Carb tuning with spacer

[gliderider06]

So, tuning a carb with a spacer. Do you think a cast, spreadbore intake with an open spacer cause issues when tuning a carburetor? Mainly A/F and idle settings is what I'm wondering. If there is a gap between the carb and the intake would it cause an imbalance by one side bleeding over to the other? This is a bone stock 318 with a TQ. Just curious

 

[318willrun]

I've put the adaptors, which are in sense 1" spacers, to put square bore Holley's on factory cast spreadbore intakes. Never an issue.

 

[scatpackbee]

A recent episode of Engine Masters on Motortrend On Demand proved there was a change in air/fuel ratio at idle when a spacer was installed under a carb on a dual plane intake. The idle air/fuel ratio had to be adjusted, but the fuel distribution at higher RPM was more even, If I remember correctly.

It has to do with the signal the carb sees at idle with and without the spacer. Basically horsepower was improved with an open spacer on a dual plane intake.

Mototrend on Demand is on sale for $1.00 a month which is an awesome deal.

It's worth it just for the Engine Masters show.