Hello, I'm trying to start a 37 plymouth that has been sitting for about 15 years. Original motor, inline 6, gas tank and fuel lines are clean. Pour gas in carb and it will start and run a few seconds, hooked up a electrical pump with same results, wants to run but just dies. Any help will definitely be appreciated.

If you remove the air cleaner from the carburetor and move the linkage (engine not running) do you see fuel squirting? I would suspect a plugged jet.

- EM

Runs, then dies suggests fuel (spark is usually all or nothing).
I'd suggest cleaning the carb carefully.
I hope you cleaned the oil pan and checked the pickup, lubed the cylinders and checked for oil pressure too.
I would hate for a minor problem to cause a major problem when running.
Also, if running it for a while, keep an eye on temps.
The water distribution tube is a common failure on old sitting engines.

http://p15-d24.com/forum/20-technical-archives/

Remember, those older engines run well when properly maintained, they just need more maintenance than even 1960s engines. Waking one after years takes a bit of effort!

could you post some pics of this car please ? always nice to see other's projects.

Think RodStRace has given you some good advice.

Here is some inspiration. My 37 Plymouth coupe and the 230 flathead that I built for my 48 Plymouth coupe. It was my daily driver for about 5 years in Dallas traffic. The flatheads can be very reliable if in good condition.

Yours should be a 201 (82 HP). A 218 (95 HP) from a late 40s or a 230 (132 to 138 HP) from a mid to late 50s would be allmost a bolt in for you with the right bellhousing and starter. Either would offer a good boost in performance. I know when I went from my original 218 to the 230 there was a big seat of the pants improvement. Another think I would suggest is a Borg Warner R6 overdrive transmission. I put an R10 in my 48 and it was the single best modification I made to the car.