Hi-comp 2.4S or 3.x????

[BK911]

I have a 2.2S engine I am considering stroking to a 2.4. I am also considering selling the complete engine and buying a 3.x. This is for a DE/AX car and maybe an occasional trip around some back roads. I am not concerned with race classification at this point.

If you were me, what would you do? I can't decide and I'd like to get rolling soon. Especially with that 3.0 currently in the classified section!

Thanks,
BK

[Jim Richards]

BK, since your back roads (in Central FL) are pretty wide open, I think the 2.4 (carbs or MFI) would be a gas. That's what I'd do.

[LakeCleElum]

I think an early "S" engine is getting pretty valuable? No?

[BK911]

Hey Jim, I am leaning towards the 2.4. Mainly because I already have all the parts so it will essentially be free. Plus I've always wondered what this engine would be like. I have the 73.5 T case sitting on a shelf, so the 71S short block would be up for sale to help fund the other stuff I 'need'.

But... I could probably get ~$5k for the engine with the MFI. I can get a nice 3.0 for about the same price. Or a core for a bit less. Replace the CIS and cams and the end result is a lot more Hp.

And yes, the back roads around me are wide open, but they are also flat and straight. BORING!! I can't wait to get out of Florida.

And yes again, the early S stuff is getting pretty valuable. Hopefully somebody will need a 71S short block, so I can sell it to help fund all the projects I have going on.

Thanks for the replies. Please keep them coming. I am confused!!

[Grady Clay]

BK911,

First off, your complete and running 2.2S with the original MFI is very valuable. I think your $5K estimate is possibly low. There is a Pelican here in Colorado with a ’70-‘71 911S that is in need (he has a 2.2T in it). Please let me know if you decide to part with the engine as he is a willing buyer.

I absolutely don’t recommend you spread the original 2.2S parts around. Keep it all together.

Good for you keeping your ’73.5 engine all intact.

Yes, selling the 2.2S you could fund a 3.0 with carbs and some cams & CR. That would be the most bang for the buck. You might even have money left over.

A really fun (but more expensive) option could be to buy a 2.4T/MFI good core and build yourself an 11.5:1 CR, 2.8S, MFI, twin plug with 250+ hp @ 7300. Quite a number of Pelicans have gone this route very successfully. In a light early 911 or 914-6 this is neck-snapping fun.

Best,
Grady

[Jim Richards]

BTW BK, the S parts I bought from you a while back are doing quite nicely in my 2.7RS engine.

[BK911]

Good to hear that Jim. I knew we did business before but I couldn't remember the exact details. I was also considering a 2.7RS spec. I assume you have nothing but good things to say about yours?

And Grady, a 2.8S? Why did you have to go there? I was already confused enough!

So I guess the real question is...

What engine would you put in a gutted out 73 Coupe?

[YTNUKLR]

Brian, for the best bang for the buck, a 2.4 and 3.0 are the way to go, the 2.4 being the cheaper (total cost) choice.

Your 2.2S motor is worth more complete, by a long shot. I personally would sell it complete, then find other heads and suitable P/C, rather than strip parts from it. I bet $5k would be pretty easy to get for it, if it's a good core.

This is actually my own personal dilemma: 2.4 high-compression MFI motor, or 3.0 w/ carbs or MFI. The 2.4 will save a grand or two over the 3.0 in the end, sounds awesome and is period-correct, but a 3.0 w/ cams and induction/exhaust will make a veritable bottle rocket out of an early 911.

Beware, however, the 3.0 on the street may end up costing you a lot more in speeding tickets!

For me, it boils down to keeping period correct sound and "911S feel" with a smaller engine, or pure grunt/acceleration/fun w/ a 3.0.

FWIW.

[Grady Clay]

Brian,

No confusion. Search on 2.8S. Sorry that I am such a tempter, ask why I like these so much. This is built from a readily available street Porsche engine. All the parts, services and technology are currently easily available. It has very high specific power. Reliable if built and maintained correctly. Light weight. Period correct. Great fun.

The only down-side is it is relatively expensive and time consuming when done correctly. On the other hand, every engine project like this is due that level of attention.

Yes, you can get more torque for less money with a 3.0… but there are compromises. With a 2.8S, your ’73 can be lightest possible in the rear; that is probably the most important aspect of a pre-993.

Best,
Grady

[randywebb]

11.5:1 CR,...


- where are you gonna find gas for it?

10.5:1 OK

[dd74]

I had a high-comp stock 3.0, and now have a high-comp 2.7.

The 2.7 is much stronger, lighter, more lively, and in general more entertaining than the 3.0.

The 2.7 is as reliable as the 3.0.

A nice plus is the gas mileage with the 2.7 (Webers), is only slightly less than the 3.0 (CIS).

[Avery]

Grady: Can you post up that link describing the 2.8S motor? I've tried searching to no avail. Thanks!

[Grady Clay]

Try here: (I searched on “ 2.8S Grady RSR twin” as using only the first two gave 258 hits)
http://forums.pelicanparts.com/search.php?action=showresults&searchid=2513731&sortby=lastpost&sortorder=descending&exactname=yes&searchuser=

Building a 2.8S from a 2.4T is relatively straightforward. The expensive parts are the set of Mahle Nikasil 92 mm RSR pistons & cylinders and the necessary twin plug setup. Almost everything else is the same as building a 2.7RS clone. Some of the significant expense there is rebuilding the 911T MFI to 911S/RS specs.

The difficulty comes if you want to lower the CR. These RSR pistons with 2.2, 2.4 or 2.7 (not RSR) heads give very high CR when set with proper deck clearance and “squish.” The change from 8.5:1 CR to 11.5:1 CR gives more performance gain than the 20% gain in displacement (2341 to 2808 cc). Remember, you are essentially starting with a 190 hp 2341S and adding 40+% (190 hp X 1.4 = 266 hp).

Randy’s concern about fuel is of note. I use leaded race gasoline (112 octane) delivered in 55 gal drums. It is currently about $5/gal, not too bad considering the relatively limited annual use.

If you don’t want very high CR, using the 90 mm 2.7RS Mahle Nikasil P&Cs is a viable alternative. The stock 8.5:1 CR can be slightly increased with care. This allows continued use of pump gasoline in most places.

I am not in favor of the aftermarket pistons (JE & others) because of the relatively short life (20K mi?) and poor ring control. Mahle Nikasil are expensive and worth every penny. The original 2.8RSR P&Cs in Pelican rs911t’s engine are just fine after 30+ years of use (we built that in ’74 and the case still hasn’t been split).

Even if you don’t install a twin plug setup, it is desirable to have the heads machined for the 12 mm exhaust sparkplug while at the machine shop. You can simply plug the hole for later use. It is best to use the 12 mm sparkplug for clearance issues to the head nuts. These are common 12 mm motorcycle plugs (something like the NGK DCPR9EIX for $7 retail) and work great.

The very high CR works satisfactorily with a full fin fender cooler and the 1.82:1 engine fan. On track it benefits greatly from the “Rubbermaid Solution.”

Best,
Grady

[Jim Richards]

BK, I love my 2.7RS engine. It is a huge improvement over my old 2.4E engine in terms of acceleration and the top speeds I hit on the tracks I run on. It's also very streetable.

Grady, you are evil. I really wanted to do the 2.8S project, but had the 2.7RS p's & c's and was anxious to move forward. Still, I always wondered what might have been.

[randywebb]

you could always sell the p/c's and buy the 2.8 set.

I'm a big advocate of twin-plugging - you get much better running, some more power, and a LOT of safety if gas quality drops during the next crisis (and you know there will be one in a few years if not sooner).

[Jim Richards]

Randy, are talking to me? Please, please, don't push me further down that slippery slope!



BTW, my heads are twin-plugged.

[pieterk]

Originally posted by Grady Clay
A really fun (but more expensive) option could be to buy a 2.4T/MFI good core and build yourself an 11.5:1 CR, 2.8S, MFI, twin plug with 250+ hp @ 7300. Quite a number of Pelicans have gone this route very successfully. In a light early 911 or 914-6 this is neck-snapping fun.

Ah, the great temptation rises again!

Grady, you might remember me asking you about this before; I've read all the threads and am quite enamored of this idea. It would remain generally period correct for my car and be in the same broad family as my 2.7RS.

However, a few weeks ago, I ran across this thread by Henry Schmidt in which I learned about the 2.8SS, something I'd never heard of. It looks like a much more hybrid approach, but it too is quite interesting.

If you have a minute, I'd love to hear your take on this motor and how the two might compare. This would be for use in a car built and tuned entirely for the track, although it sees very occasional road use.

[Bobboloo]

Pieter the motor you outline is a 3.2SS.

A 2.8SS would be a 76/77' 3.0 Euro Carrera case with 66mm crank and 95mm P+Cs

[pieterk]

Originally posted by Bobboloo
Pieter the motor you outline is a 3.2SS.

A 2.8SS would be a 76/77' 3.0 Euro Carrera case with 66mm crank and 95mm P+Cs

Oops. You're right; sorry. I was sloppy in looking at the older thread. I'll delete that part. Thanks for the correction.

[Grady Clay]

Pieter,

Thanks for bringing this to the front. There are potentially two 2.8 engines. The original 2.8 (92x70.4 = 2807.95 cc) is built from a 2.7 (or 2.4) and the other (95x66 = 2806.93 cc) starts with a 3.0 (’74-’77 Turbo or C3), back dates the crank and is a collage of parts. There are advantages and disadvantages to each.

Using the aluminum 3.0 case makes the engine stronger but heavier. The 2.4/2.7 magnesium case isn’t as rigid and almost always will need reconditioning at the onset. The short stroke allows higher rpm (>8000) for the same stress level.

I think the best reason for using the “long stroke” is you can start with a complete 2.4T MFI engine and only need to change the P&Cs, cams, mod the MFI and add twin plug. A good 2.4T is much easier to find than the collection of a low production 3.0 case (this isn’t an SC) and the right collection of parts from many years. Below Henry didn’t spec the pistons. If JEs, I question the longevity.

From ”Short Stroke 2.8“
“IT'S DONE
AFTER OVER A YEAR IT'S DONE
2.8 SHORT STROKE 66 MM STROKE 95 MM BORE
2.2 "S" CRANK
3.0 TURBO CASE
TURBO OIL PUMP
SC HEADS PORTED TO 40 MM IN 38 MM EX
TITANIUM VALVE SPRING RETAINERS
TWIN ANDIAL DISTRIBUTOR
DC80 CAMS (JOHN DOHERTY) camgrinder on this forum
10.5 TO 1 COMPRESSION
MODIFIED 2.2 '"S" MFI PUMP, SEALED W/ BREATHER
41.5 MM BUTTERFLY HOUSINGS
41.5 X 46 MM MAG STACKS
SUPERTEC FUEL INJECTOR LINES
SUPERTEC ENRICHMENT DEVICE
EURO RACING HEADERS (George does a nice job)
226 FAN W/1.3 TO ONE DRIVE RATIO
SINGLE WIRE ALTERNATOR
RSR SHROUD ( GETTY DESIGN)
SOLID TENSIONERS (never fail)

THIS BAD BOY SHOULD MAKE 300+ HORSE POWER AND TURN 8500 RPM”

I suspect the DE80 cams are close to Carrera 6 (935) GE80 race cams. The GE60 (911S) cams are far more suitable for street and most DE. The same issue is with very large intake runners.

I personally would never use a small diameter or low ratio engine cooling fan on any high performance (or even stock) engine in warm weather. There is great benefit keeping the heads and cylinders cool. For on track competition, the Rubbermaid Solution is legal and most effective.

I appreciate the use of lightweight components. Anything you can do to lighten the ars end of a 911 is of benefit. The ’69-’71 mag MFI intakes are slightly lighter than the plastic 2.4 & 2.7 MFI. One thing you can do is to consider every 2.8RSR lightweight component and evaluate the cost/benefit for your project. Remember the RSR used titanium rods, jackshaft and even hardware attaching the plastic “tin.” Even the cam drive sprockets were aluminum. Real benefit can be had with very light deck lid, license panel and rear quarter bumpers.

I agree with Henry using solid tensioners for a race only engine. I feel the best compromise for a street engine is a “Turbo” tensioner with stroke-limiting protection. I don’t see the Carrera tensioner (with pressure lube) adding to reliability or functionality because it has more complexity.

This short stroke is a fun project and is something that Henry is an expert at. The long stroke 2.8 is something mortals can accomplish within a reasonable (but still expensive) budget. There have been quite a number of Pelicans who have successfully done this DIY. If you don’t DIY, this translates in far less cost because of less inventiveness.

The time cost in this long stroke 2.8S project is insuring proper piston-to-head clearance and the best “squish” when the piston approaches the head. If you can safely (no chance of contact) get 13:1 CR, so much the better.

The time cost with the short stroke is as above plus accumulating the hard-to-find Porsche parts from many different engine types. Note “…AFTER OVER A YEAR….[”

What is the time consensus for current DIY builders? In the ‘70s, we did this commercially in about 10-14 weeks. Of course all the parts were much newer.

To placate Randy’s concern, I have previously posted on a safe and suitable system for home fueling with race gasoline. I’ll again put emphasis on SAFE. All this is very dependent on your ability with local zoning, covenants, fire laws, EPA, etc. It can be done appropriately.

No one should feel I’m dis’n Henry in any way. He is a great guy, one of the best Porsche engine experts and is very creative. (And, buy the way, builds great engines.) These fun “arguments” benefit everyone

It would be great to spec here a current 2.8 (both) with all the details. I can offer my lame little.


I only wish I could get my computer back where it was a month ago. Nothing works right. Ugh. In a week or few I’ll post on OT for some Pelican help. First I need to define what it is I need.

Best,
Grady