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Air Bleed Sizes Holley and ProForm |
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PHAT69AMX 
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Joined: Jul/07/2007 Location: West Virginia Status: Offline Points: 5919 |
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 Topic: Air Bleed Sizes Holley and ProFormPosted: Oct/30/2011 at 1:45pm |
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Wondering if anyone has messed aroud with Air Bleeds.
Newer Holley and the ProForm replacement carburetor Main Body
have changeable screw-in Air Bleeds like fuel jets. The ProForm body comes with Air Bleeds and the instruction say
when used with a 2-Corner Idle Holley carb, to use Air Bleeds: Idle Main Main Idle Have an old 1977 Holley 4779-2 750 Dbl Pumper 2-Corner Idle Idle Main Main Idle Those are fairly major difference in Air Bleeds.
Understand that Air Bleeds effect air fuel mix / emulsion
as well as effect start-up timing of a circuit, and work as
a "brake" or "air leak" to stop fuel flow when carb is closed. If all worked well with the original old 750 Main Body with Has anyone done one of these and tried it with smaller Air Bleeds Edited by PHAT69AMX - Oct/30/2011 at 8:51pm |
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stonedblue
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Posted: Oct/30/2011 at 2:43pm |
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I just bought a new proform and its on my .060 over 360, 9-1, 280h, unported 090 heads. I haven't played with the bleeds, changed main jets to 71s. Runs great 'sept for the dreaded off idle stumble. Gonna increase squirt to 33 thinking that will do the trick. This carb is double pump/4 corner idle idle. Here are the out of box specs...
 Edited by stonedblue - Oct/30/2011 at 2:44pm |
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I can build an engine, but, I can't drain oil without a mess.'04Ram,'99Plym.Van,"96Exploder,'79Dodge pickup, '71Jav. '68Jav, and '90 Gold Rush trailer
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PHAT69AMX
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Posted: Oct/30/2011 at 4:00pm |
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Ah, looks like ProForm has changed the suggested Air Bleed sizes.
Info on-hand was downloaded earlier this year from the Summit web site that said
Idle Main Main Idle
#73 - #36 --- #36 - #73 Pri (fixed boo boo, was incorrectly #75) #36 - #36 --- #36 - #36 Sec  Edited by PHAT69AMX - Oct/30/2011 at 8:53pm |
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stonedblue
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Posted: Oct/30/2011 at 4:57pm |
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Looks like the body has larger bleeds and jets than my street series carb.
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I can build an engine, but, I can't drain oil without a mess.'04Ram,'99Plym.Van,"96Exploder,'79Dodge pickup, '71Jav. '68Jav, and '90 Gold Rush trailer
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PHAT69AMX
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Posted: Oct/30/2011 at 5:18pm |
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The stumble you mention in theory could be air bleed related, in theory.
How quickly the Main Circuit starts up depends on the Main Air Bleed size.
A smaller Main Air Bleed will make the Main Fuel Circuit start up sooner / faster.
The stumble could be the mains being just a tad slow coming online
following the transfer slot fuel delivery and exhaustion of the accel pump shot.
Have ya checked the Primary Transfer Slot exsposure at idle ?
Primaries too far open at idle can also cause a stumble.
This is what's behind the reason for making this post.
Wondering if anyone improved performance using the ProForm Main Body
by using Air Bleeds smaller than those ProForm suggest using.
In theory smaller bleeds should start-up the mains sooner
and maybe get rid of an off-idle or hammer down bog or stumble.
Sucks how much a complete set of bleeds costs.
In the ProForm specs you posted they show Air Bleed sizes much closer to
what was in the old 4779-2 I have and measured
than the size Bleeds called for in the ProForm info I got from the Summit website.
Specs from Summit for 2-Corner:
Idle Main Main Idle
#73 - #36 --- #36 - #73 Pri (correction, was incorrectly #75) #36 - #36 --- #36 - #36 Sec Idle Main Main Idle
#70 - #31 --- #31 - #70 Pri #70 - #31 --- #31 - #70 Sec old 4779-2 Bleeds I measured for 2-Corner:
Idle Main Main Idle
#70 - #31 --- #31 - #70 Pri #28 - #25 --- #25 - #28 Sec Edited by PHAT69AMX - Oct/30/2011 at 8:54pm |
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stonedblue
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Posted: Oct/30/2011 at 7:55pm |
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I'm guessing the specs you have from summit are for the proform race body, (without choke tower) my carb is a street version with tower, that maybe the reason for diff. specs. This carb also has billet base and meter blocks as does the race series.
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I can build an engine, but, I can't drain oil without a mess.'04Ram,'99Plym.Van,"96Exploder,'79Dodge pickup, '71Jav. '68Jav, and '90 Gold Rush trailer
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PHAT69AMX
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Posted: Oct/30/2011 at 8:48pm |
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Ah, yes, you sir are correct. The Air Bleed specs were for the replacement Main Body with no choke horn. I failed to realize the info ya posted was for a complete ProForm Street HP carb....
Does it have PINK pump cams on it ?
The pink pump cams have the least aggressive ramp to'em.
Seen this self generated line graph from self collected data ? (dotted = hole #2)
It's fairly in agreeance with the line graph Holley has online.
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stonedblue
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Posted: Oct/30/2011 at 9:54pm |
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Yep, pink cams. That was another thought to the stumble, though the squirt seems to come in early, but may need to be more agressive. This is really my first real carb tunning experience, been tunning Hilborn F.I. all my life, never had a street car that I really had desire to fool with.
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I can build an engine, but, I can't drain oil without a mess.'04Ram,'99Plym.Van,"96Exploder,'79Dodge pickup, '71Jav. '68Jav, and '90 Gold Rush trailer
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stonedblue
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Posted: Nov/02/2011 at 8:21pm |
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Well PHAT, swapped the 31 squirts for 35s, the bog is minimal, probly 75% better. Next is a cam swap, thinking green using the graf you posted. Hoping I can close the idle screws a bit after the swap, the idle is a bit rich, not to the point of stinky, but still rich. The air bleeds I have are already smaller than yours so I'm gonna let them alone for now. I'll keep you updated.
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I can build an engine, but, I can't drain oil without a mess.'04Ram,'99Plym.Van,"96Exploder,'79Dodge pickup, '71Jav. '68Jav, and '90 Gold Rush trailer
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PHAT69AMX
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Posted: Nov/02/2011 at 10:32pm |
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I usually go in little steps on the cams, after Pink, first try the White, then the Red.
With an old 4779-2 750 from 1977 on a 366 auto 3k stall Torker 3.73 the Red cams work good.
The Red and White cams level off sooner than the Orange and Green.
Might wanna try the White or Red before jumping straight t the Green.
Red & White, good strong initial shot, but then tapers off.
Once there's air flow and the Mains come on-line, not as much shot is needed.
The Orange & Green continue to deliver shot when it may not be needed.
But for drag race launches at the strip with the 3k converter
I switch over from the White or Red on the street to the Orange or Green
since the car is already past some of the White/Red cam stroke when lauching at 3k.
The Air Bleeds in your ProForm 750 Street carb with the choke horn
are real close to those in my old -2 750 DP with choke horn
except my old one is a 2-Corner Idle, so it has smaller secondary Idle Air Bleeds.
Reason for the post is the ProForm HP Main Body that has no Choke Horn
is what comes with so much larger Air Bleeds than the stock carb with choke horn.
The choke horn is only on the primary side, secondary side is kinda the same
between old 750 and the Proform body, so I wonder about the air bleeds PF suggest.
My old 750 is on the car, and have a PF Body to assemble with other Holley parts
from another 2-corner Holley 750 DP, except I don't have any of the smaller air bleeds yet.
Was wondering if anyone had already tried a PF HP Main Body with 750 DP parts
but had used smaller air bleeds than those that come with the PF HP Main Body,
air bleeds about the size of those in the stock 750 DP with choke horn main body
which are about the same as the air bleeds in your PF carb with the choke horn.
In my old 750-2 I have #35 shooters and red cams in both the primary and secondary.
Since the larger shooters helped on yours, it's letting more of the pink cam
pump shot discharge sooner, and maybe it's running out of pump shot too soon
since the pink cam is so soft. Would think that along with the bigger shooters
a little more pump cam will make the larger shot also last longer, cure remaining 25%.
How many turns out on the Idle Mixture Screws is it at now ? Is it 4-corner idle ?
Using a vacuum gauge to set idle mixture ?
Are ya adjusting both the Primary & Secondary Idle Speed screws also ?
To keep the transfer slot exsposure minimized on the primary side ?
I try to keep the primary idle Speed screw at a max of 3/4 of a turn opened from fully closed.
From there then make idle speed adjustments using the secondary idle speed screw.
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