JE Pistons, 11.5 cr into a 3.2 flat 6?

[911hillclimber]

Have on order 10.5 cr Pistons for my 3.2 engine.
Cannot get them anytime soon.supplier has a set of 11.5 cr Pistons instead in stock.

Hillclimb engine, ge60 Cams and 99 octane petrol.

Any comments if 11.5 will be ok?

[Gary71]

Twin plug, 99 octane. Sounds ideal

Might need to be more careful on the ignition map I guess?

[911hillclimber]

Many say the same over on the tech side of the hillclimb forum I use Gary.

The pockets in the 3 different cr 's available are all the same depth as each other, the cr is increased by the raised crown, so with twin plugs all should be good, the reason I've done it in fact.

I think I will go with 11.5 cr
Can always get the Head Shop to skim the crowns if need be.

I'm dreading the ignition side of this lot and subsequent mapping, but will use Clewitt I think.

[PeterK]

You could always add thicker base gaskets if you're worried

[911hillclimber]

Indeed Peter, always an option.
I've asked to change the order to the 11.5 cr set, hope to have that confirmed today and get them in the very New Year when the Xmas busyness has eased.

[Gary71]

Does the 3.2 have a knock sensor? Might be worth looking at fitting one whilst it’s apart so you can use it during mapping.

[Cortina]

Bird in the hand .... if it was me , I would machine back to give a compromise of 11.0 .................. 11.5 , is just starting to get on the high side ??

[Gary71]

My sons Honda is 11.7

[911hillclimber]

I think I will be ok.
I can add barrel base shims to give a little more height.

The CR is attained by raising the piston crown, the pocks are the same dimension on all cr's of this design from the wrist pin.

They have sold the 11.5 cr piston set last week, BUT a fresh set are arriving late next week.

I learn something new every day.

Talking this morning with a local Porsche (water cooled expert) engine re-builder he advised strongly to use a tapered sleeve piston ring compressor.

I had never heard of this before, but just bought a 95mm dia one for £47.
This seems a no brainer to safely and evenly load the pistons into the barrels.

So, today I have
2 working Con rod bolt stretch measuring tools
2 12 point tight fitting sockets for the bolts
A Snap-On 1/2" 12 point ring spanner, new
A DTI to 1/10 thou and a variety of spindle nose pins
A tapered piston ring compressing ring

A very clean crankshaft
2 clean engine cases
A load of essential bits.

Talk about "All the Gear, and No Idea'!

[Gary71]

I used a tapered ring compressor on my build. It’s SO easy to use, such peace of mind that the rings survive the process.

The thought of smacking pistons through those wonky bands of steel used to fill me with fear!

[911hillclimber]

Yes, it seems the right thing to me too, instant purchase decision!

While I'm here:
If I do need to ease the cr of the pistons I can raise the base of the barrels using thicker copper gaskets. The gasket kit I have has seals of 0.33mm.

Ds911 etc sell 0.5mm thick ones though I thought the stock size was 0.25mm.

Anyway, can these gaskets be stacked?

ie adding a 0.5 an a 0.33 with seal 574 on their surfaces?

[Cortina]

Yes, it seems the right thing to me too, instant purchase decision!

While I'm here:
If I do need to ease the cr of the pistons I can raise the base of the barrels using thicker copper gaskets. The gasket kit I have has seals of 0.33mm.

Ds911 etc sell 0.5mm thick ones though I thought the stock size was 0.25mm.

Anyway, can these gaskets be stacked?

ie adding a 0.5 an a 0.33 with seal 574 on their surfaces?

I would have said yes (Think about the design of a Cometic head gasket !) ... but dry (and clean ............ very clean !!)

[PeterK]

There are different thicknesses of base gaskets available - for example, you would need one if only one head is skimmed, or the heads on one bank. Porsche show them in several thicknesses.
Whilst stacking is possible and a good 'if needs must' solution, IIRC, Wayne doesn't recommend it.

Curil T is the alleged sealant of choice for base gaskets.

[911hillclimber]

My last 3 rebuilds I've fitted them dry, but clean, no leaks.
It is a last resort if clearances get too tight.

I can only find 0.25 and 0.5 mm thick gaskets.
Are thicker available?

[911hillclimber]

On the 11.5 cr, these pistons are the most popular pistons sold by JE for the 3.2, so many have fitted them to the 3.2.

Each of the heads have a drilling for temperature sensor to drive the ecu on the stock Bosch DME.

Can these head tappings be used for a knock sensor (if the Clewitt ignition system uses such a sensor?