Brought to you in part by:

.

Shop Eastwood for your Auto Restoration Needs!


  Mustangsandmore Forums
  Ford Racing
  Squaring Carb

Post New Topic  Post A Reply
profile | register | preferences | faq | search

UBBFriend: Email This Page to Someone! next newest topic | next oldest topic
Author Topic:   Squaring Carb
Ken&Shell
Gearhead

Posts: 614
From: Mocksville, NC
Registered: May 2000

posted 10-22-2001 06:32 PM     Click Here to See the Profile for Ken&Shell   Click Here to Email Ken&Shell     Edit/Delete Message   Reply w/Quote
Some of the guys at the track have started talking about squaring their carbs which another poster also mentioned. What is everyone's opinion on this? My buddies are saying it takes one more variable out in drag racing and I was wondering if any of you racers agreed with that?


Shell
ladyracer

IP: Logged

capri man
Gearhead

Posts: 2689
From: doerun, ga.
Registered: Nov 2000

posted 10-22-2001 06:47 PM     Click Here to See the Profile for capri man   Click Here to Email capri man     Edit/Delete Message   Reply w/Quote
i assume you are talking about squareing the jets. that is a good starting point but only if you dont have a power valve in the front. again assuming you are talking about a holley. of course we all know what assuming will do for you! hee hee

------------------
mike r
racing is real
everything else is just a game.
81 capri-7.56 @88mph 1/8
1.56 60 ft.

IP: Logged

Ken&Shell
Gearhead

Posts: 614
From: Mocksville, NC
Registered: May 2000

posted 10-22-2001 06:51 PM     Click Here to See the Profile for Ken&Shell   Click Here to Email Ken&Shell     Edit/Delete Message   Reply w/Quote
quote:
Originally posted by capri man:
we all know what assuming will do for you! hee hee


All of your assumptions were correct darlin. It is a holley 750 without power valve and yes I meant squaring the jets.

My next question of course is any recommendations on jet size.

Shell

IP: Logged

capri man
Gearhead

Posts: 2689
From: doerun, ga.
Registered: Nov 2000

posted 10-22-2001 07:18 PM     Click Here to See the Profile for capri man   Click Here to Email capri man     Edit/Delete Message   Reply w/Quote
ALEX!!!!! HEEEELP!!!!! assuming again that you are running a smallblock. i would start in the 81-84 range. just my opinion i could be wrong.

------------------
mike r
racing is real
everything else is just a game.
81 capri-7.56 @88mph 1/8
1.56 60 ft.

[This message has been edited by capri man (edited 10-22-2001).]

IP: Logged

Ken&Shell
Gearhead

Posts: 614
From: Mocksville, NC
Registered: May 2000

posted 10-22-2001 07:45 PM     Click Here to See the Profile for Ken&Shell   Click Here to Email Ken&Shell     Edit/Delete Message   Reply w/Quote
MIke darlin you do a lot of assuming. I run a 351W with stock heads ported and polished. I run 7.30's in the 1/8th mile. What else you wanna know?

Shell

IP: Logged

Dave_C
Gearhead

Posts: 666
From: Gadsden, Al
Registered: Aug 99

posted 10-22-2001 07:57 PM     Click Here to See the Profile for Dave_C   Click Here to Email Dave_C     Edit/Delete Message   Reply w/Quote
For a track only car the square jetting does remove a variable. The mixture is the same from start to finish, no change by a pv opening or closing at a slightly different point.

For reference: The 950 HP that I just installed: started out with 81 square, was lean. Jetted up to 85 square. Might be a touch rich, will back off to 84.

I removed a 750 dp. The 750 worked well at 80-81 square or 73 square with 3.5 pv's front and rear. The 3.5 pv's made it idle cleaner and the numbers were low enough that they didn't affect the consistency very much.

Later,

David Cole

IP: Logged

Ken&Shell
Gearhead

Posts: 614
From: Mocksville, NC
Registered: May 2000

posted 10-22-2001 08:09 PM     Click Here to See the Profile for Ken&Shell   Click Here to Email Ken&Shell     Edit/Delete Message   Reply w/Quote
OK, Carb lesson time.. What exactly does the power valve do and why use one or not use one?

Shell

IP: Logged

capri man
Gearhead

Posts: 2689
From: doerun, ga.
Registered: Nov 2000

posted 10-22-2001 08:11 PM     Click Here to See the Profile for capri man   Click Here to Email capri man     Edit/Delete Message   Reply w/Quote
The 750 worked well at 80-81 square per dave


see i toldja so, (well i was a litle high) but pretty close for a wild guess, huh? hee hee good luck

------------------
mike r
racing is real
everything else is just a game.
81 capri-7.56 @88mph 1/8
1.56 60 ft.

IP: Logged

steve'66
Gearhead

Posts: 5659
From: Sonoma,CA,USA
Registered: Mar 2000

posted 10-22-2001 08:57 PM     Click Here to See the Profile for steve'66   Click Here to Email steve'66     Edit/Delete Message   Reply w/Quote
Shell,

The power valve opens at a set lower vacumm level to add more fuel to the mix. It's purpose is to add more fuel when a street car hits a hill and the engine's vacumm drops. This helps the car maintain the same speed.
But a race only car like yours doesn't need a power valve. The power valve adds enough fuel to compensate for about 6 jet sizes. So with a front power valve, most people run a jet size 6-8 sizes smaller in the front than the rear.
With no power valve the jets should be the same all the way around or "squared" so all cylinders have the same air/fuel mix. Street cars also want to be leaner on the primaries so they can use less fuel for normal driving, then richen the mix up when they open up the secondaries. Make sense?

SteveW

IP: Logged

capri man
Gearhead

Posts: 2689
From: doerun, ga.
Registered: Nov 2000

posted 10-22-2001 09:08 PM     Click Here to See the Profile for capri man   Click Here to Email capri man     Edit/Delete Message   Reply w/Quote
yea, what he said!!!

------------------
mike r
racing is real
everything else is just a game.
81 capri-7.56 @88mph 1/8
1.56 60 ft.

IP: Logged

bluestreek
Gearhead

Posts: 1086
From: Athens,GA
Registered: Jul 2001

posted 10-22-2001 10:39 PM     Click Here to See the Profile for bluestreek   Click Here to Email bluestreek     Edit/Delete Message   Reply w/Quote
I like to square my 289 street carb and use a 4.5 power valve . That way it's there if I need it, but there has to be a pretty good load on the car before it begins to come in.. One thing I noticed with Holleys is the PV jets tend to be a little too large for stock 289/302 heads, so I like to tweak the two PV jets with different size wires, depending on the engine combinations. It works for me.

IP: Logged

Moneymaker
Administrator

Posts: 18704
From: Lyons, IL, USA
Registered: May 99

posted 10-24-2001 11:37 AM     Click Here to See the Profile for Moneymaker   Click Here to Email Moneymaker     Edit/Delete Message   Reply w/Quote
"Squaring" does not work on a SBF regardless of carb. The carbureted intake design does not lend itself to it. The rear cylinders are always leaner than the fronts. We run a 8 to 10 size variance front to rear on our stuff. Most street cars that I set up are at least 6 sizes different.

------------------
Alex Denysenko
Co-Administrator and Moderator
NHRA/IHRA/SRA member
NHRA and IHRA SS/LA National Record Holder '00 & '01
Fleet of FoMoCo products
Moneymaker Bio
US Class Nationals link

IP: Logged

Ken&Shell
Gearhead

Posts: 614
From: Mocksville, NC
Registered: May 2000

posted 10-24-2001 01:43 PM     Click Here to See the Profile for Ken&Shell   Click Here to Email Ken&Shell     Edit/Delete Message   Reply w/Quote
Thanks for the lesson on power valve Steve.

quote:
Originally posted by Moneymaker:
[BWe run a 8 to 10 size variance front to rear on our stuff.

[/B]



Alex that is without power valve, right?

Shell

IP: Logged

Moneymaker
Administrator

Posts: 18704
From: Lyons, IL, USA
Registered: May 99

posted 10-24-2001 05:56 PM     Click Here to See the Profile for Moneymaker   Click Here to Email Moneymaker     Edit/Delete Message   Reply w/Quote
Correct Shell. I do not use a power valve in MM, BUT..... I still never have gone quicker with ANY SBF using ANY carb with square jetting. Windsors by their inherit design need more fuel to th rear cylinders. Not even on my old Modified Production 351C tunnel ram twin 660 68 coupe. Even that thing had to have some stagger in it, but I blame old intake technology on that deal knowing what I know today.

------------------
Alex Denysenko
Co-Administrator and Moderator
NHRA/IHRA/SRA member
NHRA and IHRA SS/LA National Record Holder '00 & '01
Fleet of FoMoCo products
Moneymaker Bio
US Class Nationals link

IP: Logged

bluestreek
Gearhead

Posts: 1086
From: Athens,GA
Registered: Jul 2001

posted 10-24-2001 09:57 PM     Click Here to See the Profile for bluestreek   Click Here to Email bluestreek     Edit/Delete Message   Reply w/Quote
quote:
Originally posted by Moneymaker:
"Squaring" does not work on a SBF regardless of carb. The carbureted intake design does not lend itself to it. The rear cylinders are always leaner than the fronts. We run a 8 to 10 size variance front to rear on our stuff. Most street cars that I set up are at least 6 sizes different.


For some reason mine seems to like it.. Maybe it has something to do with my highly modified intake plenum and 1" open spacer..?? My 650 DP works the best with 72 jets squared and 4.5 PV in front and back..

One other thing that you may not believe is my 289 pulls strong from 2000-7200 rpms with a little old 230 /.512" lift hyd. cam and open chamber heads. ( still has pressed in studs and rail rockers) .. If I could just figure out a way to keep the oil from slinging out of the dipstick tube.

IP: Logged

Butch Jennings
Gearhead

Posts: 534
From: California
Registered: Apr 2000

posted 10-24-2001 10:14 PM     Click Here to See the Profile for Butch Jennings   Click Here to Email Butch Jennings     Edit/Delete Message   Reply w/Quote

The Victor on my 460 seems to like the jetting squared up...86 jets with 4.5 power valves with a 1050 dominator.

------------------
Butch
460 powered 1967 Comet Cyclone
10.271 @ 130.069
Butcher's Home Page
"Friends don't let friends drive Chevys"

IP: Logged

Moneymaker
Administrator

Posts: 18704
From: Lyons, IL, USA
Registered: May 99

posted 10-25-2001 12:37 AM     Click Here to See the Profile for Moneymaker   Click Here to Email Moneymaker     Edit/Delete Message   Reply w/Quote
We have a 289 running around that pulls to 7500 RPM with a C7FE leMans cam in it. It is in a 65 fastback with an auto and runs 12.60's. Butch, I have always found that the 385 series engines like a lot of carburation and very little stagger if any. Especially with a dominator.

------------------
Alex Denysenko
Co-Administrator and Moderator
NHRA/IHRA/SRA member
NHRA and IHRA SS/LA National Record Holder '00 & '01
Fleet of FoMoCo products
Moneymaker Bio
US Class Nationals link

IP: Logged

All times are ET (US)

next newest topic | next oldest topic

Administrative Options: Close Topic | Archive/Move | Delete Topic
Post New Topic  Post A Reply
Hop to:

Contact Us | Mustangsandmore Front Page

Copyright 2003, Steve LaRiviere. All Rights Reserved.


Ultimate Bulletin Board 5.47d

Amazon Honor System Click Here to Pay Learn More

[The M&M Gearhead Gear Store]

[Build a free Mustangsandmore.ws Home Page!]

[About M&M][Acronyms][Calendar][Chat][Classifieds] [Links] [Members' Pics] [M&M Mug Shots] [Tech] [ Mustangsandmore.com Bookstore] [Advertise on Mustangsandmore.com] [Mustangsandmore.com T-Shirts]