Go Back   The Ford Barn > General Discussion > Early V8 (1932-53)

Sponsored Links (Register now to hide all advertisements)

Reply
 
Thread Tools Display Modes
Old 11-11-2015, 04:49 PM   #1
Bassman/NZ
Senior Member
 
Bassman/NZ's Avatar
 
Join Date: May 2010
Location: Napier, New Zealand
Posts: 2,001
Default A very perplexing problem.

My C59A engine feels like it's running on 7 and 1/2 cylinders.
It's stock except heads milled for 45thou clearance over pistons, has had new rings, bearings, valve grind and valve guides, valves set to 10thou in and 14thou ex. New Best copper gaskets, dissy rebuilt by Bubbas (including condenser) and points set at 15thou. New plug leads and plugs set at 28thou, Ford 94 with mating surfaces flat, 50thou jets, all orifices blown out, leather plunger, power valve checked and seating, float set right. Bosch 12v coil with external resistor.
Runs best with the advance plate (it's a crab) set two notches down from top, but still not as smooth as a V8 should be. I'm running 91 octane gas (no ethanol).
Plugs have good tannish colour across all 8, compression test (dry) with WOT gives variation of 5 lbs across all 8 cylinders (150-155 lbs).
I guess I'm brain-storming here, trying to see if I've missed anything. One thing I have noticed is it starts to get a bit ragged when approaching the upper rev limit.
Things I've tried.... different plugs and different heat ranges, every setting on the dissy advance plate, from full advance to full retard, air cleaner on and off, different jets and power valve.
I'm getting quite frustrated.
Bassman/NZ is offline   Reply With Quote
Old 11-11-2015, 04:57 PM   #2
deuce_roadster
Senior Member
 
deuce_roadster's Avatar
 
Join Date: Oct 2011
Location: Shelton, WA
Posts: 3,777
Default Re: A very perplexing problem.

Are the points NOS Ford points? Aftermarket ones can have weak springs and other issues. Was the distributor set up on a machine so you can see at what RPM it starts to get ragged? I have crabs that go to 5500 with no problems. Your bushing must be good to keep the shaft from wobbling also.
deuce_roadster is offline   Reply With Quote
Sponsored Links (Register now to hide all advertisements)
Old 11-11-2015, 05:08 PM   #3
39topless
Senior Member
 
Join Date: Sep 2013
Posts: 1,027
Default Re: A very perplexing problem.

Have you checked for a vacuum leak? Usual culprit is the vacuum line to wipers.
39topless is offline   Reply With Quote
Old 11-11-2015, 05:21 PM   #4
zzlegend
Senior Member
 
zzlegend's Avatar
 
Join Date: May 2010
Location: Reseda, Calif.
Posts: 2,188
Default Re: A very perplexing problem.

Just a question here. You state that you are running a Bosch 12v coil with external resistor. I am running the same on two of my flatheads but with no external resistor. Mine have internal resistors and installed them after reading the information that Bubba gives. Perhaps yours is a different coil than I am running. Just a thought. Hope you find the problem.
zzlegend is offline   Reply With Quote
Old 11-11-2015, 07:10 PM   #5
Bassman/NZ
Senior Member
 
Bassman/NZ's Avatar
 
Join Date: May 2010
Location: Napier, New Zealand
Posts: 2,001
Default Re: A very perplexing problem.

Quote:
Originally Posted by deuce_roadster View Post
Are the points NOS Ford points? Aftermarket ones can have weak springs and other issues. Was the distributor set up on a machine so you can see at what RPM it starts to get ragged? I have crabs that go to 5500 with no problems. Your bushing must be good to keep the shaft from wobbling also.
Yep, crab was rebuilt by Bubbas and tested to 5500.
Bassman/NZ is offline   Reply With Quote
Old 11-12-2015, 06:40 AM   #6
Terry,OH
Senior Member
 
Terry,OH's Avatar
 
Join Date: May 2010
Posts: 4,725
Default Re: A very perplexing problem.

Sponsored Links (Register now to hide all advertisements)
Do put a vacuum gauge on it to see how the gauge reacts. and check to make sure the resistor is necessary for the Bosch coil. Both good suggestions.
Terry,OH is offline   Reply With Quote
Old 11-12-2015, 07:24 AM   #7
JSeery
Member Emeritus
 
JSeery's Avatar
 
Join Date: Nov 2012
Location: Wichita KS
Posts: 16,132
Default Re: A very perplexing problem.

It's an easy test to figure out what the coil resistance is, I would start there. (Vacuum test is easy as well as far as that goes!)
JSeery is offline   Reply With Quote
Old 11-12-2015, 02:00 PM   #8
Bassman/NZ
Senior Member
 
Bassman/NZ's Avatar
 
Join Date: May 2010
Location: Napier, New Zealand
Posts: 2,001
Default Re: A very perplexing problem.

Quote:
Originally Posted by Terry,OH View Post
Do put a vacuum gauge on it to see how the gauge reacts. and check to make sure the resistor is necessary for the Bosch coil. Both good suggestions.
Yep, I'll do both of those this weekend. Thanks for the input.
Bassman/NZ is offline   Reply With Quote
Old 11-12-2015, 04:37 PM   #9
BUBBAS IGNITION
Senior Member
 
BUBBAS IGNITION's Avatar
 
Join Date: May 2010
Location: SPEEDWAY INDIANA
Posts: 4,148
Default Re: A very perplexing problem.

The bosch coil needs no resistor. If a resistor is used with the bosch blue coil the voltage will be too low to rev up....
__________________
If it Makes Spark, we do it !!!!
www.bubbasignition.com
[email protected]
BUBBAS IGNITION is offline   Reply With Quote
Old 11-12-2015, 06:07 PM   #10
Bassman/NZ
Senior Member
 
Bassman/NZ's Avatar
 
Join Date: May 2010
Location: Napier, New Zealand
Posts: 2,001
Default Re: A very perplexing problem.

It's a black coil, I'll check tomorrow. What should the output of the coil be ideally?
Bassman/NZ is offline   Reply With Quote
Old 11-12-2015, 06:15 PM   #11
BUBBAS IGNITION
Senior Member
 
BUBBAS IGNITION's Avatar
 
Join Date: May 2010
Location: SPEEDWAY INDIANA
Posts: 4,148
Default Re: A very perplexing problem.

Quote:
Originally Posted by Bassman/NZ View Post
It's a black coil, I'll check tomorrow. What should the output of the coil be ideally?
I am sure it isnt a output problem. With the flatheads compression ratio and fairly low rpm band it might need 10-15000 volts going up a hill wide open throttle.
It becomes a current flow issue high current burns up stuff , and low current or voltage (primary voltage) wont allow the coil to produce enough spark.
__________________
If it Makes Spark, we do it !!!!
www.bubbasignition.com
[email protected]
BUBBAS IGNITION is offline   Reply With Quote
Old 11-12-2015, 06:51 PM   #12
Bassman/NZ
Senior Member
 
Bassman/NZ's Avatar
 
Join Date: May 2010
Location: Napier, New Zealand
Posts: 2,001
Default Re: A very perplexing problem.

So what should the resistance be on the coil terminals?
Bassman/NZ is offline   Reply With Quote
Old 11-12-2015, 08:56 PM   #13
JSeery
Member Emeritus
 
JSeery's Avatar
 
Join Date: Nov 2012
Location: Wichita KS
Posts: 16,132
Default Re: A very perplexing problem.

Current = Voltage / Resistance. So, if you want a max. of around 4 amps, That would be 4A = 7V / 1.75Ohms. So the resistance needs to be in the 1.5 to 1.75 Ohm range. I believe that 1.5 ohms is want is normally wanted in the system. This needs to be divided between the coil and the ballast resistor. If the coil checks ~1.5 ohms then you wouldn't use a ballast resistor. If it is more than the 1.5 - 1.75 ohm range then the coil has to much resistance for a 6-7 volt system. If it is less, then it needs a ballast resistor to make up the difference.
JSeery is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Sponsored Links (Register now to hide all advertisements)


All times are GMT -5. The time now is 06:36 PM.