How to build 2.2 with 9:1 compression

[ajwans]

Counterweighted crank. The T engines were produced with cheaper
components, non-forged pistons, cast iron cylinders, and the crank
was not counterweighted.

andy

[TimT]

This thread is weird...

OP wants a 2.2 with 9:1 cr he didn't mention using his stock T pistons... that I could tell

Ive seen answers recommending offset grinding rod bushings, milling (fly cutting?) the heads...that will give the desired results...

It easy.. call JE give them your specs... viola a few weeks and a coupla hundred georges you have pistons that meet your specs..

[TimT]

BTW I know a bunch of racers who use non CW cranks in their 8500 rpm 2.0L hand grenades..Non CW crank= lower MOI

They rebuild the engine a few times a year.... replacing the crank isn't a big deal

[tom1394racing]

I pulled some pistons off the shelf and took some pics and measurements to give us an idea of the differences between the factory 2.2 and 2.4 pistons.

Shown in the pics are the 2.2T, 2.2E, 2.4T, 2.4E and 2.4S pistons (I do not have any 2.2S pistons).

You can clearly see the difference in dome ht between the T,E and S pistons. Also note that the 2.2 pistons have higher domes because of the shorter stoke crank they were designed to run with.

The relative dome hts as measured from the top of the wrist pin hole to the top of the dome are as follows:

2.2T - 30.5mm
2.2E - 33.0mm
2.4T - 27.5mm
2.4E - 28.5mm
2.4S - 31.0mm

Note that these are only relative measures of dome ht and that CR is dependent on the dome volume (not ht).

[304065]

Tom, the "blueprint" compression height is 34mm, that is center of pin to theoretical deck. Pin diameter is 22mm. So if you add 11mm to your figures you get total height including dome above theoretical deck.

2.2T - 30.5mm +11 = 41.5mm -34mm = 7.5mm dome height
2.2E - 33.0mm - 23 =10mm
2.4T - 27.5mm - 23 = 4.5
2.4E - 28.5mm -23 = 5.5
2.4S - 31.0mm -23 = 7mm

This is actually pretty interesting because it shows you how the size of the "bump" scales down as the bore diameter goes up to maintain the target compression ratio.

[304065]

Originally Posted by Vintagemotion

To look at this a bit more quantitative I still like to know what the compression heights of a 2.2E, 2.2T 2.4E 2.4T. Distance wrist pin to piston top?

All 34mm. This geometry didn't change until the 3,2.

As a general rule with our aircooled engines it's not a good idea to monkey with the deck height unless you are a highly skilled engine builder who can manage the tolerance. You certainly can get a compression bump by skimming the head and effectively reducing chamber size, which requires less dome volume, so you can trade off reduction in chamber size for dome volume to improve flame propagation. This is, in fact, what the factory realized in 1970 when they reduced the combustion chamber size and changed the valve angle.

You want to target between 1.5 and 1.0mm deck height. You get there through a combination of the following factors

Rod length (130mm for a 2,2)
Cylinder height (search here for cylinder height information)
Cylinder base gaskets (.25mm is basic height, not usually altered)
Cylinder head mating surface- stock or cut (a small truing cut is usually made)
Spigot height, this is a function of whether the case was machined
Compression distance (stays at 34mm unless you try to move the pin, experts only)

The basic geometry is this: half the stroke of 66mm = 33mm + center-to-center rod length (130mm) = 163mm + compression height of 34mm = 197mm + 1mm deck height = 198mm. Cylinder head mating surface should be 198mm above the centerline of the crank. Same numbers for a 2,4, the rod was shortened by half the distance of the longer stroke (70.4mm).

This information is all here in the engine rebuilding forum, a simple search brings it all up.