3810 holley problems

[Timothy B.]

Just started my 67 300 HP after two years sitting but before I stored the car, I changed the oil, treated the gas and had the carburetor overhauled because it ran rich at idle and never ran gas through it after putting it back on the car.

The car started and ran fine, idles at 550 on the tach but I think is still rich at idle. Crazy as it sounds the air/gas screws are out 1/2 turn from seat and engine vacuum is approx 19" and steady. If you turn the idle stop screw to increase RPM, engine sputters a little when just cracking the throttle plates, if the air/gas screws are opened another 1/2 turn that goes away but engine will not idle nice as before with screws just 1/2 turn from seat. No gasoline appears to be dripping in the carburetor and throttle plates look dry the next day. After sitting overnight a small pool of gas on passenger side intake manifold in front and behind choke stove.

I removed the carburetor and found the main body and throttle plate surface not flat. The four corners where the screws attach are like ears on the main body and were pulled slightly so I filed flat to correct The two middle screws are not tapped but I have thought about tapping and installing screws. Car idles better very smooth but still 1/2 turn out on air/gas screws and seems rich. Smaller amount of gas in manifold the next day. I am thinking I need holley gaskets but would like other suggestions because I know others have had the same issues and wanted to ask before I $$$$ on stuff I may not need. Thanks and sorry for the long post.

[Clem Z.]

Re: 3810 holley problems

i would "straight edge" all the rest of the gasketed surfaces to see if they are flat including the metering bodies. also the brown paper gaskets work better on older carbs than the so called "reusable" one ones because they have the thermosetting adhesive which seals better

[Joe C.]

Re: 3810 holley problems

Just started my 67 300 HP after two years sitting but before I stored the car, I changed the oil, treated the gas and had the carburetor overhauled because it ran rich at idle and never ran gas through it after putting it back on the car.

The car started and ran fine, idles at 550 on the tach but I think is still rich at idle. Crazy as it sounds the air/gas screws are out 1/2 turn from seat and engine vacuum is approx 19" and steady. If you turn the idle stop screw to increase RPM, engine sputters a little when just cracking the throttle plates, if the air/gas screws are opened another 1/2 turn that goes away but engine will not idle nice as before with screws just 1/2 turn from seat. No gasoline appears to be dripping in the carburetor and throttle plates look dry the next day. After sitting overnight a small pool of gas on passenger side intake manifold in front and behind choke stove.

I removed the carburetor and found the main body and throttle plate surface not flat. The four corners where the screws attach are like ears on the main body and were pulled slightly so I filed flat to correct The two middle screws are not tapped but I have thought about tapping and installing screws. Car idles better very smooth but still 1/2 turn out on air/gas screws and seems rich. Smaller amount of gas in manifold the next day. I am thinking I need holley gaskets but would like other suggestions because I know others have had the same issues and wanted to ask before I $$$$ on stuff I may not need. Thanks and sorry for the long post.

Too bad you didn't run the engine at any time after the carb rebuild. Am I reading you correctly............if so, then you can safely assume that the rebuilder $%^&*%@$* your carburetor. Can you tell us how it was running before the rebuild?
The fuel leaks only after it sits.......not while it's running? Probably fuel perking out the bowls during heat soak. Expands and flows up the emulsion tubes and out the boosters. Check float levels. Check needle/seats for debris or sticking. Check all passages in primary metering block, especially emulsion tubes and idle/main air bleeds. Rinse in lacquer thinner and blow all passages with compressed air.
Check primary idle transfer slots, which requires removal of carburetor. They should be exposed to the extent, that if you look at them from below the throttle plates, they appear as perfect squares, and NOT rectangles:

http://www.mustangandfords.com/techarticles/mufp_0603_ford_carburetors/photo_19.html

The slots should only be exposed about .040"-.050" with the throttle hitting the "closed" stop.If they are exposed too far, you'll find that your idle mixture screws will be rendered useless, and you'll experience a severe off-idle stumble/flat-spot.

Joe

[Timothy B.]

Re: 3810 holley problems

You guys are going to think I am nuts. I have straight edged all surfaces, only problem is base of carb where the screws and heat distorted the corners a bit. I actually took a nice flat file to that and kept working it until flat, there was definitly a problem there. Took a file to the throttle plate as well but all other surfaces check OK so I saw no need to go further, everything taken apart and checked. Installed a new base gasket from left over kit (it looked like the correct one with bore hole size correct) and the car idles good with no miss and 19" vacuum. There is a slot in the throttle plate that supplies idle circuit fuel to secondaries on both sides of the plate and my gasket had a hole located on the slot and I am wondering if that's not right and vacuum is finding gas there.


It's hot here in MD and after the car is shut down heat soak gets the carburetor hot. I wonder if two year old gas could have something to do with expansion and leak. Heat slots are plugged and manifold gasket and stainless shield are in place for originality. Power valve is not holley but sucks closed OK, as I said the car does not flood just seems rich and I would like air/gas screws further out because lean miss when transfer slots are exposed with slow opening of the throttle. If I turn the screws out another half that goes away. Going from my memory on Thursday the .040 bottom of the transfer slots are not even exposed at idle, the car is running completely on the idle circuit.


Has anyone experenced problems with gaskets in aftermarket, I am being told to use holley parts. Thanks for all suggestions.

[Clem Z.]

Re: 3810 holley problems

You guys are going to think I am nuts. I have straight edged all surfaces, only problem is base of carb where the screws and heat distorted the corners a bit. I actually took a nice flat file to that and kept working it until flat, there was definitly a problem there. Took a file to the throttle plate as well but all other surfaces check OK so I saw no need to go further, everything taken apart and checked. Installed a new base gasket from left over kit (it looked like the correct one with bore hole size correct) and the car idles good with no miss and 19" vacuum. There is a slot in the throttle plate that supplies idle circuit fuel to secondaries on both sides of the plate and my gasket had a hole located on the slot and I am wondering if that's not right and vacuum is finding gas there.


It's hot here in MD and after the car is shut down heat soak gets the carburetor hot. I wonder if two year old gas could have something to do with expansion and leak. Heat slots are plugged and manifold gasket and stainless shield are in place for originality. Power valve is not holley but sucks closed OK, as I said the car does not flood just seems rich and I would like air/gas screws further out because lean miss when transfer slots are exposed with slow opening of the throttle. If I turn the screws out another half that goes away. Going from my memory on Thursday the .040 bottom of the transfer slots are not even exposed at idle, the car is running completely on the idle circuit.


Has anyone experenced problems with gaskets in aftermarket, I am being told to use holley parts. Thanks for all suggestions.

i would go out and get a genuine holley kit # 37-1537. those aftermarket power valves do not even have a vacuum opening number stamped on them.

[Timothy B.]

Re: 3810 holley problems

Thanks Clem,

The power valve does NOT have a opening # stamped but does seem to hold closed easily with suction. I think the holley kit is my best corse of action at this point. Where is the best place to purchase the kit in your opinion and is this a minor overhaul kit? Do you think I should tap the two screws in the center of the base?

Vacuum at 19" is good for my car and the gaskets that came off did not stick, they removed easily, it probably does not take much internal gas leak to do what I am experencing. Not a happy camper at this point!!

I appreciate all advice, Tim

[Clem Z.]

Re: 3810 holley problems

Thanks Clem,

The power valve does NOT have a opening # stamped but does seem to hold closed easily with suction. I think the holley kit is my best corse of action at this point. Where is the best place to purchase the kit in your opinion and is this a minor overhaul kit? Do you think I should tap the two screws in the center of the base?

Vacuum at 19" is good for my car and the gaskets that came off did not stick, they removed easily, it probably does not take much internal gas leak to do what I am experencing. Not a happy camper at this point!!

I appreciate all advice, Tim

most chain auto parts can get them and if not summit or jegs can mail order one. the extra screws should not be necessary. if you go to a auto parts tell them you want a genuine holley kit.it will contain all gaskets,power valves and needle/seats

[Joe C.]

Re: 3810 holley problems

Thanks Clem,

The power valve does NOT have a opening # stamped but does seem to hold closed easily with suction. I think the holley kit is my best corse of action at this point. Where is the best place to purchase the kit in your opinion and is this a minor overhaul kit? Do you think I should tap the two screws in the center of the base?

Vacuum at 19" is good for my car and the gaskets that came off did not stick, they removed easily, it probably does not take much internal gas leak to do what I am experencing. Not a happy camper at this point!!

I appreciate all advice, Tim

Almost certainly not the power valve, which should begin to open @ 6.5 in-hg. Fumes would burn your eyes at idle and be belching smoke. To check power valve, remove air cleaner, idle car, and cover both bowl vents with thumbs. If car stalls, power valve NG.

I think you know how to check for vac leak. Spray all mating surfaces of carb, and intake manifold with oil, and see if idle speed drops.

Check your distributor. Are your advance weights deploying too early? Is your vac can operating as it should? Too much advance at idle will force you to close throttle plates too far in order to to idle engine down.

Are your secondary throttle plates adjusted properly? Same principle applies to sec plates. If they are open too far, forces closing primaries too far in order to idle down.

Check this link for pertinent info for your carburetor:

http://www.holley.com/data/TechServi...%20Listing.pdf

[Clem Z.]

Re: 3810 holley problems

rebuild it with the holley kit and follow the instruction for settings. using the idle speed screw set the idle transfer slots at .020,looks like a square opening,install on the engine,start the engine. if the idle speed is too high or too low after the engine is warmed and the choke is clear off look at other things like the distributor/timing etc. set the idle air mixture screws at 1-1/2 turns out to start. if the idle transfer slots are open too far the idle air mixture screw have very little effect and if they are closed too far you will have a hesitation when accelerating.

[Gerard F.]

Re: 3810 holley problems

Tim,

If it has been sitting for 2 yearrs the base gasket is probably dried out and you have major vacuum leaks. Put on a new base gasket, take a nice long run, let it get real hot, then retighten the carb to manifold nuts. Let the gasket take a set.

Then start doing your idle mixture adjustments.

Actually 1/2 turn out on the mixture adjustment and idling smoothly at 550 rpm with 19" vacuum is really pretty good.

Also check your idle vents in the air horn to see that they are open and not plugged.

[Joe L.]

Re: 3810 holley problems

You guys are going to think I am nuts. I have straight edged all surfaces, only problem is base of carb where the screws and heat distorted the corners a bit. I actually took a nice flat file to that and kept working it until flat, there was definitly a problem there. Took a file to the throttle plate as well but all other surfaces check OK so I saw no need to go further, everything taken apart and checked. Installed a new base gasket from left over kit (it looked like the correct one with bore hole size correct) and the car idles good with no miss and 19" vacuum. There is a slot in the throttle plate that supplies idle circuit fuel to secondaries on both sides of the plate and my gasket had a hole located on the slot and I am wondering if that's not right and vacuum is finding gas there.


It's hot here in MD and after the car is shut down heat soak gets the carburetor hot. I wonder if two year old gas could have something to do with expansion and leak. Heat slots are plugged and manifold gasket and stainless shield are in place for originality. Power valve is not holley but sucks closed OK, as I said the car does not flood just seems rich and I would like air/gas screws further out because lean miss when transfer slots are exposed with slow opening of the throttle. If I turn the screws out another half that goes away. Going from my memory on Thursday the .040 bottom of the transfer slots are not even exposed at idle, the car is running completely on the idle circuit.


Has anyone experenced problems with gaskets in aftermarket, I am being told to use holley parts. Thanks for all suggestions.

Tim-----


If you have not already done so, I highly recommend that you plug the holes at the ends of the "heat slot" on the manifold's carburetor flange. These are about 3/8" holes and can be plugged with the manifold installed on the engine by driving in 3/8" soft plugs. Off the engine, I drill and tap for allen head pipe plugs.

Doing this will greatly reduce carburetor deterioration and main component "warpage".