Not enough carb heat

Was out flying yesterday which was a perfect day for carb icing. So I thought it would be good to check the carb inlet temps. During cruise it was 17F and with carb heat it was only 32F with OAT of 30F and the same at low rpm. Sutton exhaust with normal EGT on number 2 cylinder. O-320 b2b that we recently did a top overhaul with new Lycon port and polished cylinders. Prior to the top I would get carb inlet temps of 38F with OAT around 10-20F. Airbox etc. double checked and functioning well and properly installed. RPM drop about 50 with carb heat applied. How can I improve carb heat temp with the sutton exhaust or am I overthinking this and just fly. Steve

A quote from from CAR Part 3. This has been discussed. I'm not judging or offering an opinion just pasting what's there:

§ 3.606 Induction system de-icing and antiicing
provisions. The engine air induction
system shall incorporate means for the
prevention and elimination of ice accumulations
in accordance with the provisions in this section.
It shall be demonstrated that compliance with the
provisions outlined in the following paragraphs
can be accomplished when the airplane is
operating in air at a temperature of 30° F, when
the air is free of visible moisture.
(a) Airplanes equipped with sea level
engines employing conventional venturi
carburetors shall be provided with a preheater
capable of providing a heat rise of 90° F. when
the engine is operating at 75 percent of its
maximum continuous power.

Gary

If you do a search you will find some post on improving the Sutton carb heat. I would definitely look into improving what you have.
DENNY

Is it possible your temperature readings are off?

I would be looking to get better heat for sure.

What setup are you using to measure carb inlet temp? If it's the venturi probe tap on the carb then it can be lower than incoming air.

Gary

I am using ECI gauges and yesterday I checked the accuracy as my plane is blanketed and preheated the CHT EGT and carb inlet temps all read the same 135F. Noticed that by accident when I went to see if my carb temps where in centigrade units which would have made sense. I also got to thinking that there is a cut out in the nose bowl for the skytec starter that allows almost direct flow of cold air into the low pressure side of the cowling to the carb heat inlet. When ever the wind stops blowing a little duct tape and test flight will be in order. I have not looked but I suspect the probe must be at the venturi probe tap as it was reading 17F when it was probably 35F outside. I got carb ice once after taking a shot at a coyote so very low level and the ice cleared quick enough I did not crash with the current set-up.

Okay so I covered up the nose bowl cut out with duct tape and did a test flight. OAT 22F carb air temp with heat applied 25-38F. So essentially no help. Has got me thinking that my carb air temp must be on the venturi side and not the inlet as Gary questioned. Don't know what I am looking at when I look at the probe installation on the carb but it must be in the venturi side. Is a venturi temp of 35F okay. As I said I got carb ice once and it cleared fairly quickly on a colder day. Also I get 50 rpm drop

While not the same type of gauge you might read this manual for further info: https://www.mcico.com/Assets/products/InstallationManuals/B-5revF_im.pdf Their recommendations are towards the end. Also note what ECI suggests. Either way I'd do whatever it takes to be able to stay out of the yellow arc below.

Gary