impco 225 mixer modification question

hansje2000 · Post by **hansje2000** » Wed Sep 20, 2006 5:02 pm

Hello guys,

I have a little question for modifying my impco 225 mixer.

I have a jeep Cherokee 5.2 V8 running on gas (impco e-type) what is mixed by a impco 225 mixer.
In the beginning my jeep had a poor acceleration by using this mixer.

The first thing I did was dismantled the mixer and drill the 4 little holes in the mixer backup plate a little bigger.

When I fire up my car the acceleration was increase by factor 3.

So now my question:
Can I drill this holes a little more for a perfect situation?
In my opinion the little holes are transporting the inlet air to the gas/air mix camber (correct me if am wrong).

Thanks for reply

sleepybu · Post by **sleepybu** » Fri Sep 22, 2006 11:09 pm

do you have pics of your mods?

C3H8 · Post by **C3H8** » Sat Sep 23, 2006 1:14 am

You are correct about the holes transferring vacuum to top of the diaphragm. This vacuum is generated by the air flow through the mixer. Drilling them would cause the gas valve to lift quicker. Unfortunately it will also cause your mixtures to be very rich at part throttle and cause excessive fuel consumption. You don't mention if you tried adjusting the power valve or any other items to correct the power problem. Another method would have been to add a VPV (vacuum power valve) from the vaporizer to the base of the mixer. This would give you a temporary enrichment of the mixtures during acceleration and not affect the fuel economy.