The Ford Barn

corvette8n · 05-10-2022, 07:37 AM

I have a spare ‘40 flathead with no starter,generator,carb,ignition. Can I spin it over with a breaker bar and get a reading? My gauge has a threaded adopter I can screw into the head.

Joe KCMO · 05-10-2022, 09:15 AM

First impression from personal experience, yes but it will not be easy work. Model T experience would be very helpful(crank to start). A 40 should have the crankshaft adapter for a crank/lug nut crank, much easier!

19Fordy · 05-10-2022, 09:42 AM

You'll get a reading BUT, it won't be accurate.

ford38v8 · 05-10-2022, 10:01 AM

About all that will tell you is you’ve got pistons and valves. A compression check you can really use is done at cranking speed with a fully warmed up engine, all spark plugs removed, carb propped open at full throttle, 4 cycles per each cylinder. Record the readings, then do it again after a good squirt of oil down the spark plug holes.

Bored&Stroked · 05-10-2022, 10:02 AM

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You'll be able to tell that it has compression, but really no idea as to how much. I'd throw a starter on it.

05-10-2022, 07:37 AM	#1
corvette8n Senior Member Join Date: Jul 2010 Location: 36 miles north of Albany NY Posts: 2,950	Compression checking question I have a spare ‘40 flathead with no starter,generator,carb,ignition. Can I spin it over with a breaker bar and get a reading? My gauge has a threaded adopter I can screw into the head.

05-10-2022, 09:15 AM	#2
Joe KCMO Senior Member Join Date: May 2010 Location: Miami, Florida Posts: 423	Re: Compression checking question First impression from personal experience, yes but it will not be easy work. Model T experience would be very helpful(crank to start). A 40 should have the crankshaft adapter for a crank/lug nut crank, much easier!

05-10-2022, 09:42 AM	#3
19Fordy Senior Member Join Date: May 2010 Location: Coral Springs FL Posts: 10,944	Re: Compression checking question You'll get a reading BUT, it won't be accurate.

05-10-2022, 10:01 AM	#4
ford38v8 Senior Member Join Date: Jul 2011 Location: SF Bay Area Posts: 6,645	Re: Compression checking question About all that will tell you is you’ve got pistons and valves. A compression check you can really use is done at cranking speed with a fully warmed up engine, all spark plugs removed, carb propped open at full throttle, 4 cycles per each cylinder. Record the readings, then do it again after a good squirt of oil down the spark plug holes. __________________ Alan

05-10-2022, 10:02 AM	#5
Bored&Stroked Senior Member Join Date: Jan 2011 Location: Central Ohio Posts: 5,067	Re: Compression checking question Sponsored Links (Register now to hide all advertisements) You'll be able to tell that it has compression, but really no idea as to how much. I'd throw a starter on it.