2.4S to modify or not to modify?

[Cain DeVore]

It's true that my 1972 S has a factory 2.7 RS engine in it. I love it! The low end grunt is great. I think it's one of the better all-around driving conditions engines Porsche made. Certainly of the early cars. It can race...but it's so sweet to street.

Although I have never owned a straight 2.4S engined car (all Es previous to the 72), I have driven them. I like the 2.7 better. There is a big reason why the press & racing circuit back in 73, and now 30 years later...the press (still) and all of us true enthusiasts are so crazy about the RS cars...the engine! It's just a great heart.

Having said that...

I agree that if you have an original, matching 2.4S engine and you want to pony up...take it out, crate it in the corner of the garage...and build a new engine on a 7R case. And yes...they are out there. Tom was selling a great 7R case that was already beautifully machined @ Dunkel Bros. I don't know if he sold it or not...but his # is 760-731-7535. Tell him that I refered you. He'll charge you MORE.

As to twin-plug. I asked many about that concerning a future project. Most of the hard-core, lifer mechanics I talked to said that a really well dialed in 2.7 RS spec engine doesn't need it. They love that power-train, just as the factory set it up. Yes...they suggest more modern Ps & Cs. They also do some reinforcing and performance machining to enhance the engine. And they all told me that if I went to a 2.8 or 2.9 set up...to twin-plug. But there are a lot of additional costs tied in to doing that.

Buhain and Jack Olson might even suggest a 3.6!

I have never seen an S with the original, #s matching 2.4 engine that was built into a 2.7 using that case, devalued on the market. The right buyer might have wanted to do that anyway.

But ultimately I agree that once you know all the options...follow your heart. Well...and of course...your budget.

Cain
_______________
1972 911S Coupe (Factory RS Engine)
1957 Speedster (Super)
R-Gruppe # 212

[yopurp]

Sorry for being absent, I started a new job in UK last week and hadn't had a moment to check the bboard. Suffice it to say, my few options have now expanded into many new ones given allthe opinions that were added. Given my budget constraints (considering the whole restoration), I think I'm going to just stay with the original (rebuilt) 2.4S engine, add the modified SCams, and the 2.2S Pistons for the higher compression. Then, I'm going to drive the snot out of the car for a while and enjoy it. After that, we'll see what comes next. Obvously if the cost becomes a non-issue later on (read: my wife lets me) then I'd entertain a 2.7 modification. I've decided to skip the twin-plugs for now. i need to get more educated on the benefits before I incur the costs. I'll be back in the US next week, and will be checking in on my project. I'll post an update then over on the General Topics list.

Untill then, Cheers to all and thanks for the input.

[OLDYELLOWS]

I have a '71 S 2.2 that will be picked up next week after a thorough rebuild. I researched the issues for two years and I agree that the original cars should stay "mostly original". The body is bone stock. The engine was done to show quality with the cams reground to modified S by Elgin, 964 oil pump with oil mods, case fully machined, ARP hardware, extensive head work and finally bored and rebuilt throttle bodies. Car was on the dyno last week and pulled 181 hp at the wheels or estimated 210 gross at the flywheel. I would suggest you use the 2.2S pistons and have the rebuilder adjust the compression with the various size gaskets available. You should get a great result.

[Bobboloo]

Yopurp,

Putting 9.8:1 pistons from a 2.2L motor on a 2.4L motor will give you a CR in the 10.3:1 region. That is a motor you should definently twin plug to avoid detonation. You could shim up the cylinders to raise the deck height as suggested but then you would have to also shim the chain boxes. This having the effect of lowering the CR.

An alternative is using 2.2E pistons that are 9.1:1 when used on a 2.2L motor. They would give you a CR of around 9.5:1 on a 2.4L motor. Safe for pump gas and single plugs.

Twin plugs don't add HP per say they just help flame travel just as race gas does. Either allows you to use higher CR which gives you more torque off the line.

[yopurp]

Well, found out I'm having a 3rd kid so back to plan A budget-wise. Stock 2.4S rebuild, adding Modified S cams for better power band, twin plug. I'll save the rest for later. My mechanic had the same issue on the 2.2S heads raising the compression too much and recommended the E's as well. Since this will be my daily driver, I think the better maintenance with twin-plugs and the better driveability of the new cams will be reasonable. I'm told the new cams also add ~10-15HP at the top end anyway. I'm sure that'll be enough for a while.

[Cain DeVore]

Congrats on the 3rd kid! That's even harder to find than a new, un-numbered 7R Case! And MANY more years of maintenance.

Thanks for the update on your decision. Sounds great!

Cain