Is my rocket stove getting hot enough?

Hello permies people: I have recently built a TMRS and have no benchmark to judge it by. My design is taken from Ianto's book - an 8" "J" design, with a 2" gap between top of heat riser(fire brick)and the barrel lid. I was careful to maintain a 7x7" configuration throughout the system which is routed up through the roof rising 1 foot above the ridge.. I can only achieve 300 -325 degrees F. and find that wood splits longer than 12-14" tend to smoke (i am using seasoned fir. I have come to suspect that perhaps I have a flow restriction at the base of the heat riser where the exhaust meets the thermal mass manifold (8" "T" cleanout. When I look in thru th cleanout I see a 3/4 -7/8" gap between the hardware cloth and the leading edge of the manifold T. Could this be my problem (assuming 300F is below potential ) The thermostat is located 2"below the top of the barrel. Lets talk Kip

Not sure I understand your manifold given the description. It does sound like you might have a restriction in flow. How much exhaust duct do you have in the mass (length, elbows?) If the exhaust out the bottom of the barrel doesn't go from a larger opening into the 8" duct then you could have a problem. If the manifold area is not smooth ie. no edges/sharp corners it can hinder the flow. Can you measure top of barrel temps? 325 might be a bit cool for max burn, but IIRC my system temps are ~650+ on top, but only 325-350 near the top on the sides.

Kip Roberts : Welcome to permies.com, our sister site richsoil.com, and a Big Welcome to the Rocket and Wood stoves Forum Threads, with 21,000
fellow members world wide you should be able to come here nearly 24 / 7 and find someone who wants to talk about what you want to talk about, with different
perspectives on nearly everything they will stretch your mind while you are stretching theirs !

The Area where the cooling exhaust gasses fall before turning 90 degrees to flow horizontally is a likely source of problems with your build so lets look the usual
suspects! The book is a little vague as the geometry of the adjacent parts makes regular english a difficult medium to describe the area(s)

Your Cross sectional area C.S.A., at the opening into the manifold can be 3Xs any other C.S.A. the idea is to taper smoothly down to meet the horizontal pipe for
your thermal mass, with gently flowing curves and a nice bell shape sweeping inward towards that horizontal pipe, the walls should be as smooth as glass but we
can settle for finished sheetrock smooth !

You will need to go in there and fill in that gap, rewet the area liberally with wet rags sponges and try to increase the area as much as possible, then work on the
sweeping curves and the bell opening of your horizontal piping, and sand every thing down smooth, if you can tell where your hardware cloth is you may not have
a lot of room to work with, without removing and reinstalling the hardware cloth, but that area should be sanded smooth enough to make it hard to see where you
embedded the Hardware cloth !

Assuming that your individual bricks are tightly stacked and at least clay slipped together, and at least the heat Risers bricks are mortar'd with no leaks thru the
bricks, It would be good to weigh your bricks to be sure you got what you wanted, go to the post office, Fed Ex, Ups, or similar Clone or use the produce scales at
your grocers, AND give dimensions.

You did not specify where and what type of insulation you used around and under the Burn tunnel and around the heat riser !

Too much coals and ash in the Burn Tunnel can cause you troubles, the ignition of the wood splits should occur in the feed tube section and only the pyrolyzed wood
gases should be burning in the Burn Tunnel his would generally choke down your fire and create smoke back after a short run where you never came up to
temperature

Finally, how many Feet of horizontal pipe and how many elbows/ 'T's with cleanouts, and how many ft of vertical pipe ?!

Also you never said if yourHorizontal pipe was in fact covered with Cob !

The important thing is this is your build, and all we can do is make Educated guesses, there will come a point where we will be able to tell you something definitive,
often after the fact like the geologist who after the prospector has gone out there and done all the work looks at the ore containing rock and says - of course, you always
find 'X' in Quartz like this !

Keep plugging and keep coming back, if there is a Rocket in your future we will help you make it possible !