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> 914-6 overheating PSA
mb911
post May 31 2020, 07:25 PM
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After being involved in porsche flat 6s for 20 years now and building 400 whp turbo engines this is my 1st go around with a overheating issue I couldn't put my finger on. I felt this would be very helpful for others building a 914-6 specifically.. The car in question is a 74 that last fall I put an unknown but healthy sounding 2.7 in for @jwinner . The car ran hot last fall on his drive home but ran well. We talked over the winter and decided at least under trunk oil cooler would be necessary as the car was running 250 on 50 degree day after getting off of a 20 minute highway run. We had also talked about how the engine mount as designed sits lower then I prefer as there are no way to seal the engine tins to the chassis because of the mount positioning.. That was the 1st issue that really could not be resolved easily. The second issue was we had no idea if the carbs were set correctly or the timing..

So last week happens and he brings the car down. I remove the oil tank and discover one of the porsche fittings has a crack in it but no worries going all AN fittings on this with the oil cooler.. Then put a new used engine oil cooler on (what a bitch in the car with an amber 1 piece shroud) . I button everything up after a 3 day Marathon working session completely sore head to toe and mentally done as well.. Fire it up drive around my town for 10 minutes and runs 210 no problems..

Call James to pick up the car as its ready. He drives it home and 250 happens a few minutes from his house.. He is disappointed for sure and so am I.. Now thinking ok timing issue? Jets? Electric fan? The 74 911 factory manual says 250 is ok but we were hoping for cooler temps.. So after sleeping on it and texting back and forth James decided to take out the new appbiz engine sound pad and try that.. It fixed it.. The temps went down to 190-200 max.. Absolutely incredible as I never had a mat in any 914-6 before I thought that was crazy..

So note to self before getting all crazy with front oil coolers(though still happy to sell you the GT setup) take a look at removing the sound pad if you really are dealing with cooling issues..
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Matty900
post May 31 2020, 07:29 PM
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Good to know. Did it have the cooling fins that hang down off of the firewall?
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mb911
post May 31 2020, 07:35 PM
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QUOTE(Matty900 @ May 31 2020, 05:29 PM) *

Good to know. Did it have the cooling fins that hang down off of the firewall?



It did yes..
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JmuRiz
post May 31 2020, 07:43 PM
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Good info!
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mepstein
post May 31 2020, 07:47 PM
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So I guess the engine pad was blocking enough air to starve the fan. Maybe it was even sucking in the pad at higher rpms. Good to know.
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mb911
post May 31 2020, 07:48 PM
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I would suggest painted dyna mat as an alternative
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Retroracer
post May 31 2020, 08:01 PM
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Interesting find - thx for sharing. That gap between the firewall and the fan shroud is pretty narrow - if the pad was blocking it, then the fan was probably sucking in air from the crankshaft / fan belt area - warm air.

- Tony
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rgalla9146
post May 31 2020, 08:02 PM
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This was the thick foam grey one ?
Were the tabs holding the perimeter in place....was the center loose from the firewall ?
Great diagnosis.
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mb911
post May 31 2020, 08:04 PM
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It was new last fall put on with 3M super 90.. Either way I won't ever suggest that nor the mount for a conversion moving forward unless running just headers and track oriented build.
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roblav1
post May 31 2020, 10:05 PM
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This is good information Ben.

I used typical racecar thin foil matting on the rear of the firewall and a foil fronted soundpad covered by 1/4" wool felt on front. Plenty of room for the air flowing to the fan. Hopefully have it started for the first time in about a week. Electrical almost done.
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raynekat
post May 31 2020, 11:29 PM
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No mat on my firewall. The 2.7 MFI RS engine so far has been running very cool (190-200F max like above example) in "normal" weather/temps. We'll see how the onboard engine cooler does this summer. I'm hopeful additional cooling/coolers won't be needed.
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ctc911ctc
post Jun 1 2020, 06:33 AM
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Running down this same issue on my 914-4.

I used the EZ-Mat Soundproof (I think that is the name) AND the Sound Mat.

Perhaps I have starved the engine of air flow........Will check this out!
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mb911
post Jun 1 2020, 07:24 AM
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I think its likely though the 4cyl fan is not as close to the firewall as the 911 engine.
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ConeDodger
post Jun 1 2020, 07:52 AM
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Another caveat; your engine oil temperature sender must match the gauge. Otherwise, you get dramatic gauge numbers on a perfectly happy engine. (IMG:style_emoticons/default/blink.gif)
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mb911
post Jun 1 2020, 07:52 AM
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QUOTE(ConeDodger @ Jun 1 2020, 05:52 AM) *

Another caveat; your engine oil temperature sender must match the gauge. Otherwise, you get dramatic gauge numbers on a perfectly happy engine. (IMG:style_emoticons/default/blink.gif)



Yup been there as well.
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horizontally-opposed
post Jun 1 2020, 08:49 AM
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A good PSA, and a good data point.

After hemming and hawing, we left my 73's factory mat in on the engine side. Was in nice shape and not loose anywhere. Hot 2.2 seems just fine, running 180-210° F indicated on warm or even hot days. Seems to get hottest in steady-state freeway driving.

Rob's post has me wanting to double check the gauge and sender (again), as the opposite can also be true: You can get a nice reading on an unhappy engine.
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Mark Henry
post Jun 1 2020, 12:05 PM
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I have the stock pad, heavily modified, glued and screwed to the access hatch and I haven't had any over heat issues. Was a bit hot at first, but since I did my jets I run normal street car temps.
(IMG:style_emoticons/default/confused24.gif)

One thing I could see a loose mat being sucked towards the fan like a flapper valve.
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sixnotfour
post Jun 1 2020, 01:32 PM
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2.7 ? Does still have 5 blade fan ? (IMG:style_emoticons/default/happy11.gif) (IMG:style_emoticons/default/driving.gif)
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914Toy
post Jun 1 2020, 01:44 PM
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My 2.7 with carbs and matching cams and 11 blade fan never gets above 200, with a front oil cooler with thermostat set at about 190, which routes the oil forward to the cooler only when high speed cruising or long uphill climbs. Check your air/fuel (A/F) ratios - high A/F's (above15) equals high engine temperatures.
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mskala
post Jun 1 2020, 02:12 PM
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Is this the reason the factory didn't install the pad on the 914-6?

I don't have the pad, but in upgrading from 2.0 to 2.3L -6, I went through a few
experiments with temperature and there are a bunch of factors that can affect
the temps, like plugging holes where HE paper hoses used to be, and regular lid
vs. GT all-mesh lid, underside flaps, and of course engine tuning.

Fan speed also can be changed with different fan (same blades though) with
appropriate pulleys. This is where it sucks that half the pulley is part of the fan.
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