Looking for advice on flathead motor that won’t run well.
Vehicle:
1937 Ford pickup
1937 85 hp flathead engine
Holley 94 carb
Converted to 12 volts
History:
Based on the license plate on the truck, it was last driven in 1974.
Owner before me purchased the truck that way, and got the truck “running” in 2015. It started and could drive in and out of the garage, but was not driven at driving speeds.
After I purchased it, I wanted to make it road worthy.
I added the electrical stuff that was missing – alternator, headlights, tail lights, switches, etc. That stuff all works well.
I changed all the fluids and spark plugs.
I road tested it and it did not run well.
It would idle ok.
It would not rev up to any decent rpm, but I was able to shift through the gears and drive it.
Ran really rich, would burn your eyes in the garage and make the cab stink while driving.
Seems to have a lot of blow by out of the breather cap.
After the road test, about 5 miles of driving, the new plugs were very black with a lot of soot.
I cleaned the soot off the plugs with a wire brush for the next few tests.
Thinking it may be a carburetor issue, I tried the same model 94 off of a spare motor that I have. It behaved the same way.
I suspect it may have the wrong fuel pump on it because it has the sediment bowl attached to it. I measured the pressure and it was about 7 psi, so I purchased a Mr. Gasket fuel pressure regulator for it. It did not run any better at about 1.5 psi.
I bought a carb kit and rebuilt the original carb.
Set the float to 1.34”
Did not run any different with rebuilt carb.
I purchased an electronic ignition three bolt distributor, coil, and plug wires.
No vacuum advance for timing on this distributor, so I plugged the old vacuum line from the carb/manifold.
Timing (measured with marks made on the front pulley) is about 4 deg before TDC.
No noticeable improvement with ignition upgrade.
Tried advancing the timing to 10 deg, did not seem to help, maybe worse.
Put it back to 4 deg.
Mr. Gasket regulator was very erratic, so replaced with a Holley regulator and added a permanent fuel pressure gage. Set at 2 psi now, but trying at lower pressure does not seem to help.
Still running very poorly, seems to be getting worse.
Hard starting.
Hard to keep running without half choke
Will sputter and backfire as throttle is increased. Sometimes will smooth out but quickly degrades again.
Still running rich, making soot on plugs.
Vacuum taken at the fitting below the carb is about 12 – 15 in Hg, sometimes less. It is hard to tell because it runs so poorly the vacuum fluctuates when manipulating choke and feathering throttle to try and keep running.
Idle mixture screws are set at 1.25 turns. I can turn them all the way in and it doesn’t seem to help or hurt.
Dry compression on cylinders 1 to 8 are
90
75
80
82.5
87.5
90
90
85
My vintage Chevy trucks run like a top. I would like to think the flathead is capable of this too, but so far all it has been good for is an outlet for my profanity.
Thanks for any advice you may have.
Vehicle:
1937 Ford pickup
1937 85 hp flathead engine
Holley 94 carb
Converted to 12 volts
History:
Based on the license plate on the truck, it was last driven in 1974.
Owner before me purchased the truck that way, and got the truck “running” in 2015. It started and could drive in and out of the garage, but was not driven at driving speeds.
After I purchased it, I wanted to make it road worthy.
I added the electrical stuff that was missing – alternator, headlights, tail lights, switches, etc. That stuff all works well.
I changed all the fluids and spark plugs.
I road tested it and it did not run well.
It would idle ok.
It would not rev up to any decent rpm, but I was able to shift through the gears and drive it.
Ran really rich, would burn your eyes in the garage and make the cab stink while driving.
Seems to have a lot of blow by out of the breather cap.
After the road test, about 5 miles of driving, the new plugs were very black with a lot of soot.
I cleaned the soot off the plugs with a wire brush for the next few tests.
Thinking it may be a carburetor issue, I tried the same model 94 off of a spare motor that I have. It behaved the same way.
I suspect it may have the wrong fuel pump on it because it has the sediment bowl attached to it. I measured the pressure and it was about 7 psi, so I purchased a Mr. Gasket fuel pressure regulator for it. It did not run any better at about 1.5 psi.
I bought a carb kit and rebuilt the original carb.
Set the float to 1.34”
Did not run any different with rebuilt carb.
I purchased an electronic ignition three bolt distributor, coil, and plug wires.
No vacuum advance for timing on this distributor, so I plugged the old vacuum line from the carb/manifold.
Timing (measured with marks made on the front pulley) is about 4 deg before TDC.
No noticeable improvement with ignition upgrade.
Tried advancing the timing to 10 deg, did not seem to help, maybe worse.
Put it back to 4 deg.
Mr. Gasket regulator was very erratic, so replaced with a Holley regulator and added a permanent fuel pressure gage. Set at 2 psi now, but trying at lower pressure does not seem to help.
Still running very poorly, seems to be getting worse.
Hard starting.
Hard to keep running without half choke
Will sputter and backfire as throttle is increased. Sometimes will smooth out but quickly degrades again.
Still running rich, making soot on plugs.
Vacuum taken at the fitting below the carb is about 12 – 15 in Hg, sometimes less. It is hard to tell because it runs so poorly the vacuum fluctuates when manipulating choke and feathering throttle to try and keep running.
Idle mixture screws are set at 1.25 turns. I can turn them all the way in and it doesn’t seem to help or hurt.
Dry compression on cylinders 1 to 8 are
90
75
80
82.5
87.5
90
90
85
My vintage Chevy trucks run like a top. I would like to think the flathead is capable of this too, but so far all it has been good for is an outlet for my profanity.
Thanks for any advice you may have.
