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Update for new thinking/research:

Revised plan is a 2.4 with Solex Cams, target is 170 HP with an updated cooling shroud and NO external cooler, turbo fan pulley and updated cooling tin. The 1967 911S (160HP) did not use an external cooler, nor did the 1975 2,7 (167HP) which admittedly had overheating issues, but these were associated with the five-blade fan and thermal reactors. This is approximately 13 lb/hp or slightly better than a '67S with better torque and drivability for around-town.

Heads: 2,2-2,7 heads-- 68mm combustion chambers, should be same from 1970-1977. 1977 CIS heads will not have the MFI port which obviates the need to weld it up. 46/40 valves, 35/35 ports. Valves are the same size as a 2,2 and port size is 76% intake, 88% exhaust, compared to 82% intake, 91% exhaust for the original engine.

Crank. 70.4 from 2.7.
Rods: 127.8mm from 2.7
Oil Pump: From 2.7, 1977 Style. Also updated oil bypass system
Rockers: Cast style from 2.7. Save forged originals.
Rocker shafts: 6mm pinch bolt from 2.7 Save 5mm originals.

Case modifications:
Piston squirters, 1.0mm 911 style
Oil bypass modification
Align bore if necessary
Deck spigots if necessary
Update case for new style main bearings
Install intermediate shaft bearing

Cylinders: 84mm Nikasil (vendor TBD)
Pistons: 84mm 9.1:1 compression, 25cc dome volume, 32mm compression height.
Deck height: 1.0mm

Any thoughts or suggestions are welcome. Anyone built an engine like this? It's basically a stock 2.4 on an aluminum case that will have the external appearance of a 2.0.
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Old 10-31-2006, 07:05 AM
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Why not 9.5:1 or 9.8:1? Lack of external cooling I presume?
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Old 10-31-2006, 07:27 AM
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Sounds like fun. Signing-up.-
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Old 10-31-2006, 07:45 AM
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Charles,

A fine question. Yes, the lack of external cooling is the major factor. I have thought long and hard about running oil lines through the rockers like a '67S or even a 911R style dual cooler setup like my race car has, but the need for originality trumped both ideas. So that imposes a limit on the power. Also, the car will be keeping the original suspension and brakes so the power-to-weight can't get out of hand.

Charles, is a 9.5 JE piston an off-the-shelf item? According to my spreadsheet the difference between 9.1 and 9.5 to 1 is only 2cc of dome volume. It wouldn't trouble me to use "shelf" pistons to save a few bucks. My goal in using the 2.2-2.7 heads is to take advantage of the revised combustion chamber shape and better head sealing surface as well as the larger ports and valves.
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'66 911 #304065 Irischgruen
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Ex-'88 Carrera (Sold 3/29/02)
Ex-'91 Carrera 2 Cabriolet (Sold 8/20/04)
Old 10-31-2006, 08:26 AM
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John, I don't know if it's the same for your larger application, but my 81mm 9.5:1 JE's were not a shelf item.
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Old 10-31-2006, 08:52 AM
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Thanks Jon, good to know. It's entirely possible that many of the less-common 911 pistons are custom only. Not a huge deal with JE's and I like the idea of going custom near the price of stock. It does increase the temptation, however, to go out to 87.5 x 70.4 for 2540cc and 10 more horsepower!
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Old 10-31-2006, 09:04 AM
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John, While your plan involves considerably more displacement than mine, I was surprised that I did not have to install an external cooler. With the 81mm 9.5:1's, a bit larger than stock valves, and solex cams, the later engine shroud seems to have done a remarkable job. Especially where I live. I haven't seen temps near the 210 mark. You've got an exciting project going, and I'll be anxious to see how it comes along.
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Old 10-31-2006, 09:23 AM
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Another option, albeit as expensive as Mahle Motorsports, would be our 87.50mm Nickies cylinders with some custom JEs to get your compression right where you feel comfortable. I've even done some slip-fit 89s, but the skirts are just a hair thin! :-)
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Old 11-02-2006, 02:45 PM
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70.4 crank ? 2136 higher compression with stock pistons and better low end from the longer stroke.
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Old 11-02-2006, 04:35 PM
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Hello John:

I'm curious-- Have you decided which way you're going on this one?
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Old 11-29-2006, 08:53 AM
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Jon,

I have been giving the matter a great deal of thought lately and am actually leaning in the direction of lower displacement, at least for the moment.

The limiting factor is oil cooling. I don't intend to use an external cooler, as the car is to be kept original. So that imposes a practical power limit of about 160, or '67S territory. Also, as brakes will also remain original, tons of power won't be safely usable.

So here's my thought process: you can learn a lot from tearing an engine down even if you don't intend to build it back up. So for my own education, I'm going to tear the 901/05 down to the crank and mic everything. Not much I can screw up that way.

The idea of nikasil cylinders is very attractive from the standpoint of heat. The case will have piston squirters installed to bring down the temperatures and to facilitate the use of Nikasils. The early jugs have a gap in the fin area, like yours do, so this may take a bit of work to preserve the appearance of originality while upgrading to the better material. I don't know whether 2,2 jugs have the gap, but it's easy enough to crawl under my race car and check.

Because of the power limit, I don't think anything larger than about 2.2 is a good idea, so I've thought about 84x66 or 85x66. The current 66mm crank has had the journals ground .50 under, but I have no idea whether the right fillet radii were used or whether that crank is straight. If it's usable and the radii are OK, I'll probably use the same crank. If not, I'll look for a STD/STD '66.

I had thought of getting a 70.4 crank but that would mean new rods also, which would be great for increased displacement, but more expensive. That being said, if I have to replace the current crank a 70.4 may be a good alternative. That would mean a 2,4- lots of torque from the increased displacement, but I'm still worried about heat above the 2,4 T power level.

Rods will be reconditioned normal rods with ARP hardware.

Rockers-- currently forged, I think the ratio is 1.6. These are a bit lighter than the later cast ones which I think have a 1.5 ratio, so I'll keep them.

Rocker shafts-- these were changed from a 5mm bolt in '65-66 to a 6mm bolt in the later years-- if the early shafts can accomodate a larger bolt I'll use them, otherwise I'll get a later set of shafts.

Heads. Since I'm going to 84 jugs I'm going to change to 2.2 heads. These will be indistinguishable from the original because the casting numbers are invisible when the cam towers are installed. Cams will be Solex and the carbs are Weber 40IDA, so I'll probably go with E ports.

Pistons will probably be JE with a close wall clearance and coated skirts to reduce friction. Not much higher than 9.1, I don't want detonation on the reconstituted Panther Pee they call gasoline here in the Empire State.

So bascially I'm going to use the heads, cylinders and pistons from a 2.2E. These should be available on the used market. If not. . . well I could always build a stock 2.4S motor for the race car, reclassify in G-stock and use the E parts for the '66. . . heh heh heh.

I'll start tearing the engine down this winter and will post plenty of photos of what I find. I can't wait to get started. . . now if I could just get the engine on the stand!
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Old 11-29-2006, 09:50 AM
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Sounds very nice! I can only dream about having the machine-work done, that is so easily accomplished on the mainland. Oh well, life in paradise does have some draw-backs. I'll look forward to your build. I'll be starting my 3.0 project about the same time.
Thanks for the reply!
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Old 11-29-2006, 12:36 PM
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Well, the engine is on the stand awaiting teardown. I would like to thank Sir Isaac Newton for his pioneering work in mechanics and The Great Doktor In The Sky for not toppling the engine during this evolution.

The casting numbers on the heads are NOT invisible, although it would take a pretty pernicious judge with a flashlight to see them. Likewise to count the fins.

This weighs very heavily in favor of sticking with 2,0 for originality sake and because increased displacement was associated with larger valve size (although the ports remained at 32mm in the E.)
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Old 01-16-2007, 07:00 AM
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Go for the 85mm pistons; the 84mm jugs can be machines safely to that spec with no distortion problems. You can then brag that your car's engine has the same dimensions as the first 911ST! Since yoiu are going JE, it is only $50 per cylinder to bore the cylinders and no additional cost for the 85mm pistons.
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Old 01-16-2007, 03:31 PM
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Interesting idea... I will be sticking with the 2,0 heads because of the originality issue, and a set of overbored 85mm birals would appear externally the same as the 80mm that are there now. There is another option for an original-appearing cylinder but I don't think that's for public discussion here. So the heads would have to be cut for 2,2 cylinders, and could probably stand being opened up to 36mm while retaining the original valve sizes.

Decisions. . .decisions. This will be a lot easier once the engine is torn down and I can make a true assessment of what I'm dealing with. . . stay tuned. . .
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Old 01-17-2007, 08:48 AM
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I am no sure about that...cutting the heads that is. If the pistons are custom JEs, the crowns can be made to roder, right?
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Old 01-17-2007, 08:56 AM
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Piston to head or valve clearance is not the issue I was thinking of-- 2,0 heads use a different head gasket than 2,2-2,7 heads and have a different sealing surface. In order to use 2,0 heads on an 84mm cylinder, the sealing surface of the head must be cut.

More here: 81mm 906 cylinders
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Old 01-17-2007, 11:00 AM
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Ah yes; thanks for the reminder.
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Old 01-17-2007, 11:08 AM
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The little-known 901/30 engine, stuff of legend. . .

80x66 Birals and High-Compression "S" Pistons (9.8:1)

911T heads- small valves (39I/35E) with small ports (32mm intake and exhaust)

Early S cams

46mm Webers (whoa big fella!)-- Maybe they put smaller venturis in them or just liked the fuel curve, but that's probably way too much for a street-driven car.

=150 HP

John Luetjen estimates that this engine had a maximum gas speed of approximately 93.5 m/sec at an estimated max HP speed of 6800. Summarizing his conclusions elsewhere, while this engine's small valves and ports were not able to fully utilize the full lift of the Early S cam, because the ports don't flow any more at the higher lift, the increased duration and overlap was responsible for a performance gain over the original configuration (which I am guessing was around 140 HP with Solex Cams and '67S heat exchangers nee' SSI)

Additional food for thought. The fixed elements of the combination are almost in place and everything else will be a compromise oriented around them.
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Old 01-23-2007, 02:25 PM
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So is that the final config John? It would be interesting how it works in reality as opposed to theory. Are you planning on dyno'ing it? I was referencing the fairly vague listing on the engine table of BA's book, but the HP quoted sounds reasonable for that configuration.
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Old 01-23-2007, 02:47 PM
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