I'm really getting sick of this Holley carb on my cat...I've adjusted it about 10 times (with a vacuum gauge) and it keeps coming out of adjustment after two days....the crazy thing is, the float adjustment screws almost come all the way out before it idles normally, but then drinks gas like a truck. whats with this screwy carb? is it the rebuilders fault? it seems like vibration shakes it out of tune.
carb from hell
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Do you mean idle mixture screws (one the side of the carb)? If yes, does the engine run better if you gradually limit the air at the top of the carb with your hand? If yes, you have a vacuum leak (which is my guess based on what you described).
Regards,
Bob
thx guys! I think it's the metering block, because the adjustments screws are not really affecting anything. But as far as a vacuum leak, I dont see where it could come from, there isn't much accessories attached to my vacuum ports...and the hoses are new, (I checked the one on the transmission for leaks too) no go...strange
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It is a leak at the metering block between the block and the main body. Remove the bowl and the block and check the gasket. If it is a 4150 carb, with a block in the secondaries check that one also. Run carb cleaner through every port in the carb to check for restrictions, then blow out with air. It is also possible that you have the wrong gasket between the main body and the base plate.
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Yepper - also check that the metering block(s) is square/flat and hasn't warped.....not unusal at all. Might need a little "massaging"
http://www.carcraft.com/techarticles/ccrp_1104_holley_carburetor_rebuild/photo_03.html
http://www.carcraft.com/techarticles/ccrp_1104_holley_carburetor_rebuild/photo_03.html
DAMN THE FUEL DISTRIBUTION GREMLINS!!!!
This carb is driving me nuts!!! once again its sputtering and then taking off like a rocket, drinking gas like a detuned 460
Okay theres one screw on the top of the float then one on the side on each end of the carb. Then theres two little screws on the metering block. What are those screws?
This carb is driving me nuts!!! once again its sputtering and then taking off like a rocket, drinking gas like a detuned 460
Okay theres one screw on the top of the float then one on the side on each end of the carb. Then theres two little screws on the metering block. What are those screws?
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There is no way that you are properly adjusting this carb if you don't know what the screws are for. Here are the instructions for a 3310.
The little screw in the center of the metering plate is the idle mixture screw. The large flat screw in the side of the bowl is the site plug. The screw in the top of the bowl is the lock down for float level adjustment, the actual adjustment is made by turning the nut.
Go to the Holly site to get the instructions for your carb.
FLOAT LEVEL CHECK AND ADJUSTMENT:
Primary and secondary float adjustments are set at the factory, but variations in fuel pressure could cause a change in these
settings. The following procedure shows how to make these adjustments:
1. Start the vehicle.
2. Observe the sight plug for the fuel level. If none is seen, the level is too low. Fuel should be even with the bottom of the
sight plug hole. If fuel comes pouring out of the sight hole, the float is set too high.
NOTE: A properly set float level will have the fuel level located at the bottom edge of the sight hole, as shown by the line in
Figure 12.
Figure 12
3. To adjust, shut down the engine.
4. Loosen the lock screw on top of the fuel bowl just enough to allow you to turn the adjusting nut. Hold the screw in position
with the screwdriver.
12
5. Using a 5/8” wrench, turn the adjusting nut in the appropriate direction: Clockwise to lower float and counterclockwise to
raise float.
6. Turn the adjusting nut in increments of 1/4 of a rotation.
7. Retighten the lock screw.
8. Restart the vehicle and observe the sight plug hole.
9. Repeat steps 1 through 8 as necessary.
IDLE MIXTURE NEEDLES
Idle mixture needles control the air/fuel mixture at idle. These have been preset at the factory and SHOULD NOT need any
adjustments. However, if you feel that adjustment is necessary, you can use the following procedure to do so. When tuning the
idle mixture, you’re actually tuning for the best manifold vacuum. Idle mixture needles are found on the primary metering blocks.
If you change one idle mixture needle, you must change the other idle mixture needle by the same amount. Here are the proper
steps for setting the idle mixture needles.
1. Attach the vacuum gauge to a manifold vacuum port on the throttle body (Figure 7).
2. Adjust each idle mixture screw (Figures 10 & 11) 1/8 turn at a time, alternating between each screw. Turn them equally,
until you achieve the highest possible vacuum reading without adjusting the curb idle speed screw. Turn screws in to lean
the mixture. Turn them out to richen the mixture.
Figure 9
3. Now that the idle mixture is set, it may be necessary to go back and reset the idle speed using the curb idle speed screw,
as shown in Figure 9.
4. If a vacuum gauge is not available, use a tachometer to obtain the highest RPM.
The little screw in the center of the metering plate is the idle mixture screw. The large flat screw in the side of the bowl is the site plug. The screw in the top of the bowl is the lock down for float level adjustment, the actual adjustment is made by turning the nut.
Go to the Holly site to get the instructions for your carb.
FLOAT LEVEL CHECK AND ADJUSTMENT:
Primary and secondary float adjustments are set at the factory, but variations in fuel pressure could cause a change in these
settings. The following procedure shows how to make these adjustments:
1. Start the vehicle.
2. Observe the sight plug for the fuel level. If none is seen, the level is too low. Fuel should be even with the bottom of the
sight plug hole. If fuel comes pouring out of the sight hole, the float is set too high.
NOTE: A properly set float level will have the fuel level located at the bottom edge of the sight hole, as shown by the line in
Figure 12.
Figure 12
3. To adjust, shut down the engine.
4. Loosen the lock screw on top of the fuel bowl just enough to allow you to turn the adjusting nut. Hold the screw in position
with the screwdriver.
12
5. Using a 5/8” wrench, turn the adjusting nut in the appropriate direction: Clockwise to lower float and counterclockwise to
raise float.
6. Turn the adjusting nut in increments of 1/4 of a rotation.
7. Retighten the lock screw.
8. Restart the vehicle and observe the sight plug hole.
9. Repeat steps 1 through 8 as necessary.
IDLE MIXTURE NEEDLES
Idle mixture needles control the air/fuel mixture at idle. These have been preset at the factory and SHOULD NOT need any
adjustments. However, if you feel that adjustment is necessary, you can use the following procedure to do so. When tuning the
idle mixture, you’re actually tuning for the best manifold vacuum. Idle mixture needles are found on the primary metering blocks.
If you change one idle mixture needle, you must change the other idle mixture needle by the same amount. Here are the proper
steps for setting the idle mixture needles.
1. Attach the vacuum gauge to a manifold vacuum port on the throttle body (Figure 7).
2. Adjust each idle mixture screw (Figures 10 & 11) 1/8 turn at a time, alternating between each screw. Turn them equally,
until you achieve the highest possible vacuum reading without adjusting the curb idle speed screw. Turn screws in to lean
the mixture. Turn them out to richen the mixture.
Figure 9
3. Now that the idle mixture is set, it may be necessary to go back and reset the idle speed using the curb idle speed screw,
as shown in Figure 9.
4. If a vacuum gauge is not available, use a tachometer to obtain the highest RPM.
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5,633 Posts
I start with the base idle mixture screws at 1 1/2 turn. I also prefer using a tach to make the fine idle adjustments. Write down where you had things set. Once you have idle an float levels set right, see if the car surges at 50 mph on a flat piece of road. If it does, then go up two sizes on the main jets. If it doesn't go two sizes down, until it does start to lean surge (then go back to the smallest jets where you got no lean surge.) Then with some one following you, floor it going up an on ramp. Have them look for dark black smoke. A little puff when you floor it is okay, but anything else means you are too rich.
Some lessons learned beyond basics.....been fiddling with Holleys since I was 15....I'm 46 now.
Float level....the rubber o ring on the needle/seat can dry quickly in this new ethynol.....buy many o rings and keep on hand for quick fix. You wil know this by high fuel levels. Also, plastic floats will fill up with gas. Small tab riding on needle can get bent beyond the float adjustment capability.....flip bowl upside down when removed and check static float level....
Warped metering block will cause gas to drip from the boosters....but so can a bad power valve and any other item affecting fuel level in the bowls.
Some Holleys have a small brass tube with two o rings on each end to seal the accelerator passage.....again, ethynol can kill these in a few months.
Just random thoughts on Holleys somewhat related to your plight.....good luck! Holleys are great carbs!
Mikey
Float level....the rubber o ring on the needle/seat can dry quickly in this new ethynol.....buy many o rings and keep on hand for quick fix. You wil know this by high fuel levels. Also, plastic floats will fill up with gas. Small tab riding on needle can get bent beyond the float adjustment capability.....flip bowl upside down when removed and check static float level....
Warped metering block will cause gas to drip from the boosters....but so can a bad power valve and any other item affecting fuel level in the bowls.
Some Holleys have a small brass tube with two o rings on each end to seal the accelerator passage.....again, ethynol can kill these in a few months.
Just random thoughts on Holleys somewhat related to your plight.....good luck! Holleys are great carbs!
Mikey
There is nothing special about them....all I did is grabbed a big o-ring assortment you can find at many automotive shops. Once you get a Holley dialed in, they are great. Try and avoid the new alcohol crappy gas for more reasons than just the Holley. The alcohol is just filler that you are paying high gas prices for........whats worse is that gas now puts out less BTUs of energy (lower power and worse MPGs) and messes with your finely tuned carb, too. Thanks to the feds!
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+1
Try keeping some Marine Sta-Bil (blue) in the tank.
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5,633 Posts
You would be amazed at how much better an Edelbrock will run if you tune it for your car. They have some very detailed tuning instructions that come with the carb and it is super easy to do, you don't have to drain the gas out even. The right set of needles and jets will get you better mileage, and better starting.
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8,194 Posts
For sure. Just press the gas once, turn the key and it's running.
My friend, who swears by Holleys, has starting troubles with his Cat. Rough idle, stalls, etc until it is warm enough to run OK. He thinks he doesn't need to have the choke hooked up for some reason.
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Holleys and dirt don't mix. Corrosion from alcohol fuels (and inactivity) clog tiny fuel and air passages and cause the car to run bad. An acquaintance of mine who sells Holleys once told me that 85% of the Holley carburetor returns were because of dirty fuel. I think some Holleys now come with inline filters and the warranty is void if an inline filter is not used between the pump and the carb.
Easy operation to remove the front bowl, metering block and with a $3. can of carburetor cleaner and compressed air wash out the passages. You really don't even have to remove the carb. No expensive carburetor technician is needed and most of the time no gaskets will be required.
Edelbrock carburetors are fine, seem to be resistant (not immune) to the trash problems that Holleys have.
Easy operation to remove the front bowl, metering block and with a $3. can of carburetor cleaner and compressed air wash out the passages. You really don't even have to remove the carb. No expensive carburetor technician is needed and most of the time no gaskets will be required.
Edelbrock carburetors are fine, seem to be resistant (not immune) to the trash problems that Holleys have.
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