67S Engine Rebuild

[visualfx]

I've started to strip a 67S engine I obtained from LA a couple of months ago. After removing the pistons they measure 90mm instead of 80mm ish? It’s also been fitted with “Arias” pistons which look very new.

My question is:

Can a 2.0 engine be fitted with such a large piston when still incorporating the same stroke (66)? Would the heads have been modified? The valves seem correct @ 38/42 for an early S engine

Puzzled???

Garry

[Flunder]

Garry; Sounds like you have yourself a short stroke 2,5L as 66x90=2506 built on your 901/02. This should be a very sweet running engine. Are the tops of the piston crowns chamfered around the outside circumference or are the combustion chambers chamfered around their lower circumference? Those would be the two approaches to using the big p&c with early heads.

[Neil '67 911S]

I would check on the cylinder head dates. Someone might have substituted later heads versus modifying the original 2.0 heads to work with the 90 mm cylinders.

[visualfx]

Thanks guys, I've only taken off one bank of pistons so far but checking the rod P/N (which I can't find anywhere) I think "whoever" may have changed the stoke after all. The engine was left outside for a number of years without plugs so the cylinders are looking a little sorry for themselfs.

Head manfacture dates seem spot on

By the way this engines going in my 67S RHD I'm restoring.

Even more puzzled

Pictures attached:

Thanks

Garry

[edmayo]

Why not just measure the stroke, then you'll know. Rods don't have part numbers, only casting numbers, but I'll agree, they do appear to have the beam shape of a 2.4/2.7 rod.

[304065]

Ed is right, those are 2,4 rods. Somebody probably put a 2,4 crank in there. Looks like somebody flycut the devil out of those original heads. See the casting number in an oval? Those are SWB heads for sure. Now look at the thickness of the ring between the combustion chamber and the head stud hole, and compare it to my uncut 1966 head. You can see what happened.

So congratulations you have a 90 x 90 x 70.4 * 3.1416 /4 * 6 /1000 = 2519cc motor!

[visualfx]

Measured the rods today and they size as 2.0/2.2 therefore 2.5 total me thinks?

The pistons look really sexy, so if I can get new rings from Arias I'm on a winner Still bet it's not that easy....

Big end reads -0.25 so the cranks had a shave also.

Thanks

Garry