Holley carb users, advice needed!!!
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From: spokane
Holley carb users, advice needed!!!
I understand that there are TONS of options and variations that can be used with holley carbs, but I was curious, how many of you are using the 50cc accelerator pump?
I have mostly OK throttle response slightly off idle, then a bit of a bog (shot running out?) Then throttle response kicks in hard!! So my thoughts are I need the larger accelerator pump (from what I've read any way).
My specs are a 600 cfm 4160 4bbl with blue pump cam (#1 hole), 30cc pump, and #36 size nozzles set on top of a stock 4bbl intake, on a (mildly worn out) 360 with long tube headers and 2.5inch exhaust. Everything else is stock internally.
Any and all information you can provide about what's working for you and what you might recommend to get rid of this bog is HUGELY appreciated!
Look forward to hearing from you awesome people!!
I have mostly OK throttle response slightly off idle, then a bit of a bog (shot running out?) Then throttle response kicks in hard!! So my thoughts are I need the larger accelerator pump (from what I've read any way).
My specs are a 600 cfm 4160 4bbl with blue pump cam (#1 hole), 30cc pump, and #36 size nozzles set on top of a stock 4bbl intake, on a (mildly worn out) 360 with long tube headers and 2.5inch exhaust. Everything else is stock internally.
Any and all information you can provide about what's working for you and what you might recommend to get rid of this bog is HUGELY appreciated!
Look forward to hearing from you awesome people!!
Hotshot
Joined: Feb 2004
Posts: 10,773
Likes: 2,590
From: The Shenandoah Valley
I understand that there are TONS of options and variations that can be used with holley carbs, but I was curious, how many of you are using the 50cc accelerator pump?
I have mostly OK throttle response slightly off idle, then a bit of a bog (shot running out?) Then throttle response kicks in hard!! So my thoughts are I need the larger accelerator pump (from what I've read any way).
My specs are a 600 cfm 4160 4bbl with blue pump cam (#1 hole), 30cc pump, and #36 size nozzles set on top of a stock 4bbl intake, on a (mildly worn out) 360 with long tube headers and 2.5inch exhaust. Everything else is stock internally.
I have mostly OK throttle response slightly off idle, then a bit of a bog (shot running out?) Then throttle response kicks in hard!! So my thoughts are I need the larger accelerator pump (from what I've read any way).
My specs are a 600 cfm 4160 4bbl with blue pump cam (#1 hole), 30cc pump, and #36 size nozzles set on top of a stock 4bbl intake, on a (mildly worn out) 360 with long tube headers and 2.5inch exhaust. Everything else is stock internally.
What you are describing could be the results of a leaking accelerator pump diaphragm or passage through the carb's joints between the pump and shooters ..... or a result of the vacuum diaphragm spring being too light / removed / or an old trick .... screw in linkage to manually open rear side?
If all is well, the stock accelerator pump on the 1850 is plenty adequate for the carb's primary throttle bores. The secondary side should open slowly as needed without a sudden bogging down.
I don't recall seeing a blue pump cam on mine, never needed to swap it off. My 351M (or your 360 IMHO) in a full size PU just isn't likely to need such a shot as a 50cc pump would provide.
Laughing Gas
Joined: Apr 2016
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From: Buffalo NY
I believe you are on the right track,sounds like the pump shot needs to be longer. A Holley 600 (model 1850) uses a .025 pump nozzle. Try that nozzle,and use the #2 hole for the cam.This should give a longer, more even shot of gas. Make sure the pump is adjusted correctly. At idle,there should be no clearance between the pump arm and the operating lever. At wide open throttle,push down on the pump arm. There should be .015" clearance between arm and lever.
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From: spokane
Tbear, that's a ton of great info. My carb is now on its 5th day since its last rebuild (accel pump diaphragm was leaking).
This carb came off a chevy at the junkyard so there's been no telling what was changed in it until its recent rebuild.
I did find it odd that there was no spring on the vac secondary. I'll try (temporarily) blocking the secondaries closed to see if the hesitation goes away.
Another problem I kind of forgot to mention was, if I slam the throttle from idle to WoT the engine almost stalls out. Could this also be related to the missing secondary spring?
Thanks a ton!
This carb came off a chevy at the junkyard so there's been no telling what was changed in it until its recent rebuild.
I did find it odd that there was no spring on the vac secondary. I'll try (temporarily) blocking the secondaries closed to see if the hesitation goes away.
Another problem I kind of forgot to mention was, if I slam the throttle from idle to WoT the engine almost stalls out. Could this also be related to the missing secondary spring?
Thanks a ton!
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From: spokane
Update on blocking the secondaries from opening. No change in the bog, so although I need to get a spring kit to put a spring in there, I don't think that's part of the problem.
Everything I've been reading seems to point towards needing more accel pump shot and longer. So I'm still leaning towards the 50cc pump with larger nozzle.
Other opinions or advice are much appreciated!
Everything I've been reading seems to point towards needing more accel pump shot and longer. So I'm still leaning towards the 50cc pump with larger nozzle.
Other opinions or advice are much appreciated!
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From: spokane
I believe you are on the right track,sounds like the pump shot needs to be longer. A Holley 600 (model 1850) uses a .025 pump nozzle. Try that nozzle,and use the #2 hole for the cam.This should give a longer, more even shot of gas. Make sure the pump is adjusted correctly. At idle,there should be no clearance between the pump arm and the operating lever. At wide open throttle,push down on the pump arm. There should be .015" clearance between arm and lever.
My understanding is I need more initial fuel and longer shot, therefore bigger nozzle, and bigger pump capacity. Or am I off track here?
I might be wrong on this too, but I don't think that my secondaries are even opening very much if even at all. I don't know how to verify this since they only open under load, so I don't think the secondaries are causing a problem.
I'll double check the adjustment on the accel pump arm, but I'm pretty sure its set up right.
More Turbo
Joined: Sep 2016
Posts: 559
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From: Australian Outback
Good advice all round. People tend to buy a used carb with modifications made to it, and those were made for it to run on a specific engine... always put the carb back to stock before trying to diagnose it.
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Hotshot
Joined: Feb 2004
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From: The Shenandoah Valley
Absolutely. Holleys are usually pretty near correct out of the box.
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From: spokane
Anybody know what vac secondary spring these had stock then?
It was said that a #25 nozzle was factory so I'll find one of those too.
Anybody know which cam color was stock?
I'll try bringing it to out of the box status first and go from there. After the rebuild those should be the only things that have been changed/modified.
Thanks everybody!
It was said that a #25 nozzle was factory so I'll find one of those too.
Anybody know which cam color was stock?
I'll try bringing it to out of the box status first and go from there. After the rebuild those should be the only things that have been changed/modified.
Thanks everybody!
Senior User
Joined: Sep 2013
Posts: 329
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From: Deer park, Wa.
Put a paper clip on the shaft coning out of the vac can......up near the top. Take the truck out on the road and floor it a few times. If the paper clip is slid down to the bottom then your vac secondaries are working.
Hotshot
Joined: Feb 2004
Posts: 10,773
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From: The Shenandoah Valley
Mine had a cream or maybe just stained white cam. It's possible that between the blue cam and the #33 shooters that are larger, you may simply be using up your pumps shot too fast instead of stretching it out. Like too rich and then instant lean when the engine still needs some with that air? Your 360 like my 351M is only going to rev but so fast hauling that truck.
There are several revisions over the many years that the Holley List 1850 has been in production .... (if that is the one you have). I believe I read in a Holley book that the first 1850s were used by Ford on the '57 312s .... but don't quote me. That book is a 1973 publication detailing specs for all Holleys at that time .... it is in my book stash someplace ..... now I use Google more.
Here are some good links .... that last has a section on tuning each part.
Basic Holley Carburetor Information
http://documents.holley.com/techlibr...al_listing.pdf
https://www.holley.com/support/resources/
http://documents.holley.com/techlibr..._tech_info.pdf
There are several revisions over the many years that the Holley List 1850 has been in production .... (if that is the one you have). I believe I read in a Holley book that the first 1850s were used by Ford on the '57 312s .... but don't quote me. That book is a 1973 publication detailing specs for all Holleys at that time .... it is in my book stash someplace ..... now I use Google more.
Here are some good links .... that last has a section on tuning each part.
Basic Holley Carburetor Information
http://documents.holley.com/techlibr...al_listing.pdf
https://www.holley.com/support/resources/
http://documents.holley.com/techlibr..._tech_info.pdf
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From: spokane
This is a good idea. I'll give it a go next chance I get.
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From: spokane
Mine had a cream or maybe just stained white cam. It's possible that between the blue cam and the #33 shooters that are larger, you may simply be using up your pumps shot too fast instead of stretching it out. Like too rich and then instant lean when the engine still needs some with that air?
It is very possible I'm using my shot faster than I should, but still doesn't explain why the engine almost stalls when I go idle to WoT. Its seeming like if I cure the bog with smaller nozzles and a longer shot, that's just going to make the idle to WoT bog worse.
I have my idle set to about 700, which in order to achieve this with maximum vacuum, I have to have the primary throttle butterfly almost completely closed. Is this possibly closing off (what I believe is called) the primary idle circuit too much? Because if I bump the idle speed up to about 1000 the bogs are much less apparent. This could also just be due to the extra air flow past the venturi though is my thoughts which just makes them seem like they're mostly gone.
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From: spokane
That's what has me confused because even if its a 390 (I haven't verified either way but pretty positive its a 360) a 30cc shot should be plenty. Typically I should be using smaller nozzles with a heavier vehicle but it seems like (in my mind at least) if I go smaller nozzle it will cause the idle to WoT bog to be worse.
I'm thinking that the best option is to get this thing back to out of the box specs and go from there as has been suggested by others. Then I'll at least have the base line of what holley would have built it at.