Intake & Carb
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Mountain Pass
Joined: Mar 2006
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Intake & Carb
Working on my 54 with original 239 ohv. Have tried 2 carbs,( current one had never been rebuilt) put a carb kit in it but still have a hesitation or flat spot when i try to first accelerate. I have a 2 barrel intake for the 239 and was wondering what carb would be the best and also have throttle linkage in same location as original. Have put new plugs and wires, coil and did away with points with a pertronix ignition but still have the flat spot when i first give it gas. Thanks
Senior User
Joined: Jun 2018
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What’s your timing at?
what carb is currently on the truck? Holley 94?
can you give more detail on the two barrel intake you plan to use? I suspect your talking about a late Y block with a 4 bolt pattern for the Holley 2100?
Chris
what carb is currently on the truck? Holley 94?
can you give more detail on the two barrel intake you plan to use? I suspect your talking about a late Y block with a 4 bolt pattern for the Holley 2100?
Chris
Post Fiend
Joined: Apr 2002
Posts: 19,311
Likes: 97
From: Waterloo, Iowa
Most Y-blocks should like quite a bit more initial ignition timing advance. Try about 10° BTDC. You may need to re-adjust the idle mixture after changing ignition timing. I would first recommend verifying TDC with a piston stop tool, that the "0" mark on the balancer hasn't slipped.
With all that said, does your motor utilize the LoadOmatic distributor? These require two different vacuum signals to operate, just so everyone is on the same page - manifold and venturi, from the carburetor. There is no mechanical or centrifugal ignition advance mechanism, it is strictly a load based system, so the correct carburetor must be paired with the LoadOmatic. They weren't universally loved.
With all that said, does your motor utilize the LoadOmatic distributor? These require two different vacuum signals to operate, just so everyone is on the same page - manifold and venturi, from the carburetor. There is no mechanical or centrifugal ignition advance mechanism, it is strictly a load based system, so the correct carburetor must be paired with the LoadOmatic. They weren't universally loved.
Senior User
Joined: Jul 2019
Posts: 232
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When you stab the gas pedal, there are really only a few things that happen, one is a squirt of gas from the accelerator pump which we'll assume you can rule out as you just rebuilt it. The other is timing/spark related, so I agree with the others that it's probably where your trouble is coming from. The only other common issue you could have would be a vacuum leak, though these things don't have a lot of places where vacuum can leak from, and I'd expect you might be having other issues if that was it. Still make sure that your vacuum lines are all sealed well. You only have a few of them probably so it will be an easy thing to rule out quickly. It runs well otherwise, right?
Senior User
Joined: Jun 2018
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I would also google “Holley 94 power valve”. Most of the newer rebuild kits have the wrong valve for your 94. If you don’t have a vacuum leak, the timing is checked and set then it would be worth making sure you don’t have a bad power valve.
Chris
Chris
Cargo Master
Joined: Feb 2006
Posts: 2,316
Likes: 893
From: Lititz PA
Most Y-blocks should like quite a bit more initial ignition timing advance. Try about 10° BTDC. You may need to re-adjust the idle mixture after changing ignition timing. I would first recommend verifying TDC with a piston stop tool, that the "0" mark on the balancer hasn't slipped.
With all that said, does your motor utilize the LoadOmatic distributor? These require two different vacuum signals to operate, just so everyone is on the same page - manifold and venturi, from the carburetor. There is no mechanical or centrifugal ignition advance mechanism, it is strictly a load based system, so the correct carburetor must be paired with the LoadOmatic. They weren't universally loved.
With all that said, does your motor utilize the LoadOmatic distributor? These require two different vacuum signals to operate, just so everyone is on the same page - manifold and venturi, from the carburetor. There is no mechanical or centrifugal ignition advance mechanism, it is strictly a load based system, so the correct carburetor must be paired with the LoadOmatic. They weren't universally loved.
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Mountain Pass
Joined: Mar 2006
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The 239 i have in it at one time someone did away with the loadomatic and put a 1957 distributor and it is running the original holley 94. I checked the # on carb and it is a 1957 distributor. Can you run this distributor with this carb with out problems. As i mentioned it has the pertronix instead of original points. Thanks
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Post Fiend
Joined: Apr 2002
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From: Waterloo, Iowa
OK, now we're tracking. Yes, it should run fine. Try 10° to 12° initial timing. Re-set the carburetor idle mixture from 1.5 turns out at a slow idle. Turn them in (clockwise) about 1/4 turn at a time, evenly till best manifold vacuum or highest RPM. Re-set idle RPM back down to spec somewhere in there. It's called the idle circuit, but it is important that it is set just right, for good just-off idle acceleration. After that it's a matter of checking for a good "pump shot" from the carburetor.
Cargo Master
Joined: Mar 2002
Posts: 3,132
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From: W (BY GOD) V
The 239 i have in it at one time someone did away with the loadomatic and put a 1957 distributor and it is running the original holley 94. I checked the # on carb and it is a 1957 distributor. Can you run this distributor with this carb with out problems. As i mentioned it has the pertronix instead of original points. Thanks
http://www.eatonbalancing.com/2010/0...-distributors/
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