quote:Originally posted by george pence:
Insulating the carb from heat is to address/prevent the issue of boiling of the fuel in the fuel bowls.
If you install an open spacer between a carb & a divided plenum intake manifold, you have just redesigned the intake manifold.
your friend on the DTBB
George is correct. You've just redesigned the airflow and intake manifold, and it is impossible to say what the impact will be on your engine.
I've read articles that dyno tested a whole bunch of different combinations of spacer height, intake manifold, carb, cam, etc. I don't remember any of the details but do remember the bottom line.
Some spacers added hp. Some made zero difference. None hurt hp (I think). The expert's predictions of the effect of the spacer was wrong as often as it was right, ie it was impossible to draw sweeping conclusions (dual planes will always benefit from one or not, single planes, etc)
As Rover says, the only way to tell on your engine is to buy a bunch of different heights and spend some $$ on dyno time. I'd look very suspiciously at anyone who guaranteed X hp gains.