what about the story, Volkswagen Golf pistons for a T37 - T40 ? I can not find a Volkswagen piston with the correct compression height, diameter and piston pin diameter . Do I need to ask Little Red Riding Hood or the Wolf ?

Perhaps they can only be used as blanks? (so they need rework)

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Vive la Marque !!

The only Volkswagen I found has diameter 70mm , piston pin 20mm and compression height 40mm with a recess 4mm . And who can machine a piston ?

I think you are confusing your volkswagens!
VW polo pistons were very commonly used before the UK restorers started making proper replacements, however they are far from like for like and a 37 engine still using 1970s polo pistons is likely to be slow.
1970's polo pistons supplies dried up as very few are now needed hence making proper ones.

so there is no real Volkswagen replacement for a T37 piston , better to make new pistons .

Hi Udo the polo pistons only really worked in blown cars as the crown hight was lower hence a lot of unblown cars chugging around, the BOC now make T37 pistons suitable for a blown car ie slightly lower compression ratio.

However if you want a specific hight for an unblown car talk to Malcolm at Gentry restorations though not listed on there web site they make them to your specific spec: http://www.gentryrestorations.co.uk/par ... ype=engine

When dealing with the Bugatti specialists in England it is well worth shopping around. From personal experience some are exorbitantly expensive, unreliable, dishonest or a combination of all three. However, have found Robin Townsend (not sure of spelling) to
be the best informed about the type 37/40 engine. He was conveniently based near Prescott.

Thank you for your answers . I have not a piston problem , my company is making pistons . But I got the info some days ago from a forum member the the Polo pistons fit the t37 - T40 . But I was not able to find any volkswagen piston in my piston catalogs for this cars .
Because I have a company a Polo piston cost me only 50 € , in this case I would buy them and save the time to make them . Desiderata , I am in the lucky position , that we can make anything , from pistons to crankshafts and complete engines . So I must not buy anything in england , but I know what you are talking about .
I am building a t40 engine unblown and will raise the compresion high about 3mm .I hope I can bring this engine from running like a steam engine into a combustion engine .

In the past there were two types of VW Polo pistons, one with a C/H 47mm and suitable for the T37-40 engine and another one with 40.35mm C/H which was suitable for the Brescia. These flat top pistons produced by Mahle and KS were absolute top quality and were a direct fit with 20mm gudgeon pins and three sizes Ø69.51,70.51 and 70.51. KS reference is 93 157 600.
As building a proper engine in most cases means new conrods the correct C/R was chosen by fitting longer rods. A Polo piston and 204mm rod gives a C/R around 8.1 and most times higher as the crankcase has usually been skimmed more than once.
Bugwrench

I found the Volkswagen pistons with 69,5mm in a old mahle catalog from 1993 . It looks to me like a compromise . And because I already did make the chill mould for the pistons , I make new pistons and do not change the con rods . To bad that I can not use the 37 mould for the brescia , so need to make a second one .