Number Dummy, can you elaborate on this a little more ? I have heard this before but am not sure how a thinner clynder wall would cause overheating.

Since the same amount of heat is being generated in both a stock cylinder and a bored out cylinder how could it make a difference ?

If a block was bored too far would you still be able to get pistons to fit or would you have to use some custom parts which would not be cost effective ?

This is a great discussion and very educational !

 

It has to do with the time that it takes to transfer heat. There needs to be some meat (cylinder) to absorb the heat to then be transfered into the coolant. If you've got paper thin cylinders (.060+) or whatever the max is, its gonna have the tendancy to run hotter b/c the engine is constantly hot. Think of it like an exhaust system, if a set of headers are made of 20 gauge steel, they're gonna get cherry red when running at high rpms b/c there's not alot of metal there to distribute the heat into the atmosphere whereas w/ a set that are 14 gauge, theres more meat there to absorb the heat and distribute it to the ambiant air surrounding it. Coolant is the same as air in this case, it just takes the heat and removes it to the rad where it can be cooled. Maybe someone has better wording they can use to explain this but thats pretty much the idea.

 

I had a 390 with no thermostat that was running hot because the coolant was moving so fast it could not absorb the heat. after putting a 195 thermostat in I have no more overheating problem.

 

My 390 is bored .060 over. I had to go that far with my block to get the cylinders cleaned up. I've always had some problem with overheating and I'm sure it's related to being bored .060 over. If I had it to over I would just find another block. Most 390's won't go .060 over without there being some issue.

Tracy

 

Hi guys,
New to this thread, but glad I found it. I thought I was the only one having this problem. my 69 f-250 has a 390 in it and I just got done replacing both head gaskets (boy, don't ever Want to do that again)and it was running hot, thought my temp gauge was bad so I replaced it with a mechanical one the goes from 100 to 250 then still hot got a new thermostat at 180 and still same prob, went to a 195 and flushed the rad and now idling it still goes to 230 deg. I haven't had it out on the road yet, going to do that tommorow , so I'll see if it still goes up and let you know, if anyone still reads this thread, since I see it's from 2007, but I thought I'd post any how, I've had more prob with this truck in the 2 moths I've had it then I did with my 94 ranger in 10 years that I owned it.
The guy I bought it from told me the motor and tranny was rebuilt 23k miles ago, , the thermostat was so rusted up I think it Was the original from the factory, boy if I SEE THAT DUDE I MIGHT JUST THROTTLE HIS SKINNY BUTT
If this thread has moved I hope somebody will let me know where it is cause this is a darn good bunch of info here.
BTW, has anyone found a way to solve the problem yet?
HEY, THERE'S NO SPELL CHECK ON THIS SIGHT? OR AM i MISSING IT?

 

Another common problem is too much anti freeze in the mix.... Over the 50/50 recommendation.... Straight distilled water cools best... Antifreeze is exactly what it is.. to delay or stop freezing, with anti rust, conditioners, and other additives.... It does not transfer heat very well.... that's the waters part of the job...

 

I don't know about how Physics works where you are, but here on earth, a 50/50 mix of antifreeze and water cools way better than straight water, distilled or otherwise. If what you claim was true, don't you think every NASCAR team would be using straight distilled water? Since they aren't don't you think the claim is way out in left field? Where did this info sprout from and straight water will rust the hell out of your engine, distilled or otherwise

 

Marine industry standard.... until winterization....and yes we've run straight distilled water in the Busch North series.... Yes, you should run some sort of antifreeze in the mix, to raise the boiling point, protect from freezing, and for rust prevention on the street, but if you have ever hit it going into a corner on the track, put your ice skates on... It's a not so well know fact that any mixture over 50/50 starts to not cool the engine as quickly as the antifreeze starts to degrade the heat transferring effects....

 

Pure BS, I worked in the marine industry as a factory certified mechanic for many a year until I retire 7 years ago and your claim just is not so.

 

So you don't run straight water thru a marine engine??? Never fished the Bering Sea did ya..... 10 years out of Dutch myself.... Way Off Topic Now...

Again, adding antifreeze over the 50/50 mix will not cool the engine as efficiently.....

 

BS!

 

Ignition timing that is too retarded can also cause minor overheating. You may want to check your timing.

Older engines can slowly overheat due to a build-up of crud in the cyl block and heads. A good chemical cleaner can help. You drain the system, fill with water and add the chemical. Run the engine for a while, drain and refill and add a stabilizer that comes with the cleaner. Fluish with water again and then fill with 50/50 antifreeze-water mix. If you ever rebuild the engine, have the block and heads hot-tanked.

Head gaskets installed wrong can cause overheating, but I'd say it would be much more major an issue than what you describe.

 

Teaching old dogs new tricks -- The TRUTH about Coolant - The Rice Haters Club

and the NASCAR answer -- http://wiki.answers.com/Q/Do_Nascar_engines_use_coolant

 

WHAT WOULD YOU SAY THE TIMING SHOULD BE? I think the specs call for 10 btdc. I'm willing to try anything not to have to replace those head gaskets again, I'm keeping a close eye on that new temp guage, that's for sure.
Rich

 

Im having the opposite problem, my 390 doesnt want to heat up very much. It will never get past the 1st tick mark in the winter, rarely in the summer. The only thing I can figure is I have a long spacer between the fan clutch and the pulley. The fan is an inch away from the radiator at best. So, if yours is over heating, try a longer spacer.