The Ford Barn

Philgoodtoo · 02-01-2025, 02:48 PM

I have an engine knock I hear coming from the # one cylinder. There is low to no oil pressure reading, especially upon warm-up.

I think maybe there might be a spun rod bearing. But wouldn't I have a knock in #5 also? Seeing as how two rods share a bearing? The engine looks to have been worked on. Would it be possible to get by with replacing the one bearing? Or am I just wishing.

Ken/Alabama · 02-01-2025, 03:53 PM

59A should have floating rod bearings so a spun bearing isn’t going to be your problem. The only way you’re going to know what the issue is is to pull the pan and remove the bearing that serves the front two rods. Carefully measure the crankshaft journal for wear . If it’s with specs you’ll need to remove the pistons and rods and have the rods checked to be sure they’re in spec before just replacing the bearing.

L-head · 02-01-2025, 08:03 PM

A 59A engine could have an 8BA or Merc crank in it if it has been "worked on." It could have the late model rods and rod brgs. The pan needs to come off. Better safe than sorry.

rotorwrench · 02-02-2025, 12:32 PM

Canadian 69A engines from that era also had separate replaceable bearing shells but the 69A casting mark on the block should be evident. None of the USA made blocks had anything but floaters in that time frame unless modified. Other sources of knock could be piston related if something made it's way into a cylinder or if the clearance was reduced too much by excessive planing of a cylinder head. Also check your exhaust for blown manifold gasket. One more thing would be a broken ring or burned piston. That can make a audible noise at low rpms. Compression would be low on the offending cylinder in that case. Piston slap is notable on very worn pistons.

In general, the early Ford V8 engines didn't have very high oil pressure. The indicating system after the war was basically a 60 PSI system. It's not uncommon for well worn engines to drop pressure to minimums after they are warmed up on a hot day. Driving is slow paced urban environments or pulling heavy loads didn't help since the flatheads could easily overheat if coolant flow was impeded by crud in the radiator or due to a bad thermostat if so equipped. The floater bearings did manage to be able to take some pretty low pressure.

Philgoodtoo · 02-02-2025, 02:25 PM

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Thank you all for your great input. I now have a better idea of what to look for.

02-01-2025, 02:48 PM	#1
Philgoodtoo Member Join Date: Mar 2013 Location: Monrovia, CA Posts: 34	Engine knock 1948 Flathead V/8 59 A I have an engine knock I hear coming from the # one cylinder. There is low to no oil pressure reading, especially upon warm-up. I think maybe there might be a spun rod bearing. But wouldn't I have a knock in #5 also? Seeing as how two rods share a bearing? The engine looks to have been worked on. Would it be possible to get by with replacing the one bearing? Or am I just wishing.

02-01-2025, 03:53 PM	#2
Ken/Alabama Senior Member Join Date: May 2010 Location: Alabama Posts: 3,455	Re: Engine knock 1948 Flathead V/8 59 A 59A should have floating rod bearings so a spun bearing isn’t going to be your problem. The only way you’re going to know what the issue is is to pull the pan and remove the bearing that serves the front two rods. Carefully measure the crankshaft journal for wear . If it’s with specs you’ll need to remove the pistons and rods and have the rods checked to be sure they’re in spec before just replacing the bearing.

02-01-2025, 08:03 PM	#3
L-head Senior Member Join Date: May 2010 Posts: 195	Re: Engine knock 1948 Flathead V/8 59 A A 59A engine could have an 8BA or Merc crank in it if it has been "worked on." It could have the late model rods and rod brgs. The pan needs to come off. Better safe than sorry.

02-02-2025, 12:32 PM	#4
rotorwrench Senior Member Join Date: Jun 2010 Location: San Antonio, Texas Posts: 18,006	Re: Engine knock 1948 Flathead V/8 59 A Canadian 69A engines from that era also had separate replaceable bearing shells but the 69A casting mark on the block should be evident. None of the USA made blocks had anything but floaters in that time frame unless modified. Other sources of knock could be piston related if something made it's way into a cylinder or if the clearance was reduced too much by excessive planing of a cylinder head. Also check your exhaust for blown manifold gasket. One more thing would be a broken ring or burned piston. That can make a audible noise at low rpms. Compression would be low on the offending cylinder in that case. Piston slap is notable on very worn pistons. In general, the early Ford V8 engines didn't have very high oil pressure. The indicating system after the war was basically a 60 PSI system. It's not uncommon for well worn engines to drop pressure to minimums after they are warmed up on a hot day. Driving is slow paced urban environments or pulling heavy loads didn't help since the flatheads could easily overheat if coolant flow was impeded by crud in the radiator or due to a bad thermostat if so equipped. The floater bearings did manage to be able to take some pretty low pressure.

02-02-2025, 02:25 PM	#5
Philgoodtoo Member Join Date: Mar 2013 Location: Monrovia, CA Posts: 34	Re: Engine knock 1948 Flathead V/8 59 A Sponsored Links (Register now to hide all advertisements) Thank you all for your great input. I now have a better idea of what to look for.