Manifold porting for performance

Right so… the inlet manifold now bolts to the head *BUT* the ports on the manifold are smaller than the matching ports on the cylinder head which is bad for gas flow, which is bad for performance. So I need to machine out the manifold until the exit port is the same size as the cylinder head – but how to find out WHERE to machine so that they match and align…

Attempt 1 use the paper template that I previously made to find out where to drill the head. 

This showed me that I needed to machine the holes in the manifold about 6mm wider but the paper was ragged and moved about and I needed to be precise. So I remade the template using some thick clear plastic – now I could SEE where the template needed to be machined. Using the 2 manifold mounting bolts the template was held in place and I could mark out the material to be removed.

The template was then bolted to the manifold and the restriction ground away using a Dremel and a suitable cutting bit. So now the ports match but I still need to smooth out the internal edges so that the air flow is smoother “within” the manifold.

Bolting the manifold back onto the engine, I changed my focus to the throttle linkage which would again have to be custom made but kept period looking.

Problem 1 – the throttle pedal when depressed moves a brass control bar clockwise and ‘down’ – so if I connected this to the carburettor it would ‘pull’ the throttle control on the carburettor ‘down’. The picture below shows the lever which eventually connects to the pedal

And the picture below shows the carburettor lever that needs to be pushed up. The problem is how to mount a control lever that converted the downward movement of the throttle pedal into an upward movement of the carburettor throttle arm BUT the carburettor inlet manifold is physically in the way which would prevent me putting a control arm on the back of the carburettor… 

Answer – remove the brass lever on the pedal, spin it around 180 degrees and remount it so now the shaft rotation means it rotates ‘UP’. Now all I have to do  is manufacture all the control rods so that both carburettors open at the same time from that single lever connected to the pedal… a job for another day but I have a design in mind…


Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s