The Ford Barn

FrankB · 06-30-2021, 06:45 PM

Hi everyone. I'm new to the forum and very new to the Model A world. I'm a long time gear head however. I recently acquired a 1930 A sedan and have been tinkering with it to get it on the road. I quickly discovered Mike-A-Fordables and have been ordering all kinds of goodies from him to get the job done. Most recently was a much needed downdraft carb assembly and low PSI fuel pump. The car now starts and idles really nice, but here is my dilemma. The engine has pretty much 0 compression on all 4 cylinders. The needle on my gauge just twitches as the engine is cranking but won't build pressure. I've driven the car even, up and down the road and the power seems reasonable but I don't have a benchmark to compare it to. My mechanical experience says that this shouldn't be possible. Has anyone encountered something similar before? And yes in case anyone is thinking it, I triple checked my gauge function. Am I missing something? I've got the brass washer under the adapter and the O-ring on my tester is in place and in good shape. I also had the throttle wide open and tried it both cold and warmed up.

nkaminar · 06-30-2021, 07:01 PM

Hi Frank,

Welcome. Being a gear head you should be able to figure out where the compression is going. Try putting a little oil in the cylinders before another compression check. If it improves then you need new rings.

Do you have the hand crank? If so you can hand crank the engine over while listening at the crankcase breather tube, the intake manifold, and the exhaust manifold or exhaust pipe with a helper. You will get a hissing sound that will indicate where the compression loss is coming from.

The Model A is a simple engine. In the old days a person in your position would grind the valves and throw in new piston rings while the engine was in the car. My preference is to work on the engine out of the car on an engine stand, just because it is easier for me. While you are in there check the bearings. You should have 0.001 to 0.0015 clearance. Get the mechanics books to advise you. An excellent book is the Model A Ford Mechanics Handbook, Vol. I, A Complete Guide For Service and Maintenance by Les Andrews, available at the suppliers.

Bob C · 06-30-2021, 10:40 PM

Is the Schrader valve working in your compression gauge ??

Richard in Anaheim CA · 06-30-2021, 10:45 PM

Sounds like gauge problem. It certainly won't run with 0 compression and the power sounds reasonable. Don't start tearing it apart. Drive it and borrow someone's gauge.

Bill G · 06-30-2021, 11:08 PM

If it starts and drives, there is combustion and so there must be compression of some sort. I also would suspect the gauge, not the engine.

ronn · 07-01-2021, 03:27 AM

Sponsored Links (Register now to hide all advertisements)

maybe you could take the car "mud bogging" as in a previous thread, and see how she performs?

Jacksonlll · 07-01-2021, 05:13 AM

Do the old thumb trick. Take a plug out, stick your thumb in the hole and turn the engine over. Probably your gage. Have fun with that car.

Patrick L. · 07-01-2021, 05:26 AM

Yep, what the fellas said ! Try the gauge on another engine and stick your finger over the hole and crank it over. These monsters don't have or need a whole lot of compression, but, they do need some.

WHN · 07-01-2021, 06:30 AM

If it runs good, doesn’t smoke, doesn’t make crazy noises, and most important, the car stops.

DRIVE IT!

McMimmcs · 07-01-2021, 07:05 AM

Ask for a new gauge for Christmas or any other holiday.

jayvee34 · 07-01-2021, 08:21 AM

Quote:

Originally Posted by McMimmcs

Ask for a new gauge for Christmas or any other holiday.

Shouldn't have to wait to long, 4th of July is Sunday.

Big hammer · 07-01-2021, 09:24 AM

Quote:

Originally Posted by WHN

If it runs good, doesn’t smoke, doesn’t make crazy noises, and most important, the car stops.

DRIVE IT!

X-2 Go for a nice drive and learn your new to you car, enjoy the drive!

nkaminar · 07-01-2021, 09:32 AM

Frank stated that he tested the gauge. But it would be an easy matter to test it on another car, even a modern one, or replace the Schrader valve.

FrankB · 07-01-2021, 10:26 AM

Thank you for the reply. All great ideas. My intention is to next remove the head and the valve cover/plate and to inspect and clean everything. I was wondering however if this is normal for these cars to run on such little compression? Is this simply because the nature of this already low compression design? This of course is assuming my gauge is fine. Again I tested the gauge and it works fine on straight shop air and on my other engines.

I did the thumb test and it's got some compression but it's not a strong push on my thumb. I can almost hold it down when being cranked. It should blow my thumb out of the way really hard no??

FrankB · 07-01-2021, 10:38 AM

I think I'll put another gauge assembly on it just to try. Always good to eliminate variables. Thinking more about it maybe my gauge has a fault below a certain pressure. All my check were 100psi and higher. I'll check this and report back. Thanks guys.

alexiskai · 07-01-2021, 11:00 AM

Normal compression on a stock system is ~60. 45psi would indicate some problems but likely still drivable. Below that you get backfires, misfires, exhaust in the engine bay, oil on the plugs, etc.

marko39 · 07-01-2021, 11:57 AM

I once pulled the heads on a 39 truck due to low readings on gauge. You guessed it, gauge was bad.( intermittly) was nothing wrong with engine.

Patrick L. · 07-01-2021, 12:26 PM

If you're new to the car and want to check things over, fine. take the side cover off and check the lash. If the lash is good and nothing hanging up, drive it. Taking off a head can be a real task at times.

Mine has had 45# compression since I bought it in 1975 and hasn't changed. It doesn't burn or leak a thing. I drive it every day day I can.

WHN · 07-01-2021, 01:52 PM

Quote:

Originally Posted by FrankB

Thank you for the reply. All great ideas. My intention is to next remove the head and the valve cover/plate and to inspect and clean everything. I was wondering however if this is normal for these cars to run on such little compression? Is this simply because the nature of this already low compression design? This of course is assuming my gauge is fine. Again I tested the gauge and it works fine on straight shop air and on my other engines.

I did the thumb test and it's got some compression but it's not a strong push on my thumb. I can almost hold it down when being cranked. It should blow my thumb out of the way really hard no??

Addition advice from an OLD GUY.

Please don’t start taking things apart before you know if there is something wrong.

“Drive the car”!!!

When you go to the doctors office. He just doesn’t start surgery. They check you out first. See how you walk, talk, and breath.

Do the same.

Enjoy.

Pete · 07-01-2021, 04:38 PM

You still haven't said if you put oil in the plug holes and tried a test.

06-30-2021, 06:45 PM	#1
FrankB Junior Member Join Date: Jun 2021 Posts: 9	No compression but starts and drives??? Hi everyone. I'm new to the forum and very new to the Model A world. I'm a long time gear head however. I recently acquired a 1930 A sedan and have been tinkering with it to get it on the road. I quickly discovered Mike-A-Fordables and have been ordering all kinds of goodies from him to get the job done. Most recently was a much needed downdraft carb assembly and low PSI fuel pump. The car now starts and idles really nice, but here is my dilemma. The engine has pretty much 0 compression on all 4 cylinders. The needle on my gauge just twitches as the engine is cranking but won't build pressure. I've driven the car even, up and down the road and the power seems reasonable but I don't have a benchmark to compare it to. My mechanical experience says that this shouldn't be possible. Has anyone encountered something similar before? And yes in case anyone is thinking it, I triple checked my gauge function. Am I missing something? I've got the brass washer under the adapter and the O-ring on my tester is in place and in good shape. I also had the throttle wide open and tried it both cold and warmed up.

06-30-2021, 07:01 PM	#2
nkaminar Senior Member Join Date: Jan 2012 Location: Western North Carolina Posts: 3,899	Re: No compression but starts and drives??? Hi Frank, Welcome. Being a gear head you should be able to figure out where the compression is going. Try putting a little oil in the cylinders before another compression check. If it improves then you need new rings. Do you have the hand crank? If so you can hand crank the engine over while listening at the crankcase breather tube, the intake manifold, and the exhaust manifold or exhaust pipe with a helper. You will get a hissing sound that will indicate where the compression loss is coming from. The Model A is a simple engine. In the old days a person in your position would grind the valves and throw in new piston rings while the engine was in the car. My preference is to work on the engine out of the car on an engine stand, just because it is easier for me. While you are in there check the bearings. You should have 0.001 to 0.0015 clearance. Get the mechanics books to advise you. An excellent book is the Model A Ford Mechanics Handbook, Vol. I, A Complete Guide For Service and Maintenance by Les Andrews, available at the suppliers. __________________ A is for apple, green as the sky. Step on the gas, for tomorrow I die. Forget the brakes, they really don't work. The clutch always sticks, and starts with a jerk. My car grows red hair, and flies through the air. Driving's a blast, a blast from the past. Last edited by nkaminar; 06-30-2021 at 07:08 PM.

06-30-2021, 10:40 PM	#3
Bob C Senior Member Join Date: May 2010 Location: So Cal Posts: 8,741	Re: No compression but starts and drives??? Is the Schrader valve working in your compression gauge ??

06-30-2021, 10:45 PM	#4
Richard in Anaheim CA Senior Member Join Date: May 2010 Location: Anaheim California Posts: 551	Re: No compression but starts and drives??? Sounds like gauge problem. It certainly won't run with 0 compression and the power sounds reasonable. Don't start tearing it apart. Drive it and borrow someone's gauge.

06-30-2021, 11:08 PM	#5
Bill G Senior Member Join Date: Jun 2017 Location: Walla Walla, WA Posts: 1,045	Re: No compression but starts and drives??? If it starts and drives, there is combustion and so there must be compression of some sort. I also would suspect the gauge, not the engine.

07-01-2021, 03:27 AM	#6
ronn Senior Member Join Date: Feb 2011 Location: NNNNNNNNJJJJJJJJJJ Posts: 6,784	Re: No compression but starts and drives??? Sponsored Links (Register now to hide all advertisements) maybe you could take the car "mud bogging" as in a previous thread, and see how she performs?

07-01-2021, 05:13 AM	#7
Jacksonlll Senior Member Join Date: Jul 2012 Location: Michigan-- Member of Oakleaf of MARC Posts: 1,686	Re: No compression but starts and drives??? Do the old thumb trick. Take a plug out, stick your thumb in the hole and turn the engine over. Probably your gage. Have fun with that car.

07-01-2021, 05:26 AM	#8
Patrick L. Senior Member Join Date: May 2010 Location: Largo Florida Posts: 7,225	Re: No compression but starts and drives??? Yep, what the fellas said ! Try the gauge on another engine and stick your finger over the hole and crank it over. These monsters don't have or need a whole lot of compression, but, they do need some.

07-01-2021, 06:30 AM	#9
WHN Senior Member Join Date: Mar 2017 Location: Connecticut Shoreline Posts: 1,820	Re: No compression but starts and drives??? If it runs good, doesn’t smoke, doesn’t make crazy noises, and most important, the car stops. DRIVE IT!

07-01-2021, 07:05 AM	#10
McMimmcs Senior Member Join Date: Sep 2019 Location: Fort Gratiot, Michigan Posts: 2,296	Re: No compression but starts and drives??? Ask for a new gauge for Christmas or any other holiday.

07-01-2021, 09:32 AM	#13
nkaminar Senior Member Join Date: Jan 2012 Location: Western North Carolina Posts: 3,899	Re: No compression but starts and drives??? Frank stated that he tested the gauge. But it would be an easy matter to test it on another car, even a modern one, or replace the Schrader valve. __________________ A is for apple, green as the sky. Step on the gas, for tomorrow I die. Forget the brakes, they really don't work. The clutch always sticks, and starts with a jerk. My car grows red hair, and flies through the air. Driving's a blast, a blast from the past.

07-01-2021, 10:26 AM	#14
FrankB Junior Member Join Date: Jun 2021 Posts: 9	Re: No compression but starts and drives??? Thank you for the reply. All great ideas. My intention is to next remove the head and the valve cover/plate and to inspect and clean everything. I was wondering however if this is normal for these cars to run on such little compression? Is this simply because the nature of this already low compression design? This of course is assuming my gauge is fine. Again I tested the gauge and it works fine on straight shop air and on my other engines. I did the thumb test and it's got some compression but it's not a strong push on my thumb. I can almost hold it down when being cranked. It should blow my thumb out of the way really hard no??

07-01-2021, 10:38 AM	#15
FrankB Junior Member Join Date: Jun 2021 Posts: 9	Re: No compression but starts and drives??? I think I'll put another gauge assembly on it just to try. Always good to eliminate variables. Thinking more about it maybe my gauge has a fault below a certain pressure. All my check were 100psi and higher. I'll check this and report back. Thanks guys.

07-01-2021, 11:00 AM	#16
alexiskai Senior Member Join Date: Apr 2018 Location: Mebane NC Posts: 2,350	Re: No compression but starts and drives??? Normal compression on a stock system is ~60. 45psi would indicate some problems but likely still drivable. Below that you get backfires, misfires, exhaust in the engine bay, oil on the plugs, etc.

07-01-2021, 11:57 AM	#17
marko39 Senior Member Join Date: Oct 2016 Location: harpursville ny Posts: 1,040	Re: No compression but starts and drives??? I once pulled the heads on a 39 truck due to low readings on gauge. You guessed it, gauge was bad.( intermittly) was nothing wrong with engine.

07-01-2021, 12:26 PM	#18
Patrick L. Senior Member Join Date: May 2010 Location: Largo Florida Posts: 7,225	Re: No compression but starts and drives??? If you're new to the car and want to check things over, fine. take the side cover off and check the lash. If the lash is good and nothing hanging up, drive it. Taking off a head can be a real task at times. Mine has had 45# compression since I bought it in 1975 and hasn't changed. It doesn't burn or leak a thing. I drive it every day day I can.

07-01-2021, 04:38 PM	#20
Pete Senior Member Join Date: May 2010 Location: Wa. Posts: 5,407	Re: No compression but starts and drives??? You still haven't said if you put oil in the plug holes and tried a test.