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RE: Head Porting

Subject: RE: Head Porting
From: "Jerry Causey" <>
Date: Fri, 29 Nov 2002 09:09:44 -0800
I'm no expert on gas-flow, but from talking to people who are (when I 
was shopping to have head-work done for my 'B):

> don't forget the intake manifold...Just as important to clean it up, 
Cleanliness is always a good thing. 

> open it, 
This is not a good thing. You can cause the air/fuel mixture to lose 
velocity and cause fuel to separate out of the mixture.

> match it up 
Better to make the exit from the manifold to the head slightly smaller 
than the entrance to the intake port. The lip creates an anti-reversion 
effect that keeps wave pulses from bouncing back into the fuel 
mixture trying to get out of the manifold. The reverse is true for the 
exhaust port-to-manifold connection.

> and polish it up.
Also not a good thing. Some smoothing is OK, but some roughness, 
and consequent turbulence,  is necessary to keep the fuel at the 
boundary layer from collecting on the sides of the manifold rather 
than staying suspended in the air.

Recontouring a head and manifold system is part science, part art. 
Best left to wizards such as Peter Burgess (UK) and Mike and Sean 
Brown (USA), who have the equipment and the experience to do it 
right. If you've never carved up an MG head before, it is very easy to 
wind up with 45 pounds of fine English cast iron junk by doing it 


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