Replacement cylinder height (delta) class

[Tom F2]

The specifications for the 2.2 liter motor say that cylinders come in two basic classes, 5 and 6. (What happened to 1 through 4?) There are different specifications for replacement cylinders in "R5" and "R6" classes, which I am guessing are intended as single replacements for an engine that still has 5, or fewer, of its original class 5 or class 6 cylinders. The specifications line up like this:

• Class 5, height 85.400-85.425
• Class R5, height 85.150-85.175
• Class 6, height 85.425-85.450
• Clase R6, height 85.175-85.200

My question is, why are the replacement cylinders shorter than the originals?

I am looking into this, because I have a single, new cylinder for a 2.2 E, marked class 5. The originals are class 6. Yet, when I mount two of the originals and the replacement class 5, I find that the class 5 cylinder is taller by over 0.05 mm.

I take it that single cylinders, these days, come out of broken up piston/cylinder kits. I am guessing that the R5 and R6 classes have long been unavailable.

[Flat6pac]

I ve never seen an R class cylinder, only delta 5 or 6.
Bruce

[BoxxerSix]

Have you measured the heights of your "original" class 6 cylinders to find if they have been machined previously and are now in a class 5 deck height range.

I have come across this in many of the motors I've rebuilt over the years, with mismatched cylinders machined to fit the remaining cylinders in the set.

[Jon B]

Originally Posted by Tom F2

My question is, why are the replacement cylinders shorter than the originals?

Tom,
The Specs booklets refer to R cylinders as "replacements", the '72 workshop manual as "reconditioned". The difference appears to be .25mm, the size of one cylinder base gasket. Like Bruce, I don't recall ever seeing one.

As Adam suggested, you should measure all your cylinder heights, preferably on a surface plate, and adjust them to match if necessary.

[tom1394racing]

I believe the "reconditioned " cylinder height refers to height targets for cylinders that are re-cut to true up either the upper or lower sealing surfaces during an overhaul.

Similar in concept to the undersize crank journal target sizes.

[Tom F2]

Originally Posted by Flat6pac

I ve never seen an R class cylinder, only delta 5 or 6.
Bruce

Have you ever assembled an engine with mixed 5 and 6 on one bank?

[tom1394racing]

Mixing different height classes in a given bank of cylinders can lead to inadequate clamping on the short cylinder and a leak at the cylinder to head interface.

Cylinder heights should be checked to make sure all cylinders are within the allowable height variation.

[Tom F2]

Originally Posted by tom1394racing

Mixing different height classes in a given bank of cylinders can lead to inadequate clamping on the short cylinder and a leak at the cylinder to head interface.

Cylinder heights should be checked to make sure all cylinders are within the allowable height variation.

I am more worried about misaligned camshaft bearings.

[tom1394racing]

The heads will mate to the cam towers with no problem and the cam will spin nicely.

You need to be more concerned with the cylinder to head interface. I have seen several cases where heights have been mixed with resultant leaks and ruined cylinders and heads.

[Tom F2]

Thanks, Tom. Kind of hard to understand, with the heads being separately held by bigger fasteners, but those cam carriers are really rigid.

[willtel]

Are these numbers the same for 930 3.3 cylinders? I think I had a mix of 4s and 5s when I took mine apart.