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Lightning Pistons

TouringComet

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Steve Hamel runs up in that range of compression ratio on petrol, in his Bonneville racer.
 

timetraveller

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The thing to remember here chaps is that one has to consider other things than just the compression ratio. A Vin runs very happily and tractably on 10:1 or even 10.5:1 if a cylinder head with a squish band is used. I know nothing of the internals of the Buell but it would be instructive to learn about both the cylinder head shape and the top of the piston shape. Also is it using fuel injection or a carb? Some of the modern fuel injection systems are using five separate injections per injection cycle to improve the burn efficiency. I have never seen anything as to why this works but it clearly does if one looks at the fuel consumption figures of some of the modern cars.
 

Spqreddie

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VOC Member
GPM in italy has still in is "Catologo Storico" (hystoric Catalogue, Itmes i think only made to order, but they still ahve all the patters)
high compression pistons up to 9:1 for the Vincent:
http://www.gandini.it/www/pistoni_s...cat_articoli=VINCENT / HRD&idcat_articoli=GPM


VINCENT / HRD

Clicca sulla misura scelta per visionare la scheda tecnica articolo

Veicolo - MotoreCodiceØ nom.PrezzoVariazione Prezzo %
Euro/cad.12
Motore E 7/8 - O.H.V. - C.R. 8 :1
P841284,00198,00 --
punto.gif
Motore E 7/7 - O.H.V. - 1950/55 C.R. 7,3:1
P8412A84,00198,00 --
punto.gif
Motore E 7/7 - O.H.V. - 1950/55 C.R. 9 :1
P841384,00198,00 --
punto.gif

If you click on the product line gives you basic specification and piston top design,

i.e.: for the 9:1 piston: http://www.gandini.it/www/pistoni_s...cat_articoli=VINCENT / HRD&idcat_articoli=GPM

VINCENT / HRD
Veicolo - MotoreCodiceØ nom.Prezzo
Variazione Prezzo %
12
Motore E 7/7 - O.H.V. - 1950/55 C.R. 9 :1
P841384,00198,00
--


Nr cilindriCompressioneForma TestaQuotaSpinotto Ø
1/231,75
12dis.jpg
11,5522,22

I know that for a time after end of prodction of Specialloid and others in England, GPM were one of the only few option for the Vincent engine but i dont know anything about thier performance and material currently used.

i think many uses Omega now, but they come only in 7.3 and 8:1 C.R. Right? GPM seems to offer 9:1.

If somebody is interest i can try to call and ask some more info in italian!
Ciao,
Edmondo
 

bmetcalf

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Does "Quota" mean the height above the gudgeon pin centerline or above the top ring groove? Google Translate says "Spinotto" means "Jack" in English, so what does it mean here?
 

Spqreddie

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VOC Member
Ciao Bruce,
Quota, normally should be the height from the center of the gudgeon pin to the top of the piston, but seems preatty slim! can not be only 11,5mm, i'll cal tomorrw and ask them how they measure it.

The "Spinotto" is the gudgeon pin, therefore this give you the pin diamater.

i'll try below to give a rough translation of the tables,
Edmondo


Veihcle - Engine
Code
Ø nom.Price
Price Variation %
12

Engine E 7/7 - O.H.V. - 1950/55 C.R. 9 :1
P841384,00198,00
--



Number of Cyl.
Compression
Head Shape
need to ask for this!!
Gudgeon pin Ø
1/231,75
12dis.jpg
11,5522,22
 

vibrac

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VOC Member
spares company has 7s and 8s and some 9 sizes at £120 (non member) for my methanol I got a very resonable 13:1 made by venolia in USA a lot less that 198 euros (I suppose that is the price in the picture)
 

bmetcalf

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VOC Member
Thanks for the translation and investigation. Does spinotto also mean jack? What kind of jack? Enquiring minds want to know.
 

Spqreddie

Well Known and Active Forum Website User
VOC Member
Bruce,
Spinotto in means in general pin, or yes in electornic jack or plug.
but in this case is gudgeon pin.

I've called "GANDINI INDUSTRIA SRL" and i spoke with the techincal service.
They have at the moment no pistons in stock, but they have still the castings so they can produce some if needed. Minimum order would be 10 per diameter.
They use shell casting as means of production,
and the alloy used is a low expansion 12% Silicon alluminium alloy. ISO code 48000, that should correspond to the british LM13.
the price advertised do not include VAT, but they can do a reduction if a consisten lot is ordered.
Coming back to the measures, i've asked clarifications so please if you go back to the table please read "Compressione" as the measure of the height in mm between the gudgeon pin centre and the pistons top circonference, the "quota" is the height between the piston top circonference and the top of the piston head dome. Hope is clear!

Edmondo
 
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