The Ford Barn

uncle buck · 04-06-2026, 12:48 AM

Since the 260 and 289 both have the same stroke is it possible to bore a 260 to a 289 bore?
Thanks

5851a · 04-06-2026, 09:32 AM

I don't believe so. That would be a 29 cubic in overbore. These are thin wall castings.

miker98038 · 04-06-2026, 11:24 AM

Whatever answer you get, I’d sonic check it first. Cheap insurance before spending the $ for machine shop time.

paul2748 · 04-06-2026, 02:41 PM

If I remember correctly. .030 is about all you can take these out to. Sonic test is your best bet .

Bleach · 04-07-2026, 09:27 AM

Quote:

Originally Posted by paul2748

If I remember correctly. .030 is about all you can take these out to. Sonic test is your best bet .

I second that. It’s a 60 year old block. I’m sure rust in the water jackets will have degraded it too. You need to make sure to see if it’s been bored out already.

darrell · 05-05-2026, 03:31 PM

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i bored one back in 72.took me 2 evenings.a shovel full of shavings each night.it lasted no problem an d didnt heat.i was on another side where a guy said he did several on sunbeam tigers.he warned not to use the 62 block.they were different with narrow mounts.so much for thinwall castings.

rotorwrench · 05-06-2026, 01:59 PM

The max was .060" back when the castings were good. Most shops stop at .040" over bore due to the liability and that's after a sonic check. These and the early 289 have the different rear bolt pattern that changed for 1966.

ms fowler · 05-07-2026, 05:32 AM

The answer is "no". you cannot bore the 260 out to 289. I believe the core centers on the 289 were shifted a little above and below the centerline to gain enough wall thickness to permit the 289 bore.

darrell · 05-07-2026, 11:14 AM

i love people who have an answer to something they never tried.

rotorwrench · 05-09-2026, 08:53 AM

Quote:

Originally Posted by darrell

i love people who have an answer to something they never tried.

Are you inferring that the smaller 260 can be bored from 3.80" out to 4.00"? Thats 200 thousandths! That's only 50 thousandths from 1/4".

paul2748 · 05-09-2026, 09:03 PM

Maybe you should explain just what you mean

Quote:

Originally Posted by darrell

i love people who have an answer to something they never tried.

rotorwrench · 05-10-2026, 02:29 PM

When Ford was designing the small block, they were going for as light a weight an engine as possible. This was the reason for the thinner cylinder walls and small short stroke design. There isn't much distance between cylinders on those little rascals. The 351 Windsor was a whole new design with some of the original characteristics but larger mains and the much taller deck. The 302 on down were all very similar but had their subtle differences. I don't know how thick the cylinders were. Only a sonic test could get close to actual thickness. Ford was more careful with their mold cores than they were in earlier years when cylinder wall thicknesses were substantial in order to compensate for more core shift during the foundry work. Ford didn't make them to last forever. I figure the wall thickness was somewhere between 1/8" and 3/16" with somewhere in between like .160" being optimal. 0.200" is over 3/16" at .1875". I'd be surprised if they were much thicker than that. I've seen a 289 with a hole in a cylinder wall and I recall that there wasn't much there at the time. Maybe someone else can shed more light on the actual thickness of either a 289 or a 260. The 221 and later 255 are not common engines to find laying around anymore. The 302 engines are a lot more common plus the 3" stroke. I agree though that the 289 with the smaller stoke was quicker to wind up the rpm. A friend had a 66 pony car and it ran pretty damn good for the time. It only started out with a 2V carb set up but would still give other folks a good run for their money.

04-06-2026, 12:48 AM	#1
uncle buck Senior Member Join Date: May 2010 Location: Snohomish,WA Posts: 1,131	Boring a 260 Since the 260 and 289 both have the same stroke is it possible to bore a 260 to a 289 bore? Thanks

04-06-2026, 09:32 AM	#2
5851a Senior Member Join Date: Oct 2014 Location: NE Iowa Posts: 1,797	Re: Boring a 260 I don't believe so. That would be a 29 cubic in overbore. These are thin wall castings.

04-06-2026, 11:24 AM	#3
miker98038 Senior Member Join Date: Mar 2013 Location: Kent, WA. Tucson, AZ Posts: 1,766	Re: Boring a 260 Whatever answer you get, I’d sonic check it first. Cheap insurance before spending the $ for machine shop time.

04-06-2026, 02:41 PM	#4
paul2748 Senior Member Join Date: May 2010 Location: Midland Park, NJ Posts: 4,406	Re: Boring a 260 If I remember correctly. .030 is about all you can take these out to. Sonic test is your best bet . __________________ 48 Ford Conv 56 Tbird 54 Ford Victoria

05-05-2026, 03:31 PM	#6
darrell Senior Member Join Date: Dec 2010 Location: p.e.i. Posts: 1,065	Re: Boring a 260 Sponsored Links (Register now to hide all advertisements) i bored one back in 72.took me 2 evenings.a shovel full of shavings each night.it lasted no problem an d didnt heat.i was on another side where a guy said he did several on sunbeam tigers.he warned not to use the 62 block.they were different with narrow mounts.so much for thinwall castings.

05-06-2026, 01:59 PM	#7
rotorwrench Senior Member Join Date: Jun 2010 Location: San Antonio, Texas Posts: 18,007	Re: Boring a 260 The max was .060" back when the castings were good. Most shops stop at .040" over bore due to the liability and that's after a sonic check. These and the early 289 have the different rear bolt pattern that changed for 1966.

05-07-2026, 05:32 AM	#8
ms fowler Senior Member Join Date: Mar 2022 Posts: 201	Re: Boring a 260 The answer is "no". you cannot bore the 260 out to 289. I believe the core centers on the 289 were shifted a little above and below the centerline to gain enough wall thickness to permit the 289 bore.

05-07-2026, 11:14 AM	#9
darrell Senior Member Join Date: Dec 2010 Location: p.e.i. Posts: 1,065	Re: Boring a 260 i love people who have an answer to something they never tried.

05-10-2026, 02:29 PM	#12
rotorwrench Senior Member Join Date: Jun 2010 Location: San Antonio, Texas Posts: 18,007	Re: Boring a 260 When Ford was designing the small block, they were going for as light a weight an engine as possible. This was the reason for the thinner cylinder walls and small short stroke design. There isn't much distance between cylinders on those little rascals. The 351 Windsor was a whole new design with some of the original characteristics but larger mains and the much taller deck. The 302 on down were all very similar but had their subtle differences. I don't know how thick the cylinders were. Only a sonic test could get close to actual thickness. Ford was more careful with their mold cores than they were in earlier years when cylinder wall thicknesses were substantial in order to compensate for more core shift during the foundry work. Ford didn't make them to last forever. I figure the wall thickness was somewhere between 1/8" and 3/16" with somewhere in between like .160" being optimal. 0.200" is over 3/16" at .1875". I'd be surprised if they were much thicker than that. I've seen a 289 with a hole in a cylinder wall and I recall that there wasn't much there at the time. Maybe someone else can shed more light on the actual thickness of either a 289 or a 260. The 221 and later 255 are not common engines to find laying around anymore. The 302 engines are a lot more common plus the 3" stroke. I agree though that the 289 with the smaller stoke was quicker to wind up the rpm. A friend had a 66 pony car and it ran pretty damn good for the time. It only started out with a 2V carb set up but would still give other folks a good run for their money.