260 piston question

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Watry

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The pistons that came out of my Tiger’s 260 all look like the attached. Four apparent ring grooves, three rings. Empty top groove is .058” tall and about 5/32” deep. All other grooves are more like 7/32” deep. All 8 pistons have just the three rings: two compression, one oil.

Pistons are .040” over stock-type cast, engine built at a South Bay shop 1983, never run, pistons have 1106 and 79 cast in a circle on the inside. Maybe 79 is the date?

Factory Ford engine book lists two compression rings, not three, though in one poor photo it appears to show this setup. Anyone have any idea about this? Key question: should there be a ring in that top groove or not? Thanks for any help.

Andrew
 
260 pistons

Recently I read that the top groove is a "Carbon" grove". nothing goes there. You have a very early piston. Bill.
 
So it'd be a bad idea to use them? I'm looking to build a basically stock engine, but if they're not a good design...
Thanks very much.
Andrew
 
They Good

Why not use them? A Pro assembled the engine. They fit the 0.40 over bores! And they have zero miles on them!!

Rick

Watry said:
The pistons that came out of my Tiger’s 260 all look like the attached. Four apparent ring grooves, three rings. Empty top groove is .058” tall and about 5/32” deep. All other grooves are more like 7/32” deep. All 8 pistons have just the three rings: two compression, one oil.

Pistons are .040” over stock-type cast, engine built at a South Bay shop 1983, never run, pistons have 1106 and 79 cast in a circle on the inside. Maybe 79 is the date?

Factory Ford engine book lists two compression rings, not three, though in one poor photo it appears to show this setup. Anyone have any idea about this? Key question: should there be a ring in that top groove or not? Thanks for any help.

Andrew
Click to expand...
 
Well, if they're a terrible design, that would be a reason not to use them. But the block was presumably bored to them, so once I get it back from sonic checking, will make sure clearances are good.

Thank you.

Andrew
 
It's also getting harder to find 260 pistons and rings, especially oversized parts, so that may figure into deciding if you use them or not.
I recently had a lot of trouble finding .030" over 260 rings.
 
If the cylinder walls check out, I'm inclined to use this block. It's the original to the car, though I realize that isn't that big a deal, and 289 parts are way easier to find.
Pistons are fine, rings are perfect, so I can just go back together. Might use ARP rod bolts. Crank is 10/10, I'll do new bearings, have the 30-YO valve job checked. Cam bearings were done, new cam, new lifters, mostly can be reused.

Pics on disassembly. I bought another three-core-plug 260 for insurance, but it's bored .040" as well.

Andrew
 
260 Ford

Remember- these pistons are true flat tops -they have no valve reliefs. Watch for any interference if you plan to use a cam with more than stock lift.
 
Thanks, will do.

Machine shop reports good cylinder wall check. Crank magged OK, but he doesn't like the lack of fillet radius done at the 10/10 crank grind, which I agree with. I had an Alfa 1600 crank break from such a "wall" cut with no radius. So will rework that, presumably going to 20/20.

My Tiger is stashed at a friend's airplane hangar til I have room at home. Stopped in and brought home rest of engine parts yesterday. New oil pump, original oil pan is nicely smashed up on the bottom. I have two others luckily.

Andrew
 
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