Right then. I've got a pair of pistons and barrels and a pair of cylinder heads winging their way to my house. I'm planning on building a roadgoing engine which is a bit more powerful than the standard 2CV engine, but I want to be able to use it on the road. I'm going to have 0.3mm machined off each barrel to raise the compression a bit but has anyone got any other tips? I'm very much on a budget so much as I'd like to get into engine management systems and reprofiled camshafts, I can't really afford to. Anyone know of anything else I can do cheaply and easily?

Stepping back a little,
if those pistons are 9.0:1 C.R., by machining 0.3mm off the top of the barrels, you could end up with a 'pistons meet cylinder heads' situation...

Even if it didn't, the increase in C.R. to 9.3 would make the use of 98 octane fuel advisable, with the ignition timing probably needing to be retarded as well.

ken.

no real secrets

start off with a good crank, cam and new oil pump
and basically build it as per the manual

if you go with the skimmed barrels try turning it over before the rockers go on but with the heads torqed to make sure there is clearance

another old trick is to use really soft springs on the valves to check the clearance between valve and piston over a cycle, well the tdc bit- by soft springs i mean ones you can move by hand

you can check the volume of the heads and even them up
weigh everyting to the nearest gramme (cheap digital scales can be made more accurate by using butter beans lego anything that 10 of them make a gramme)and make sure the pistons pushrods rockers etc are all as close to even as you can get them

have a look at the race regs and do all the stuff thats been made illegal

dont polish the inlets or remove much metal from them
be carefull with 2-1 exhausts the exhaust IS a tuned item and you can loose power by messing about with it
dont cut blades off the fan

the further you get from standard the more temprimental/fragile its going to get when stuck in bankholiday traffic

Sean

Thought I'd ask my question on this thread as it's kind of in context.

On the race cars, most of them seem to have the "hot spot" pipes cut out of the exhaust side of the manifold, is this necessary? My engine has shortened barrels, Simons old race engine heads, waisted valves etc.

Basically, should I go and hack up my manifold tomorrow?

spanners,
only if you want poorer vaporisation of the incoming mixture, meaning that you'd probably need to richen the mixture.
The engine would be more prone to carb icing as well.

However, if the overriding requirement is peak power, hack away.

ken.

Ken, that's precisely the answer I was hoping for.

That means the engine will be back together a day earlier than expected.

How much are your barrels shortened by Jon? 9:1 pistons? Any problems with clearance? And what have the heads had done to them?

Re The heads - We don't really know that much about them, apart from as the Racing Rules say 'had metal removed or added'

depends on who has done them

welded heads have some of the machining left over from the walve guide and seat process welded up then re ported

people have taken metal out others put it in doesnt appear to make a huge overall diferance just moves peak up and down the rev range.

Sean