Anyone measured the squish angle of a Thunderstorm piston before?

I always thought they had a 15 deg squish angle:

From - http://www.nrhsperformance.com/tech_thunderstorms.shtml


From - http://www.nrhsperformance.com/tech_squish.shtml


http://xlforum.net/vbportal/forums/arch ... 22842.html


but when I actually measured one (out of a 2002 PBS X1):



The part number itself doesn't tie up with the part number in the parts book for Thunderstorm pistons (which come with rings), however I think I remember asking Ursus a similar question when I last had a Thunderstorm top end, before I sold it, and (I think) he looked on HDNET and it said it was the PN of the piston only and was listed as part of the set.

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08 Specialized Langster

Nearly finished my crisps...

The plot thickens. I got rid of the step on the heads so I could measure the squish angle there:


Not far off 15 deg, but we know this is cast and pretty rubbish.

So, back to the piston... Is the piston (22645-98YA) correct for the engine?

I quick call to Riders to do some HDNET digging:

The Thunderstorm piston kit, 22676-98Y comprises:
1 x 22765-88 - Piston Pin
1 x 21920-83 - Piston Ring Set
2 x 22589-83B - Lock Ring - Piston Pin

But no piston

They did however have one kit in stock in Bridgwater, so a quick call to the parts department with a request to open the box, and it had the piston inside (one mystery solved) with the 22645-98YA part number engraved in it (second mystery solved).

So, in summary:

1. I have the correct pistons in this engine
2. The piston squish angle is 10 degrees
3. The head squish angle is 15 degrees
4. Google suggests that nobody else has reported this before

Could it be that piston 22645-98YA supersedes 22645-98Y which had a 15 deg squish angle? This is a 2002 engine. I had pistons with the same engraved part number out of a 2001 engine which went in SoG.

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08 Specialized Langster

If it was a real part number then YA would indeed be a superceded number for Y. However, that number doesn't appear to exist at all. Found 22641, 22642 and 22643 all with 86D suffixes which were pistons but no 22645. You do enjoy a good mystery don't you, Pash?

Steve

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Back on the road again!

Yeah, that's what I'm on about... But it's on the piston, clear as a metallic tattoo... And not just on one, but on two sets that have passed through my hands and a brand new one sitting on the shelf at Riders.


No 50 Shades of Grey for me

But check it out, found someone else finding the same issue (with a 22645-98Y as a 10 deg too - so no change in angle from Y to YA):

http://xlforum.net/vbportal/forums/show ... stcount=28

but if you follow the thread to page 2, you will see that the pictures with evidence have been removed. Maybe the HD MIB (Men in Black not Management Information Base from IEE 802.3.1) have deleted it:

http://xlforum.net/vbportal/forums/show ... 600&page=4

Time to respond...

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08 Specialized Langster