I know this question probably has been asked before. So sorry for the repeat.

I have owned my 74 914 since I was 19 and am now over 40 and finally getting to put a six in her.

I have a 74 2.7 with CIS; however I love the look of carbs.

Questions are; can I use the fuel pump from the 1.8 for the carbs? Should I keep the CIS (not sure yet how well it works, pieces seem to all be there) for the better fuel MPG?
I live in northern IN pretty much 5 miles from the MI line and 35 minutes east of Lake Michigan and the change in weather here can affect their performance.
Local shop said to go with carbs for the ease of wiring the six into the 914.
I plan on using it as a daily driver when the weather is nice.

Any help or thoughts

No on fuel pump, the FI pressure is waaay to high. Carbs run on 3.5-5 psi (from memory). Recommend pressure regulator for Webers or Zeniths. Webers seem to boil over in hot weather.

Carbs were fine in early 911s and will work for you. Not as efficient, but much sexier IMO. Might want to consider PMOs. Webers offer flexibility over Zeniths, and for goodness sake - no Solexes.

And I'd look for real Webers - made in Italia stamped on.

Why not Solexes?

Not tunable supposedly ... actually 3 individual single barrel carbs mounted to a manifold. Zeniths for the same reason ... not as tunable as Webers

Carbs make noise, suck on mileage and altitude changes.

Stick with the CIS. The shop that is telling you it is easier to wire a Carb setup over CIS probably has not done a conversion and shouldn't be touching ANY car.

The only CIS that would present a problem is on the 3.0L and up with the Lambda Sond frequency valve (which is just another control pressure valve) as it would require the LS Brain and an oxygen sensor in the exhaust system or the Motronic system. Your '74 2.7L is a piece of cake to wire into the existing /4 harness.

Oh and with a good pressure regulator with tank return, you can use any high pressure pump as long as you get the feed to the carbs down to <5 psi.

I have a 74 2.7 with the CIS on it and it is fine. However, if you want to go with carbs you would be better served by changing the pistons in your engine to full domed rather than the semi domed CIS pistons. You can change the cam as well and really wake that engine up. The 74 is a good year as it did not have the thermal reactors that cooked the lower part of the engine. Check the head studs and look for case savers in the block before you do anything. If you have to fix a stud, you might as well change all the parts I mentioned, get some carbs, and put out some good power

Check with you state law's on engine swaping. Most state's require all the
emission equipment to left install on that engine when doing a engine swap.

Thank you all for your input.

Does any one have a "how to guide" to connect the CIS into the 914 wiring harness if I stay with it.

I have the CIS and would have to buy a set of carbs...so

I do, I have to find it. I know I have scanned it and sent it to folks before. As for the smog poo, it depends on the year you are putting it into and IN laws. I'll look for the diagram.

CIS is crap.

Given a choice between carbs, cis, and EFI.


EFI, carbs then CIS as a last resort.

Fuel distributors are expensive, injectors for cis are expensive. Both are super prone to getting crapped up by small particles and CIS running problems will make you want to stab babies.

Personally I would go with standalone EFI running off head temp sensor(s)

Fuel distributors rarely fail. Failure is mainly leaks or a stuck center piston from sitting for years with fuel in them. Yep, $500 for a rebuilt one or 3-4 cans of brake cleaner @ $2.00 can to clean them up. Oh yeah, and the cost of compressed air.

Mechanical injectors rarely fail. Failure of these units would be an internal broken return spring or fouling from fuel sitting in them for years. $60 each new or a couple of cans of brake cleaner to clean them or pay someone about $25-$30 to clean them.

Filters are for keeping the small particles out of the distributor and injectors just like your EFI system. Additionally, you have the leakage failure of electric injectors which are plastic toppped metal cylinders (unless late model), the potential failure of the solenoid in the injector itself and broken pintles.

Now, spit that one out again.

Ron, do you still have the CIS schematic I scanned for you? I cant find it on my computer and will have to scan is again if you dont have it.


I agree, CIS is hard to beat.

Really? 30+ year old mechanical distributors that have had 30+ years worth of fuel with an unknown moisture content floating through them rarely fail?

Been there done that, you have a 50/50 chance of that crappy distributor coming clean with brake clean and compressed air.

You are right, they do not outright fail but the control plunger metering slits get shit up, and when you decide to pull it apart and rebuild it you have a 50/50 chance of it working and running proper once together even if you do it clean room style and ensure that every mating surface is flat.

Mechanical injectors do in fact fail, the springs get weak, they leak and the mesh filter screens get full of crap because they are about 30 years old.

Also CIS injectors last time I checked were 100$ a pop for watercooled VW's. A fuel distributor? 300$ for a watercooled VW.

At this point you could have batch fire standalone fuel injection with a wideband o2 sensor. Not some shitty mechanical fuel injection that is constantly pissing on the back of your intake valves and never quite runs right.

Filters do a great job over 30+ years, apparnetly which is why I have taken apart and cleaned more than my share of CIS distributors and injectors only to have a car run immeasurably better when retrofitted with EFI or even carbs.

CIS also restricts airflow with counterpressure by fuel to avoid the metering plate flying up and in return restricts the path of airflow and you have poor throttle response.

This is not 1970, or 1980. CIS is crap, EFI or carbs are a better way to go. The only good thing CIS can do is CIS injectors rock at atomizing fuel.

Now spit that one out again.

Ok, I will ... I've cleaned up CIS Systems that have been sitting for 20+ years and they ran fine.

While modern electronics are wonderful, the EFI systems suffer from some of the same problems. While CIS is old technology, it still works pretty damn well.

No reason to junk a functional CIS system and that is why I posted what I did. Saving money is not a sin.

That's what I spit out anyway.

Good day.

CIS gets a bad rap. It's on my '74S and all I've had to do is adjust the mixture and replace the injectors once. It has superior cold start characteristics and gets good gas mileage.

I went through my fuel distributor once. Waste of time. The plunger was squeaky clean and only a couple bits of dirt were in there. The plunger, at least mine, is a solid piece of turned metal. No issues there.

Another good point is...it has one adjustment screw. One. 40IDA carbs have how many? 12? MFI, 14? EFI? (I honestly don't know). But the lack of small pieces of electrical equipment relying on low voltage is another plus for CIS.

A new 2.7 with CIS (Non-S) has 150hp minimum. Plenty of power. Save some dough and keep the CIS.

My .02

"Fine" is relative. CIS systems may run "fine" but they are crude compared to even batch fire EFI which can be had for a few hundred dollars now.

I have had CIS cars that were the best running CIS cars ever, and when I moved to a map sensor with EFI the car gained massive throttle response, was faster, and spun up faster.

Great if you want to be period correct, but CIS is a hassle worse than carbs when it does not run right. You can have a control plunger that is great until it is in place and sticking in operation for some reason.

Been there, done that. Been every which way with all CIS systems from CIS basic, full mechanical to CIS-E, CIS-Lambda, and CIS-Motronic.

I have a good 2.4 /6 set, 3.0 /6 set and 2.7 /6 set I am partial.

Aren't we all?

personally i have no problem running cis, given one factor, cost

why don't you step up to the mike and tell the man who is diggin deep for his conversion what your stand-alone efi sys is going to cost
And while we are there, lets cost out some "working" carbs
oh yeah...lets check out the pmos....cause we can
opps cha-ching pistons and cylinders too

Yup...i would say figuring out a way to keep your cis
will keep your wife happy too
cause you will be doin enuf of this before you are finished
steve

I didn’t mean to smack a bee hive with a 10 pound sledge.
Thank you all for your input. Yes I am trying to do this with out getting divorced. She doesn’t understand the obsession of a 914ner. Maybe it is because she has never ridden in one? I put the car in storage 12 years ago one winter after having to rebuild the motor and then life kind of took over and between job (way too many hours) and then starting a family other things took first place.
I don’t have a lot of money to throw at it and have been trying to save a little bit here and there to do this conversion. I was able to take a ride/drive in a local 914 with a 3.0 and I was completely struck by the “gotta haves”. The sound, the push you in the seat feeling, man it was great. He has moved away from the area and I have not been able to track him down for advice. I have been lurking here and reading everything I can to learn from this group. The thing I like best about this group is you all seem willing to help out a guy who doesn’t know but wants to know. Also, obviously; I love how passionate you all seem to be about these cars. I have owned this 74 1.8L for 22 years and have heard every thing from “you need to feed the hamster more” to “wind up the rubber band better next time”
And of course the always present “that’s not a real Porsche”. Afterwards I have taken some of these people for rides and then they “get it” and want one. There is no better car to do a reverse 180 than the 914, fun to freak the passengers out then tell them to get out and try that with their car. I don’t really care what other people think of the 914, I love this car the way it handled even with a low powered 1.8L engine and hope to one day have it as a daily driver during the sunny days around here.
Again thank you all for the advice. keep it coming, and thank you Steve for the e-mail and pictures. I will try and give you a call as I try and complete this conversion

Hey, we just share our passions here. I don't care what induction system you run. I am just a CASOB and like to make things work without running out and buying a whole new setup 'cause technology has advanced. I know it is better. I still like to tinker and make it work or, at least, screw it up worse than it already is.

I am also a old crotchy recalcitrant shithead asshole with a really bad attitude. Most of the people on the board would agree with that statement and probably add to it a few chosen words..........Don't do it Clay...........

You will get all the opinions and help here that will ensure that the clamp around your ankle with the attached chain and ball stays in place.

Same here the SS check don't go that far!

well that push you in your seat effect will really only happen with a good high HP engine IMHO if you have a budget stick with what you have. Now when the budget increases then go balls out. IMHO the webers and other carbs are a bear to tune but IF you can go PMO (I have) then you will be pleased....

I say all this again becuase I have MY opinion and that is all....:-P

CIS = Hacking the firewall to make fit
Carbs = Sweet.. but like with a type 4, you would want to re-cam the motor to take advantage of carbs

Also, some CIS parts are hard to come by nowadays.. SC owners are having the same issues (WURs for instance seem hard to find when they fail) for example. However, I liked my CIS SC vs my old carbed 914. So much "smoother" to drive.

You dont have to hack your fire wall with CIS. You do need to remove the lid latch and move it to the passenger side if you want it. I just removed the springs and the whole system for the lid and use pins now.

CIS parts are not hard to find either. Like I said, I have 3 full sets and I didnt even want them

What about the Bitz Racing EFI conversion using the CIS runners, etc? For about the cost of a used pair of Weber carbs, you can have a modern EFI system that works well and is happy with today's oxygenated fuels.

Would this be a wiring schematic we are talking about? I'd like to get my hands on a copy of that too pleeze. My 3.0 CIS conversion has been on hold for a couple years but I'm close to getting back to it and the wiring is one thing that has me worried. I have a set of Webers too, just in case the CIS is toast, but having gone the Weber route before I'm going for the drivability and mileage of the CIS.

I have not been able to find the images as yet. I checked 3 'puters. I need to fire up another one this weekend to see if they are on there.

Mike's (Dr. Evils or Evil Doctor) diagrams are for use with the point CDI system.

Your 3.0 is a hall effect reverse rotation distributor and uses the 6 pin CDI unit which is going to require some modification to the wiring diagram for dizzy hookup.

Additionally, you might want to check now and see if your alternator is internally regulated. That wil also make a slight change to the diagram for wiring.

Are you going to use the /4 relay board or wire direct into the main loom?

Yup...correct, I have the 6 pin CDI unit. Alternator is internally regulated. I'm open to using the 4 relay board or not. The car was last running a 2.4 with Zeniths and was using the 4 relay board....if my memory is correct.
Thanks

How long has this CIS engine sat around un-used? CIS injection systems don't like sitting around unused for a year or more. The gas in the system gums up, turns to varnish. Then many FI parts need to be cleaned or replaced.

If the CIS engine runs OK today, then keeping the CIS will be the cheapest option by far.

I have 2 CIS injected Porsches. The CIS fuel Injection system on both cars have been trouble-free (no failures), are tuning symplicity (1 mixture adjustment), and then always stay in tune. The 2.4L-CIS engine in the 914 has 290K miles on it now (200K in the 914). The 3.0L-CIS engine in the 911SC has 324K miles on it today(its never been apart!).

CIS related repairs for the 2 cars, for the past 24 some odd years 461K miles combined, has been:
1 set new injectors in both cars (required? probably not).
2 sets new rubber manifold boots, both cars.
add pop-off valve to both cars (preventative measure).
1 fuel distrubutor for 2.4L (because the engine was in storage for 2 years before I got it).

Putting carbs on a CIS engine will kill the gas milage. I know a fellow who owns a 914-6 with a 2.7L six in it. That 2.7L still has the CIS pistons and cams, but he installed the Webers from the original 2.0L engine on the 2.7L. He always complains that the car gets 165 miles per tank of gas, or ~13 mpg. My own 2.4L-CIS 914 gets 21-25 mpg city/hwy mix, 32 mpg on sprints up to Reno/Lake Tahoe.

>>CIS = Hacking the firewall to make fit
Nope! My 914 firewall is un-hacked. I did move the engine-lid latch and it's perch to the right side of the engine bay.