As a break from the bodywork, I've made the exhaust header. To be honest, I had to make it because the design has been causing me sleepless nights!
Do I go 4-2-1, or 4-1?
4-2-1 is better for torque, 4-1 better for high rpm horse power.
The original system is 4-2-1, merging the outlets from each head together. There is some followers of the "cross-over", where the back ports are linked together, then the front pair. It gives a smoother sound and possibly a little more bhp.
I can get quite nerdy about exhausts. Probably explains the sleepless nights!
I decided on following the original idea of a 4-2-1, but obviously my headers are much shorter. They are however, equal length. The primary tubes are 440mm long.. This is calculated so that the exhaust pulse from the first cylinder has passed the join before the next pulse reaches the join. The motion of the first pulse helps to "pull the next out of the cylinder.
My tubes are 304 stainless steel starting at 38mm od and going up to 45mm at the last joint.
The 3 bolt flange isn't welded in yet. I will do that, and make the silencers, once the engine is in place and the bodywork made. Or at least designed.
This flange is actually the same size as some of the vw beetle aftermarket silencers, so I may end up using one of them
I put the engine on the table upside down so I could work out the routing easier.
Anyway, here's the pictures
And some m8 brass nuts with 11mm spanner size.