The V8 Owners Forum -

Have searched for this info but can not seem to get a definative answer on it as there seem to be many different options.....building a kit car at the moment RV8 3.5 no special mods apart for slightly hotter cam, am at the stage of plumbing in the cooling system and need advice on a header/expansion tank.

The radiator I have has the normal inlet/outlets plus it has a separateinlet about 1/3 the way down the radiator below the inlet. The inlet manifold has a small pipe slicking out to the front of the engine which I believe is a vent pipe but I stand to be correct if it is not!!

The set up I want to use is as follows,

Radiator inlet to thermostat housing,
Radiator outlet to the water pump,
Header tank outlet to the small inlet on the radiator below the main radiator inlet to allow the system to be filled through the expansion tank,
Small outlet on the inlet manifold to a small inlet on the header tank to allow the system to vent air.
Standard heater matrix set up from the rear of the inlet manifold.
Expansion tank with a pressure cap to vent if pressure builds up
Headrer tank needs to be the highest point in the system (what level above the vent pipe on the inlet manifold)....

Would this work, am I in danger or problems, or what am I doing wrong!!

cheers

Chris

sorry forgot to mention engine is running on SU's at present......

Basically, Yes what you want is about right, But I seem a bit confused to why you want a header tank and an expansion tank,
Expansion tank is used when the rad has no pressure cap and tank does, and a header tank is just for keeping non pressurised overflow fluids from the cooling system when the rad or piping has a pressure cap,
I have used in the past inline Moroso water necks with pressure caps to fill amd vent my plumbing systems and run the pipe to catch can, I know this is not ideal as you have to keep an eye on the coolant level bit is dead simple to plumb, Probably not SVA legal, but its works for me,
I suppose the is no reason why you cant use a similar style neck to fill the system and vent to an expansion tank, it woild be so much easier.
Ian

Ian....cheers for the feedback.....I put header/expansion as was not sure which to use, I guess header tank would be the best way to go.....

On a header tank if pressure builds above the cap PSI rating does this simply spew the coolant out or would there normally ba some form of plumbing to vent the pressure away?

correction expansion not header!!!! will get it right in a minute.....

ian.stewart wrote:Basically, Yes what you want is about right, But I seem a bit confused to why you want a header tank and an expansion tank,
Expansion tank is used when the rad has no pressure cap and tank does, and a header tank is just for keeping non pressurised overflow fluids from the cooling system when the rad or piping has a pressure cap,
I have used in the past inline Moroso water necks with pressure caps to fill amd vent my plumbing systems and run the pipe to catch can, I know this is not ideal as you have to keep an eye on the coolant level bit is dead simple to plumb, Probably not SVA legal, but its works for me,
I suppose the is no reason why you cant use a similar style neck to fill the system and vent to an expansion tank, it woild be so much easier.
Ian

If you have a pressure cap on your rad with the overflow going into a header tank, as long as the hose end is below the level of coolant it will suck it back into the system when your motor cools down. There is a seperate low pressure valve in most rad caps. The header tank doesn't have to be higher than the rad or engine or anything like that.

My Morris is set up like this. I did have a catch can, but changed it for a plastic header tank I found in my shed as the catch can was too small, but it still emptied the catch can on cool down.