74 911 240 Degrees?

[ARCSinAK]

I have a newly acquired 74 pre-thermal reactor 911 and she seems to be running hot. I hit about 240 the other day for a limited time after a spirited drive. This car does not have the optional front mounted cooler. What are areas that I can check to address this issue. If I drive at a normal pace she seems to run at about 210-215, I have yet to drive more than about 40 mins at one stent. I have read that 2.7 were prone to running hot hence the know head stud issues ect. This car came with no history except for a verbal mention rebuild at some point. She runs strong and pulls up to 6 K. I plan to preform a leak down soon but my seat of the pants impression feels good. Almost faster than my 80SC, I sure like the 7/31 in the 915 box. It would be great to hear from any mid year owners that have experience or advice with hot running 2.7's.

Regards-
JS

[giladblum]

Hi there,
I have a76 with front cooler,
I run at 190-210 all the time on a hot day with AC on,
From my knowledge 240 I to hot for this engine, you should consider installing a front cooler
Let us know what you are planning

[Trackrash]

'74s should have the old style heat exhchangers, which is good. You might want to verify that.
I would have the air to fuel ratio checked. If it is running lean it would cause it to run hotter.
A friend of mine, who has a '74, added a Carrera style cooler which works well.

[Driver_X]

I had the same setup as you. When ambient temps are 70+ those engine temps are not unusual. Lack of cooling is the reason, and the answer is a fender mounted engine cooler. I swapped out my 2.7 for a 3.0 this spring and added the oil lines & cooler (a trombone cooler). Temps never get above 210-ish and that's on the highway @ 90 degrees ambient temp. Most of the time, temps gradually climb to 180, the thermostats open and there it sits, right above 180.

My feeling is that everything is normal, and that if you live in a warmer climate the front mounted cooler would be the way to go. You can save yourself a little $ and install the trombone type, as most of the cooling happens in the lines anyway.

[gwmac]

Added a 50 row seatrab cooler to the front of my 74, 220 on a 100degree NM day.

[chrismorse]

My dad bought the 74 new and the dealer installed AC. He lived in Santa Barbara.

I can recall taking many drives with him and remarking on the insane oil temps accompanied by frighteningly low oil pressure - just scary. He used a local well reputed independent and said he was told not to worry.

After his passing and my acquisition of the car, I needed to drive it 650 miles home, so took it to the shop and asked them to check timing, look for vacuum leaks and make sure that the car wasn't running too lean because I didn't want to ruin the $11,500 engine rebuild done 10k miles ago.

They adjusted the timing a bit and the CO as well and sent me on my way. The car ran 200-240 all the way home without the AC on.

Dad had just driven the car around town for the last 10 - 15 years.

I got it home and it was leaking fuel from a return line that ran too close to the heat exchanger dump valve - Scary. New lines and stratoflex heat shield, (cool stuff)

The 20 year old Pirellis were fine just a bit harsh. Installed Dunlop Direzzionales.

One of the cv boots was toast and the rear Carrera bar was missing. Installled two new axles.

The shifter had gotten sloppy on the drive home, so I installed the factory short shifter and new bushings.

I pulled the AC to install some factory brass lines, new thermostat and 85 cooler with fan.

Temps dropped immediately to 185-215. (I still need to get more air to the cooler).

A month later, after a 1/2 hour drive, I stepped on it to pass a geriatric driver and saw a massive plume of blue white smoke obscuring my rearward view shut it off and coasted to the side of the road.

At some point in its life, the thermostats' 6 mm studs, (in the mag casing) had been overtightened and it popped up out of the case with the cooler oil andhigher pressure, it took only 5 seconds and 6k rpm to dump 7-8 quarts of synthetic all over the engine, exhaust, brakes and the back of the car.

Get the big cooler, check your t-stat bolts. good luck,
chris

[Charles Freeborn]

My '74 with trombone cooler runs @ 185-90 with normal driving, 210ish when driven hard and 220 or so when stuck in summer traffic.
There is nothing more damaging to a Mag case engine than heat. Get a cooler.
-C

[Dodge Man]

In the short term, you may look at cleaning the stock BEHR on the motor. I was running hot years ago and found that debris/paper had sucked down onto the BEHR. Lots of Simple Green & hose action with some care. Front cooler is a great idea and you will probably be able to stay cool with a stock trombone cooler & lines from an SC. Elephant from our host has Carrera cooler upgrade kits too if the trombone is not enough. You may also want to look at the bumper scoops too to get more air thru the cooler. 74 is a good year. Enjoy

[manbridge 74]

My first 74 had no front cooler but I never ran it in high ambient temps for it to get above 210.

My current 74 has always ran cool but I found out it the CO was set at above 4%. Too rich. It was close to 220 in traffic the last 90-95 degree day we had here in Colorado after I had reset the CO to spec. And I have a front cooler but no fan.

I'd suggest to the OP to make sure the timing, mixture and basic tune is correct while waiting for a front cooler. And take a look behind alternator at engine mounted oil cooler. It might benefit from some cleaning. You could try setting the CO at about 3.5% to see if that helps.

[Flat Six]

Also, might consider fan swap if you're currently running 5-blade (not sure when P switched over from early 11-blade to 5-blade).

[kodioneill]

Check for mouse nests under the shroud and check that the seal around the engine isn't cracked or missing (very important). Are the hoses for the heat system in good shape? It helps keep exhaust temps down.

[chrismorse]

One of the great things about the factory oil thermostat for the front cooler is that it has a pressure bypass, as well as a Presure bypass for the oil to go back to the fender tank. This is where the mocal thermostat set up is a bit lacking. I am not sure about the size of the internal oil passages in the mocal unit, but I think the factory unit has bigger holes.

I must say that I have a mocal -12, 180 t'stat on my other car and it works well - but it is water cooled. If I had the ability to go back and do it over again, I would prefer to have a thermostat with a pressure bypass. I lost an oil cooler once on cold start up and it was no fun being stranded 600 miles from home.

I got a set of used lines from Elephant, shipped for a good price. I got the rest of the bitts from our host.

IMHO, it is safer to have more cooling than you need, rather than just enough, kind of like brakes. You sleep better.

Given the critical nature of the magnesium cases' reaction to heat, I would opt for a serious cooler.

end of rant... :-)
chris

[Tidybuoy]

My '74 has a Carrera front cooler (without the elect fan). I also have SSI heat exchangers (not sure if that makes a difference). I consistently run 180 degrees unless I have a lot of stop & go traffic on a hot day - in that case, I could get up to 200 degrees. This is in Fresno, CA where it typically gets over a hundred degrees all summer.

On long trips, usually driving fast, the car stays steady 180-185 degrees.

Lastly, I generally keep my engine spotless and wash/wipe it down every time I wash the car. I also spray the hose right thru the fan while the engine is running and that gets all of the gunk off the cylinder and head fins.

[E Sully]

Without a front cooler, 240 in not unusual on a hot day. My manual states temps above 265 are a problem. Before I added a front cooler it would occasionaly hit 240 on hot days.

[manbridge 74]

From the late, great Bruce Anderson...

230 is warm
240 is hot
250 is too damm hot

And I should've mentioned in my post above that both 74s I've had were "geared" to turn the highest fan speed by combining the largest crank pulley to smallest fan pulley, IIRC (If I Recall Correctly).

I also think that some type of thermocouple measurement should be used to confirm gauge temps as they might not be exact after 40 years.

[ARCSinAK]

Sure appreciate all of your comments. I had to remove the alternator and noticed the cone behind had a broken fine, used epoxy resin and glass to fix that, clean the top of the case it had about 3/8 of gunk encasing it. I am in hawaii and do not need a heater. If I block of the ducts to the heat exchangers will that help direct more air over the case? Can you take a long meat thermometer or the like and place it in the oil tank to check to see if it reads the same as the gauge? I have found lately on my 80SC that when I turn on the headlights my oil temp rises 10 degrees? I sespect this is a issue with the gauge? Has anyone else experienced this change in oil temp reading with the introduction on additions electric demand?

[Flat Six]

Originally Posted by ARCSinAK

. . . clean the top of the case it had about 3/8 of gunk encasing it.

^^^ this

[Ronnie's.930]

Originally Posted by ARCSinAK

I am in hawaii and do not need a heater. If I block of the ducts to the heat exchangers will that help direct more air over the case?

You can't do that if you leave the heat exchangers in place (if you don't cut them off the headers or replace with "no heat" headers) as with no air passing through them they get superheated. I dumbly did this once with a 914, long ago in my early 20s, and was shocked at the heat generated.