71 911T engine options - help me decide!

[RickWhite]

Originally Posted by RichC 911T

Thanks for the pointers. Just to be clear that would be S sway bars with 930 torsion bars as a good road set up?

Correct. S sway bars are the factory. You can certainly go with beefier, but if this is casual driving and not on track, there is no benefit. It is really that some sway bar is 100x better than no sway bar, particularly as you get toward 200 hp.

Separately, as someone who has run carbs, MFI, and EFI in a ‘71 with these engines, carbs are easy. So easy. And cheap. MFI is expensive, and you need someone with knowledge. EFI can be great, but can be a total cluster. Carbs may be a headache, but it is a headache you can fix with a screwdriver. EFI can implode and not work. Ultimately, I’d ask the guy who is going to take care of your car, not the internet.

[tdskip]

Properly set up carbs will hold a tune for a good amount of time, but nothing like modern EFI.

Going with a modern ITB set up does pretty much get you both modern reliability and the sound. Dear Lord - the sound....

[RichC 911T]

Thanks to everyone for the advice.

Of the options I've got for the swap it sounds like the 911/01 gearbox with a 2.7 built from the 7R case is the way to go. 9.5:1, S cams, ITBs/EFI if the engine builder can work with one of the more cost effective kits, webers or PMOs if not.

If I go with carbs and decide they're not for me then they can ways be sold and swapped out for EFI later down the line.

From what I've seen the ITB/EFI kits that are easily available in the UK are Jenvey or AT Power. Both at the upper end of the cost scale. If the x-faktory kits are just as good and still offer a decent saving once import duties are factored in then I'd be tempted to give one of those a shot.

Thanks again for the words of wisdom.

Rich

[RichC 911T]

Originally Posted by RickWhite

EFI can be great, but can be a total cluster. Carbs may be a headache, but it is a headache you can fix with a screwdriver. EFI can implode and not work. Ultimately, I’d ask the guy who is going to take care of your car, not the internet.

This is a good point. A few years ago I had a 205 gti with a modern supercharged engine swap - great fun when it was running but a huge PITA when it wasn't as nobody wanted to touch it. Will see what the engine builder and the local porsche specialist think and go from there.

[tdskip]

Originally Posted by RickWhite

Ultimately, I’d ask the guy who is going to take care of your car, not the internet.

I know this was likely not your intention, but to dismiss the vast amount of experience and real-world wisdom here on the "internet" is hugely myopic.

[silverc4s]

Originally Posted by RickWhite

Take the 7r case, bump it up to 2.8 and use e-cams if it is for street use. You can use either the 911 or 915 tranny with the engine, just depends on whether you like the dogleg. Just don’t go crazy in first. As someone else said, unless you live somewhere frigid, you’re going to need a front oil cooler too.

You’re also going to want sway bars and bigger torsion bars (930). You don’t need overkill, the stock S bars and 930 bars are perfect.

I agree with Rick White here. best early engine I ever had on a budget was a 2.4 L E engine with webers, and a 901 box with 69 T gearing, It was more fun than a barrel of monkeys up to 125 mph!! Car was a 69 Targa. E cams for a street/ track comprmise.

[RichC 911T]

There's a lot to be said for keeping it simple! I'll do a bit of reading around cam profiles. All options are still on the table at the moment!

[RichC 911T]

On that note, it's not an option for the swap as such but if a stock 3.0 was to fall into my lap would the general feeling be to stick with the 2.7 build or ITB the 3.0 and not think twice about it?

[targa72e]

ITB 3.0 all the way if it fits your budget. At that point might as well make short stroke 3.2 (98 x70.4). Your 901 tranny might not be happy.
With stock 3.0 CIS induction and cams you are limited on how much power you can make. Since you asked dyno below is 2.7 Mod S cams vs 3.0 with CIS. 3.0 Engine had 78 big port heads, later 9.3 to 1 pistons and headers. This 3.0 engine was from PCA stock class race car so limited in mods that could be done. I have dynos from several top stock class 3.0L engines and they are all about the same power. This was on the same dyno but different cars 2.7 was in 914 and 3.0L was in 911SC.



on 3.0 with better intake you can add about 15-20HP over CIS on big port 3.0. That was result with two similar engines one with 3.2 Carrera intake and one with carbs. Add pistons and cams for even more.

john

[hheine]

Originally Posted by RichC 911T

A few following strip down. It's a bit crispy!

A bit crispy indeed, very cool! Keep the updates coming

[RichC 911T]

Slow going at the moment but thanks to all for the input. The shell is next in line at the restorer's so he should be able to get going on it in the next 2 - 3 months when he finishes his current project.

In the meantime I'm keeping an eye out for a 3.0, although they seem to be few and far between. Probably no bad thing as I need every penny I can get for the shell at this point. I've got a better idea of what I want now though at least.

3.0 to be taken out to 3.2 SS (if I can find one) is first choice. Probably on carbs to start with then ITBs when funds allow. Failing that I'll go 2.7. Either way I'm swaying towards the 915 box as it'll give me the flexibility to change things up if I go 2.7 and decide I should've gone 3.0.

Albert Blue. RS flares. 15x7 + 15x8 fuchs. Slightly lowered. Can't wait! Just need to work out how I'm paying for it all now.

[RichC 911T]

For anybody who has been on the edge of their seat for the last 12 months waiting for a conclusion, a low miles 3.0 ROW SC engine has just fallen into my lap. Well, not quite but money has changed hands so I now have a good running engine to drop in to my 70T when the shell is finished. Which it isn't. Not by a long shot...

[RichC 911T]

That being the case I have plenty of time to decide on the final spec but I'm still aiming for a 3.2 SS in the long term, probably when the SC engine eventually needs a rebuild. The engine is still running the CIS injection system which I know has its fans but I don't think I'm one of them. It looks terrible and better sounds/performance are only a set of itbs/efi away.

Bearing in mind that this engine will end up a 3.2 SS at some point and I'd prefer not to buy parts now that can't be used as part of that build, I have a couple of options:

1. Drop the 3.0 SC engine in complete with CIS and drive it as is for a while to get a feel for the car and better understand what mods I might want to make.

2. Ditch the CIS from the get go and install ITBs/efi that can be used with the eventual 3.2 SS build. Maybe cams as well.

I'm pretty sure I'll just pony up for the ITBs (and possibly cams) as the looks/sound is a major part of the attraction and it might be a while before any major rebuild.

[RichC 911T]

The SC engine doesn't come with headers or an exhaust so I was thinking SSIs (I'll need heat in the UK) and a Dansk 2 in 2 out sports exhaust.

As for cams, valve/piston clearance looks to be the limiting factor so I'd be looking at 964 or 20/21 cams with the stock pistons.

What I'm not sure about is whether I could use the SSI headers and piston friendly 20/21 cams with the eventual 3.2 SS build? Well, I'm sure I could use them but would they end up being a bottle neck on performance and defeat the object?

I've read elsewhere that SSI headers aren't generally recommended for a 3.2 engine, although that was in the context of a later carrera 3.2. Would this set up be any good for a 3.2 SS?

Similarly if I get new 98mm pistons and cylinders later down the line that would open up options for a more aggressive cam choice. Would sticking with 20/21 cams in a 3.2 SS build be leaving too much on the table? This will be a street driven car so I'd like to maintain low end torque if possible with cams that still give a reason to take it to the red line. A broad power band appeals rather than something that's completely flat below 4000 rpm.

I might well be asking the impossible and if the answer is that I need to choose appropriate cams for the given set up rather than trying to second guess how hot SC cams might perform in a future 3.2 SS rebuild then that's fine. I'm sure that a 3.0 SC engine with itbs/efi and 964 or 20/21 cams will do nicely in an early car in the meantime!

Rich

[kent olsen]

3.0L was my choice in my 72T. I wanted something I could run the daylights out of then take it home and once a year adjust the valves and change the oil. With the help of my friend Mike Bruns we build it up with webers, twin plugs, 9.5:1 pistons, ARP rod bolts and a special cam from Dougherty that has a lower torque peak. On the engine dyno it showed 245hp/6900rpm and 230ft/lbs/4800rpm.

I've put about 20,000 on this engine and it has been great, no issues.

[RichC 911T]

Some healthy numbers there. I'd be very happy with that in my 70T. I think the stock ROW SC pistons are 9.8:1 so I should hopefully be able to achieve something similar with EFI and cams.

[PeteKz]

Congrats on getting the 3.0. See my signature line. I run an SC engine I built to a long stroke 3.2 in my 1973T. "There's no replacement for displacement."

Tranny: Since you want to go big, get a 915. No brainer. I further recommend that you get one with an 8:31 R&P. In a light car with lots of torque, that makes 1st gear useable for more than just getting started uphill, and it makes 5th a reasonable highway gear.

Engine: since you think you will eventually build it into a 3.2, you will end up with different pistons, and therefore different cams, and therefore different induction. I would not do anything inside the engine now. If it runs, install and drive it. Keep the CIS (I practice what I preach, and remember that the turbo engines kept CIS up to 1990). It's simple and it works well on the SC engine. AFTER you have some experience with the car and engine, then decide on your next steps.


LOTS of options for suspension, and those are mostly going to depend on your intended use and personal preferences. Go look at those threads, particularly recommendations from Bill Verberg and Ian Carpenter.

[RichC 911T]

Originally Posted by PeteKz

Engine: since you think you will eventually build it into a 3.2, you will end up with different pistons, and therefore different cams, and therefore different induction. I would not do anything inside the engine now. If it runs, install and drive it. Keep the CIS (I practice what I preach, and remember that the turbo engines kept CIS up to 1990). It's simple and it works well on the SC engine. AFTER you have some experience with the car and engine, then decide on your next steps.

That would probably be the most sensible option. I'll see how my budget is looking once the shell is finished but I suspect that ITBs/efi is the way I'll end up going. I've no doubt that a properly set up CIS set up can be made to perform very well but it's as much about the looks/noise for me as anything else.

Out of interest PeteKz, I see that you're running M1 cams which seems to be less of a well trodden path than some of the other options for the SC engine. How do you find them? Did you end up trading off much at the bottom end? I've read up a little on them but the specs seem to be a fairly closely guarded secret. What made you go with those over 964 or 20/21 cams, say, assuming that SC piston compatibility was a factor in the mix?

[PeteKz]

Rich, here's what I wrote in another thread a couple months ago:

"Back to the M1 cam: I haven't got my car on a dyno yet to do the final tuning, so I don't know what the numbers are. I will post those after I do that. That said, I do know from my measurements as I timed the M1 cam that it uses all the room available for lift and duration on 3.0 and 3.2 engines without the valves hitting the pistons. Therefore, one has to stay very close to the recommended cam timing, because retarding or advancing the timing more than a few degrees, WILL result in cam/piston interference. I measured that. So, yes, "it leaves performance on the table" IF you want higher RPM power, but are willing to give up low-mid RPM torque.

If you choose different pistons with valve pockets, you can choose a more "radical" cam, but you will give up low RPM torque and smoothness. As Henry observed, to a racer, high-RPM power is most important, but a high-RPM engine is a lousy street driving experience.

What the M1 does for a street car is give a wide range of torque. As I noted before, I have retained CIS on my car, and I can floor the gas pedal at just above idle, in the higher gears, and it will pull smoothly all the way to redline. I like that for a street car, especially with the crappy-shifting 915 transmission. I also get close to 30MPG at constant highway speed. Not shabby for an old engine design. Even if I don't get to my desired 230 RWHP @6000RPM in my tuning, I like the driving characteristics enough that I would build another engine with it."
-------------------

Therefore, if you plan to stay with the pistons designed for the 3.0 or 3.2 engines, use the M1 cam because it was designed to get the most out of these pistons. Given my measurements, I don't think it's possible to get any more without piston/valve interference.

If you plan to change the pistons and cams, you have to pick your tradeoffs. To get more power, you WILL reduce low speed torque and smoothness, and make it less pleasant to drive in traffic. Lots of people don't mind trading off some low-RPM street driving smoothness to get a more rev-happy experience. I've owned cars like that too. But the reality is I drive 95+% of my miles on highways and local roads. So I built my engine to maximize that torque, with reasonable high-RPM power, and good efficiency.

Be honest with yourself about how you will really use the car. Lots of people have built high-RPM power engines and then come back to engines that produce a fat low- to mid-range torque curve, because it works better for how they really drive the car.

If you want more details, contact William Knight, since he's the proprietor.

Late edit: If you decide to change the pistons and cams, then the exhaust system becomes more important too, so plan on buying headers or the large SSI's or something like that, along with a different muffler.

[RichC 911T]

Thanks for the detailed reply. I'll be sticking with the stock pistons for the time being and my car won't see any track time so it's good to know that the M1 cams perform well on the street with a good spread of torque from low rpm but still managing reasonable high rpm power.

In that respect they sound similar to 20/21 cams which prioritise a broad power band and get glowing reviews on this forum from those who have them. If anything, though, the M1 cams appear to be more precisely optimised for CIS engines. There probably isn't a bad choice between them for a fun street car.