2.7L CIS Upgrade

I have a 1976 911S Targe 2.7L CIS. I have read Bruce Andersons Porsche handbook on the available upgrades for this engine. He suggests replacing the CIS with Webers and going to E or S cams. He also recommends backdating the exhuast system to a 1974 style. I have done the exhuast upgrade. I priced the weber/cam upgrade and for the same sort of money I can look at upgrading to a 3.0L or 3.2L. Are there any other options available. I have read numerous requests on web sites with similiar questions about performance upgrades for 2.7L engines. There is always a lot of concern about pulling head studs. Does anyone know of an aftermarket fuel injection system that would allow the use of more aggresive CAMs? Has anyone installed a supercharger on a 2.7L CIS engine? I have heard of an outfit in Knoxville that does some supercharing but I cannot find their name. The other option is to try to find a mechanical fuel injection system. This seems to be an impossible task. Any help or information would be greatly appreciated.

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If you've read Bruce Anderson's book, he tells you the name of the outfit in Knoxville in that book. I think it's called Supercharging of Knoxville, or something like that, but check the book--I don't have it with me right now.

I have an opinion on aftermarket systems, but I should warn you first that I do NOT have, and have never had, a 2.7 CIS engine. I have a 3.3 (actually bored and stroked to a 3.5) CIS engine from a 78 930, from which I have extracted the CIS and the distributor for a stand-alone fuel and ignition computer.

There are several options for this--the big 3 for Porsche seem to be Electromotive (the cheapest, but the hardest to program and not as tweakable as the next two), Zytec (more precise fuel computer but relies on a distributor instead of direct fire for igniton, I think, and more expensive), and Motec (basically the best around, and priced likewise). There are others--Haltech, EFI, etc., but I haven't run into too many people using those systems on their Porsches.

Also, the vast majority of those who use the first 3 use them on turbo Porsches, so they might be overkill on relatively smaller, normally aspirated cars. Maybe with them, Webers and hotter cams are the way to go, as Bruce says. Dunno. But to squeeze the most reliable, safe power out of a turboed car, at least, the aftermarket systems can't be beat.

The answer to your question depends entirely on how much money you are willing to spend. A 3.2 swap is probably the most bang for the buck and you can later extract more power from it when your wallet recovers. I have spoken with the Supercharging of Knoxville folks many times and have driven a 3.0L car with one installed. They do not do 2.7L applications - I don't know why. The centrifugal blower runs $5K, the whipple runs +$7K. Huge bucks for no more than you gain. A friend has had BOTH on his '78SC and had them both on the dyno - no guesswork here. The stock engine with SSIs put 185HP to the rear wheels. The same engine with the whipple put down 260HP and blasted high 12's in the quarter (he runs the piss out of this car). The engine had to be rebuilt two times 'cause he blew it up using too much boost. Only a 3.3L tubo block can take the stress of a blower or turbo at boost. Unless you have deep pockets or are willing to lock the boost in at a low level - and leave it there - I wouldn't do it.
The most you can expect with cams, webers, and exhaust on your 2.7L is maybe 25HP, and you just spent $4K. Aftermarket fuel injection systems alone cost this much and more. That is why the 3.2L swap starts to look so good - and you can sell your motor to lower the cost even more!

Thanks, I found the address for Supercharing of Knoxville in the back of the Bruce Anderson handbook. Basically I want to go to more aggressive CAMS but the CIS will not allow it. The CIS sets the fuel injection rate based on the vacuum created by the engine. With more aggresive cams, there is more overlap and less vacuum created which in turn screws up the CIS. This is all spelled out in the Bruce Anderson Porsche 911 Handbook. I have hesitations going to Webers. Although it will allow me to go to more aggressive cams, I live in update NY and I'm woried that I will have to tune them seasonally. I like the simplicity of the CIS. My other concern is that I'm looking at a pretty good dollar to pick up some 40IDA webers and have new cams installed. I would love to find a mechanical fuel injection system, but they are rare. Do you know if the fuel injection systems that you mentioned set the fuel rate by the engines vacuum? After installing these injection systems would I be able to go to more aggressive cams. Thanks for the help.

John, if that last question is to me the answer is yes, but also heed what Brian said--these systems are not cheap! My full TEC II cost me 5 grand installed. Zytec is at least 8, and Motec, I believe, is more. Spending that kind of dough to sex up a 2.7 doesn't make a whole lotta sense to me, but we're all different! The engine swap makes more sense for dollars per reliable horsepower.

Not sure what all is involved and what you're looking for exactly but, I was hanging out at www.paulwier.com and he does some 2.7 mods... 2.7 to 2.7RS, 2.8RS and 2.9. From the reading there, it sounds like he has the parts to do just about anything you like.

Mark
'74 911S

I'm not having any issues with webber tuning in Omaha, NE where we commonly range from 100 degres / 90% humidity to 15 below

Based on this I wouldn't worry about retuning for weather.

I wouldn't be afraid of Webers, they are more simple than CIS and clean up the engine bay as well. If you don't try to achieve perfect fuel/air ratios all the time then seasonal tunes aren't necessary. I have found Webers to be more tunable and easier to work on than CIS, more power potential, but reduced gas mileage. Drivability does not suffer. They free you to modify the engine for much more HP. All this comes with a pricetag though. It's probably more economical to sell your setup and swap in a 3.2L. I have a complete MFI stock unit off a 2.4L that I converted to Webers for the reasons listed above. I do not know how or if you can make it work on a 2.7L, if you're interested let me know.

Thanks for all the information. Brian B. why did you remove the MFI from the 2.4L. My understanding of MFI is that this type of injection will still allow the use of a more aggressive cam. Did you notice a big difference between the MFI and the Webers? Let me do some research to find out if the 2.4L MFI may be installed on my 2.7L. I appreciate everyones input. If anyone is interested, these are my final conclusions on the upgrade; I have abadoned the notion of any type of supercharer or fuel injection replacement. I can't justify the cost of either of these. I bought the car bought $6500. Since then I have installed oil fed tensioners, headers & two inlet sport muffler, carpet kit, raceware head studs, tires, alternator, volage regulator, warm-up regulator, etc. If I can find a pair of 40IDA Webers at a resonable cost I may make the conversion, otherwise I may be done for a while. I realized that the 2.7L engine was not very sought after when I bought the car, but I did not think that I would reach the cars potentional upgrades in one year. I don't have anything left to figet with. Does anyone know what a pair of webers is going for? I have seen anywhere from 1K to 2K.

John,

I know Motor Meister (www.motormeister.com/html/911_weber_kit.html) sells a complete kit for $1995.00. This includes all the fuel system parts to convert over to Webers. They also sell a Solex kit. Vertex Automotive (www.**********.com/c2used.htm) has some used carbs for sale. I've never called as all my money is tied up in just trying to get my car running.

Mark
'74 911S Coupe

I removed the MFI for several reasons. The first is repair and rebuild costs if any part of the system malfunctions - very expensive. The second was tunability. The engine produces no power - I mean none - if you open the exhaust. I couldn't find any information on tuning. Third was simplicity. Webers are easy to tune, lots of information on them, they accomodate many engine modifications, and they look good. I cannot tell you if there was a HP difference because the 2.4L was bone stock. When I put headers and supertrapps on the care it lost power. When I put the stock (restrictive) muffler back on with the headers it ran as if stock once again. The Webers and supertrapps went on at the same time so I could tune it from both ends easily for street or track use. This did make a noticable power increase. Webers go for $1K used to $2K new. Unfortunately you do reach a performance plateau very quickly. From this point it gets real expensive real fast. My current car has CIS. I have considered a Weber/cam swap with it but it just runs too good - actually perfect with SSIs and a modified sport muffler. Also gets mid 20mpg on the highway. The Weber 2.4L only got 20mpg at best. I did make a ram air setup and sealed the airbox for a very noticable increase in power. Concerning the MFI swap - you need some way to run the fuel distributor. The stock setup used a belt that ran off a cam gear in the back of the motor.
Add on - Two members in my local PCA have 2.7L cars that they converted to 2.7RS specs with Webers and SSIs. These motors run really well and both dynoed at around 225HP - more than my 3.0L I'm sure. Another option!

[This message has been edited by Brian B (edited 01-11-2000).]