MSefi.com read only forum (Jan.15,2018)

I have a 350 chevy running MS1 on fuel only. I had the thing tuned pretty well and it would start on a 0 degree day and run up to operating temperature without any fuss and no throttle needed. Over the winter I switched to new cylinder heads that increased the compression ratio from 8.5 to about 9.5:1 and flow much better. Now the thing seems to be very rich during warm up. Will not idle without cleaning it out every frequently and appears to be pig rich. Does this seem normal? I would think with a higher compression ratio and better flowing heads it should be lean rather than rich. Just want to make sure I did not miss something before I start tuning the warm up. Still to cold to take it out on the road since we still have snow on the ground.

Is it idling OK when it is warmed up, just running rich when cold? Also, did you swap iron heads for aluminum, or are they both the same material?

Idles fine when it is warmed up. AFR is around 12.8 to 13.0. The old heads were cast iron and the new ones are aluminum.

It's likely the different heat conductivity is having an effect here. You'll just need to adjust the warm up enrichment as needed. Maybe the ASE too.