Idle speed too high

[rdwhite]

I recently put a Chrysler 265 in my M37 to replace the old 230. I'm using the original ETW1 carb. The engine seems to run fine, except I can't get the engine to idle under 800 rpm even with the throttle screw backed all of the way out. So I'm trying to figure out what the problem is. I would assume that this is some sort of carburetor problem. But, it also occurred to me that perhaps air is coming into the intake manifold through the PVC check valve. Any suggestions? Thanks, DW

[just me]

First thing I would do is make sure the butterfly isn't binding or hitting anything that prevents it from closing all the way. Or the linkage isn't binding.

[RMS]

I would think the 230 carb is way too small for the the mighty 265. Im running two weber dgv 32/36 on mine.

[just me]

In actuality, the smaller carb is more efficient and will produce more torque. It won't rev as high or as quickly. The air velocity is higher through the smaller Venturi creating a better fuel air mix. This was most noticeable on old Taxis and city trucks with large engines and tiny 1bbl carbs.

[rdwhite]

I have not noticed a deficiency in engine power using the smaller carb. I pulled the spark plugs not too long ago and the insulator tips have a nice color indicating the fuel mix is about right. The only snag I ran into was adjusting the governor to operate correctly with the higher air flow. DW