robin427

I have an LS1 in my Cobra and it's an awesome engine. However, at a recent meet (Le Mans) someone suggested that I had my coolant system plumbed completely wrong.

To summarize:

My heater pipes go straight from the engine to the aftermarket heater matrix, nothing in between. The large coolant pipe from the top of the engine goes to the header/filler tank, which then goes to the top of the radiator. The bottom pipe from the rad. then goes to the large (~2") connection at the water pump. There is a thinner pipe from the top of the engine that goes to the header tank too - I think this is an overflow

He said that his header tank was installed in the heater circuit and that mine might be running cool as a result. I don't really trust the accuracy of my Smiths gauges, but the PCM is stock and only switches the fans on when I've been sitting idling for quite a while - otherwise it just maintains temperature without the fans

Not at home at the moment so can't post pictures, but if someone know what the hell I'm going on about, then please let me know!!

SMAX

iTrader: (11)

It sounds like you have it right. I am assuming that you have a good size aluminum radiator and probably running a 160* thermostat? If this is true it is possible that your cooling system working very efficiently, and if you are running a 160* stat and the computer is not tuned to turn the fans earlier it is still looking for the 200*+ of the stock stat.

robin427

As far as I know, the stat. is stock (it's from a Pontiac Firebird). The radiator isn't ally, it's copper/brass (or whatever normal rads are made from). My mileage isn't as good as I'd expect, about 23mpg (that's British gallons) when I'd expect closer to 27mpg. I'll drop a temperature probe into the system to see what it is actually heating up to

Is the comment about choke a valid one? I'm not getting any smoke from the exhausts, it's just that at low revs, the engine doesn't sound quite silky smooth - has been suggested I change the plugs, although I thought they were supposed to last 100,000 miles. Will also try cleaning the idler motor

SMAX

iTrader: (11)

I don't understand what you mean by "header tank" is this the overflow?

Should be-
-hose on top of water pump to top of radiator
-hose on bottom of water pump to bottom of radiator
-2 hoses on side of water pump to heater core
-small hose from crossover(on the heads)to the top of radiator just below fill cap

robin427

Yes, it's a stainless tank that sits at the highest point of the coolant system, with a pressure cap. Expansion tank?

SMAX

iTrader: (11)

Ok, it sounds correct. I would check the stat it maybe stuck open. These engines are designed to operate at around 200* so if it is not getting up to temp that could exlpain the less than expected mpg and the rougher idle to off idle characteristics.

robin427

Is this something that might get gunked up, and thus could be cleaned, or would I have to replace it?

SMAX

iTrader: (11)

I would just replace it. If it is stuck open probably no major damage can be done to the engine, but if you clean it and it then sticks shut you are looking at overheating which is never good. Cheap insurance

garys 68

iTrader: (1)

The expansion tank can be anywhere in the heater or radiator hoses. It just needs to be at the highest point. On the 60s vettes they were in the heater lines because that was the easiest way to get above the level of the heads.
The FE motors on the AC cobras used an expansion tank connected to the thermostat mount forward of the engine.
Gary

robin427

OK, new thermostat it is then - wonder if I can get one in the UK (otherwise it's not so cheap!!)

jannes_z-28

I have Smiths instruments in my Camaro, the tempsender is mounted in the waterpump and it reads between 90 - 100 Centigrades. No matter how I drive or is in traffic jam, it nevers goes above 100. I have set the fans to start at 96 centigrades.

Jan

robin427

Mine generally reads below the 90 mark - the sender is mounted in the side of the block. Will play with it when they let me go home (away on business at the moment )

Happy Jim

Somewhat like this

robin427

Christ, Jim, how much was that blue heater hosing? Rest of it looks a bit Dax - considering mine comprises the connector off the back of a toilet as the intake (no word of a lie). How much do GD want for their intake, which is what I presume you've got fitted?

Happy Jim

Heater hoses were the cheap bit (straight lengths don't cost that much).

Air intake box and Filter is £258

Bling is good.....as long as you thrash it mercilessly

Rgds

Jim