EGT with Carburator

I am getting 1420 EGT on Cyl 1 and 2 and only 1270 EGT on 3 and 4.
O 360 A1A with Precision MA-4-5 Carb. Advanced probes and engine monitor.
No air leaks at gaskets nor induction tube connectors. Probes are all equal distances from flange.
I suspect its just the way it is.
Was looking for spec from Lycoming on Max EGT.
additionally cylinder temps are even across all at 330's

I think a lot depends on probe location, with trends being more important. My O-320 is carbureted and I usually see EGT's around 1450 when leaned properly for cruise. Plugs look great every year and the engine runs great. Cruise CHT's in the low-mid 300's.

EDIT: Below comment is also spot on with the carb - at WOT I have a large spread between front and back cylinders, partially closed there seems to be better fuel distribution and more even EGTs.

Chris

EGT spread (as opposed to the actual value) will depend on throttle position, since that affects mixing, and mixture setting.

Dave

If you Try to adjust your carb heat valve and throttle valve you may see the change in airflow mixing influence things.

Your goal might be not even EGT, rather seeing them all EGT peak at the same Fuel Flow reading when leaning. So, your trying to avoid 1 peaking, then a gallon an hour leaner see the second EGT peak. If you can mess with these two variables and get them to peak at the same time you have achieved the same mixture in each cylinder. Now fly lean of peak at power setting below 65% and enjoy the savings.

Allan Moore said:

Was looking for spec from Lycoming on Max EGT.
additionally cylinder temps are even across all at 330's

Click to expand...

There is no spec from lycoming on max EGT. The actual temperature isn't important, but the distance from peak is what you are looking for.

I have an 0-360-A1A with a Sam James intake. I have spent considerable time and effort trying to normalize my cylinders so that I can run better LOP.
I have done the following:

- Replaced stock oil sump with a Superior Sump (better intake geometry.
- Modified the carburetor exit to flow smoothly into the sump intake (The stock set-up had a small shelf there.
- Replaced the magnetos with duel P-mags.
- Modified the geometry of the Sam James intake plenum.

None of the above made a noticeable difference, though the P-mags are a nice improvement all around and help with going deeper into LOP (5.6 gpm at full throttle).

The one thing that did help was installing an airflow straightener on the bottom of the carburetor. This is counter-intuitive because turbulent air should cause a better mixture distribution, but I can not argue with the results. I think one on the carburetor exit would be more effective, but there is no vertical space for that.



<a href='https://postimg.cc/k6pxp9YZ' target='_blank'><img src='https://i.postimg.cc/k6pxp9YZ/January-2017-066.jpg' border='0' alt='January-2017-066'/></a>

The problem with these engines is the distribution of fuel in the air stream. Cracking the throttle helps a tiny bit, Carby heat helps, but the airflow straightener works and has been used on all kinds of engines over the decades.

I am keen to know if you made one or was able to buy one. I know a few folk who would benefit from it.

I made mine. I bought some aluminum honeycomb with a 5:1 depth to opening ratio. I then epoxyed it to a thin metal base place the same shape as the carb base. I will find some photos and post them. It is a very easy project.