The Ford Barn

Whitecap50 · 10-24-2013, 05:00 PM

Hello gentlemen. I have a 1946 v8 flathead that runs well until higher rpm's are reached(2000-2500) , then starts sputtering, looses power, just won't go. Shift and things are good again until that magic rpm is reached. I put a spark checker on it ,so I have determined that it is spark. Will do it in the garage when reved. Hold the throttle open and the spark checker just starts to diminish and then stops flashing. Shows strong spark up until that. New condenser, coil. Points are good(.016) as is cap and rotor. Plugs were new 3 weeks ago(.025). Still has the cloth wires but they have been replaced also. Thank you for any and all help. Whitecap50

koates · 10-24-2013, 05:30 PM

Hi there, you seem to have covered nearly everything. You say points are good but not new ??. So mabee the points spring tension is a little weak. Fit new points or bend and retension points springs. Also check for any side movement of cam and shaft, should be none. Both these items could cause point bounce at higher RPM. Regards, Kevin.

skidmarks · 10-24-2013, 05:34 PM

i had the same issue with a V8-60 and it turned out to be the coil. swapped out a few used ones and then it ran fine

oldford2 · 10-24-2013, 05:49 PM

Sounds like bad points. Weak springs and the points float at higher rpm's. I have been there. Maybe an easy fix with a new set of points. John

BUBBAS IGNITION · 10-24-2013, 06:38 PM

Like the others have said points or condensor is the most likely cause.

A weak condensor wont hold a charge at higher rpm and cause a miss fire. A weak spring on the points will do the same.
Incorrect dwell wont allow the coil to ramp up with higher revs.
Not uncommon to see a new set of points do this. I usually run 2-5 of these a day on a test machine and i run them all from idle to 5000 rpm for a period of time.
In my case i can see the condensor arc at the contacts and each cylinder firing , too much arc is a weak condensor.

I suggest a set of CS47 points and FA54 condesnor from NAPA, OR send it to me and i will test it .

Whitecap50 · 10-24-2013, 07:32 PM

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I thought coil as well. Put New 6 volt coil on and no difference. New points and condensor have been ordered from NAPA. Thanks to all. Will let you know results. Whitecap50

10-24-2013, 05:00 PM	#1
Whitecap50 Junior Member Join Date: Jul 2013 Posts: 3	Lose of spark at higher RPM's Hello gentlemen. I have a 1946 v8 flathead that runs well until higher rpm's are reached(2000-2500) , then starts sputtering, looses power, just won't go. Shift and things are good again until that magic rpm is reached. I put a spark checker on it ,so I have determined that it is spark. Will do it in the garage when reved. Hold the throttle open and the spark checker just starts to diminish and then stops flashing. Shows strong spark up until that. New condenser, coil. Points are good(.016) as is cap and rotor. Plugs were new 3 weeks ago(.025). Still has the cloth wires but they have been replaced also. Thank you for any and all help. Whitecap50

10-24-2013, 05:30 PM	#2
koates Senior Member Join Date: May 2010 Location: Melbourne Australia. Posts: 2,078	Re: Lose of spark at higher RPM's Hi there, you seem to have covered nearly everything. You say points are good but not new ??. So mabee the points spring tension is a little weak. Fit new points or bend and retension points springs. Also check for any side movement of cam and shaft, should be none. Both these items could cause point bounce at higher RPM. Regards, Kevin.

10-24-2013, 05:34 PM	#3
skidmarks Senior Member Join Date: Aug 2010 Location: newark, delaware Posts: 3,735	Re: Lose of spark at higher RPM's i had the same issue with a V8-60 and it turned out to be the coil. swapped out a few used ones and then it ran fine

10-24-2013, 05:49 PM	#4
oldford2 Senior Member Join Date: May 2010 Location: pittsfield, MA Posts: 2,086	Re: Lose of spark at higher RPM's Sounds like bad points. Weak springs and the points float at higher rpm's. I have been there. Maybe an easy fix with a new set of points. John

10-24-2013, 06:38 PM	#5
BUBBAS IGNITION Senior Member Join Date: May 2010 Location: SPEEDWAY INDIANA Posts: 4,148	Re: Lose of spark at higher RPM's Like the others have said points or condensor is the most likely cause. A weak condensor wont hold a charge at higher rpm and cause a miss fire. A weak spring on the points will do the same. Incorrect dwell wont allow the coil to ramp up with higher revs. Not uncommon to see a new set of points do this. I usually run 2-5 of these a day on a test machine and i run them all from idle to 5000 rpm for a period of time. In my case i can see the condensor arc at the contacts and each cylinder firing , too much arc is a weak condensor. I suggest a set of CS47 points and FA54 condesnor from NAPA, OR send it to me and i will test it . __________________ If it Makes Spark, we do it !!!! www.bubbasignition.com [email protected]

10-24-2013, 07:32 PM	#6
Whitecap50 Junior Member Join Date: Jul 2013 Posts: 3	Re: Lose of spark at higher RPM's Sponsored Links (Register now to hide all advertisements) I thought coil as well. Put New 6 volt coil on and no difference. New points and condensor have been ordered from NAPA. Thanks to all. Will let you know results. Whitecap50