60 HP vs 90 HP?

[Conrad Carter]

What is the difference parts wise? Head, cam, carbs, etc?
Conrad

[Vic Skirmants]

The three "C"s; cam, compression, carburetion.

[Conrad Carter]

Does the compression come from different pistons or heads with smaller combustion chambers?
Conrad

[Dick Weiss]

Either one or both.

[Martin Benade]

I believe for a given year since around 1957 the compression was raised by taller pistons. Not sure about earlier engines. For example a N, S and S 90 had increasingly taller pistons. The S 90 head was different but I don't think the chamber was much smaller.

[Jim Alton]

Doesn't the 356B Super 90 have different crankshaft bearings than the 356B Normal? My personal experience is with the 356A.

Also, parts wise, the pistons in a Normal and a Super (let alone a Super 90) are quite different. I believe the Super pistons are shorter top to bottom (but taller from the pin to the piston top). Don't the Super pistons have three rings as opposed to four in a Normal?

And finally, wouldn't a 60 hp Normal have iron cylinders while an S-90 would have alloy?

[Steve Fox]

160 hp.

[Dick Weiss]

Jim,

Actually the 'N' pistons will have flat tops, the 'S' pistons w/have a medium chamfer on its slightly higher dome, and the S90 will have
a more-higher higher dome w/a larger chamfer and deeper exhaust valve clearance/pockets; The 'C/SC' piston tops just have a radius.
The early chromed-aluminum 'S' cylinders will have thick 3-rings; The later OEM pistons in cast iron & Biral cylinders (except S90 & early SC Ferral & early 912s) will have 4-rings. Most all of the 'SC' & similar 912 pistons went back to 3-rings again.
There may be some variations w/aftermarket PCs.

Dick

[Dick Weiss]

I really meant the pistons for the early chromed-aluminum cylinders have thick 3-rings.

[Jim Alton]

I think what I was trying to express was that Normal pistons have a deeper skirt than Super pistons.

At least that's what i recall from rebuilding my 356A engine back to Super specs several years back. At the time the choices were Normal pistons & cylinders vs. SC pistons & cylinders (I wound up putting JE pistons in iron cylinders).

[Conrad Carter]

So, adding hotter cam and bigger carb won’t get me there?
Conrad

[Dick Weiss]

Yes Jim,

S90 main bearings are for the 55mm journals, and the Super pistons have shorter skirts.

Conrad,
"What's in Your Wallet" will determine how far you want to go, and nothing's wrong w/Zenith carbs if set up properly..
You don/t want to overstress an earlier case and limit the RPMs if you use a B/bore PC set.


Dick

[Richard Holler]

Excuse my ignorance, but what positives/negatives were there going 4 ring vs 3 ring cylinders? less oil consumption?

[C J Murray]

Having an oil control ring below the wrist pin is dopey in my opinion. Oil just goes inside the piston and works its way past the pin above the oil ring. Modern pistons generally have 3 rings, 2 compression and 1 oil control ring. Some of the latest high performance engines use only 2 rings. Some may be using only 1 ring now.

Quite a bit of improvement has happened in the design of piston rings and they work much better and last much longer than when our cars were made.