymz
Moderator

Posts: 11429
From: Reno Nv USA MEM#1240
Registered: Apr 2001

posted 01-16-2003 02:18 AM     Click Here to See the Profile for Fastymz   Click Here to Email Fastymz     Edit/Delete Message   Reply w/Quote
I think that if your VE is low then a bigger carb will make your car run even worst.

------------------
SCOOP
oddly obsessed with big scoops on little Mustangs

2.26 60'S
14.9 @ 90.86MPH

65 coupe,351w,C4,Big Boss 429 hood scoop,8"3.40 TracLoc,Cragar SS,Black Suede.

https://mustangsandmore.com/ubb/Fastymz.html

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69 Sportsroof
Gearhead

Posts: 1202
From: Valley, Alabama, USA
Registered: Mar 2002

posted 01-16-2003 09:34 AM     Click Here to See the Profile for 69 Sportsroof   Click Here to Email 69 Sportsroof     Edit/Delete Message   Reply w/Quote
I think that ve has more to do with the cfm rating of the cylinder head than anything else. If you put a long duration, high lift cam on a set of 260 heads your not going to get the same ve as if you used 351 heads. In short, you need a bigger carb only if you can move the intake charge that it will produce while maintaining the exhaust flow to match. Where's Alex when we need him?

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Moneymaker
Administrator

Posts: 19704
From: Lyons, IL, USA
Registered: May 99

posted 01-16-2003 10:59 AM     Click Here to See the Profile for Moneymaker   Click Here to Email Moneymaker     Edit/Delete Message   Reply w/Quote
There are many other factors to consider when choosing carb size in a race car such as exhuast scavenging, plenum signal and more.
A street car will never utilize all of the available carb flow regardless of size.
Two rules that are near full proof when choosing a carb for a street car.
1) The milder the engine the smaller the carb. If you are thinking 600 then get a 550 if you can.
2) The wilder the engine the bigger the carb.
MOst 650 carbs cannot feed the demands of a 300 inch engine with a good set of heads, intake and cam of .500 or more. This is the case where slightly over carburated will always offer better performance.

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Alex Denysenko
Co-Administrator and Moderator

NHRA/IHRA/SRA member and licensed Superstock driver
MCA member# 53321
NHRA and IHRA SS/LA National Record Holder '00,'01,'02,&'03
Fleet of FoMoCo products including 88 ASC McLaren Mustang #28
Professional Manwhore
The Barry of BarrysGrrl

Quote #1: "I never met a magazine mechanic I liked."
Quote #2: "Make sure brain is in gear before engaging mouth!"
Quote #3: "If you can't run with the big dogs, stay on the porch!"
www.moneymakerracing.com

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Dubz
Gearhead

Posts: 443
From: Manitoba Canada
Registered: Oct 2002

posted 01-16-2003 05:59 PM     Click Here to See the Profile for Dubz   Click Here to Email Dubz     Edit/Delete Message   Reply w/Quote
so for the street go undercarbed...and for race go overboard??

i was looking at a 750 previously but thought a 351W might need less carb than that...will be running 9:1 comp, dual-plenum intake, a 270H cam and stock heads ported and polished until rebuild and/or new heads

------------------
1974 Gran Torino, 351W
1970 Mustang Grande, 289

Just a young buck

[This message has been edited by Dubz (edited 01-16-2003).]

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Moneymaker
Administrator

Posts: 19704
From: Lyons, IL, USA
Registered: May 99

posted 01-16-2003 06:00 PM     Click Here to See the Profile for Moneymaker   Click Here to Email Moneymaker     Edit/Delete Message   Reply w/Quote
FYI, the 290 HP 69 4v 351W came with a 570 CFM 4300 series Autolite carb.

------------------
Alex Denysenko
Co-Administrator and Moderator

NHRA/IHRA/SRA member and licensed Superstock driver
MCA member# 53321
NHRA and IHRA SS/LA National Record Holder '00,'01,'02,&'03
Fleet of FoMoCo products including 88 ASC McLaren Mustang #28
Professional Manwhore
The Barry of BarrysGrrl

Quote #1: "I never met a magazine mechanic I liked."
Quote #2: "Make sure brain is in gear before engaging mouth!"
Quote #3: "If you can't run with the big dogs, stay on the porch!"
www.moneymakerracing.com

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Dubz
Gearhead

Posts: 443
From: Manitoba Canada
Registered: Oct 2002

posted 01-16-2003 06:40 PM     Click Here to See the Profile for Dubz   Click Here to Email Dubz     Edit/Delete Message   Reply w/Quote
allright, so we have 600 or 750....BIG difference

which would you throw on alex?

------------------
1974 Gran Torino, 351W
1970 Mustang Grande, 289

Just a young buck

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Fastymz
Moderator

Posts: 11429
From: Reno Nv USA MEM#1240
Registered: Apr 2001

posted 01-16-2003 07:31 PM     Click Here to See the Profile for Fastymz   Click Here to Email Fastymz     Edit/Delete Message   Reply w/Quote
Unless your going to some better heads soon.I'd go with the 600 carb.
I run a 600 holley on my 351w and I know at this time 750 wouldn't make it run any better.

------------------
SCOOP
oddly obsessed with big scoops on little Mustangs

2.26 60'S
14.9 @ 90.86MPH

65 coupe,351w,C4,Big Boss 429 hood scoop,8"3.40 TracLoc,Cragar SS,Black Suede.

https://mustangsandmore.com/ubb/Fastymz.html

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Moneymaker
Administrator

Posts: 19704
From: Lyons, IL, USA
Registered: May 99

posted 01-16-2003 07:39 PM     Click Here to See the Profile for Moneymaker   Click Here to Email Moneymaker     Edit/Delete Message   Reply w/Quote
If you have a big heavy car with a stock or near stock engine then a 600 CFM carb is plenty.

------------------
Alex Denysenko
Co-Administrator and Moderator

NHRA/IHRA/SRA member and licensed Superstock driver
MCA member# 53321
NHRA and IHRA SS/LA National Record Holder '00,'01,'02,&'03
Fleet of FoMoCo products including 88 ASC McLaren Mustang #28
Professional Manwhore
The Barry of BarrysGrrl

Quote #1: "I never met a magazine mechanic I liked."
Quote #2: "Make sure brain is in gear before engaging mouth!"
Quote #3: "If you can't run with the big dogs, stay on the porch!"
www.moneymakerracing.com

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Fastymz
Moderator

Posts: 11429
From: Reno Nv USA MEM#1240
Registered: Apr 2001

posted 01-16-2003 07:45 PM     Click Here to See the Profile for Fastymz   Click Here to Email Fastymz     Edit/Delete Message   Reply w/Quote
quote:
Originally posted by Moneymaker:
If you have a big heavy car with a stock or near stock engine then a 600 CFM carb is plenty.


So are you saying my car should have more carb?

Either you speak above my head sometimes.Or you just get asked the same things all the TIME.Or both!

------------------
SCOOP
oddly obsessed with big scoops on little Mustangs

2.26 60'S
14.9 @ 90.86MPH

65 coupe,351w,C4,Big Boss 429 hood scoop,8"3.40 TracLoc,Cragar SS,Black Suede.

https://mustangsandmore.com/ubb/Fastymz.html

IP: Logged

Moneymaker
Administrator

Posts: 19704
From: Lyons, IL, USA
Registered: May 99

posted 01-16-2003 07:48 PM     Click Here to See the Profile for Moneymaker   Click Here to Email Moneymaker     Edit/Delete Message   Reply w/Quote
Ron, you have a stock cam I thought.
Stock 351W with just a 4v intake and some headers. Yes/no?

------------------
Alex Denysenko
Co-Administrator and Moderator

NHRA/IHRA/SRA member and licensed Superstock driver
MCA member# 53321
NHRA and IHRA SS/LA National Record Holder '00,'01,'02,&'03
Fleet of FoMoCo products including 88 ASC McLaren Mustang #28
Professional Manwhore
The Barry of BarrysGrrl

Quote #1: "I never met a magazine mechanic I liked."
Quote #2: "Make sure brain is in gear before engaging mouth!"
Quote #3: "If you can't run with the big dogs, stay on the porch!"
www.moneymakerracing.com

IP: Logged

Dubz
Gearhead

Posts: 443
From: Manitoba Canada
Registered: Oct 2002

posted 01-16-2003 07:55 PM     Click Here to See the Profile for Dubz   Click Here to Email Dubz     Edit/Delete Message   Reply w/Quote
quote:
Originally posted by Moneymaker:
If you have a big heavy car with a stock or near stock engine then a 600 CFM carb is plenty.

and what would make the car not close to stock anymore??


PARTS THAT DIDN'T COME WITH THE ENGINE ORIGINALLY!



[This message has been edited by Moneymaker (edited 01-16-2003).]

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Fastymz
Moderator

Posts: 11429
From: Reno Nv USA MEM#1240
Registered: Apr 2001

posted 01-16-2003 08:02 PM     Click Here to See the Profile for Fastymz   Click Here to Email Fastymz     Edit/Delete Message   Reply w/Quote
quote:
Originally posted by Moneymaker:
Ron, you have a stock cam I thought.
Stock 351W with just a 4v intake and some headers. Yes/no?


YES

------------------
SCOOP
oddly obsessed with big scoops on little Mustangs

2.26 60'S
14.9 @ 90.86MPH

65 coupe,351w,C4,Big Boss 429 hood scoop,8"3.40 TracLoc,Cragar SS,Black Suede.

https://mustangsandmore.com/ubb/Fastymz.html

IP: Logged

Moneymaker
Administrator

Posts: 19704
From: Lyons, IL, USA
Registered: May 99

posted 01-16-2003 08:18 PM     Click Here to See the Profile for Moneymaker   Click Here to Email Moneymaker     Edit/Delete Message   Reply w/Quote
quote:
Originally posted by Fastymz:
YES



Okay then Ron, what part of stock or near stock didn't you understand????????????

When you upgrade cam or heads etc. then it would be time for a larger carb. FOr right now you are in good shape with a 600.

------------------
Alex Denysenko
Co-Administrator and Moderator

NHRA/IHRA/SRA member and licensed Superstock driver
MCA member# 53321
NHRA and IHRA SS/LA National Record Holder '00,'01,'02,&'03
Fleet of FoMoCo products including 88 ASC McLaren Mustang #28
Professional Manwhore
The Barry of BarrysGrrl

Quote #1: "I never met a magazine mechanic I liked."
Quote #2: "Make sure brain is in gear before engaging mouth!"
Quote #3: "If you can't run with the big dogs, stay on the porch!"
www.moneymakerracing.com

IP: Logged

Fastymz
Moderator

Posts: 11429
From: Reno Nv USA MEM#1240
Registered: Apr 2001

posted 01-16-2003 08:21 PM     Click Here to See the Profile for Fastymz   Click Here to Email Fastymz     Edit/Delete Message   Reply w/Quote
quote:
Originally posted by Moneymaker:
Okay then Ron, what part of stock or near stock didn't you understand????????????

When you upgrade cam or heads etc. then it would be time for a larger carb. FOr right now you are in good shape with a 600.


Just the BIG HEAVY part of what you said.The stock part I have a handle on.
I've never thought of my car as BIG or HEAVY.

------------------
SCOOP
oddly obsessed with big scoops on little Mustangs

2.26 60'S
14.9 @ 90.86MPH

65 coupe,351w,C4,Big Boss 429 hood scoop,8"3.40 TracLoc,Cragar SS,Black Suede.

https://mustangsandmore.com/ubb/Fastymz.html

IP: Logged

Moneymaker
Administrator

Posts: 19704
From: Lyons, IL, USA
Registered: May 99

posted 01-16-2003 08:28 PM     Click Here to See the Profile for Moneymaker   Click Here to Email Moneymaker     Edit/Delete Message   Reply w/Quote
I was referring to Dubz 74 Torino project Ron.

------------------
Alex Denysenko
Co-Administrator and Moderator

NHRA/IHRA/SRA member and licensed Superstock driver
MCA member# 53321
NHRA and IHRA SS/LA National Record Holder '00,'01,'02,&'03
Fleet of FoMoCo products including 88 ASC McLaren Mustang #28
Professional Manwhore
The Barry of BarrysGrrl

Quote #1: "I never met a magazine mechanic I liked."
Quote #2: "Make sure brain is in gear before engaging mouth!"
Quote #3: "If you can't run with the big dogs, stay on the porch!"
www.moneymakerracing.com

IP: Logged

Fastymz
Moderator

Posts: 11429
From: Reno Nv USA MEM#1240
Registered: Apr 2001

posted 01-16-2003 08:35 PM     Click Here to See the Profile for Fastymz   Click Here to Email Fastymz     Edit/Delete Message   Reply w/Quote
quote:
Originally posted by Moneymaker:
I was referring to Dubz 74 Torino project Ron.


DOH,That makes a lot more sense to me now.I'll try to keep from sticking my noise into things.

------------------
SCOOP
oddly obsessed with big scoops on little Mustangs

2.26 60'S
14.9 @ 90.86MPH

65 coupe,351w,C4,Big Boss 429 hood scoop,8"3.40 TracLoc,Cragar SS,Black Suede.

https://mustangsandmore.com/ubb/Fastymz.html

[This message has been edited by Fastymz (edited 01-16-2003).]

IP: Logged

Dubz
Gearhead

Posts: 443
From: Manitoba Canada
Registered: Oct 2002

posted 01-16-2003 08:37 PM     Click Here to See the Profile for Dubz   Click Here to Email Dubz     Edit/Delete Message   Reply w/Quote
yes, the car is a little tubby at ~3650lbs, but a guy i know is getting into the buisness of fabricating fiberglass bodypanels for torinos, so it's all good

Anyway, here is the question Alex...270H in a 351W, slightly better flowing heads then stock, dp intake, and 1 5/8" headers, what carb size??

Thanks again

------------------
1974 Gran Torino, 351W
1970 Mustang Grande, 289

Just a young buck

[This message has been edited by Dubz (edited 01-16-2003).]

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Moneymaker
Administrator

Posts: 19704
From: Lyons, IL, USA
Registered: May 99

posted 01-16-2003 08:38 PM     Click Here to See the Profile for Moneymaker   Click Here to Email Moneymaker     Edit/Delete Message   Reply w/Quote

------------------
Alex Denysenko
Co-Administrator and Moderator

NHRA/IHRA/SRA member and licensed Superstock driver
MCA member# 53321
NHRA and IHRA SS/LA National Record Holder '00,'01,'02,&'03
Fleet of FoMoCo products including 88 ASC McLaren Mustang #28
Professional Manwhore
The Barry of BarrysGrrl

Quote #1: "I never met a magazine mechanic I liked."
Quote #2: "Make sure brain is in gear before engaging mouth!"
Quote #3: "If you can't run with the big dogs, stay on the porch!"
www.moneymakerracing.com

IP: Logged

Moneymaker
Administrator

Posts: 19704
From: Lyons, IL, USA
Registered: May 99

posted 01-16-2003 08:40 PM     Click Here to See the Profile for Moneymaker   Click Here to Email Moneymaker     Edit/Delete Message   Reply w/Quote
quote:
Originally posted by Dubz:
yes, the car is a little tubby at ~3650lbs, but a guy i know is getting into the buisness of fabricating fiberglass bodypanels for torinos, so it's all good

Anyway, here is the question Alex...270H in a 351W, slightly better flowing heads then stock, dp intake, and 1 5/8" headers, what carb size??

Thanks again


600 to 670 CFM max. Preferably a 4150 series.

------------------
Alex Denysenko
Co-Administrator and Moderator

NHRA/IHRA/SRA member and licensed Superstock driver
MCA member# 53321
NHRA and IHRA SS/LA National Record Holder '00,'01,'02,&'03
Fleet of FoMoCo products including 88 ASC McLaren Mustang #28
Professional Manwhore
The Barry of BarrysGrrl

Quote #1: "I never met a magazine mechanic I liked."
Quote #2: "Make sure brain is in gear before engaging mouth!"
Quote #3: "If you can't run with the big dogs, stay on the porch!"
www.moneymakerracing.com

IP: Logged

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