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Topic Review (Newest First)
08-14-2007 03:22 PM
Not A T 25
Quote:
Originally Posted by Tech @ BG
68'S I'd say to go down to 66's on the center carb...
Thanks I will get a set ordered.
08-14-2007 03:08 PM
Tech @ BG
Quote:
Originally Posted by Not A T 25
Can you tell me which numbers come stock in the carb?
68'S I'd say to go down to 66's on the center carb...
08-14-2007 02:59 PM
Not A T 25
Quote:
Originally Posted by Tech @ BG
First I'd say we need to jet down a little on the center carburetor (2 numbers) to help lean down the cruise a touch. From there I've got a few other thoughts that I'll let you know once we see what that does.
Can you tell me which numbers come stock in the carb?
08-14-2007 02:58 PM
Tech @ BG First I'd say we need to jet down a little on the center carburetor (2 numbers) to help lean down the cruise a touch. From there I've got a few other thoughts that I'll let you know once we see what that does.
08-14-2007 02:55 PM
red65mustang hooray! Tech @ BG arrived just in time....I defer to him!

"accellerating" normally from a stop sign, Hg will drop to 9-10 with alot of pedal....you want the other carbs to come in with more gas/richer for power

once the speed stabilizes at 65mph....you want to cruise on the center carb only jetted to about 15-16/1 A/F.....
08-14-2007 02:22 PM
Not A T 25
Quote:
Originally Posted by red65mustang
because a motor is "loafing" at cruise, you can run a leaner mix for better mpg.....you've seen the statement:"only takes about 30-50hp to keep a car at 70mph"

every motor/car combo will have a lean burn limit A/F ratio...here's a guide attached...

for my car
to change the "jetting" on a Edelbrock, all you have to do is swap the rods to thicker with a given jet size, the rods extend thru the jet and make a bigger flow restriction....motor cfm is constant per given rpms.....less fuel thru the jets is leaner....
90% of my miles is in town, the thinner rods are alot more pedal responsive....I do put in the thicker rods for the 250 miles trip to my daughters....running leaner and a little hotter burns out all the crap in the cylinder heads
So it is likely I am running rich at cruse and just can't tell by checking the plugs since I have not done as Frisco suggested and shut the car off and placed in neutral and coasted to a stop. I still don't understand how to get to my cruse speed of 65 MPH on center carb only with out providing more fuel from the center carb (larger jetting)
08-14-2007 01:52 PM
red65mustang because a motor is "loafing" at cruise, you can run a leaner mix for better mpg.....you've seen the statement:"only takes about 30-50hp to keep a car at 70mph"

every motor/car combo will have a lean burn limit A/F ratio...here's a guide attached...

for my car
to change the "jetting" on a Edelbrock, all you have to do is swap the rods to thicker with a given jet size, the rods extend thru the jet and make a bigger flow restriction....motor cfm is constant per given rpms.....less fuel thru the jets is leaner....
90% of my miles is in town, the thinner rods are alot more pedal responsive....I do put in the thicker rods for the 250 miles trip to my daughters....running leaner and a little hotter burns out all the crap in the cylinder heads
08-14-2007 01:47 PM
Not A T 25
Quote:
Originally Posted by red65mustang
first, when you find out "which" comp cam, use this link.....click on that cam graph to see all the details including carb idle Hg....higher is a little less fouling but 15Hg+ is fine

http://www.compcams.com/technical/DynoSheets/

second:
where the Heck is "Tech @ BG" when we need him!!!!
he is a well respected board member who works for Barry Grant....
sorry...I have no experience with their six shooter...
I'll send a pm to Tech @ BG and ask him to read this thread
it is the 268H cam.
08-14-2007 01:35 PM
red65mustang first, when you find out "which" comp cam, use this link.....click on that cam graph to see all the details including carb idle Hg....higher is a little less fouling but 15Hg+ is fine

http://www.compcams.com/technical/DynoSheets/

second:
where the Heck is "Tech @ BG" when we need him!!!!
he is a well respected board member who works for Barry Grant....
sorry...I have no experience with their six shooter...
I'll send a pm to Tech @ BG and ask him to read this thread
08-14-2007 01:28 PM
Not A T 25
Quote:
Originally Posted by red65mustang
swap in "thicker rods" for leaner on the Edelbrock carb....65mph=20Hg...about 2mpg better than 18Hg @ 3,000
red65mustang not sure I understand the last statement can you elaborate some. Are you saying that leaner condition at cruse helped your vacuum and mileage? I was thinking that I need to go fatter on the center carb to finish getting off the secondary carbs?
08-14-2007 01:20 PM
red65mustang Not A T'

some Hg numbers from my mild/typical (250hp/320tq) 302 to use as a scale(?) for your motor.....

on a downshift 3rd to 2nd at 50mph no gas pedal....Hg reads 25-26"....(my rings and valves are sealing great...fresh build)....
at 3,000rpm in my garage just rev'in the motor in park....Hg reads 21....(motor friction, alternator, etc etc dropped it 5Hg)
at 3,000rpms/65mph/3400lbs....Hg reads 18....(wind/tires resistance, weight etc etc dropped it another 3Hg)
swap in "thicker rods" for leaner on the Edelbrock carb....65mph=20Hg...about 2mpg better than 18Hg @ 3,000
08-14-2007 12:45 PM
Not A T 25
Quote:
Originally Posted by red65mustang
Not A T',
"actual" cfm on/thru a 383 cube motor (changes some but not alot with cam/etc)....

2,000rpm=163cfm
2500rpm=223cfm
3000rpm=286cfm

......5500=540cfm

I agree, time to try just the center carb...with 48* cruisin...for higher Hg

comment?:
at 13Hg, a carb is at the borderline for the gas not atomized by enough velocity, not suspended in the air for a good mix...
you will gain ALOT of velocity using only the center carb
red65mustang Wow now this is good information I have a mild comp cam sorry I don't remember the number but have them at home. Do you think changing to larger jets on the middle carb is the way to go or is there another way to achieve using the center carb only for cruse. I am out of adjustment on linkage with out giving up WOT
08-14-2007 12:26 PM
red65mustang Not A T',
"actual" cfm on/thru a 383 cube motor (changes some but not alot with cam/etc)....

2,000rpm=163cfm
2500rpm=223cfm
3000rpm=286cfm

......5500=540cfm

I agree, time to try just the center carb...with 48* cruisin...for higher Hg

comment?:
at 13Hg, a carb is at the borderline for the gas not atomized by enough velocity, not suspended in the air for a good mix...
you will gain ALOT of velocity using only the center carb
08-14-2007 11:38 AM
Not A T 25
Quote:
Originally Posted by red65mustang
Not A T,
thought this was going to be a easy one till I looked in your gallery!

3 2V's!

with the new timing.... 14base/24cent/10vac= 48* total just cruisin' 65mph....Hg should read 18"+...the 383 is totally loafing in your light car....
at 13-14Hg you are "tipping into" a richer mix/lousy burn...due to the 3 dueces????
"if" it is now 18"/65mph, and your vacuum can is adjustable....I would use 12/24/14Vac for 50 total cruisin'

depending on your cam and CR....I would be a little careful....WOT with 38* can be ping/knock
what does the Hg read on a mild downshift engine at temp?...
Since this post I have recurved the distributor to be all in at 2400 RPM with 48 deg total. I did not record the vac at a kick down but it does drop to near nothing. I have a pretty good feeling that I am just getting into the secondary carbs at cruse since if I let off slightly it goes up to around 22" and if I accelerate slightly it starts to drop off significantly. my progressive linkage is adjusted all the way out and the only thoughts I had was increasing the jetting in the middle carb to get me all the way off of the secondary carbs but I am concerned that I may run fat at that point. The carbs in the picture are the old set up I have the demon six shooter on now it runs very nice just trying to get a little better mileage out of them.
08-14-2007 11:25 AM
red65mustang Not A T,
thought this was going to be a easy one till I looked in your gallery!

3 2V's!

with the new timing.... 14base/24cent/10vac= 48* total just cruisin' 65mph....Hg should read 18"+...the 383 is totally loafing in your light car....
at 13-14Hg you are "tipping into" a richer mix/lousy burn...due to the 3 dueces????
"if" it is now 18"/65mph, and your vacuum can is adjustable....I would use 12/24/14Vac for 50 total cruisin'

depending on your cam and CR....I would be a little careful....WOT with 38* can be ping/knock
what does the Hg read on a mild downshift engine at temp?...
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