Bensons86

How hot can you normally take a c4 before it blows a head gasket?

87 vette 81 big girl

Best answer to your question is dont let your C4 engine get Hot.
Like above 230- 240 degrees F.

Your C4 will happiest if Stock with water temps of 190 - 220 degrees F during normal driving and WOT runs.

Brian

Bensons86

I know that over 220 is getting hot, but I am asking a more specific question. In attempting to break in my cam.......20 minutes at 2000 rpm's.....we weren't able to complete the full 20 because it was getting too hot. So, im asking how hot can you take it before you have troubles.

RollaMo-LT4

220 is not that hot.
With the proper coolant mix and pressure cap, the coolant won't reach the boiling point until close to 260° F.

At 220, your cooling fans probably are not even on yet.

You won't "blow" a head gasket until you get up over 260.

87 vette 81 big girl

Try not to let the coolant temps get over 220 degrees F.

Because once the water temp gets over 228 degrees F C
in a C4, the temp can run away - climb higher quickly.

I have an Electric Cooling Fan Manual Bypass switch hooked under the dash of my 87 Vert.

Flip the switch on, and my coolant temps never get over 195 degrees F regardless of long idling periods, or working under hood of my car with the engine running.

Get a large home furnace style blower.
Put it about 2 to 3 feet in front of your C4.
That will help greatly keeping the coolant temps down.
Blow the air forcefully to the Front Lower Air dam.
Air will be Rammed into the radiator then.

Dont want to overheat the engine while breaking in your New camshaft and Lifters.

brian

HlhnEast

Temp warning lamp (on my '85 anyway) doesnt come on until 260* so I would figure that is about the point where things start getting hurt.

WW7

87 Vette has the right idea, I used a 4 foot shop fan in front of my car when I started the break in start up.. These put out large air and helped keep the motor cool . It did such a good job my car fan never came on....WW

87 vette 81 big girl

Goodbye piston skirts, piston compression rings, and engine bock cylinder walls @ 260 degrees water temp.

There is only 1 brand dino oil that will protect the engine at those very high water temps.

Maybe 3 synthetic oils that will protect the same also.

I speak from 1st hand experience. Racing Pontiac Powered cars for years.
Blowing headgaskets is nothing new to me.

People hate talking about oils here on C4, so I wont.

But I do know what actually works and better than most everyone else does here.

Just a few other professional racers and engine builders here on C4 know what actually works best like I do.

Brian

Bensons86

Well here's the deal guys. I feel a little embarrassed because this project has gone miserable from day one, but here goes. I wanted to be sure to break in the cam properly, but the temps were creeping up there. I got 12 minutes in at 2000 rpm's when we finally shut it down. The temp was 260 when I pulled the plug. When we first fired it up, there was so much smoke...it was insane. The thing is...it looks like the same smoke that its pumping out now....which is anti-freeze burn off.....so it makes me wonder if it leaked from initial start up. The car runs and idles at 7 to 800 rpm's...doesn't have a miss or anything. Seems fine. But we have coolant in the oil and its smoking like a champ. It makes me think that we killed the gaskets in break in, but I would think that it would run like crap if this was the case. Im honestly not sure what to do and Im pretty discouraged at this point.

c4cruiser

One of the things you should have checked was the cleanliness of the radiator for any debris that would have blocked air flow. Same for the A/C condenser. If air can't go thru the radiator to allow it to keep the coolant at a normal temp, you will have problems not just for cam break-in but out on the street.

And if there wasn't sufficient airflow inside a shop, using a large fan would have helped to keep temps down assuming that air could move thru the radiator.

Did you install a new thermostat? Was the cooling system filled properly and did you use a 50-50 mix of anti-freeze and water? Any air pocket could easily cause a rise in temps and can impair coolant flow.

What temps did you see? Did the main cooling fan come on? Should have come on around Does your car have the auxiliary fan in front of the A/C condenser? If so, did it come on?

c4cruiser

Might want to pull the plugs to look for any discoloration. If you think there is a bad head gasket, get a "block test" kit from a parts store. This will check the coolant for any indication of combustion gasses. If a head gasket did fail and is dumping coolant into a cylinder, the can explain the smoke. If it's a white color, it would be more steam than oil.

vader86

For aluminum heads I'd start worrying at 250 and pull off and kill it at 260.

Iron headed cars can generally handle just a little more but I'd pull off at 260 as well.

I would pull those plugs right now, don't run it.

flightmate

I don't know how it generally works but when I lost the head gasket on my boat with a chev 350 inboard it ran just fine as well, and the only way I found the problem was water in the oil. I agree you need get a kit and test it before running the engine anymore.

JrRifleCoach

My 86e saw temps well in excess of 260. ONCE.

That was two years and 5000 miles ago.
So far, so good.

383vett

Piston rings can start losing their tension around 250-260.

Joe C

some of you may throw up a , but my son's 85 hit 296 (dash indicated) due to a water pump failure. new water pump, and she's running okay. ran a compression test, and the readings were around 168, average across 8 cylinders. L98's, at least iron head L98's, are pretty tough little motors.

kimmer

ok,

Bensons86

The main fan did come on. I don't have another fan that Im aware of. I did replace the thermostat with a new one before we fired it up. It also has new freeze plugs for what thats worth. We made sure it was full of antifreeze before we started it and did use a 50/50 mixture.

So discoloration in the spark plugs indicates piston wear or just a head gasket leak? There is definitely moisture in the oil....it showed over filled only after the break in and there seems to be coolant coming out of the exhaust. We pulled a valve cover also and there is indication of moisture in the cover as well.

Do you think I am looking at another head gasket job? Do you think it was my temp that caused this or some other problem? This sucks.

87 vette 81 big girl

Yes it can suck very badly when you have to go back and make repairs on the same thing you fixed just before.

You live and learn is such ways.

Advice from others and me don't mean much unless you apply them to your own Corvette.

Attention to details make every bit of difference in the final outcome of engine repairs and builds.
Also applies to Transmissions, Rear differentials, suspension work, electrical repairs, even ignition & EFI tuning.

Something went drastically wrong during your last headgasket replacement.

Brian

87 vette 81 big girl

When you work in a GM Dealership as a Master Mechanic and have to make repairs again for the same problem............the GM Shop Owner does not pay you the 2nd time to make repairs again Right.
He makes you work for free.
Forget about equal rights, freedom of speech, OSHA, Illinois State Laws, ect, because they dont apply in Illinois.
Especially Chicago.
Its called GM Flat Rate.
And it sucks *** like the Service Writer does to you when you bring your vehicle in for repairs. lol

You learn to make repairs right and correct the 1st time around perfectly every single time and make or beat that GM Flat Rate Book.

Or you dont eat for the week and your family at home starves.

Brian