Reply to "Header temps"

These are 4180 Holleys. They have a separate fuel jet in the metering block behind the fuel jet unlike other series Holleys.

Fuel is premixed (atomized) and the adjustment screws just effect the idle rpm. They don't change the a/f ratio.

This is done to lock out the possibility of changing the a/f ratio at idle.


I have already pointed out that this is how the Weber IDA idle system works as well. The idle a/f ratio is set with a fuel jet and and air jet. The idle screws there are also just for volume and is how you set the idle rpm.

That does not affect the air fuel ratio at idle either.


It has a four corner idle adjustment.

All other systems in the carb are tuneable just like any other Holley is.


Just the idle circuit needs to be modified because it is so lean. The idle air bleeds need to be closed down which means removing them and using Allen set screws as jets.



Plug has about 500 miles on it.

The headers are too hot. I'm going to play with plug heat range, fuel a/f for a while and see what happens.

I have a nice set of 1850's waiting if these don't work out.