SMC 18 - What to Expect in Temperature Difference Between Top and Bottom Racks?

[Ken Hendrix]

I have done a couple of cooks on my SMC 18 within the last week or so and have a question about the temperature differential between the top and bottom racks. Cook before last I had the whole top rack covered with 3 racks of ribs and chicken thighs. The remaining 5 or 6 thighs that wouldn’t fit on the top rack went on the bottom rack. During the course of this cook the bottom rack temperature was anywhere from 30 to almost 40 degrees less than the top rack as measured by my Guru controller and a separate temperature-monitoring device I borrowed from my neighbor. My last cook I had a 7.5 # butt on the top rack and nothing on the bottom rack. Just for grins I compared pit temps again between the two racks using the same two temperature monitoring devices. During this cook the bottom rack was only 10 – 12 degrees less than the top rack. Is it normal to have such a wide temperature differential between the top and bottom racks depending on how much food is on the top rack? This recent cook was my first time to use the bottom rack. I want to make sure I know what to expect should I decide to use the bottom rack again in the future. So far my experience makes me wonder if it is practical to use both racks if it is likely that the lower rack temperature is going to be significantly affected by how much food is on the top rack.

 

[Charlie L]

the Water pan full or empty acts as a heat deflector. since the bottom grate is right over the bowl, its gets more heat deflected away. My bottom rack, with an empty foiled water bowl is often 25 degrees cooler then the top.

Some possible solutions:

If you are using a guru, set the guru at the average heat between top and bottom racks and rotate meat during cook. Be careful with uncooked poultry on top rack dripping on non poultry on the bottom rack.

My latest mod is building a third rack using an extra cooking rack and carraige bolts as legs. It can fit above top rack or in between top and bottom. Either way its further from the water bowl and closer to the top rack so the temperature variation from rack to rack would be less.

 

[Ken Hendrix]

the Water pan full or empty acts as a heat deflector. since the bottom grate is right over the bowl, its gets more heat deflected away. My bottom rack, with an empty foiled water bowl is often 25 degrees cooler then the top.

Some possible solutions:
If you are using a guru, set the guru at the average heat between top and bottom racks and rotate meat during cook. Be careful with uncooked poultry on top rack dripping on non poultry on the bottom rack.

Charlie- thanks for the reply. I suppose I should have been a little more descriptive of my recent experiences. I did not use the water pan either time but instead used a foiled clay saucer. These 2 cooks were the only time I have done that. I just wanted to see what it was like.

My latest mod is building a third rack using an extra cooking rack and carraige bolts as legs. It can fit above top rack or in between top and bottom. Either way its further from the water bowl and closer to the top rack so the temperature variation from rack to rack would be less.

My plan initially with the first cook with ribs and chicken thighs included an additional top rack inverted on top of the existing top rack setting on the brackets. I had the existing top rack loaded up with the thighs. When I attempted to place the inverted top rack on the existing top rack it would not work because the inverted rack was setting on top of the thighs on the existing rack. I would be curious to see some pictures of your modification and how much clearance it gives you.

 

[Charlie L]

Charlie- thanks for the reply. I suppose I should have been a little more descriptive of my recent experiences. I did not use the water pan either time but instead used a foiled clay saucer. These 2 cooks were the only time I have done that. I just wanted to see what it was like.



My plan initially with the first cook with ribs and chicken thighs included an additional top rack inverted on top of the existing top rack setting on the brackets. I had the existing top rack loaded up with the thighs. When I attempted to place the inverted top rack on the existing top rack it would not work because the inverted rack was setting on top of the thighs on the existing rack. I would be curious to see some pictures of your modification and how much clearance it gives you.

The Flipped grate idea sounds cool but its too shallow for most foods. Chicken wings would work but i dont know much else.

Here is a quick photo when i did the initial mod. I have improved since by adding a fourth bolt, and flipping the bolts so the bolt head is on top like this (not my photo):

I didnt actually build it for my WSM, that was a bonus.

I wanted a raised grate to lift my pizza stone when doing pizza on the kettle and to have an upper grate for additional indirect cooking space on my performer

I used 4" carriage bolts so get just under 4" of clearance which is fine for chicken pieces, ribs (placed flat), steaks (for cooking indirect first if im doing reverse sear).

If you dont want to spend $15-20 on SS hardware, guys have used empty soup cans, to hold up the grate:
http://www.virtualweberbullet.com/increasecapacity.html

 

[Charlie L]

Here's the updated grate

 

[Ken Hendrix]

Charlie- thanks for posting the pictures. Those mods look pretty slick. Looks like that makes for an efficient cooking setup.

Gotta love this site for all the feedback, advice and info that is shared here.