The Ford Barn

JT FORD · 08-25-2021, 11:59 AM

Going to do a test on my 8BA engine. Have some questions? No. 1. does it make any difference if I remove one plug at a time and test and reinstall or remove all the plugs and test with all plugs removed?? No. 2

should I remove the feed line from the tank to the fuel pump so there will be no gas going to the engine, with all the gas engine would be flooded! Engine warmed up, trodduol wide open, coil wire pulled.

tubman · 08-25-2021, 12:16 PM

Remove all of the plugs; you'll get a more accurate reading because he engine will turn faster and it's easier on the starter.

I have never disconnected the fuel line when taking a test; I do disconnect the coil and block the throttle open. Because all of the plugs are out, it won't develop sufficient suction on the intake stroke to draw in a problematic amount of fuel.

ford38v8 · 08-25-2021, 12:23 PM

JT, All plugs are to be removed to ensure that the engine will spin fast enough to provide a good consistent reading on all cylinders. The carburetor will have been topped out by the fuel pump, thereby closing the float valve to prevent overfilling of the carburetor by the pump. With the throttle wide open, there will be zero vacuum to draw in fuel from the carburetor.

Watch the gauge as you spin the engine, the compression reading will pump up to it's maximum potential within 3 compression cycles. Record this reading for each cylinder, and compare results to each other.

JT FORD · 08-25-2021, 06:17 PM

Thank You fellows for the advice. Its just been almost 70 years since I did a test like this........

GB SISSON · 08-26-2021, 08:44 AM

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And don't forget to remove the brick from the gas pedal before you start it back up!

08-25-2021, 11:59 AM	#1
JT FORD Senior Member Join Date: May 2010 Location: N.W. Iowa Posts: 306	Compresson Test Going to do a test on my 8BA engine. Have some questions? No. 1. does it make any difference if I remove one plug at a time and test and reinstall or remove all the plugs and test with all plugs removed?? No. 2 should I remove the feed line from the tank to the fuel pump so there will be no gas going to the engine, with all the gas engine would be flooded! Engine warmed up, trodduol wide open, coil wire pulled.

08-25-2021, 12:16 PM	#2
tubman Senior Member Join Date: Dec 2013 Location: Minnesota, Florida Keys Posts: 10,312	Re: Compresson Test Remove all of the plugs; you'll get a more accurate reading because he engine will turn faster and it's easier on the starter. I have never disconnected the fuel line when taking a test; I do disconnect the coil and block the throttle open. Because all of the plugs are out, it won't develop sufficient suction on the intake stroke to draw in a problematic amount of fuel.

08-25-2021, 12:23 PM	#3
ford38v8 Senior Member Join Date: Jul 2011 Location: SF Bay Area Posts: 6,641	Re: Compresson Test JT, All plugs are to be removed to ensure that the engine will spin fast enough to provide a good consistent reading on all cylinders. The carburetor will have been topped out by the fuel pump, thereby closing the float valve to prevent overfilling of the carburetor by the pump. With the throttle wide open, there will be zero vacuum to draw in fuel from the carburetor. Watch the gauge as you spin the engine, the compression reading will pump up to it's maximum potential within 3 compression cycles. Record this reading for each cylinder, and compare results to each other. __________________ Alan

08-25-2021, 06:17 PM	#4
JT FORD Senior Member Join Date: May 2010 Location: N.W. Iowa Posts: 306	Re: Compresson Test Thank You fellows for the advice. Its just been almost 70 years since I did a test like this........

08-26-2021, 08:44 AM	#5
GB SISSON Senior Member Join Date: Jan 2014 Location: Orcas Island Washington Posts: 4,924	Re: Compresson Test Sponsored Links (Register now to hide all advertisements) And don't forget to remove the brick from the gas pedal before you start it back up! __________________ Owner/Operator of 'Jailbar Ranch' on the side of Mt. Pickett. Current stable consists of 1946 1/2 ton pickup turned woodie wagon with FH V8, 1947 Tonner Pickup (red) mostly stock with exception of a cummins 6at turbo diesel, 1946 Tonner Pickup (green) with 226 cu in 6 cyl flathead, 1979 Toyota landcruiser wagon, completely encased in 1947 Ford Jailbar sheet metal. Ok, cornbinder rear fenders..... 'Rusty ol' floorboards, hot on their feet' (Alan Jackson)