LS Steam Tube

I have read in the Superlite Build Manual that the steam tube from the LS motor can be run straight to the Header (pressurized) tank in the coolant system rather than run to the radiator and back to the header tank. That would certainly make things easier, but is it better? I plan to mount the Header tank high enough to serve as the air bleed. I would hate to run it to the radiator if I don't need to, but will do it if it results in some level of improved performance. Should I run from the LS steam tube directly to the Header Tank?

Howard Jones

Mark. Mid engine cars can be very difficult to bleed. I have a GT40 and a SLC and I did both the same way. The Air in the system just self bleeds without any special process straight from a complete refill on both cars.

All bleed lines are AN-4. One line runs from the top of the radiator (I tied both sides together to a "T" and then ran one line back to the side of the header tank). Then I added two steam ports to the back of the intake manifold, T'ed them together and ran a single line back to the top of the thermostat housing. These are the three points that are the top of the system in the engine. From there ( Tstat housing) another line goes to side of the header tank along side the 1st one that came from the radiator. Both are near the top of the tank.

Now you have every high point in the system connected to the header tank. The header tank must be placed as high as possible in the car so that it is now the air accumulator for the whole car. This is the only place that air should be in the coolant system, and then no more than required to provide for expansion.

You can use the header tank as a common point in the mid engine SLC whereas the radiator is apparently used for this purpose in the Corvette. But the idea is to provide a way for air in the system to work its way back to the header tank.

Neither of my cars have a heater. I have wondered if the heater core should be treated the same as the radiator. Anybody have an idea on that one?
Hi Howard , i have a rover mgf that is midengine and it has a air bleed on the heater core in the front boot and it stops that last bit of air from hiding in the heater core but the biggest trick with a mid engine is to jack ip the rear of the car as high as you can get it when bleeding and running the engine to force the air out .
Howard - Your explanation is always so thorough. It makes sense to "vent" both the radiator and the cylinder heads. I have the -4 AN hose and the AN attachments for the LS motor. How do you attach AN lines to the top of the radiator?
I used a fill kit that establishes a vacuum in the system which is a leak check and once no leaks are confirmed you activate the suction valve and the entire system gets filled bubble free.
The LS-style bleed system is more than a way to help fill the system without an air pocket. Engines produce vapor when are run hard and need a place for this vapor to condense. The header tank serves this purpose. Having the phase change at hot spots is an efficient way of locally cooling due to the high heat transfer. Cooling the exhaust seats is an area that produces vapor at high load.
There are some differences in radiators supplied by RCR. Howard has one of the older versions with both in/out tubes welded to the bottom. The newer ones have the outlet at the very top, even higher than the bleed port! Personally I'm omitting the extra steam line from front to back. I'm just not clear that it's providing any additional benefits for the failure points that it creates. That line is so long would it even have any significant suction to it by the time it reaches the radiator? Why not just let whatever air is mixed in at top of the radiator exit and be separated at the engine steam ports?

Howard Jones

Ya if I had the top radiator outlet I would delete the bleed port on the radiator if trial and error showed me it wasn't necessary.

In the end ya gotta go with what works. This isn't completely science. There is a bit of magic thrown in here and there.