The V8 Owners Forum -

In relation to my last post about the diff, does anyone know what the minimum amount of coolant is and smallest system a bog standard, old 3.5 would require for ticking over at 700rpm and short blasts up to 6000?

Not enclosed in a hot engine bay so air on all sides, I'm guessing I would still need a radiator, maybe a mini one with viscous fan or something?

Anyone? I know trial and error will work eventually but an answer would be better!

Hi Tom
I would guess you could get it down to about 3.5 to 4 pints of coolent if you really tried, half fill the block with block filler and use a thin high efficiency rad from say a gsxr 1100 actually you could probably got down to a 600 sized rad with it in a well designed cowel and a good air supply. To this I would add an ally sump and keep the exhausts well away from the sides of the block. The other thing you would need to do is make the whole cooling system so that it cycles the coolent more quickly through the system, no stat high flow water pump spun more quickly and carefull attention to all the ports in and out the block.
Best regards
Mike

What makes you think that a bike rad is going to be more efficient than an Austin mini one mike?!

I'd say no radiator

Join the uper and lower outlets with a single tube (convoluted would be good) and for an idle to the start line and 15 seconds your will get a warm engine at the end of the run.

Consider how long it will take that engine to get to normal running temp - 3 - 4 miles at a guess so a 1/4 mile run - no problems

If you are worried make the convoluted pope a bit longer for slightly more water.

Drain the water when you get back to the pits and refill

Ian

Hi Tom
Bike rads tend to be larger frontal area, thinner front to back for a given cooling capacity and designed to work with smaller cooling fans driven off bike electrics holding less coolant. You were asking about minimum cooling capacity, I was presuming you were thinking of saving weight, a bike rad will belighter than a mini one. I am looking into similar ideas for the new project, I intend running a low capacity cooling system rather than dry block so I can get back to the pits without a tow vehicle.
My thoughts are slightly different though, I am thinking of going for electric pump of low medium flow, a small radiator ( from a 100 bhp bike or one from a small "shopping trolly", say nisam micra) and have a reserve of cold water in some way to cool it after the run but as yet I haven't come up with a full plan. Basically enough cooling to stop it overheating dangerously but no intention of being able to run the engine for more than about 5 minutes at a time, more than the 90 seconds or so for line up, burn out, run then shut down after the line as a dry block would limit you to (requing a to back to the pits). May be we need to talk further??
Best regards
Mike

No not weight saving- just looking for something really small and able to keep it cool whilst ticking over and a few revs, I was thinking about a mini rad (pipes correct places and size good) and then a big header tank.

Hi Tom
an ally mini rad for an uprated 1275 with enough air shoved through it and the water pumped through it fast enough would probably keep a 3.5 cool if it does not spend too much time at high revs, it would be a case of optimizing water flow wise and getting air volume through it, difficult with too thick a core.
Best regards
Mike