Re: Carby Spacers on Single plane manifolds
I've seen dyno results make a significant improvement on HP and TQ by fitting a carb spacer.....significant with reference to the cost of a spacer. Engine I'm recalling had a smaller manifold like a weiand xcelerator and medium size solid cam and other basic go fast bits. 2 inch, 4 hole spacer gave it about and extra 20HP & ft/lbs TQ.
I recall the funnelweb sits quite high and an extra 1-2" may give you clearance issues - easy fixed with an angle grinder to the bonnet!
It all really depends on how your brother's engine is set up already. Cam, heads, headwork, exhaust, carby etc. Don't expect eye watering results with a spacer - one of those things you fit and try a dyno run to confirm results (1", 2", open or 4 hole).
If you fit one, don't use a metal/aluminium one. Use a plastic/composite type - spacers also act as an insulator to keep your carby and fuel cooler for a denser charge adding to your power.
393 Tremec TKO 9"