1950 Plymouth Deluxe Engine Bogging Down

[Jonathan]

I converted my 1950 Plymouth Deluxe 251cc Flathead from a 6 volt to a 12 volt system. Got the alternator from a friend replaced the original generator with it. The alternator charges well and has a module / sensor to determine if charging is needed.

 

The problem: when the engine is at idle and I remove the positive battery post, the engine runs so much smoother. Put the cable back on the battery post and the engine labors quite noticeably. Revving the engine with the battery post off, it revs well and responds quickly. Revving the engine with the battery post on, is labors and it revs noticeably slower.  

 

Any thoughts?

[nonstop]

Do you have a picture of it?  How is it regulated ( internal or external)?  It sounds like it MAY be full fielded, causing it to be charging all the time (just a guess).

[SteveR]

Are you running a + or - ground? Are all your groundings the same?

[squirebill]

Never personally heard of an alternator or generator bog down an engine.  My next step would be to disconnect the electrical connections of the alternator and just use the alternator as a tensioner pulley and see if the problem goes away.  If the problem goes away then the alternator is the culprit.  If the problem still exists it is something other than the alternator . I might suspect  something in the starter circuit/system. Regards.

[Sniper]

It happens, yesterday I was running some diagnostic checks on my 51.  Primarily I was testing out my new engine analyzer I mentioned elsewhere.  When the electric fan kicked on the system voltage dropped to about 13v and the engine lost about 50 rpm as the alternator was putting out about 25a to support the load of the fan.  You could hear the difference in rpm.   It was in neutral at idle and I noticed no difference in the smoothness of the engine though.  As a test of the charging system I turned on all the electrical items it has, such as they are, to see if the alternator could keep up.  It did, barely, I suspect I will need to upgrade it to handle the planned AC and EFI systems.  Should have thought of that to begin with, now I will have to eat the cost of the alternator I have, guess it could be a spare for the Cuda.

[Jonathan]

The car is now negative grounded. I believe my groundings are the same, will double check.

 

I am not sure how it is regulated. I will ask my mechanic friend to confirm that.  

[Jonathan]

Figured out the problem. The alternator was improperly wired - both wires coming off the alternator were connected and therefore causing some problems. Once rewired, it works significantly better. Thanks!