Hello,
I am building the pattern to cast new cylinder blocks . Modern technology , and for sure modern materials . My question is , to use double ignition or not ? How many had double ignition ? Or is it better to go for single ignition ?

This is for the Royale, I presume?

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Vive la Marque !!

What´s wrong with the old material ? Not good enough ?
What was the old material anyway ?

Old park railings is how John Gardner described it.The main problem with most Bugatti blocks was as discovered by King in america the dismal lack of water around the valve seats and combustion area.My daughters block has cracks in the valve seats on two cylinders.It will no doubt seem anethema to most Bugatti enthusiasts but I would like to see a slight change to the internal water passages in the head area.As to the old question about plug positions,The plug should really be on the exhaust side to help the plug do it's work.Maybe less important with modern oils but nonetheless advantageous.I would very much like to see a Bugatti block which swopped inlet and exhaust sides.That is to say with four inlet ports to four valves.The exhaust will always get out ! But the inlet passages are much more important.This is why Bugattis go so very much better with superchargers.Years ago an australian enthusiast made a detachable head block for his T37.I never did find out what happened to this project.If you do fit twin plugs,it would be better to fit them on both sides of the block.The twin plug positions of the T46 and T49 are not ideal.The better place for the plug is in the center of the block and not at an angle to the block centerline.

The old material was cast iron , normal cast iron from 1925 . If you machine it, everything is black including you . And it is not very strong , you can break it very easy .Modern cast iron is very strong . All modern cars have a cast iron crankshaft for example . And if you machine it , you do not look so black . The differend is the carbon .In the modern cast iron ( I do not know the name in English , in German sphero cast iron )the carbon is in little balls , in the old one in little fins . You can cast it very good , and after heat treadment the risk of cracks is very small . For example GGG40
I think there is enough water around the spark plugs and the valve seats . Only in the middle between the intake and exaust can be a small problem . So , better to seperate them with 2 mm distance . Sparke plugs at the exaust side and 4 valves is not realy a problem , but is it still a Bugatti ?

YES it is a Brescia

It looks like , I better stay with one spark plug in the center . Any comments what should be changed and still looks like a Bugatti cylinder block ?

What type of Bugatti are we discussing here?

the drawing says :37 - 40 - 44 - 49
the next cylinder block will be the 35 . How many engines did use the 35 Block ?

you should make it with the plug in the center,but there is no harm in putting a second boss in the core so that someone could machine for a plug on the other side.

you mean the possibility to have a spark plug at the exaust side ?

yes.Although my personal experience of double plugs in engines has always been very good.I have several dual ignition engines.With two flame fronts the rate of expansion is greatly increased.But if there could only be one plug then I would prefer it to be on the exhaust side of the block.

I think it is a very good idea to have the possibility for a second spark plug at the exaust side . All the aircraft engines have it this way . I do not like this side by side design .

Might it therefore make sense to actually machine a second plug hole in the exhaust side ...Then fit a blanking plug- it is there if necessary- and machined correctly -without need for serious dismantling..presumably better done at the production stage when all costly and necessary equipment is available...?
[will the hole and thread be to take modern plug sizes ?]

good question ? Modern plug sizes , like 14 mm ?
new design , one spark plug each side .