Hey there boys and girls, I have a 51 Desoto flat six that I finally got to run well kinda it starts and runs for about five minutes and once it warms up it just dies and then the warmer it gets the harder it is to start and sometimes will get some backfiring through the exhaust it dose have a bit of valve noise when running. I have not checked or adjusted timing the carb has been rebuilt, new points, cap, rotor, wires, plugs new fuel pump and gas line to the tank. I did try and turn the distributor but the dam thing is sized and won't turn so any suggestions on that would be great was thinking of trying a little heat. Any thoughts on my running problem would be great thanks Posted using the Full Custom H.A.M.B. App!
Timing might be it, but your starting it OK. I would look at the fuel supply...its it heating up somewhere...like vapor lock? Does it cool down...start...then die again? if so, I'd be checking out the fuel system. Also, double check all your new work. Might be something moving around and grounding out somewhere stalling the engine?? If all the electrics are working properly, you should be able to start the car...unhook the battery and the car will stay running...try that as well. Murph
When it is ice cold it starts fine and then runs for about 5 min and then dies and then it seems like you have to pump the gas more and more to get it started aging, as it gets warmer it won't run as long that's why I put a knew fuel pump and line on it didn't seem as if I was getting enough fuel volume I guess I could pull the air horn off the carb next time it dies and see if the bowl is empty I didn't clean out the tank could have some crud in there too or could of miss adjusted the float in the carb Posted using the Full Custom H.A.M.B. App!
You didn't mention Tank Cleaning....Could be your entire problem! Now, you need to check the complete fuel system, incl. your new work.
You could just run a hose from a fresh can of gas to the supply side of the pump. If it stays running, clean the tank. If not, you'll probably have to recheck your new work. (New parts are as good as they used to be.)
Are you using a 12v battery? If you are the coil could be overheating although it usually takes longer than 5 minutes. Could also be a condenser. Your car has a 6v + ground system. And left hand threads on the left side wheel bolts. And it has a flathead engine, not a flat engine. You don't need to take off the whole air filter, if you unscrew the wing nut and lift off the top part you can peek inside.
Yea I think I am going to just try disconnecting the line from the tank and run it to an external tank/gas supply and see what happens I am sure there is crud in the tank and that could be the whole problem I would think if the timing was of it wouldn't start so easy when its cold Posted using the Full Custom H.A.M.B. App!
I don't know how warming up an engine gets the gas dirty, and letting it cool down makes it clean again. I do know that coils can fail when they get hot and work OK again when they cool down.
Your exhaust valves have no clearance! As soon as the stems warm up and get longer they quit sealing then compression goes to hell.
Check and clean the jets in the carb. Assuming the choke is on when when cooled down you may be by passing the main jets in the carb. When the choke turns off it's possible it's starving for fuel through clogged jets. Anyway standard procedure would be to first make sure the valves are set correctly, then the timing, then other adjustments such as the carb. BTW, I just picked up a 50 Desoto convertible and will be trying to start it in a week or two, after at least 10 years of sitting.
Sweet pick up on the 50 I did clean and rebuild the carb but they could still be clogged when the thing is running if you watch down the carb it seems as its barley getting any gas and once it dies you can pump the throttle and it squirts down the carb I would think if the bowl ran empty I wouldn't get that squirt Posted using the Full Custom H.A.M.B. App!
Also is it a pain to adjust the valves and do I have to pull the intake and exhaust manifold to do it Posted using the Full Custom H.A.M.B. App!
I don't have the specific valve adjustment procedure offhand (still waiting for my service manual to arrive), but on other old Mopars I've owned access was thought the passenger side wheelwell. Remove the tire and remove a cover to get access to the valve covers. Others may know the specifics. Also p15-d24.com is a good forum for info on these old Mopars.
from the p15-d24 site tech tips: Valve Adjustment Proper valve adjustment is critical for quiet and efficient operation of a flathead six and is the first line of defense against burned valves. Compared to overhead valve engine the flathead is a very simple design. A tappet follows the contour of the cam lobe pushing a valve up and open at the appropriate time. The only adjustment is the clearance between the tappet and valve stem. Accurate adjustment can only be made while the engine hot. To complete the job you will need a valve gasket set, set of go/nogo feeler gauges, pair of tappet wrenches and a pair of gloves to protect you from burns on the exhaust manifold. While the valve covers are readily visible from the top of the engine, dont attempt this job from above the manifold. Instead raise the right front on a jack stand and remove the right front tire. Inside the wheel well is an access panel approximately 3 feet wide and 18 inches high. Remove the bolts holding the access panel. When removed you will have straight on access to the valve covers. Start the engine and bring it up to operating temperature. After the engine warms up, stop the engine and manually turn it over to Top Dead Center (TDC). Verify piston #1 is in firing position by checking the position of the distributor rotor. If should point around 7 oclock. If it points to the 1 oclock position, you have piston #6 in firing position. Manually turn the engine one full revolution and you are ready to start. Remove the valve covers and use the following sequence for the order of the valves to adjust. Exhaust valve clearance .010 Intake valve clearance .008 Stage A, #1 and #6 at TDC, #1 in firing position Stage B, #1 and #6 at TDC, #6 in firing position To move from Stage A to B, manually turn the engine 1 revolution. Stage A Adjust #1 Both valves, #2 Inlet valve, #3 Exhaust Valve, #4 Inlet valve, #5 Both valves. Stage B Adjust #2 Both valves, #3 Inlet valve, #4 Exhaust valve, #5 Inlet valve, #6 Both valves. Using the two tappet wrenches you can use one hand to adjust the tappet, leaving the other hand free for the go/nogo gauge, The go/nogo gauge has three steps cut into it. If the adjustment gap is too wide, you will be able to slide it to the third step. If the gap is too narrow only the first step will slide between the valve and tappet. What you want is the middle step to fit snugly. Adjust each valve as specified in the adjustment sequence. It is better to err on the side of too much clearance versus not enough. Too much clearance may result in a slightly noisy tappet, while too little may burn the valve. After you finish the adjustment, reinstall the valve covers with the old gaskets. Bring the engine back up to operating temperature and you will notice the engine is much quieter. Sometime you will need to readjust a single noisy valve. Just make sure it is fully off the cam lobe and totally closed. If everything is OK remove the valve covers and install the new valve cover gaskets (780-469) with sealer. When re-tightening the valve covers don go overboard. They just need to be snug, letting the gasket and sealer do the work. Too tight distorts the sheet metal cover and usually results in leak. Reinstall the access panel and tire and you are back on the road. Properly adjusted valves result in a quiet running engine and help protect against damaged valve train components. If you have done the job right it will be difficult to tell if the engine is running from five feet away because it so quiet!
Thanks for the info I think next week I may have some time to actually work on the car I will give updates as to my findings Posted using the Full Custom H.A.M.B. App!
Not to hijack this thread, but the original color was a very light Tan, The PO started to disassemble for paint 10 years ago and never finished it. The body is rock solid, unheard of here in NE, and all the trim is with the car. Original drive train is in place and undisturbed. The PO even had the seats reupholstered to original back then so they are pristine. First saw it more than a year ago and took some persistence to convince the PO to let it go. It's a project but a nice foundation to start off of.
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