2.4 MFI --> 3.0 CIS / 3.0 carbs swap

[cds72911]

Hi all,

I'm looking for advice about an engine swap. I'm going to put a late 70's 3.0 SC engine into my '72 911 (was 2.4 T MFI). I'm wondering if anyone has any tips, advice, things to look out for, etc. when doing this swap.

I'm not soliciting opinions about whether I should do it or not - I've made up my mind and the 3.0 is a good fit for my intended use. I found a good donor engine that is owned by a very friendly and reasonable seller. I do not mind sacrificing the vintage correctness of the '72 in exchange for reliability and more displacement.

In the interest of economics (as in I only have so much money to spend on the 911 right now) I am swapping in the stock engine with the CIS fuel injection system.

I would like to put a set of carburetors on first, but for now I will run the CIS system. This is not my preferred route, but in the short run it will provide me with a running car and time to save up for the carburetors. Who knows, I may love the CIS setup.

The seller has been really great and is letting me drive the engine in the car, do a compression check and check out the head studs when I pick it up. I plan to put the engine into my car as-is in stock condition with the CIS fuel pump, 7 pin CDI unit and ignition. I am getting the fuel pump, fuel lines, oil lines, entire engine from flywheel to exhaust. Are there any other parts I should make sure to get from the donor car?

Are there any things to look out for when converting from the '72 2.4 MFI set up to a late '70s 3.0 CIS engine?

Later, I would like to change the CIS to carburetors (when my finances recover from the swap). I understand that for the street the Weber 40 IDA 3C carbs can be set up nicely for the 3.0 SC engine. I do not plan to use this as a race car, so the 46 IDA even though it may potentially put out more horsepower will not be my first choice. What will need to be done to make the CIS to carburetor conversion work? Will the carbs bolt right up to the intake manifolds without modification? Will I have injector ports to plug? Will I need any machine work?

Thanks in advance for whatever you can share.

Charlie
'72 911 T
'66 912

[This message has been edited by cds72911 (edited 06-11-2001).]

[Early_S_Man]

Charlie,

Well, the '72 had such a unique oil tank and lines that you have a real fabrication problem on your hands! I think you should get the complete oil system off the SC, including the dry sump tank and all lines, external thermostat, lines, and front cooler. Although you may be able to keep your front tank, putting the later one in would be a lot easier!

Are you planning to use your old heat exchangers and muffler on the SC engine?

The SC tachometer is needed, as well as Voltage regulator, just to be sure it is matched to the SC alternator. The fuel tank and space-saver spare are 'extras' not necessary, but something to think about, as is the 915 transaxle and speedometer!

The '72-'83 set 2, Vol. 3-6 of the factory service manuals would certainly be a good idea to ease the transplant!



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Warren Hall
1973 911S Targa

[cds72911]

Warren,

Thanks for the reply.

I am getting the oil lines and tank from the SC, as well as a sheet metal cut from the right hand side of the engine compartment (I believe the opening is larger on the SC than on my '72 T). I should have everything I'll need to "update" to the newer configuration. The question remains whether I should do this, as the external oil filler was one of the reasons I liked the '72 body. Decisions, decisions. I have SC quarters coming so "deleting" the oil filler is not a challenge, it is just an aesthetic question. I'll have to see how different the SC plumbing is.

The exhaust/heat exchanger question is one I am up in the air about. I've been told it is good for some extra horsepower on the 3.0, which would certainly be nice. However, I want to make sure whomever purchases my 2.4 has everything they need to make it run correctly with the MFI. The heat exchangers have that extra tube for the MFI pump thermostat line that they'll need. I saw replacements in tweeks that were $699, but I wouldn't want to saddle the new owner with that cost right up front. If the buyer is going to carburate, then I won't feel bad keeping them since they won't need the MFI specific exchanger.

I guess the short answer should have been, yes, I would like to backdate the exhaust to my 2.4 system.

So, I will need the SC tachometer and voltage regulator. Where would the voltage regulator be located on the SC donor? I do not think the tachometer from the donor is an option so I guess I'll have to find a used one elsewhere. Will the new tach work with the existing wiring harness or am I in for some long nights deciphering wiring diagrams by candlelight? ;-)

Unfortunately I don't have the budget for the newer 915 tranny, so I am sticking with my early one. I think mine has a lower geared R&P though, so it may not be an all bad decision. I hope I'm right on this one.

Thanks!

Charlie

[cds72911]

Another question: Is there a significant weight difference between a 2.4 and 3.0 engine (both non-ac)?

I'd assume the 3.0 is a bit heavier since it is Al not Mg. How much? Anybody have weights for these guys?

I'm thinking about suspension issues that I may want to address...

Thanks,
Charlie

[emcon5]

This was posted on Rennlist last week, the source is a book called: "Porsche 911 Engine History & Development" by Tobias Aichele
The weight listed is in kilos, and is without tranny.


64 to 68 ===== 184 kilos
69 911T======176
69 to 73 911E & S==182
74 911, 911S & Carrera 182
75 911 ===== 195
75 S, Carrera==200
75 Turbo===207
76 & 77 911====195
76 & 77 Carrera==200
76 & 77 Turbo===207
78 & 79 911SC ====200
78,79,80, Turbo ==== 230
80,81,82 SC===190
81,82 Turbo ==245K
83 SC ======200
83 Turbo ====230
84 Carrera === 210
84,85,86 Turbo === 253
85,86,87,88,89 Carrera === 219
87,88,89 Turbo ========269
89,90 Carrera 4 ======= 238
90, Carrera 2, Carrera 2 CUP = 238
91,92,93,94 Carrera 2, Carrera 4 === 238
91,92,93,94 Turbo ==== 275
95 Carrera, C4,RS ==== 232
95 Turbo === 268
96,97,98 Carrera,C4,C4S, == 239
96 ,97Turbo == 268

[CamB]

I can't help it... I call ass on the numbers.

I find it difficult to believe my 1975 magnesium cased 2.7S is heavier than the SC engines.

Sorry to be so negative. But I play the ass card.

Cam

[Early_S_Man]

Charlie,

Kind of hard to be sure about the weight of the SC engine without knowing the year and version of the engine. More than likely, 40 lbs more than a Mg engine, which is 401 lbs. Same weight in spec books for 2.4 and 2.7 CIS engines, but the USA SC engine is 441 lbs!

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Warren Hall
1973 911S Targa

[cds72911]

Warren,

It is a '79 3.0 SC engine replacing a '72 2.4 T engine - neither has AC. I believe it is a US spec (non-california) engine.

Out of curiosity, why will I need to replace the Tachometer?

Thanks,
Charlie



[This message has been edited by cds72911 (edited 06-12-2001).]

[Early_S_Man]

Charlie,

The 930/04 engine is 441 lbs.

The MFI engines had tachometer driven by the signal from the points, whereas the SC tach. is driven by signal generated by the six-pin CDI-unit.

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Warren Hall
1973 911S Targa

[cds72911]

Thanks Warren.

Does this mean I also need the whole wiring harness or will my body wiring harness plug into the newer tach and the newer engine electronics?

Oh good news, the seller has factory manuals and is letting me use the appropriate sections!

Charlie

[This message has been edited by cds72911 (edited 06-12-2001).]

[cds72911]

Also, what is the benefit of using the newer fuel tank and space saver spare? Is it a larger volume tank or something?

Thanks,
Charlie

[Early_S_Man]

Charlie,

There aren't any changes needed in the body/dash wiring at the tach. No new body harness needed, and just a couple of minor changes at the 14-pin connector.

And, yes, the later fuel tank is 21+ gallons!


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Warren Hall
1973 911S Targa

[cds72911]

I guess that begs the question: what are the changes necessary at the 14 pin connector? Do you happen to recall?

Thanks,
Charlie

[Early_S_Man]

Charlie,

No, I don't recall at the moment, but I do have a document around here that I discussed with another board member last year!
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Warren Hall
1973 911S Targa

[This message has been edited by Early_S_Man (edited 06-12-2001).]

[cds72911]

Warren,

I wan't able locate it using the search feature of the BBS. Perhaps I am looking for the wrong words.

If you come across it, I'd love a copy.

Thanks,
Charlie

[Rufblackbird]

Charlie,
What will you be doing with your 2.4MFI? Will you be selling it? Thanks!

------------------
Jeff
1976 911S

[cds72911]

Jeff,

Yes I am selling it. I have only advertised it on the Pelican classifieds so far.

I am selling it all including the whole MFI setup, fuel pump, and engine electronics (CDI box, etc.), plus all of the new parts I have purchased recently (tune up parts - plugs, wires, cap, rotor, gaskets, new metal fuel line).

The only thing I'd like to keep is the exhaust - but that is negotiable.

Charlie

[This message has been edited by cds72911 (edited 06-12-2001).]

[cds72911]

For the archives:

Up-fixin Volume VII pp.83-86 has a decent article about swapping a 3.0 into an earlier car. The article covers each of the things that need to be changed, but with regard to the wiring at the 14 pin harness unfortunately just says you need to look at the factory manual.

If anyone (Warren?) happens across more information about the wiring changes in the 14 pin connector, I would be very interested.

Thank you,
Charlie

[Roland Kunz]

Hello

Can´t see where is a problem to use the oiltank setup.

As long you use old Heatexchangers.

On the CIS you only need to fabricate the vent hose coming from the oiltank. The 914/6 or using the CIs unit on the hose end will work.

If you run newer Heat exchangers then the SC oillines need a redesigning.

SC alternators have a built in regulator.

The SC body wireloom is simpler by delting the one 14 pin connector under the rear electric board. So you have to keep your old wireloom for the electric board and fit the engine wire harness to it.

Best is using your old board and bolton the new CD unit incooperate the wires and thats it. If you will make the heaterblower functional you can make the 74 setup ( with ignition ) for later setups you have to run a wire in the middletunnel. SC do have the fuelpump in front but thats no problem.

You also need the fuelpump and the fuellines from a pre 77 CIS car.

CIS to Carb swap:

You need the manifolds the linkage your MFI aircleaner, fuelpump can reuse the MFI fuellines. The injectors are in the manifolds so no plugs like on MFI needed.

carb and MFI have the same pullrod for the acceleartor linkage. CIS has an other unit. The lehnght and the design vary.

Grüsse