Whats a 'safe' max temp for the engine to run to

[pad4]

With having the ally 8 port head Im wondering what a 'safe' limit would be for the engine temp to get to- - obviously it does run hotter with it being what it is, but when should the alarm bells start to ring.

(its not running mega hot or anything - just wondering thats all)

PD

[guru_1071]

90-110 would be ok as long as the pressure cap is ok etc

id say that anything over 120 would be a problem

if it gets hot enough to melt the solder in the temp sender and the oil cap melts into the engine then that is too hot!

[pad4]

cheers Rich, id say its running between 85 and 100, so well within normal working temps.

Alls good there then..

Ta

[Ronnie]

Paul just to qualify what Rich has stated when he said," as long as the pressure cap is OK".

What is critical is that the water in the engine does not boil (water cools a gas[when it boils] does not), hence the mention in his answer about the pressure cap!

[pad4]

Yep understand all that - what would be the best pressure rating for a cap then ??

[Ronnie]

A standard S cap will do the critical thing is to check that it is blowing at the correct pressure and not early.

[YMJ]

On the cast iron racer (any capacity), I'd switch off and pull in to the side at 100degC, whatever cap I had.

Maybe be a little too safe but at 20K a pop, I'd rather finish as unclassified.

[pad4]

I think i will take that advise as well - 100 degs and its fingers on the off switch

Thanks again chaps

[andy1071]

As you are running an alloy 8-port head, I presume you're after power?
In which case you should be trying to get your engine temperature in the 75 - 85 deg C range.
The pressurised cooling system will normally allow you to run up to 110 - 120, but you'll be losing power.
90 - 110 is fine for a 'normal' road engine -this helps to get everything nice and warm, so emissions are stable, and the oil works better and can deal with the combustion by-products (talking about standard engines).
With tuned egines, you'll be changing the oil more often, so it's not a problem.

At the higher temps you start getting micro-boiling (local boiling around exhaust guides / seats) -this is bad news, as the steam doesn't conduct the heat away like water does.

I would suggest getting some temperature strips (Demon Tweeks, Merlin Motorsport etc) and put them at various places on the engine, such as: close to the thermostat hosing, top hose, end of head by heater valve.
-The strips are pretty accurate, but are a "one time only" indicator of the temperature.
-Putting them on the oil pipes will also tell you about the oil temp (so you can see if you need a cooler or not. Or can cover part of it).

[pad4]

GOOD IDEA !!!

ill get those ordered and take it for a nice 30mph drive over the tops

CHEERS

PD