'63 361 skipping

[Hulkd700]

I have a 1963 d700 dumptruck with a 361 motor. It has a skip when you get it up to about 18-1900 rpm. It is fouling the plugs also. We've tried more things to rectify than I can remember: plugs, wires, cap, rotor (we had put electronic ignition on it and put the points/condenser back in just to eliminate that) intake gasket, checked timing gears and distributor. The carb had been professionally rebuilt by Treadwell Carburetor.
Thanks in advance for any guidance.

[Kaegi]

was carb rebuilt after problem started or before?

[PwrWgnDrvr]

Have you done a compression test? How many miles on the engine?
Ring and guide wear lets oil burn, which fouls plugs. Everybody forgets the valve seats in old engines are NOT hardened for unleaded gas and erode away quickly.

[Hulkd700]

The problem started after the carb was rebuilt. We have done the valve seals. Compression checks out at 105 to 110psi. 63000 miles on engine.

[Jim100]

Try a different carb? Send that rebuilt one back? Adjusted wrong? What kind of carb is it?

[Hulkd700]

It has a Carter carb. I think we are going to have someone else look at it. We have had it apart and found nothing wrong...
I forgot to mention that the tach flutters when it's skipping. I suppose this would be expected.

[Jim100]

I know its summer but could the carb have been making ice? I had a carter two barrel that was known for it.

[Kaegi]

if its a 361 medium duty truck engine it came with hardened valve seats and sodium filled exhaust valves. the car 361s probably didnt.

if it started with new carb then 90% chance its the carb. does it fall on its face over the missing rpm range?

[Hulkd700]

It does loose power when its skipping. It gets worse as the plugs foul more.
Kaegi, you say it has hardened valve seats? even being that old?

[Kaegi]

It does loose power when its skipping. It gets worse as the plugs foul more.
Kaegi, you say it has hardened valve seats? even being that old?

yes all the truck 361s and 413s did. those engines are so well built the factory warrantied them for 100K back in the 60s. they run gear drive no chain on the cam too. totally bullet proof.
hardened valve seats were something that almost every company started to use in the 30s before leaded gas was around much. mopar flatheads got hardened seats in 33 till end of Flathead production in the 70s. Ford I think in 34 on V8 flatheads. then after WW2 lots of higher quality leaded fuel was everywhere so they stopped using hardened seats in everything except prewar engines that came that way and medium duty and HD truck and industrial engines. example a 67 power wagon with a 251 flathead still has hardened seats. 1 ton and under trucks and cars with post war engines do not have hardened seats until 75 and later they started using them for unleaded.
If you have a factory shop manual see the engine specs for 361 and 413 in the back. they are made to last forever basically. I have heard from older guys that ran them in fleet trucks back inthe day and 350 to 450K miles was doable

I think I will keep my 61 with 361 for a long time. always a combo I wanted and this one was rebuilt before install. I might put in higher compression pistons at some point but just gonna drive for a few years and use it to finish my house projects

[Hulkd700]

We had a "dodge guru" look at the carburetor, he couldn't find anything wrong with it. I think we are going to cry uncle and send the whole truck to him to see if he can figure it out. I have to say it's been frustrating to say the least.

We acquired a 1972 motor home on a Chrysler chassis. It has a 413 with an automatic transmission. Will this bolt directly in the '63 d700? Our plan was to keep the engine as a spare. Is an engine of this vintage built as well as the '63? How much more power would the 413 realistically have than the 361?

[Kaegi]

I am not sure but I dont think the 413 in a motor home has the hardened valves seats and other upgrades the 361 and 413 from medium duty trucks had. it will have more power tho. dont know how much.

[Kaegi]

could you have a bad coil? does it get worse after about 10 miles? only visual check you can make on a coil is if the bottom is bulged out its bad or if there is oil underneath the coil wire its bad. or they can look fine and be bad.

[Hulkd700]

we finally figured out the skipping issue: the distributor shaft was worn. I found a new old stock distributor online and she now runs perfect. Thanks for all of the input.

[Wildergarten]

Is this behavior different when cold v. hot? What type of plug fouling? Carbon? Is the exhaust pipe heavily carboned up? If it is, can you tell us more about how it behaves through the power band under various manifold vacuum conditions? Putting a vacuum gauge and it on a long hose so that you can observe it while driving might give you the data to know when the mixture goes bad. This kind of problem with a carb can be caused by multiple problems, from jetting to a balky choke linkage or bad choke-vacuum diaphragm.

[Wildergarten]

we finally figured out the skipping issue: the distributor shaft was worn. I found a new old stock distributor online and she now runs perfect. Thanks for all of the input.

Guess I should read the whole thread before posting.