Going to look at a fantastic 1973 911S tomorrow. Need a bit of advice.

[NorthernThrux]

Good points. Increasing torque/hp was never on the agenda with my engine rebuild. I went with stock stuff, including the valves, heads, cylinders, pistons and muffler. Just a few concessions to reliability like the oil bypass, PartsKlassic CDI box, updated tensioners and ARP studs. Pretty much invisible.

The valve seat project was something Robert undertook on his own...because that's just the way he is. And he didn't ask. And of course it took months longer as a consequence. Winter months, which normally wouldn't matter, but health issues made getting this back more urgent. As far as I can tell, he decided to do this project because he got a new multi-axis mill in the shop, whereas previously he used to send that stuff out. He has played with porting in the past, but all you get from that is a reduction in flow velocity that does no good. He did touch up the bowls, with intake and exhaust different as you note because of the flow directions.

He freely admits that most of his experience is with T, E and RS motors including many race versions. So experimenting on an S was something new. Yep, it's a rabbit hole one can easily go down. But it is an attribute that I can relate to. I designed and built the 6 zone HVAC system in our house 15 years ago, and spent 5 more years fine tuning it to perfection. Who does that other than OCD people?

Of course if I had wanted to build a modded 2.4 S, there are many other things I would have done, but the aim of this project was really to be original and resist things like wider wheels, prototipo steering wheels and the like. Early on in this thread, with the input of this community, I decided to not put a radio back in (there had been some aftermarket '80s crap in there) because the car did not come with a radio in the first place. The only glaring exceptions on the originality front were the headliner (non-hex) and the rear latch panel (we couldn't find a good used one over a year of looking and RD didn't make that version until a couple of years later when the longhood market took off).

[beh911]

Sounds like the situation is turning for the better, based on your comments. I hope it continues to go your way.

Re: the space cam work. While it sounds like the wear/out of spec affected performance, I'd be interested to hear how much of the work is compensating for the very different quality and composition of modern fuels compared to what was on the market when the 2.4S was made.

[frederik]

It’s great that you are happy with his work, and at least there is progress. But it seems very strange to me to start experimenting on a customer’s car without asking for permission first. Well let’s hope work will proceed smoothly from here and that you’ll soon be able to finally enjoy your car.

[NorthernThrux]

Things are always better when one can talk with the restorer face-to-face instead of via third-party intermediaries texting back and forth.

Regarding the space cam, I do not believe that my space cam was significantly worn and hence altering AFR. It's profile was essentially identical to a new 60 (RS) cam Robert had. The mid-throttle mid-rpm flat spot is the same on both cams and has been documented historically as well, notably in Bruce's book, but also in the reviews of the day. What was worn was the arm that plugs into the cam and allows the throttle to move it circumferentially. Both the ball that inserts into the cam and the hole at the other end were worn. These both lead to hysteresis in the lever (and hence cam) position and hence some variation in throttle position dependent fueling. Most noticeable at idle where the CO2 and AFR values tended to bounce around more than they should from run to run. There really needs to be no slop in these linkages. Wear on the thicker cams could also have been reduced when the follower on the cam changed from the roller to the ball stylus. The ball stylus offers far less resistance to circumferential tracking (throttle angle) than the roller stylus did.

Other 2.4's he has rebuilt produce their factory rated DIN hp on current 87 octane. Which is what the 8.5:1 compression ratio S motors were designed to run on. Running on higher octane actually creates starting and vapour lock problems as you know. This may all vary a bit on where you live. Where I live, regular and mid octane fuels have 10% ethanol. 91 has no ethanol, which is why I use it in my snowblower for example, so rubber bits don't rot. We'll never know for sure because the motor was tuned for modern day 87. We'd need an old gas formulation to know for sure what changes but at least on stock engines that he has previously done, the space cam didn't need to be altered due to the fuel type. That may be different on higher compression engines, but for stock it doesn't make any significant difference it would appear. The fundamental issue on the S cam is the lean mid-range section that seems to have been placed there to meet emissions standards in the US. Why else would there be a 3000 rpm part-throttle range which was leaned out so much? That wasn't there on E and T motors, which is why I think many people had a preference for the driveability of the 2.4 E motor.

EDIT: Looking through some old bills I see two MFI pump services in the early 90’s and again in 2002. So my 61 cam could been replaced at some point. Bosch listed these cams as high turnover inventory parts, which means that they probably did wear quickly. At least the earlier, narrow ones. There was a grey coating on the narrow version of these cams, whose absence was indicative of wear surfaces (not sure about the wider versions). But by the time I saw my cam it had been heavily machined, so I can’t be sure about the wear. However, the 60 RS cam was brand new and gave the same result, so that suggests wear of the cam surface wasn’t the culprit.

[edmayo]

So this is all well and good,,,,,,when do you get the car back??? You want to have it and drive it,,,so what if there is 10 hp left somewhere,,,are you really going to care.

[NorthernThrux]

So this is all well and good,,,,,,when do you get the car back??? You want to have it and drive it,,,so what if there is 10 hp left somewhere,,,are you really going to care.

Definitely not going to care. Would have been happy with stock hp. But it has snowed for the past 3 days, so there would have been no driving anyway. I expect it back before next weekend. I have told him, no more tweaking. Put it together and deliver it.

[Trainee Fritz]

Ravi, any news? I guess we all can't wait to see you two reunited.
Peter

[NorthernThrux]

It will come as no surprise to anyone who has been following the last 4 or 5 pages of this thread that it didn't come last week. Ken is due to trailer her here next Monday and trailer another car from the area back. Even asked for my address again. So that's progress.

[BOYER73S]

Yep, not surprised

[edmayo]

I wonder if the owner of the 'other car' knows of your story?