High oil and exhaust temps questions

[snakepitt1]

Wayne suggested that I bring this question to the board for help.
1973 911T 2.4L MFI 5-speed
Here are the conditions I am seeing.
1. Oil temperatures will climb to right at 250 degrees in less than 30 minutes of normal highway driving in cool weather.

2. Exhaust temperatures apparently became so high as to melt the thermoplastic rear bumper the previous owner had installed. I have a new replacement (pressure tested and clean) engine mount stock cooler that can be installed.

3. I had the engine rebuilt 2 years ago and have put only about 1000 or so miles on it since. This high oil temp and melting bumper started late last summer. I replaced the oil thermostat on the engine because it was non functional. This did nothing to reduce the oil temp issue. I had all engine tin checked during the thermostat replacement as well as the back of the engine cooler and it was clean. I run only Mobil 1 20w50 synthetic oil. The oil & filter are changed every 500 miles since I don't drive it that much.

4. Others have mentioned that unburned fuel in the muffler could ignite and cause the over temperature condition and subsequent melting of the rear bumper. MFI is running 1 click rich.

5. Timing has been checked and was slightly retarded at the time. It has now been slightly advanced back to the point where Z1 lines up with the timing notch at idle with vacuum lines plugged. When lines are plugged the engine tends to gain RPM slightly (about 100RPM) when the vacuum line is plugged back onto the distributor, RPM drops back to 900 +/- 50 or so.

6. I have popping at the stacks at idle. After actuating the throttle quickly and dropping it back to idle, the popping is more pronounced and sounds like a butterfly valve snapping shut with a "tink" sound. This sound is only heard when the throttle is quickly opened then returned back to idle quickly.

7. I installed a oil filter mounted wrap style cooler and am thinking about the "S" hose cooler between the oil tank and cooler.
Sorry for the extensive post. I am trying to do right by my car and will accept all advice from this board.
Thanks Wayne.

Scott Harris
snakepitt1@aol.com
1973 911T Targa 2.4L MFI

[Rot 911]

Welcome to the board. First off have you independently determined that your thermostat and oil temperature gauge are working properly? Next you need to read the MFI tech articles on the Pelican Parts 911 main page. Right off I see two problems that can definitely lead to high oil temperatures. First any time you advance the timing over stock you are going to heat the engine up. Second, that popping in the stacks is to an overly lean fuel mixture. Conversly, too rich a fuel mixture will lead to popping in the exhaust.

[snakepitt1]

Kurt,
The timing mark Z1 is dead center on the crank pully with the car at idle and the vacuum line to the distributor disconnected and plugged. When I would advance the timing past this mark the car would stumble, when timing was retarded to a point before this mark the car would stumble. I also checked the timing at 5000 rpm and it was at the 35 degree mark gime or take a mm or less. I didn't hold it there very long. I initially felt that the system was running lean. So, using the correct tool (purchased from Performance Products) I went 2 to 3 clicks rich on the part idle screw, but did not touch the idle mixture yet. I haven't figured out yet exactly where that one is.

[Early_S_Man]

Pull the alternator immediately and check for nesting debris and rodent carcasses on top of cylinders and oil cooler or cylinder heads ... this has been serious enough to cause total engine failure ... so, don't dismiss the idea as loony!!!

[Dutchie]

This is what Warren means





original thread is hereBoy am I glad I pulled my plugs


I hope it,s just a nest.

Regards,

Ed