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  #31 (permalink)  
Old 03-03-2006, 10:39 AM
Technical Support Barry Grant
 
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Quote:
Originally Posted by leejoy
Dear Mr. Tech

I already did the first part of your message, now I can test the accelerator pump idea and see what that does. good idea. I may have a blown power valve. I need to help to explain. If it is blown I can see why i'm having these problems. I think when the idle mixture screws are turned all the way in there is little or no change to idle if I recall......indicating a blown (open-ruptured) power valve right? what I don't understand is if the power valve is not blown, but open, how would that affect idle? At idle it's just drawing through the idle ports anyway and so what if the power valve is open. I don't understand.

Leejoy,

A blown PV would make it run rich, but it would not allow you to screw the mixture screws all the way in and still have the engine run. There is something else wrong causing that. There isn't anything you can see that will indicate a PV being blown or not, you'll need to remove it and actually check it.

The way the idle circuits are designed if everything is working properly all of the fuel the engine gets at idle should come from your curb idle discharge ports. These are controlled by your idle mixture screws. If they are shut the engine should not be getting enough fuel to idle. If it does you have a problem. It can be that the butterflies (front or rear) are exposing too much of the transfer slots pulling fuel into the engine. It could be the float level being set too high, and pulling raw fuel out of your boosters at idle. It could be a bad PV gasket causing raw fuel to leak into the engine. A blown PV would leave it in the "open" or flowing position adding fuel to the main fuel well which is where the idle circuit gets its fuel from. This would cause a rich idle, but would not allow you to completely shut your idle mixture screws.

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  #32 (permalink)  
Old 03-03-2006, 11:03 AM
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Quote:
Originally Posted by Tech @ BG
Leejoy,

A blown PV would make it run rich, but it would not allow you to screw the mixture screws all the way in and still have the engine run. There is something else wrong causing that. There isn't anything you can see that will indicate a PV being blown or not, you'll need to remove it and actually check it.

The way the idle circuits are designed if everything is working properly all of the fuel the engine gets at idle should come from your curb idle discharge ports. These are controlled by your idle mixture screws. If they are shut the engine should not be getting enough fuel to idle. If it does you have a problem. It can be that the butterflies (front or rear) are exposing too much of the transfer slots pulling fuel into the engine. It could be the float level being set too high, and pulling raw fuel out of your boosters at idle. It could be a bad PV gasket causing raw fuel to leak into the engine. A blown PV would leave it in the "open" or flowing position adding fuel to the main fuel well which is where the idle circuit gets its fuel from. This would cause a rich idle, but would not allow you to completely shut your idle mixture screws.
Dear Mr. BG Tech

are there idle circuit slots on the secondaries of my Holley 650? I thought they were only on the primaries. They are not open to far. I checked that. they are one turn of the idle speed screw open - barely cracked open.....so it shouldnt be drawing air/fuel from the transfer slots. There is no visible raw fuel being delivered from the main metering boosters. I looked and did not see any while the engine was idleing. shall I go get a new power valve and throw it in there? It's probably only a 1 hour job to do right? I realize I will need some new gaskets also.
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  #33 (permalink)  
Old 03-03-2006, 11:10 AM
Technical Support Barry Grant
 
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Quote:
Originally Posted by leejoy
Dear Mr. BG Tech

are there idle circuit slots on the secondaries of my Holley 650? I thought they were only on the primaries. They are not open to far. I checked that. they are one turn of the idle speed screw open - barely cracked open.....so it shouldnt be drawing air/fuel from the transfer slots. There is no visible raw fuel being delivered from the main metering boosters. I looked and did not see any while the engine was idleing. shall I go get a new power valve and throw it in there? It's probably only a 1 hour job to do right? I realize I will need some new gaskets also.

Yes even though you don't have mixture screws on the rear of your carburetor it still has idle, and transition circuits. There is a constant feed hole that drips fuel in, and then the transfer slots as the butterflies open. How much of the slots are exposed. I would not go just by where the speed screw is at. I'd get a new power valve, bowl, and metering block gaskets. Also have some good spray carburetor cleaner, and compressed air. Clean out all the holes in the main body, and metering blocks, install a new PV and gaskets. Then reset your butterflies and start from there.
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  #34 (permalink)  
Old 03-03-2006, 11:21 AM
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Quote:
Originally Posted by Tech @ BG
Yes even though you don't have mixture screws on the rear of your carburetor it still has idle, and transition circuits. There is a constant feed hole that drips fuel in, and then the transfer slots as the butterflies open. How much of the slots are exposed. I would not go just by where the speed screw is at. I'd get a new power valve, bowl, and metering block gaskets. Also have some good spray carburetor cleaner, and compressed air. Clean out all the holes in the main body, and metering blocks, install a new PV and gaskets. Then reset your butterflies and start from there.
i didnt know there were idle and transfer slots on the secondaries. I can pull the float bowl, and main metering block which the carb is still on the car right? I will do as you say. you mentioned compressed air for the main body. are you saying that after I remove the main metering block that I should blow out all openings in the "main body" of the carb? what about blowing out the metering block passages? Also, what power valve setting should I get. I'm thinking like a 6.5" or less right? last time I did a vacuum check I had about 10".
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  #35 (permalink)  
Old 03-03-2006, 11:25 AM
Technical Support Barry Grant
 
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Quote:
Originally Posted by leejoy
i didnt know there were idle and transfer slots on the secondaries. I can pull the float bowl, and main metering block which the carb is still on the car right? I will do as you say. you mentioned compressed air for the main body. are you saying that after I remove the main metering block that I should blow out all openings in the "main body" of the carb? what about blowing out the metering block passages? Also, what power valve setting should I get. I'm thinking like a 6.5" or less right? last time I did a vacuum check I had about 10".

TAKE THE CARB OFF. It's only 4 bolts, 2 fuel fittings, and your linkage. It shouldn't take you more than 5 minutes to take it off and do the job properly. This way you can clean everything out properly, and set your butterflies. You CAN'T check or set the butterflies with the carb bolted down. To pick a PV you really need to know how much vacuum the engine is producing at idle. With everything you've got going on right now you really won't know, start out with a 6.5. Yes clean out all the passages main body, baseplate, and metering blocks.
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  #36 (permalink)  
Old 03-03-2006, 11:54 AM
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Quote:
Originally Posted by Tech @ BG
TAKE THE CARB OFF. It's only 4 bolts, 2 fuel fittings, and your linkage. It shouldn't take you more than 5 minutes to take it off and do the job properly. This way you can clean everything out properly, and set your butterflies. You CAN'T check or set the butterflies with the carb bolted down. To pick a PV you really need to know how much vacuum the engine is producing at idle. With everything you've got going on right now you really won't know, start out with a 6.5. Yes clean out all the passages main body, baseplate, and metering blocks.
is this going to turn into a "whole fricking carb rebuild"? I'm not ready for that right now but I will do it if that's what your suggesting. I would have to purchase a carb rebuild kit for $30 or $40, when I am planning on replacing this carb anyway for a larger one in the next 6-12 months. Or, can I just get the bowl and metering block gaskets and do that part only? Can I get just the bowl and metering block gaskets and power valve at my local AutoZone or Advance Auto Parts or Napa Auto Parts or do i have to buy them from Summit and/or Jegs and pay shipping and wait 3-5 days?
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  #37 (permalink)  
Old 03-03-2006, 12:34 PM
Technical Support Barry Grant
 
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Quote:
Originally Posted by leejoy
is this going to turn into a "whole fricking carb rebuild"? I'm not ready for that right now but I will do it if that's what your suggesting. I would have to purchase a carb rebuild kit for $30 or $40, when I am planning on replacing this carb anyway for a larger one in the next 6-12 months. Or, can I just get the bowl and metering block gaskets and do that part only? Can I get just the bowl and metering block gaskets and power valve at my local AutoZone or Advance Auto Parts or Napa Auto Parts or do i have to buy them from Summit and/or Jegs and pay shipping and wait 3-5 days?

That's up to you. You should be able to just get a PV (comes with gasket) and bowl and block gaskets from most good auto parts stores.
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  #38 (permalink)  
Old 03-04-2006, 12:50 AM
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Quote:
Originally Posted by leejoy
Dear Mr. Tech

I already did the first part of your message, now I can test the accelerator pump idea and see what that does. good idea. I may have a blown power valve. I need to help to explain. If it is blown I can see why i'm having these problems. I think when the idle mixture screws are turned all the way in there is little or no change to idle if I recall......indicating a blown (open-ruptured) power valve right? what I don't understand is if the power valve is not blown, but open, how would that affect idle? At idle it's just drawing through the idle ports anyway and so what if the power valve is open. I don't understand.
A blown power valve (sometimes happens when the engine backfires) will allow extre raw fuel to dump into the engine. The power valve is there to help the transition from idle and low throttle positions to moderately opening the throttle when you don't hammer the throttle enough to get a big squirt from the acellerator pump. When I am having problems like you are having, Holley has screw in plugs that I install in place of the power valves and go up 2 to 4 sizes on the jets.

If you are getting a really rich mixture as you would get with blown power valve, it is likely you have opened the primary throttle with the idle screw just to get it to start. It would be a very rich and smelly idle. You could achieve the above described idle condition with the idle air screws all the way in and the throttle plate idle screw cracked open.

There is a good book, Super Tuning and Modifying Holley Carburetors by Dave Emanuel which will teach you all you need to know. Then you won't have to share the women with dirty old men like me.
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Old 03-04-2006, 06:49 AM
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I was having the same problem on my BB. (No response from idle screws, poor idle) And the guys on this site helped me out tremendously. BG tech
support knows his stuff follow his advise. IO'Reilly's has a Vac. Seconday kit for just over $20. It very complete. As for me, my Secondary set screw
was holding them open too far, cancelling out my idle circuit. I unscrewed it untill the secondaries were fully closed and then screwed them in until they barely cracked open. Walla broblem was cured. I too have to small of a carb (600) but my cam is a lot smaller and I don't wan't to buy a new carb yet. Can't afford for one and the timing chain is going out of my daily driver (see Good truck engine? flexhone? post). Just my two cents. Keep working and you'll get it. Just take your time and change one thing at a time. Keep track of it's effect and go from there. Take notes if you have to, they do help and you can refer to them later. Good luck and keep us informed
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  #40 (permalink)  
Old 03-04-2006, 08:27 AM
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A 650 is way to small for that engine. And if that is a 650 spead bore the problem is even worst!

The problem sounds like the front blades need to be opened so too far in order to get eoungh into the engine. And the blades are past the transistion slots.

Drilling holes in the front blades allows a small carb to run on a big engine. and that is what you have.

So, either drill or get a bigger cab. I think a 750 would still need some small holes drilled (0.070"). Get an 850 (bigger front blades).
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  #41 (permalink)  
Old 03-04-2006, 08:41 AM
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Quote:
Originally Posted by 454C10
A 650 is way to small for that engine. And if that is a 650 spead bore the problem is even worst!

The problem sounds like the front blades need to be opened so too far in order to get eoungh into the engine. And the blades are past the transistion slots.

Drilling holes in the front blades allows a small carb to run on a big engine. and that is what you have.

So, either drill or get a bigger cab. I think a 750 would still need some small holes drilled (0.070"). Get an 850 (bigger front blades).
I think a 900...
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