Hi.
My setup is big block 400, Edelbrock E-street heads, air gap intake, Comp Cams 218 duration flat tappet cam ja Street Demon 780 carb. Compression with stock bottom end and 75cc heads should be between 8...9. Timing at idle is 18 degrees and thermostat is 160 degree. It is just street car. It will not see any racing which means driveability is priority.
My issue is that I bought AFR gauge to temporary monitor my air fuel ratio. But seeing air fuel made me thinking of some questions.
1. My idle in park is 850 rpm (afr 13.2). In gear it drops to about 650 rpm and AFR goes to about 14.2. At these low rpm-s idle is a little bit lopey and AFR is fluctuating +/- 1 point. (These afr numbers before were about middle numbers). Is this fluctuating normal? - For my logic it seems to be okey because idle is a little bit unstable with this cam.
2. Another question is that after driving a bit and then stopping engine temperature goes a little bit higher, to about 180 degrees. With this temperature idle goes about one point richer and stays this way. It does not stall or anything but should i go with higher temperature thermostat and is this thing normal? If i go to 180 or 195 thermostat should is see also 20 degree higher engine temperature and same mixture offsets?
3. I have been tinkering with one another stock spec engine before in my life and as i remember with stocker cam i had very stable idle and none of these strange things stated above. Is these things to be expected with mildly modified engine?
My setup is big block 400, Edelbrock E-street heads, air gap intake, Comp Cams 218 duration flat tappet cam ja Street Demon 780 carb. Compression with stock bottom end and 75cc heads should be between 8...9. Timing at idle is 18 degrees and thermostat is 160 degree. It is just street car. It will not see any racing which means driveability is priority.
My issue is that I bought AFR gauge to temporary monitor my air fuel ratio. But seeing air fuel made me thinking of some questions.
1. My idle in park is 850 rpm (afr 13.2). In gear it drops to about 650 rpm and AFR goes to about 14.2. At these low rpm-s idle is a little bit lopey and AFR is fluctuating +/- 1 point. (These afr numbers before were about middle numbers). Is this fluctuating normal? - For my logic it seems to be okey because idle is a little bit unstable with this cam.
2. Another question is that after driving a bit and then stopping engine temperature goes a little bit higher, to about 180 degrees. With this temperature idle goes about one point richer and stays this way. It does not stall or anything but should i go with higher temperature thermostat and is this thing normal? If i go to 180 or 195 thermostat should is see also 20 degree higher engine temperature and same mixture offsets?
3. I have been tinkering with one another stock spec engine before in my life and as i remember with stocker cam i had very stable idle and none of these strange things stated above. Is these things to be expected with mildly modified engine?