The earlier blocks have a different water jacket totally compared to the late blocks and the flow overall isn't as great on the late blocks as the early blocks from the water pump. That being said its still overall a great design there really isn't a cooling issue. However, with sleeves you are taking away much of the cooling around the cylinders. I have never really seen to much about the water jackets with the sleeves and it never really comes up. However as seeing from the pictures there is very limited space for cooling around the block. Now, I don't think it would be much of an issue with the early blocks because you have alot more depth to your jacket but with the late blocks your only working with a lot less depth.

 

Wet sleeves have no less cooling than the factory cylinders, there is actually more cooling due to the OE cylinders being machined away.

It is important to use the correct type cylinder material, machining and fit to get optimum cooling and wear resistance. Too many people **** up the machining part and the sleeves do not fit correctly.

 

+1

 

i've been wondering for a while now, what are those small holes in the sleeves around the top cylinder collars for? darton says they are to allow coolant to pass from the block to the head, but in the 951 motor those holes would be covered up by the gasket. and even if they are not covered up by the gasket, there are no channels in the head in that area to allow coolant to pass up.

wouldn't that cause an air pocket or steam cave to form around the top of the cylinder? wouldn't that lead to higher temps since air is an insulator?

 

I think you are referring to the holes in the deck plate. It should work the opposite and prevent air pockets around the head and let coolant flow the way it was intended to. There isn’t much write-up on successful darton blocks. So I can be the first to say that so far the engine is running as strong as I could ever have hoped for. Had my first track time with the new engine last weekend. With unlimited track time on Friday and limited track track time on Saturday, I put some very hard miles on the motor. With the exception of high intake temps from using the stock intercooler, everything else remained normal.

 

we are talking about the same holes around the top outside edge of the cylinders. if you look at the design, they would seal up against the 951 headgasket/head. since steam (and heat) rises, you'd think an air pocket would form around the top of the cylinders. here's another side shot that shows this area better;

 

I'm really looking forward to seeing how this design holds up. I couldn't find any successful MID motors when I was considering this option for my 3.0 build.

Wish more of these setups were being tracked here on Rennlist.

 

and here is an outline of where i think the air pockets would form (in the red area) at the mating area between the block and head (under the head gasket). note there is no place for the air/coolant to escape through the top, so the only way in/out is through the bottom of those holes at the cylinder. air rises, so how does it escape?

 

by the way, how would you track temps in that area?

 

I think it's further out and more open. It should follow the same path through the head as normal. I would imagine Cylinder head temp should pick up a hot spot from any trapped air.

 

it's not further out, i checked using both the stock head gasket as well as the cometic MLS gasket. even if it were further out, that area around the top of the cylinders still gets sealed off. you can see this in a pic with the MLS;



keep in mind that the top of the stock cylinder walls do NOT flare out like the darton sleeves do, so air can not form with the stock design. the 'normal' path of the coolant is around the top of the cylinders, not past the top to the head.

 

Sweet, track car ..........................

 

by the way, i'm doing the same darton sleeve work, which is why i'm so concerned.

 

Is that a 100m bore? On the 2.7, where the wide fire ring would go is right on the edge of cylinder wall, and the cinder wall is about ¾ inch thick. I guess only time will tell, but I really don’t think it will be a problem. Good luck, let us know how it goes. Who is doing the sleeving?

 

the last photo is from a stock motor with MLS gasket. i'm going to 2.7 bore with darton sleeves and became concerned when i noticed the holes have nowhere to vent.

i've called and spoken to darton about this, and they said these sleeves were originally designed for the honda motor which does allow the coolant to pass from the block to the head via those holes. they said they didn't know what would happen on the 951 application.

i'm actually considering cutting out some 'slots' at points around the outside edge to allow the air to escape back into the block.