The Ford Barn

PecosBill · 10-30-2022, 06:46 PM

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.

Ggmac · 10-30-2022, 06:52 PM

Possibly a blocked exhaust ?

PecosBill · 10-30-2022, 07:50 PM

Quote:

Originally Posted by Ggmac

Possibly a blocked exhaust ?

I put new pipes and Smittys on it. I suppose there could be blockage in the exhaust manifolds. Both sides seem to have the same soot problem.

drolston · 10-30-2022, 09:01 PM

The clue is that the idle mixture screws have no effect. That means it is getting fuel from elsewhere. Like spillover from the float being set too high. If that is set correctly, it could be that the needle valve operated by the float is not seating. Maybe gummed up from sitting too long. When you rebuilt the carb did that include cleaning or replacing the float valve. Even if clean, it could be sticking open on a bit of crud. Was there any crud in the bottom of the fuel bowl? Do you have a fuel filter?

38 coupe · 10-30-2022, 09:08 PM

The vacuum numbers seem low to me. If you are at low altitude you should get 20+ inches of mercury at an idle. I highly doubt blocked exhaust manifolds.

Your 85 hp should run well and have good power. Something is wrong, and it sounds like it is running rich. Have you tried looking down the carburetor throat when the engine is running? You should not see gasoline leaking down at an idle, and you should see gas spraying evenly from each side with the engine revved up.

PecosBill · 10-30-2022, 10:07 PM

Sponsored Links (Register now to hide all advertisements)

Quote:

Originally Posted by drolston

The clue is that the idle mixture screws have no effect. That means it is getting fuel from elsewhere. Like spillover from the float being set too high. If that is set correctly, it could be that the needle valve operated by the float is not seating. Maybe gummed up from sitting too long. When you rebuilt the carb did that include cleaning or replacing the float valve. Even if clean, it could be sticking open on a bit of crud. Was there any crud in the bottom of the fuel bowl? Do you have a fuel filter?

When I rebuilt the carb, I think the kit came with the float needle valve and the seat. It seems to move freely. I took it apart again after the rebuild to check if the high fuel pressure bent anything. I don't think it did, but I tweaked it a little bit anyway to help it shut just a little bit earlier. I didn't see any crud to inhibit movement.

There is no loose crud in the bottom of the float bowl. It has the visual appearance of crud, but I scrubbed it when I had it apart and it is just discolored.

For filtering, I have the sediment bowl attached to the fuel pump, and I installed a little K&N glass tube-type filter as well. I don't see crud in either one of those.

I haven't yet looked down the carb while running, it has not been running well enough lately to do that and keep it running. I'll get another set of hands to help and do that.

I only use ethanol free gas in my old vehicles, and it is fresh gas.

thanks

PecosBill · 10-30-2022, 10:08 PM

Quote:

Originally Posted by 38 coupe

The vacuum numbers seem low to me. If you are at low altitude you should get 20+ inches of mercury at an idle. I highly doubt blocked exhaust manifolds.

Your 85 hp should run well and have good power. Something is wrong, and it sounds like it is running rich. Have you tried looking down the carburetor throat when the engine is running? You should not see gasoline leaking down at an idle, and you should see gas spraying evenly from each side with the engine revved up.

I will try looking down the carb as soon as I get a helper.
thanks.

PecosBill · 10-30-2022, 10:24 PM

Quote:

Originally Posted by 38 coupe

The vacuum numbers seem low to me. If you are at low altitude you should get 20+ inches of mercury at an idle. I highly doubt blocked exhaust manifolds.

I don't see any obvious vacuum leaks. Although there is a fitting assembly on the bottom of the carb (see pic) that could potentially have leaks that are not obvious. I normally have it plugged but right now my vacuum gage is connected to it.

With the other ports plugged, where could I be losing vacuum? The rough running actually reminds me of a vacuum leak from other experience. Is running rich is also a symptom of a vacuum leak. I installed new gaskets when mounting the rebuilt carb, although I did not use any sealant.

thanks

ford38v8 · 10-31-2022, 01:15 AM

You rebuilt the carb, but with a kit from what source? There are dubious kits out there, and even the best kit from Daytona Parts.com has included a needle valve of their own design that isn't favored by many that I am aware of. The needle valve that came with the original carb is metal to metal. No other valve should be used here.

First, with whatever kit you used, remove the power valve and test it with suction from your mouth. It should hold suction to your tongue. Also, the gasket seating surface of the power valve should be flat to match the surface on the carburetor. Any mismatch or missing gasket here will flood your engine with gas, as will a blown diaphram on that unit.

Next, did you get the small check valve back into the accelerator pump system? And have you checked the function of that system? Kits often come with two different length accelerator pumps, use the long body one, and toss the blue disc, to replace it with a leather disc cut from the tongue of a shoe. Oil that leather also. Test with engine off, pump to squirt from both jets visible looking down into the carb.

The carb base you are using that has the vacuum port should work just fine as long as it is blocked as you indicated.
Don't assume that the gasket surfaces are flat. Confirm and flatten if warped with abrasive paper on a flat surface. While the engine is running, spray ether at gasketed areas of the carb and intake manifold to discover vacuum leaks which will raise the RPM when they suck in the ether.

No sealant required, just good gaskets and flat mating surfaces, a spot of grease or oil if you like to hold gaskets in place during installation.

If your manifold has a third hole, that's the heat riser hole and is intended for use with a Stromberg, not a Ford/Holley. This is not your problem now, but if you continue with the 94, you may want to also change that manifold.

Mart · 10-31-2022, 07:53 AM

The post above pretty well covers it.

I made a video showing some of the things to look out for on the 94s. Flatness of the body and base are very important. An air leak will stop the power valve from closing and you will be over rich all the time.

Here's a link:

https://youtu.be/UMiWUQyIkmg

Hope it might be helpful. A very well respected carb rebuilder told me it was a good video.

Mart.

Terry,OH · 10-31-2022, 07:57 AM

Sounds like the Carb power valve or it's gasket is leaking.
Did you install a Daytona rebuild kit, as is always suggested here

PecosBill · 10-31-2022, 08:09 AM

You rebuilt the carb, but with a kit from what source? There are dubious kits out there, and even the best kit from Daytona Parts.com has included a needle valve of their own design that isn't favored by many that I am aware of. The needle valve that came with the original carb is metal to metal. No other valve should be used here.
I purchased the kit from summit - shown in the pic. It was not the cheapest one out there so I figured it was good. Not much documentation to indicate where it really comes from. It has the non metal tip for the float valve, but it came with a mating seat. I can buy a different kit if it is that important.

First, with whatever kit you used, remove the power valve and test it with suction from your mouth. It should hold suction to your tongue. Also, the gasket seating surface of the power valve should be flat to match the surface on the carburetor. Any mismatch or missing gasket here will flood your engine with gas, as will a blown diaphram on that unit.
I will check these. I read about some power valves having a raised step or something that makes them not fit well. Mine did not have that it and it seemed to fit properly. And it had a new gasket. But I did not test suction or verify the flatness of the mating surface like you suggest. I will.

Next, did you get the small check valve back into the accelerator pump system?
Yes

And have you checked the function of that system?
I have not checked this but I will.

Kits often come with two different length accelerator pumps, use the long body one, and toss the blue disc, to replace it with a leather disc cut from the tongue of a shoe. Oil that leather also.
Are you really suggesting I make my own disc?

Don't assume that the gasket surfaces are flat. Confirm and flatten if warped with abrasive paper on a flat surface. While the engine is running, spray ether at gasketed areas of the carb and intake manifold to discover vacuum leaks which will raise the RPM when they suck in the ether.
I will check this.

Thanks.

Robert/Texas · 10-31-2022, 08:17 AM

When I bought my ’34 in 1995 it had a 94 carb on it. I couldn’t get it to run well on that carb. We had a carburetor guru in our Early Ford V8 club who tried to fix it several times. He finally gave up and sold me a 97 carb which solved the problem for many years. Since then, I had CharlieNY overhaul that carb and the one on my ’37 Ford and both cars run well with them. I might be wrong, but I thought that 97s were original to ’37 Fords.

PecosBill · 10-31-2022, 01:30 PM

Quote:

Originally Posted by Terry,OH

Sounds like the Carb power valve or it's gasket is leaking.
Did you install a Daytona rebuild kit, as is always suggested here

I did not install Daytona, the kit I got was from Summit. I talked to Daytona today and they can get me what I need. I haven't purchased it yet, I will try some of the other ideas first. If no success, then I will get the Daytona kit and maybe rebuild the other 94 I have - start from scratch.
thanks.

petehoovie · 10-31-2022, 02:24 PM

Quote:

Originally Posted by PecosBill

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:

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 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.

Hmmmm...Maybe chasing the wrong culprit here...

Are the spark plug wires married to the distributor correctly?

PecosBill · 10-31-2022, 02:47 PM

Quote:

Originally Posted by Mart

The post above pretty well covers it.

I made a video showing some of the things to look out for on the 94s. Flatness of the body and base are very important. An air leak will stop the power valve from closing and you will be over rich all the time.

Here's a link:

https://youtu.be/UMiWUQyIkmg

Hope it might be helpful. A very well respected carb rebuilder told me it was a good video.

Mart.

I watched it, I agree it is a good video.
thanks.

Automotive Stud · 10-31-2022, 02:51 PM

The erratic vacuum readings make me think you've got one or more valves that are sticky from sitting, assuming it doesn't have a burnt valve or worn valve guides.

PecosBill · 10-31-2022, 02:54 PM

Quote:

Originally Posted by petehoovie

Hmmmm...Maybe chasing the wrong culprit here...

Are the spark plug wires married to the distributor correctly?

I am fairly certain the wires are attached to right locations, I was very careful when installing them. But I can check again.

Speaking of other culprits though, I wanted to make sure I had good voltage in the ignition circuit, and I think my ignition (toggle) switch is faulty. At best it has 2 ohms of resistance and it seems to vary. I bought a new generic toggle switch today, we'll see if that helps.

Thanks.

PecosBill · 10-31-2022, 02:58 PM

Quote:

Originally Posted by Automotive Stud

The erratic vacuum readings make me think you've got one or more valves that are sticky from sitting, assuming it doesn't have a burnt valve or worn valve guides.

Yeah I was wondering about that, and also maybe stuck piston rings that could be affecting my compression. I would like to get it running well enough so it could hopefully clear some of that up on its own.
Thanks.

ford38v8 · 10-31-2022, 03:37 PM

Bill, your compression readings are fine. Don't go off and do something you don't need to do.

10-30-2022, 06:46 PM	#1
PecosBill Junior Member Join Date: May 2020 Posts: 14	1937 Flathead Won't Run Well 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.

10-30-2022, 06:52 PM	#2
Ggmac Senior Member Join Date: Jul 2016 Location: Lake worth Florida Posts: 1,101	Re: 1937 Flathead Won't Run Well Possibly a blocked exhaust ?

10-30-2022, 09:01 PM	#4
drolston Senior Member Join Date: Jun 2014 Location: Williamsburg, VA Posts: 1,627	Re: 1937 Flathead Won't Run Well The clue is that the idle mixture screws have no effect. That means it is getting fuel from elsewhere. Like spillover from the float being set too high. If that is set correctly, it could be that the needle valve operated by the float is not seating. Maybe gummed up from sitting too long. When you rebuilt the carb did that include cleaning or replacing the float valve. Even if clean, it could be sticking open on a bit of crud. Was there any crud in the bottom of the fuel bowl? Do you have a fuel filter?

10-30-2022, 09:08 PM	#5
38 coupe Senior Member Join Date: May 2010 Location: South Texas Posts: 1,631	Re: 1937 Flathead Won't Run Well The vacuum numbers seem low to me. If you are at low altitude you should get 20+ inches of mercury at an idle. I highly doubt blocked exhaust manifolds. Your 85 hp should run well and have good power. Something is wrong, and it sounds like it is running rich. Have you tried looking down the carburetor throat when the engine is running? You should not see gasoline leaking down at an idle, and you should see gas spraying evenly from each side with the engine revved up.

10-31-2022, 01:15 AM	#9
ford38v8 Senior Member Join Date: Jul 2011 Location: SF Bay Area Posts: 6,646	Re: 1937 Flathead Won't Run Well You rebuilt the carb, but with a kit from what source? There are dubious kits out there, and even the best kit from Daytona Parts.com has included a needle valve of their own design that isn't favored by many that I am aware of. The needle valve that came with the original carb is metal to metal. No other valve should be used here. First, with whatever kit you used, remove the power valve and test it with suction from your mouth. It should hold suction to your tongue. Also, the gasket seating surface of the power valve should be flat to match the surface on the carburetor. Any mismatch or missing gasket here will flood your engine with gas, as will a blown diaphram on that unit. Next, did you get the small check valve back into the accelerator pump system? And have you checked the function of that system? Kits often come with two different length accelerator pumps, use the long body one, and toss the blue disc, to replace it with a leather disc cut from the tongue of a shoe. Oil that leather also. Test with engine off, pump to squirt from both jets visible looking down into the carb. The carb base you are using that has the vacuum port should work just fine as long as it is blocked as you indicated. Don't assume that the gasket surfaces are flat. Confirm and flatten if warped with abrasive paper on a flat surface. While the engine is running, spray ether at gasketed areas of the carb and intake manifold to discover vacuum leaks which will raise the RPM when they suck in the ether. No sealant required, just good gaskets and flat mating surfaces, a spot of grease or oil if you like to hold gaskets in place during installation. If your manifold has a third hole, that's the heat riser hole and is intended for use with a Stromberg, not a Ford/Holley. This is not your problem now, but if you continue with the 94, you may want to also change that manifold. __________________ Alan

10-31-2022, 07:53 AM	#10
Mart Senior Member Join Date: May 2010 Location: Solihull, England. Posts: 8,755	Re: 1937 Flathead Won't Run Well The post above pretty well covers it. I made a video showing some of the things to look out for on the 94s. Flatness of the body and base are very important. An air leak will stop the power valve from closing and you will be over rich all the time. Here's a link: https://youtu.be/UMiWUQyIkmg Hope it might be helpful. A very well respected carb rebuilder told me it was a good video. Mart.

10-31-2022, 07:57 AM	#11
Terry,OH Senior Member Join Date: May 2010 Posts: 4,751	Re: 1937 Flathead Won't Run Well Sounds like the Carb power valve or it's gasket is leaking. Did you install a Daytona rebuild kit, as is always suggested here

10-31-2022, 08:17 AM	#13
Robert/Texas Senior Member Join Date: May 2010 Location: Burton, Texas Posts: 681	Re: 1937 Flathead Won't Run Well When I bought my ’34 in 1995 it had a 94 carb on it. I couldn’t get it to run well on that carb. We had a carburetor guru in our Early Ford V8 club who tried to fix it several times. He finally gave up and sold me a 97 carb which solved the problem for many years. Since then, I had CharlieNY overhaul that carb and the one on my ’37 Ford and both cars run well with them. I might be wrong, but I thought that 97s were original to ’37 Fords.

10-31-2022, 02:51 PM	#17
Automotive Stud Senior Member Join Date: May 2010 Location: New Jersey Posts: 832	Re: 1937 Flathead Won't Run Well The erratic vacuum readings make me think you've got one or more valves that are sticky from sitting, assuming it doesn't have a burnt valve or worn valve guides.

10-31-2022, 03:37 PM	#20
ford38v8 Senior Member Join Date: Jul 2011 Location: SF Bay Area Posts: 6,646	Re: 1937 Flathead Won't Run Well Bill, your compression readings are fine. Don't go off and do something you don't need to do. __________________ Alan