The Ford Barn

Bored&Stroked · 10-21-2019, 09:12 PM

Hey Ziggster . . . there is a lot to know about the various years of flathead designs (Ford and Mercury) as well as the various crankshafts that were used.

If you captured what he was saying correctly (about the 100 HP cranks), then he isn't correct on that either. There were 100 HP engines that used full-floating bearings that had 1 oil hole in the rod journals and there are also later 100 HP engines that used tanged (non-floating) rod bearings in some Canadian variants as well as later 49-53 Ford engines.

Also, his statements about "relieved blocks" is completely incorrect . . . the term "flathead" has nothing to do with relieved or non-relieved blocks. The term 'L-Head' is just another term for an engine with the valves in the block . . . AKA a "flathead".

Hopefully he knows these engines well enough to do the correct machine and assembly work - as some of his statements/claims make me a bit nervous.

rotorwrench · 10-21-2019, 09:38 PM

Relieved blocks generally found their way into trucks. It was a way of reducing compression without modification to the heads. In later years they just made heads to do the job.

The first 239 was the 99A and it was 95 horse power. After the war, all the 239 engines were 100 horse power. The G model 6 was 90 horse power.

I knew something about the C69 was different but I wasn't sure whether it was the rod or main bearings. Some folks just replace the crank with an 8BA type to repair them and use bearings that are more easily available. You guys are right about the mains. The rule of thumb on mains is stick with the block characteristics to choose the mains. The French SUMB engine is half 8BA series (front) and half 59 series (rear) so it figures it would use the 59 series type mains but it was late enough to use the 8BA type crankshaft.

Ziggster · 10-22-2019, 02:34 AM

Thanks guys. I really appreciate all the feedback. Yes, my block was used as an industrial engine and had a heavy duty truck oil pan and trans attached, so I'm guessing it was a "truck" application. I never really thought about relieved blocks having less compression, but I'm guessing the supposed increased airflow made up for any power losses due to the reduced C.R. For me it's not about power so much, but just knowing what it what. It's the engineer in me.

10-21-2019, 09:12 PM	#21
Bored&Stroked Senior Member Join Date: Jan 2011 Location: Central Ohio Posts: 5,064	Re: RTH - Crankshaft bearing sizes Hey Ziggster . . . there is a lot to know about the various years of flathead designs (Ford and Mercury) as well as the various crankshafts that were used. If you captured what he was saying correctly (about the 100 HP cranks), then he isn't correct on that either. There were 100 HP engines that used full-floating bearings that had 1 oil hole in the rod journals and there are also later 100 HP engines that used tanged (non-floating) rod bearings in some Canadian variants as well as later 49-53 Ford engines. Also, his statements about "relieved blocks" is completely incorrect . . . the term "flathead" has nothing to do with relieved or non-relieved blocks. The term 'L-Head' is just another term for an engine with the valves in the block . . . AKA a "flathead". Hopefully he knows these engines well enough to do the correct machine and assembly work - as some of his statements/claims make me a bit nervous.

10-21-2019, 09:38 PM	#22
rotorwrench Senior Member Join Date: Jun 2010 Location: San Antonio, Texas Posts: 16,431	Re: RTH - Crankshaft bearing sizes Relieved blocks generally found their way into trucks. It was a way of reducing compression without modification to the heads. In later years they just made heads to do the job. The first 239 was the 99A and it was 95 horse power. After the war, all the 239 engines were 100 horse power. The G model 6 was 90 horse power. I knew something about the C69 was different but I wasn't sure whether it was the rod or main bearings. Some folks just replace the crank with an 8BA type to repair them and use bearings that are more easily available. You guys are right about the mains. The rule of thumb on mains is stick with the block characteristics to choose the mains. The French SUMB engine is half 8BA series (front) and half 59 series (rear) so it figures it would use the 59 series type mains but it was late enough to use the 8BA type crankshaft.

10-22-2019, 02:34 AM	#23
Ziggster Senior Member Join Date: Aug 2018 Location: Ottawa, ON Posts: 854	Re: RTH - Crankshaft bearing sizes Thanks guys. I really appreciate all the feedback. Yes, my block was used as an industrial engine and had a heavy duty truck oil pan and trans attached, so I'm guessing it was a "truck" application. I never really thought about relieved blocks having less compression, but I'm guessing the supposed increased airflow made up for any power losses due to the reduced C.R. For me it's not about power so much, but just knowing what it what. It's the engineer in me.