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D42 flathead 6 carb and timing adj

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Hi I am new so please bare with me. I have just purchased a 1937 Plymouth deluxe P4 with a d42 flat head 6. My gas miliage is around 10mph. How can I improve this? The enging is not rebuilt but has good compression. The carb is rebuilt.

Also I have a vibration at around 50mph I can really feel it in the gearstick. When I push the clutch pedal in it does not go away. I was told the breaks have been rebuilt and they look it as well.

Thank you in advance

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Set your timing to around 5 degrees BTDC with the vacuum advance disconnected and carb side of the line plugged. Reconnect vacuum advance, and adjust idle speed to around 550-600 rpm. Using a vacuum gauge hooked up to manifold vacuum, adjust the idle mixture screw for maximum vacuum, idle speed may need to be adjusted while tuning mixture screw.


Do these first and then ask again about the vibration. If you are not able to set timing - there may be a problem with the vibration damper having slipped assuming it has one.

Edited by Dartgame

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First things first. Pull out your dipstick and see if it smells like gas.


Now the bad news. Due to ethanol in gas,you need to replace your gas line with the new copper/nickel gas line that never rusts in or out,you need to replace all the rubber hoses in your gas line with modern gas hoses,and you need to replace  or rebuild your fuel pump with a modern repair kit that will stand up to ethanol.


While you are doing this,do yourself a favor and get under the car and physically inspect your brake lines and brake hoses. If the hoses look old or cracked,replace them with new ones. If the lines look rusty or it looks like someone has spliced a section of new brake line into the old brake line,replace the brake line also. The new copper/nickel brake line is cheap insurance because you can't see if there is any rust inside your old brake lines or not.


While you have the car in the air,pull the hubs and physically inspect the brake shoes,springs,drums,and repack the wheel bearings.


Once you are through with that check your spindles,tie rods,and drag link for wear and replace anything questionable. Grease everything.


Remember,these cars are really old,and most of them have been sitting for years,or even decades. Who knows what work has been done to them over the decades,or who did the work? Or even if they knew,or cared what they were doing.


A little bit of safe is more valuable than all of the sorry in the world.


Edited by knuckleharley

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Thank you for your reply. I live in England and fortunatly we do not have ethanol in our gas. The brakes, shoes, wheel bearings have all been replaced. I feel no vibration in the stearing wheel at all. It feels more like it is in the drive train. I did notice I am leaking gear oil from the front of the gearbox.

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Thanks for your reply. I guess I will have to find my tac and timming light but since moving to England 21 years ago things get lost and I may have to buy a new one. I origionally come from the Twin Cities MN.

Thanks for the information and I will let you know how I get on.

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