Have you modified your 912/912E engine with a big bore kit?  From the original displacement to how many cc's?   Any other work necessary to the engine as part of this horsepower increase - crank/ carbs/ distributor/ etc. ??

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From: Andy Keller; Rick, It was in September 1981 that I installed a big bore kit in my 1967 912 as a part of my economy rebuild. That was at 75 700 miles. Today after about a total of 149 800 miles, including several PCA track events and 15 years of vintage racing, it still works fine.
The engine is otherwise stock.
The piston & cylinder kit was labeled "iss BIG Bore Piston & Liner Assembly". Bore was specified at 86 mm; capacity 1750 cc. Actually the calculated   swept displacement is 1719.4 ml.
As stated by the vendor, the compression ratio is 9:1.
For reliability I took some proactive measures:
The cast iron cylinders were checked for height consistency and found to be perfect by the shop that did my heads
I removed casting flash and other external imperfections between the fins for good air flow. The handiest tool was a hacksaw blade.
I sprayed a thin coat of high temperature black paint on the fins for the best heat dissipation. (Black oxide would be better.)
I equalized the piston weights to 0.1 g. (Also to get optimum balance in my home rebuild I weighed the rods and paired then according to equal weight, but I did not grind on the rods as there seemed to be little surplus material and I did not want to mess them up.)
I polished the piston tops.
Cylinder to head mating was assured by lapping with tooth paste.
Works fine and the oil temperature seems to be about the same as for aluminum jugs.
Has anyone measured the CR of the ISS set like mine?
Regards, Andy Keller

From: Graem Elliott; I used Shasta street pistons w/ a compression ratio of 9.25 : 1 and a set of original cast iron liners that were bored out. Displacement is 1720. A Norris 290 grind cam w/ main jets of 135. Finally a Bursch exhaust finishes everything off. The transformation is great, now the car feels like a mini Porsche hot rod chirps off the line and revs freely to 6200 rpm ! It seems like it rev higher but I don't want to grenade it.

From: David Cardone; Hi there, Regarding the q of the m, I have not added a big bore kit, although my 912E has been modified to a 32/36 carb. This is a horrible replacement for the injection and I am looking to go original or to a dual carb set-up when I find the right parts for the right price. If anyone has a big bore kit, dual webers or the factory injection for sale, let me know.
thanks for the greatest site out there!!!!!!!!!!!
Dave, 912E with 127K and BRAND NEW PAINT

From: McCoy Family;  Yes, I have increased the displacement of my 912 engine. I used the NPR 1720 kit that was available 10 years ago. I also have installed weber carbs, because of throttle shaft leaks on the solexes. The heads were CC'ed so not to increase the compression ratio so much that the gas we can get today would cause detention.
I have toyed with the distributor. I am interested in fully electronic product. Both no points and electronic advance. I believe most idle stability issues are blamed on the carbs , but it's the advance weight stops in the distributor that wear causing sudden timing changes at idle and thus idle speed changes.   RORY McCoy

From: James Scranton; I actually replaced the 1.6l engine with a 1969 2.0l 911 engine. A buddy of mine had a 911 with a wrecked front end, but the engine was recently rebuilt. He sold me the engine for $2000. an extremely good deal, how could I not buy it. the 912 engine I had before the 911 engine, was in the process of being rebuilt. I sold the engine piece by piece, to help pay for the restoration of the car.  The main reason for swapping the 912 to a 911 was the fact that the prior owner of the car had the 912 block cross bored which meant instead of buying $60 main bearings I now had to buy $500 main bearings. The block would never run as tight as I would like it too with the cross bore.  The 912 blocks are extremely hard to find, I searched for 2 months, found one, but the guy wanted to much for it. I would have had more money wrapped up in just the engine block to buy 2 912's. If you have a cross bored block they almost always stamp the top of the block either the front or the back with a bore number 50, 60, 70, etc... if your block is stamped the main bearings will be pricey.
The car is now for sale . there's a fairly nice color picture of it at autotrader.com. it's the red 1967 911 sunroof coupe.

From: Phil Weglein; I have a 1966 912 with a Shasta Big Bore Kit. I think it is 1720cc. Engine is very strong with excellent low end torque and great power. Runs quite. The best thing about the setup is the MSD ignition system. The engine does not skip a beat and burns no oil. I also installed breaker-less points. Thanks, Phil

From: Trenholme, Hello, Although the Big Bore Kit that I installed was into my 356 C Coupe and not my 912 it is essentially the same. I went to great lengths to make sure that I was achieving my compression ratio target of 9.25:1 by cc'ing the heads and checking the clearance of the pistons to the combustion chamber. Directly installing a 1720CC kit into your motor requires that you check a lot of key measurements prior to assembly as you could find yourself building a very high compression motor that won't run so well on today's gasoline. For those members of the registry who are not familiar with Harry Pellow's (a.k.a. the Maestro) you should really read his books that deal specifically with the rebuilding and trouble shooting of 356/912 motors. The Maestro is a big fan of the NPR Big Bore kit and has detailed instructions on how to assemble a motor correctly and get exactly the C.R. that you want. My engine in my 356 with 9.25:1 is almost too much for today's gas and seemed to always be running on the hot side. I have since gone the full flow oil filtering route with a front mounted oil cooler, thermostat and Oberg oil filter which has eliminated my heat problems.  think you will like the extra 120cc's that the big bore kit provides and with a properly balanced engine the performance of the engine is impressive. Great Web site, still working on my 912......I need to replace the front suspension pan and battery tray! Phil Trenholme Santa Cruz , CA.

From: Chris Smith; Hi Rick, I haven't done any mods to my 912E relative to internals yet. The next time around I'm planning on a cam and new cylinders and headwork. I'd be very interested to hear replies from other 912E owner mainly because of the heat and cpu issues that we have to deal with. Heat is already a major concern in California and other states. What effect are we going to experience adding more power?(..more heat obviously) What about cpu calibrations? Are we going to have enough room to move with our black boxes or are we going to be adding more heat because of lean fuel conditions after increasing size and/or flow? We also have major smog inspection/ calibration concerns in Calif. Anyway.. keep up the great work Rick and know how much us air coolers appreciate the site and your work. -Chris

From: Dale Deem; bore out 1820cc. dellorto carbs. dd lv nv

From: Ann & Gregg Dunphy;  I have not added a big bore kit to my 912E; however, I will be raising the compression via 914 2 liter 8.0:1 pistons (and cylinders) at the car's pending major rebuild. Combined with other improvements I'll be implementing at the same time, I anticipate 110 hp following completion of the work.

From: Patrick Van Asbroeck;  Rick, Don't know if my 912 has a big bore kit fitted to it. Didn't even know these kits excisted when I bought the car. Is there a way to check it without dismantling the engine? Different outside dimensions, whatever? Regards, Patrick

From: Jerry;  I recently had the lower end rebuilt using 1750cc big bore kit, stock cam, 050 distributor, stock exhaust and Solex P40-II carbs. I added a Permatune and the engine runs better than it ever has for the 25 years I've owned it.
Last rebuild about 18 years ago was with 1750 kit. The car has 184,000 miles and lives the good life now, about 2,000 miles per year. My main motivation for 1750cc was the cost of original equipment Mahles in 1600cc.
Locally they were pricing at about $1800 or so. For $2300 I had the lower end completely rebuilt including P&Cs, new bearings, new cam followers, reground cam, magnaflux crank, and balanced. I really enjoy this site -- excellent job! Jerry

From: William Todd;  Hi! I used the NPR Big bore kit that increases the displacement to 1720cc's. You'll see some calculations giving the size as 1750 or 1780. The correct one is 1720 cc's.
It is a "slip-in" kit, requiring no case machining. It came complete with pistons, rings, pins/clips and cylinders. The NPR# is 86P/USX9910A. I am to the understanding that these kits are no longer manufactured, and are becoming difficult to find. If anyone finds a source, I'd sure appreciate knowing about it!
There's two caveats that I know about the NPR cylinders. The rings with the kit are not the best in the world. I use Deeves rings available from Automotion, or I use Total Seal Rings from the manufacturer in Phoenix. They have a website www.totalseal.com I have used these rings in performance VW's and they are really great.
The second caveat is that big bore cylinders tend to "hammer" into the heads a bit. I just took my heads to German Precision in Sunnyvale, and my friend Ted trued my heads. The amount was .007 to .008 on each head. If the head isn't trued when you install it, it'll probably leak at the head/ barrel seal area.
I ran my cylinders and pistons for about 25K miles before I had to pull the heads and re-do them. I reasssembled the engine using a mixture of STP and 30 weight non-detergent oil that I heat on the stove in a coffee can. I pour the remainder of the "make-up oil" in the crankcase when I'm done assembling. I run 30 ND for 500 miles, then switch to Kendall 20W-50 high performance oil. I drilled and tapped my case for a full flow filter, and I do a new filter at the same time.
When using older cylinders with new rings, it's imperative that you do two things:
1) Hone the barrels to get a 60 degree cross-hatch on the walls
2) Fit the pistons to the cylinders and in particular note the piston to wall clearance. In my "top overhaul" (above) the wear limit was .008, but my cylinders came in at .004 after honing. I should have several more years of usage in the 912!
Another couple of absolute musts:
Make sure the piston pin retaining clips are seated in the groove in the pin bore. I had my first engine (that some yahoo overhauled) have a retainer come loose and scar up the cylinder. It hastened cylinder and ring wear, and was causing a compression leak. The groove was about .015 in depth when I pulled the engine. That gap allowed compression to leak, and oil blow-by.
Make sure that the copper seals that come with the kit are under the bottom of the cylinder where it goes into the case spigot. I recently got a "top overhaul" gasket set when my shop did my heads. The seals were flimsy and thin and near impossible to install on the barrels. I suspect that these seals were for the stock bore Porsche cylinders.  Specify to your shop that you want seals for a big bore kit. Otherwise, plan on one really frustrating time assembling the thing! I also am close to Harry Pellow in San Jose, and have his book open when I'm re-assembling. I know most of this stuff, but need a reference once in awhile. Harry's books are informative and useful. I used it to calculate my compression ratio, (9:1) and amount of shims, etc. You just don't get this info anyplace else!
I re-used my original heavy duty NPR seals by heating to cherry red and immediately dunking in cold water. This anneals the copper, and makes it a seal again. Believe it or not, I did it over the stove in my kitchen, and had a spare coffee can filled with cold agua. I used a wire form from a coat hanger to heat the ring and move it about so that it heated evenly. Necessity is the mother of invention!
Nothing else needs modification in the engine to accept these cylinders.
I have read of special cylinders being made of larger size that required the case to be bored larger. For the small amount of increase I don't see that as being worth it. I like the ability to use off the shelf
parts (well, kind of off-the shelf!) it's better than making a "one-off" and all the attendant problems that occur. I drive my 912 all over, and could just see being in Boondocks, Oregon with a failed cylinder!
I have considered going to a "muscle VW" engine of 2.4 or 2.5L to put in the 912. It is a bit of a hassle, but it is near bolt-up status. I would have to re-rig the throttle, since the VW uses a cable, and the exhaust and heater boxes are a bit of a mess, but it is doable. This size engine with Hi-Flo heads, a mild street cam and an improved oiling system would be a killer combination now that I don't have to smog it anymore! 'Bye! Bill

From: DAVID LOVATO; Hi! No, haven't had any mods to the motor other than a bit of discreet chroming and powdercoating/enamelling. In general I'm satisfied for now, but I have to say that I'm tempted by many of the ads I see in HOT VW's etc. concerning higher output mods for the type-4 engine. Although I appreciate the original concept (and I'm not trying to turn my car into a 911T!) I get the impression that some of the stress issues might hbe relieved by additional capacity and say 30 more horses!! Still, not contemplating that now.  So it's stock motor- no mods, and now approaching 90K!
With thanks for your dedication to us and our 912's!
R/Dave Lovato SEPT 75 912E 9126000496
Incidentally, I've just returned from a three week European sojourn on which I hired an Alfa Romeo 156 T-spark and drove about 3000 miles between Venice, Frankfurt, London and return to Venice! Great driving (much at speed, as you can imagine), but wish I'd been strapping my Porker instead (again!)
The Alfa's pretty decent, but I prefer our Porsche style!

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