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Discussion Topic:
No Power After Rebuild
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DHunt |
10-23-2015 @ 9:40 AM
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Member
Posts: 14
Joined: Nov 2009
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I just had my 1935 Flathead engine rebuilt by a reputable local builder. The engine starts and idles fine but has no power. No issues with back firing. Top speed is only ~ 20 mph. Engine compression is ~ 105 psi on each cylinder. We tried two different carburetors. I believe my distributor (original design) timing adjustments are correct. Any idea what I’m missing? Thanks for your ideas. David Hunt Kingwood TX
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37 Coupe |
10-23-2015 @ 11:14 AM
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Member
Posts: 362
Joined: Oct 2009
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Mayby check air going in and exhaust out. Resticted air filter or plugged exhaust.Are you sure mechanically your accelerator to carb linkage is free not binding. Try another condensor
This message was edited by 37 Coupe on 10-23-15 @ 11:15 AM
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CharlieStephens |
10-23-2015 @ 12:12 PM
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Senior
Posts: 893
Joined: Oct 2009
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Check to be sure you have full travel on your carburetor linkage. Are you opening the butterflies all the way? Maybe the linkage was bent when putting the engine into the car. Please let us know the final result. Charlie Stephens
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1932BB |
10-23-2015 @ 12:42 PM
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New Member
Posts: 104
Joined: Oct 2009
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Check gas supply to the carb. Sometimes filters can dry out during the engine rebuilding process and not pass enough fuel.
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MG |
10-23-2015 @ 5:06 PM
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Senior
Posts: 1260
Joined: Nov 2009
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Sounds like your engine running on only four cylinders - gas is getting to just four cylinders. Change the carburetor.
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37 Coupe |
10-23-2015 @ 5:50 PM
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Member
Posts: 362
Joined: Oct 2009
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Somewhere he mentioned trying two carburetors but you brought something interesting up,fuel not reaching all 8 cylinders. He could check the plugs to see if some have not fired,mayby be the plugs,spark to certain plugs or fuel not reaching a cylinder because of obstruction in manifold or the block,mayby something was left in a hole, that is plugged.
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timcolr |
10-23-2015 @ 7:29 PM
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Posts: 22
Joined: Sep 2015
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Just a thought, is the vacuum advance on the distributor OK? May have a crack or hole in the diaphram. Tim
1950 Fordor Deluxe 6
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trjford8 |
10-24-2015 @ 7:18 AM
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Senior
Posts: 4218
Joined: Oct 2009
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I think Tim may have the answer. Lack of proper vacuum to the stock distributor is the likely problem. I believe that distributor depends totally on vacuum to operate correctly. It is not advancing as you try to accelerate.
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TomO |
10-24-2015 @ 8:31 AM
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Senior
Posts: 7256
Joined: Oct 2009
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Check your spark at all cylinders. You should have a 1/2" blue spark when the engine is idling. A weak coil, a weak condenser or point gap can cause a weak spark limiting your power. If the spark is OK, check your vacuum at idle and at speed. Here is a link on how to interpret the readings. http://www.secondchancegarage.com/public/186.cfm If the readings are normal or near normal, I would check fuel delivery next. You could have a plugged fuel line, vacuum leak in the supply side or a flex line that is collapsing under vacuum. To check fuel delivery, you need a graduated 16 ounce or larger container to determine the amount of fuel delivered in a measured time. Disconnect the fuel pump line from the carburetor and direct it into a graduated container. Crank the engine long enough to get 2 ounces of gas in the container and then continue cranking for 15 more strokes of the pump. The pump should have delivered 6 more ounces of gas. The vacuum brake on the distributor prevents too much advance under load. I doubt that it would affect power as much as you are seeing. It would more likely cause overheating under loaded conditions.
Tom
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DHunt |
10-24-2015 @ 9:17 AM
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Member
Posts: 14
Joined: Nov 2009
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Thanks for all the great insight. I appreciate it. I will get to work on them David Hunt
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