SC heat backdate. Any downside?

[Fleetwood]

Considering a heat backdate for my 79 SC. Are there any downsides to this change?

I know this is a normal modification but I recall some info about a reduction of engine cooling air and in heat/defrost flow inside the car. Since heat/defrost is a requirement, I don't want to impact that much. Engine overheat is a more critical issue as I'm currently installing an elephant radiator/fan etc to reduce temperatures. Porsche evolved these systems to improve cooling and interior heating and I would certainly be unhappy if my radiator upgrade was marginalized by a visual/access improvement to the engine bay

Do the current Pelican parts replacing the tin behind the distributor fit properly or do they require "modification" or reshaping to give clearance to the cap and wires? Are there other options for a better fit?

30+ years with this jewel and I've discovered a few downsides to my "improvements" that were unanticipated. Just wanting to go into this one fully prepared. Thanks to all the Pelicans who document and post their knowledge so I can accomplish tasks that are way outside my comfort level

[lsf911]

I backdated the heat on my 83 SC several years ago. The left side piece did need modification to fit around the distributor. I'm sure you can find one that will not need to be modded, I have seen them but can't recall where.

As far as engine cooling, I have not noticed any difference in that with or without the mod.

The heat and defrost are still quite adequate but at idle it is lower than if you have the fan installed. I personally am very happy with the mod and have plenty of heat in the cabin even on cold Massachusetts days/evenings.

[Hulley]

I back dated mine last year, I bought the left side piece from our host and it fit perfectly, no regrets and heat works fine, not as strong as before but more than sufficient for me and I drive mine year round.

[GaryinNE]

Just installed the Pelican parts last week. Fit perfectly. I made the bottom tab slotted for my own ease of installation. I have not driven it so do not know about air flow yet.

[Otter74]

My SC Targa has backdated heat and the only downside I experience is that with the top off, it can’t really keep me warm enough below maybe mid to low 40s F. I very rarely drive the car with the top off in those temps so it’s not a big deal to me. Top on, no problem. I have occasionally driven it i temps down to the upper 20s and it’s fine with the top on.

[Showdown]

I drive in the winter (until the roads get salted) and with backdated heat it’s pretty much all or nothing- at idle the cabin starts to get cold, driving at anything above 2000rpm and it’s thermonuclear heat.

Not the end of the world at all but a data point to consider.

[mikesarge]

One more in the same vein- I only ever use 1/2 of the heat unless I need defrost. It’s hot. I’m running SSIs and backdated heat. It was ~20 a couple mornings this week and I was plenty warm enough to crack a window after a couple miles. Idling you’ll cool off.

[trond]

I did that and heat is now RPM dependent. No surprise but not really an improvement either if you live in a cold climate

[berndtj]

Well, I just replaced a heater blower in my SC that was very dead. I was hoping for a night and day difference with the blower installed. The defrost still sucks. Not sure if it was worth fixing vs going backdate. It sure would be nice to have less in the engine compartment, but I drive my car in the PNW winter, so I really want heat and defrost to be as good as it can be.

[PeteKz]

I have a 1973 coupe with 1979 SC RoW engine and SSIs. When I initially installed the engine, I went with the engine shroud heater air supply, rather than a separate electric fan. I like to keep things simple. I live in the PNW too.

The heat varies greatly depending on my driving. Around town, I have to crank up more heat, but when I get on the highway, I have to reduce it a lot, otherwise it will get really warm, even in 20-degree outside temps. The electric fan provides a much more constant air flow, but the heat still goes up and down depending on how hard you are driving (and thus heating up the exhaust pipes). You have to continually adjust the heat output either way, so I'll stay with the engine air system. Defrost sucks either way, unless you can use your AC system to dehumidify incoming air, like modern cars do.

I have thought about how to prevent loss of engine cooling air during the summer. It hasn't been a problem for me yet, but I am thinking about putting some simple flat plate valves in the outlets from the engine shroud to the hoses. Then I can manually close them in the summer for maximum engine cooling.

[Nditiz1]

I did it when I performed an engine swap and never looked back. It's clean. Yes RPM dependent, but it has never been an issue with year round driving in MD. Definitely a good mod.

[ross79SC]

I have a 79 coupe in which the engine bay fan was weak so don't have that to compare to. When I initially did the backdate I had stock exhaust. With the stock exhaust I had trouble clearing badly fogged up windows on startup (Same climate as PNW), my car was had factory a/c (since removed at some point), so the upper lever controls both fresh air and fan speed. So to have the fan on, the fresh is fully open. So I'd have the fan on when warming up the car, but when I started to drive with the fresh air fully open the heat would get overwhelmed, so I'd close down the amount fresh air which shut off the fan which was fine until the the first stop light, then have to turn the fan back on. This fun cycle would repeat until the exhaust/car got fully warmed up.

I then installed SSIs which not only increased the volume of heat but also sped up the time to get usuable heat, usually by the time it comes down from 'fast idle'.

The final piece in the puzzle was that I discovered that non-factory a/c cars have two levers on the upper row that give the ability to control fresh air and the fan speed independently. So I bought a non a/c control with a broken face plate and swapped it into my car.

The increased/faster heat off of the SSIs speeds the whole process up, but now I can have the fan on to aid clearing windows while stationary and still limit the amount of fresh air for driving during the warmup phase... much nicer!

[berndtj]

I also have the single lever controls and deleted A/C. I'll put dual lever HVAC control on the list. SSIs are already on the list, but that requires a bit more budget. I hadn't even thought about moving the top lever to get more air. Honestly, the whole 911 HVAC system is a mystery (I mean, I more or less get it, but seriously, this was an expensive car).

[AlKidd]

Originally Posted by Otter74

My SC Targa has backdated heat and the only downside I experience is that with the top off, it can’t really keep me warm enough below maybe mid to low 40s F. I very rarely drive the car with the top off in those temps so it’s not a big deal to me. Top on, no problem. I have occasionally driven it i temps down to the upper 20s and it’s fine with the top on.

I dont think the blower in the engine area would help going topless. It only helps at idle and thats when you wouldnt have a wind effect with the top off. I backdated my cab and some heat on the feet on cold mornings is nice. With the top up i can never stand all the heat.