The Ford Barn

Granny · 10-26-2022, 08:27 PM

Hi Guys
I would like to know If my 1951 C1BA would have any problems with being bored out to receive .060 oversize pistons. I am asking this as machinist is concerned that the block may not take it and course overheating
Thanks for any advise
Granny

tubman · 10-26-2022, 08:36 PM

No problem. I have built two 8BA's with a .125 overbore with no problem. I have heard of cases where they have been taken to 3 7/16"+.030 (.280 0ver), but I wouldn't even think about trying that. The only things that could make .060" a problem is extreme core shift or really bad rust.

By the way, have you asked your machinist if he can "sonic test" the block? That will tell you for sure. If he can't, you may want to find one that can.

Mart · 10-27-2022, 06:57 AM

Granny, if your machinist is worried at .060, that's chevy type thinking. It would appear your machinist is not familiar with flatheads or sonic testing.

Your flathead should take a .060" overbore no problem.

Tim Ayers · 10-27-2022, 07:07 AM

Agreed. .125" is a very common overbore size.

Ol' Ron · 10-27-2022, 10:26 AM

I bore all my engines .125" over, this gives me 20ci displacement increase an 1 point of compression increase. Probably the best way to improve the power and economy of the engine.. The "Perfect street engine"
Gramps

Granny · 10-27-2022, 07:16 PM

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Thanks Guys I will let him know

Mart · 10-28-2022, 04:36 AM

I'd sonic test before going .125". I had one go through to the water jacket at that size.

Bored&Stroked · 10-28-2022, 10:20 AM

If your machinist knows this little about flatheads and the blocks, what will he/she know about how to correctly do the valvetrain work?

They should have the correct guide-bore pilots (made specifically for a flathead) and not just use a standard OHV pilot inside a flathead valve guide. Do they have the correct pilots?

Do they also understand that the valves on the Driver's side of the flathead are about .043 or so higher (as compared to the deck) as compared to the passenger side? The valves are all the same length, but the relationship to the deck is different due to the crankshaft being offset. I've seen shops do things like try to deck the block to make "both sides the same", sink the valve seats on one side . . . or other dumb stuff - because they have no flathead experience or knowledge.

Think about these things and check with your machine shop . . . before they potentially do "bad things" to your engine (not even knowing they're doing them).

B&S

10-26-2022, 08:27 PM	#1
Granny Member Join Date: Jun 2010 Location: Sale, Victoria, Australia Posts: 52	0.060 oversize Pistons Hi Guys I would like to know If my 1951 C1BA would have any problems with being bored out to receive .060 oversize pistons. I am asking this as machinist is concerned that the block may not take it and course overheating Thanks for any advise Granny

10-26-2022, 08:36 PM	#2
tubman Senior Member Join Date: Dec 2013 Location: Minnesota, Florida Keys Posts: 10,404	Re: 0.060 oversize Pistons No problem. I have built two 8BA's with a .125 overbore with no problem. I have heard of cases where they have been taken to 3 7/16"+.030 (.280 0ver), but I wouldn't even think about trying that. The only things that could make .060" a problem is extreme core shift or really bad rust. By the way, have you asked your machinist if he can "sonic test" the block? That will tell you for sure. If he can't, you may want to find one that can.

10-27-2022, 06:57 AM	#3
Mart Senior Member Join Date: May 2010 Location: Solihull, England. Posts: 8,777	Re: 0.060 oversize Pistons Granny, if your machinist is worried at .060, that's chevy type thinking. It would appear your machinist is not familiar with flatheads or sonic testing. Your flathead should take a .060" overbore no problem.

10-27-2022, 07:07 AM	#4
Tim Ayers Senior Member Join Date: May 2010 Location: NJ Posts: 6,233	Re: 0.060 oversize Pistons Agreed. .125" is a very common overbore size.

10-27-2022, 10:26 AM	#5
Ol' Ron Senior Member Join Date: May 2010 Location: Chester Vt Posts: 8,890	Re: 0.060 oversize Pistons I bore all my engines .125" over, this gives me 20ci displacement increase an 1 point of compression increase. Probably the best way to improve the power and economy of the engine.. The "Perfect street engine" Gramps Last edited by Ol' Ron; 10-27-2022 at 10:33 AM.

10-27-2022, 07:16 PM	#6
Granny Member Join Date: Jun 2010 Location: Sale, Victoria, Australia Posts: 52	Re: 0.060 oversize Pistons Sponsored Links (Register now to hide all advertisements) Thanks Guys I will let him know

10-28-2022, 04:36 AM	#7
Mart Senior Member Join Date: May 2010 Location: Solihull, England. Posts: 8,777	Re: 0.060 oversize Pistons I'd sonic test before going .125". I had one go through to the water jacket at that size.

10-28-2022, 10:20 AM	#8
Bored&Stroked Senior Member Join Date: Jan 2011 Location: Central Ohio Posts: 5,176	Re: 0.060 oversize Pistons If your machinist knows this little about flatheads and the blocks, what will he/she know about how to correctly do the valvetrain work? They should have the correct guide-bore pilots (made specifically for a flathead) and not just use a standard OHV pilot inside a flathead valve guide. Do they have the correct pilots? Do they also understand that the valves on the Driver's side of the flathead are about .043 or so higher (as compared to the deck) as compared to the passenger side? The valves are all the same length, but the relationship to the deck is different due to the crankshaft being offset. I've seen shops do things like try to deck the block to make "both sides the same", sink the valve seats on one side . . . or other dumb stuff - because they have no flathead experience or knowledge. Think about these things and check with your machine shop . . . before they potentially do "bad things" to your engine (not even knowing they're doing them). B&S