3.6L Conversion & Heat w/Fabspeed headers

[Tom '74 911]

Hi -

Last spring, I installed a '90 3.6L engine in my '74 911. Up until recently, I haven't needed heat. Last week I did a 7+ hr. "fun" run and froze my a$$ off - not so fun.

My previous engine was a 2.7L w/a backdated heat setup and SSIs. I had more than enough heat w/that setup.

I have Fabspeed headers with heat boxes on my 3.6L engine w/a 3.6 RS-type heater tube that is currently plumbed on the driver's side only. I've taken out the "air mixer box" thing, so 100% of the "hot" air is plumbed directly in the driver's side defrost vent.

There is enough pressure created by the engine fan to blow air through the system that reaches the cabin - not as much as w/the SSIs, but enough. The problem is that when it gets much below 30 deg F outside, the "heat" is barely warmer than the outside air. It's cool instead of cold, certainly not warm, and certainly not hot!

I'm wondering if the heater boxes around the headers are big enough to really warm up the air that flows through them. The heat box part of SSIs seem to be quite a bit bigger and enclose quite a bit more length of header.

Does anyone else run a Fabspeed header w/heat system in the cold successfully? I'd like to hear about other system's performance heat-wise too - B&B, etc....

Thanks,
Tom

[clutch-monkey]

i have the same set up as you, 3.6 in a '78 with full fabspeed exhaust and heat boxes. worked fine.. for the climate i live in. currently removing the heat boxes though.

[Kevin Stewart]

what does your temperature gauge say, your car may be running to cool

[Tom '74 911]

Originally Posted by clutch-monkey

i have the same set up as you, 3.6 in a '78 with full fabspeed exhaust and heat boxes. worked fine.. for the climate i live in. currently removing the heat boxes though.

How cold does it get where you live? If it's much below freezing (32F, 0C) I don't get much heat - just cool to luke warm air. If the outside temp is higher, it's better. . .

Originally Posted by Kevin Stewart

what does your temperature gauge say, your car may be running to cool

This crossed my mind too. My temp gauge doesn't budge much, especially when it's cold. I have a big fender cooler and a big front mounted cooler as well. I was wondering if the oil cooler thermostat might be stuck open - in a constant state of "cooling" and not allowing the oil/engine to heat up. This AM I tried a low-tech solution - see pic below. It was 19F. By blocking off cold air to the front coolers, my temp gauge did rise to just above 120F. The heat was only slightly better though - really not by much.

I have a few other things I'm planning to try - I thought splitting the air supply to flow through BOTH sides (not just the driver's side), might slow down the flow just enough to allow the air to get hotter when passing through the exchangers.

It'll likely be a short lived experiment as the snow will start to fly any day here and I'll park it for the winter. . .

Here's my low-tech solution. I need to draw some shark teeth on it w/ a magic marker!

[Joeaksa]

Are you sure your thermostat valve to the coolers is working? Sounds like its open all the time.

I have a 3.6 conversion as well and drive it about 10 miles down the highway and the temp gauge goes to about 2mm above the first white mark (194 degrees I believe) and the thermostatic valve then opens and dumps all the cold oil from the two coolers (I have the same two cooler setup you do) into the system. The needle then drops about 3-4 mm below the 194 degree line on the gauge and stays there most of the time.

We are not as cold as you are in Idaho but were in the 40's here in AZ the last 4-5 days and no change at all in the response of the oil temps. Temps always come right up after a few miles driving but does take a good 10 miles to open the valve to the coolers.

I would drive the car for a bit, highway if possible and put your hands (or an IR thermometer would be better) on the metal piping going to the front. If the gauge in the interior is still showing 120 or so and the piping to the front is the same temp, then your valve appears to be open all the time, which would not let the oil get to temp as it should. The valve should not open and there should not be any oil flowing to the coolers until 180-190 degrees IMHO.

This can also be a bit dangerous from another standpoint. A properly operating thermostat lets the oil in the engine get up to temp and thus its a bit thinner before shuttling it to the coolers. If the engine oil flows directly to the coolers in the front before its gotten a bit thinner, its not unusual to bust a oil cooler due to high pressure on start-up, especially if the RPM's are allowed to go too high. Being up North you are at even more risk for this...

[Kevin Stewart]

your car will probably run better getting the temperature up, 120 is still not enough, think about a water car you will freeze at 120 water temperature, I'm guessing thermostat by right rear tire, i had one go also, Kevin

[JeremyD]

CozyWinters: Deluxe Heated Seat Covers - Universal Fit

[clutch-monkey]

Originally Posted by Tom '74 911

How cold does it get where you live? If it's much below freezing (32F, 0C) I don't get much heat - just cool to luke warm air. If the outside temp is higher, it's better. . .

it never really gets below 5-10C except for some early morning winter runs out to the track, so i only really use it to defrost the windows even then.
which it does really well, i just comment on how effective it would be for heating the cabin at temps lower than that.