I am ALMOST done with the vortec head install/top end rebuild. It's an L48 from 76. I have replaced the water pump, cam for a lunati voodoo (specs elude me right now, but it's mild), new intake, vortec heads with a valved and spring job, new radiator, and a new fuel pump.

I'm wanting to break in the cam, but it idles HOT. After 5 minutes of running, it hits 200. So I kill it. My neighbor thinks it's the fan clutch not working. The fan DOES wiggle a bit, and I'll grant him that the clutch probably no longer works...but would that affect the temp at idle? I thought the fan clutch only comes into play at higher rpms and such?

Thoughts or ideas?

 

The last cam I put in I rolled the car outside and let water run down the front of the radiator during breakin.

 

Rad stays cool. T stat is working, it GUZZLED anti freeze after the first 5 minute idle run. Water pump is also working, you can feel the pressure on the upper hose. Has to be the fan, right? Does it really make THAT much of a difference?

 

Rad shouldnt be cool if pump is circulating , therm open and engine is overheating.

 

That's what I mean. I just don't understand how this is happening. It did this before I did the rebuild, too. I just assumed that the water pump and radiator were shot. But both have been replaced. Brand new T stat. Hell, even got a new temp sending unit, too. I'm stumped.

 

How did you fill your system ? I always remove the plug in the top of the pump and do the initial fill there so I don't get an air lock.

 

You DO know you are not supposed to let it idle during a cam break in right??? They can run warm during break in.....

If its a hyd flat tappet, you need to keep the rpms around 2000 or so for 20 mins. If the water temp climbs and you know you have the system full of coolant and everything is working, I would trickle the water down the radiator with a water hose to keep it cool for the 20 min break in.....but keep it running and finish the break in before it wipes a lobe...Check the timing while its running, that can be making it get hot quick....But I would check the thermostat, if it hit 200* in only 5 mins, I bet the stat is not working....I always remove the stat, fill the engine up with coolant through the stat hole on the intake, then top off the radiator and start it up for the first time....I go back and add the stat after it is broken in, timing set and running ok.....That will help keep it cool longer through the break in of the cam.

A fan clutch is what helps keep the fan locked at higher temps at low engine speeds.... You MUST have a good fan clutch on it or it will run hot at idle / slow speeds. The fan clutch is operating opposite of what you are thinking it does.....It cools at low speeds, not as much at high speeds.. And if you are getting a wiggle, you better damn sure replace it. If you are using the 7 blade stock fan, go with the Hayden #2799 severe duty fan clutch....That will cool you down and you can get it at any auto part store for $65.

 

Wow , just took a look at the 2799, looks like a beefy one. I'll have to try one the next time I need a clutch.

 

How did you measure the 200 degrees? If by gauge not not trust it. Always verify with IR gun. Yes fan is very important. If it did not lock up and roar at 200 (real temp) it's bad.

I would replace the fan, remove the thermostat, make sure system is full, set initial timing to 12 and retry break in. Try to keep idle at a minimum. Keep the cap off and be prepared to fill as it circulates and heats up. Replace cap once system is full and level begins to raise. Keep an eye on temp with IR gun at pump, hoses, radiator. 200 would not bother me to much at break in but if it keeps raising you have other problems. After successful break in you'll want to replace the thermo, get timing dialed in and have fun.

 

Incorrect timing could lead to a higher temperature. I placed several fans in front of my car during break-in. Used an IR Gun at the water neck for correct temp. After a rebuild and using a different temp sending unit usually results in an incorrect reading as the temp sending unit is calibrated with the gauge. As Lee said, keep the radiator cap off and fill as needed. Hope you are using the right oil and lubrication for break-in.

I can email you or try and post my break-in video?

 

Always leave the thermostat out when breaking in a cam.

 

Never read or heard of this before.

 

I've been a mechanic since 1982 and have always done it that way. You can get this system full of water and don't have to worry when or if the thermostat is going to open.