Newly rebuilt engine overheating - cause?

jakermc · 09-07-2009, 04:03 PM

Quick background, I've been racing the last 3 years with a 993 3.6L VarioRam in my '83 widebody chasis. I lost the engine a few months ago when a valve retainer failed and decidely for a complete rebuild given the significant damage that occured.

The new engine is in but in early testing on the track I am hitting oil temps of 250 degrees within 10-15 minutes or so. The old engine never had a problem regardless of the ambient temps and the length of the race.

The rebuild consists of a 964 bottom end, including cams and tensioners, 993 VarioRam intake, rods from L&N Eng., ARP bolts, titanium springs, etc. The case was modified to accept an oil filter on the engine just like the 993 had.

Cooling originally consisted of a Carrera coller in the fender (with air intake and ductwork) and a Setrab 150 cooler in the nose. The old engine ran this without a problem. After the first day of running hot the nose cooler was upgraded to the larger Setrab 172 with the RS duct but it had no effect. The thermostat was also replaced. Running Redline 15w-50 oil right now.

I can't get much better coolers in place than I already have, and quite frankly, I should not have to. Any ideas what could be going wrong? What do I check next?

Rot 911 · 09-07-2009, 04:59 PM

My first question: Is the oil cooler getting hot? If not then you have a thermostat problem.

jakermc · 09-07-2009, 05:15 PM

Quote:

Originally Posted by Kurt V

My first question: Is the oil cooler getting hot? If not then you have a thermostat problem.

Yes, oil ines and coolers are getting hot.

unclebilly · unclebilly's Garage

Is the new engine making more power than the old engine? For every kilowatt of power you make, you make 4 - 5 kilowatts of heat... something to consider.

jakermc · 09-08-2009, 02:04 AM

Quote:

Originally Posted by unclebilly

Is the new engine making more power than the old engine? For every kilowatt of power you make, you make 4 - 5 kilowatts of heat... something to consider.

10 rwhp LESS than the old one.

unclebilly · unclebilly's Garage

Is the lower HP just internal friction until it is broken in? This would equate to more heat but probably not enough to cause your problem.

jakermc · 09-08-2009, 03:51 AM

Quote:

Originally Posted by unclebilly

Is the lower HP just internal friction until it is broken in? This would equate to more heat but probably not enough to cause your problem.

The lower horsepower is at least partly related to that, but mostly we think there is a problem between the the VarioRam induction, the 964 cam, and the old ECU chip from the previous engine which we reused.

One thing we are chasing, which may be causing some heat is the air/fuel mixture. But if I remember right it was lean on the lower rpm bands and back in range above 4k rpms. The engine heat issue manifest themselves abover 4k rpm and in fact temps drop down quickly on the cool down lap when I keep it under 4k.