1978 911 SC Engine Rebuild

[casor]

1978 911 SC engine rebuild and restoration

Posting some photos and information on a 78 SC engine that I am just about ready to stick back in the car. Hoping that this can help someone else with their rebuild or resto.

The car barely ran when I bought it with 80k miles as it had two broken head studs and so the engine required a complete rebuild. This is a common “SC” thing and furthermore I suspect that it was not very well maintained as it needed pistons and cylinders.

There was a lot of “while I’m in there” going on, but I really didn’t want to do this again so I just did what I felt I should do. One of the main goals was to keep the engine pretty much stock and to make it nice to look at. Bill Boys of Possum Hollow Motorsports did the engine and transmission rebuild. All the ancillary stuff I did myself.

Engine rebuild items:

• New Mahle 3.0 pistons and cylinders
• Raceware head studs
• New valves, seats, seals, springs, rockers and shafts
• New connecting rod bearings
• New engine mounts
• New engine wire harness

I did not attempt to up the compression nor do anything fancy internally with the engine for more power. These cars are not that fast anyway and I wanted something reliable. Plus, there seems to be a much greater upside in this regard with an aftermarket exhaust, so I did that instead for a bit more “smoke” and a lot less risk.

Modifications:

• Elimination of the smog air injection pump and lines
• Elimination of the cat (shhhhhhh!)
• SSI headers - which are each 3 into 1 and therefore have no crossover to the other bank
• Dansk 2 in 2 out stainless muffler
• I had to modify the car’s rear valance and side skirts to accommodate the dual exhaust vs the single exhaust normally found.
• Silicone spark plug wires
• Turbo lower valve covers
• Elimination of the deceleration valve on the CIS system
• Airbox pop off valve
• Solid state voltage regulator

Restoration, refurbishment and replacement items:

• Rebuild of all CIS electronic systems – control pressure regulator, electronic air valve, fuel pump, fuel distributor
• New fuel injection lines
• All hardware re-plated gold cadmium as appropriate
• Brackets, surrounding shrouds, fan housing, duct tubes, engine mount beams and other fittings powder coated black
• Repainted the fan half black, half white for you Messerschmitt fans
• New hoses and tubing
• Rebuilt the original alternator
• Rebuilt 915 transmission
• New ignition coil
• New heater tubes
• New CIS boot (“bishop’s hat”)
• New CIS warm-up injector
• New CIS gaskets and seals
• New heater fan motor (I rescued the expensive squirrel cage!)

In a later post I will go into some detail on the above

[Geronimo '74]

Lookin good!!

What's the deal with the bicolor fan???

EDIT, Messcherschimdt fans, I missed that the first time round.... So there is no practical use?

[TibetanT]

I am in the process of rebuilding a 1978 3.0L and am interested in where you obtained the new plastic fuel lines. I was planning on using steel fuel lines from a later CIS (1983) system.

Just curious as to manufacturer/supplier of the plastic lines since that would keep it stock.

Good job!

[OldTee]

Very purdy!!

Hate the idea of putting that in a car and driving over a dirt road!

Add to modification list: Pressure fed chain tensioner kit.



Couple of questions;

Did you split the case?

If not, why not?

Question is to spark debate. At what point is splitting the case recommended? Kind of a cost benefit question.

When I overhauled my 79SC engine with 150K miles I did it all. Found a punk oil pump and bad lay shaft bearings which I blame for the hot running condition at the track.

Nice

[jwasbury]

Nice job!

Amazingly clean.

[casor]

Guys - thank you for all the comments.

I am not racing this thing. It's a Sunday and trip car only.

Bill of Possum Hollow who has over 30yrs of aircooled exp recommended that I not split the cases so I deferred to his judgement. Yes, it does add a new dimension in cost to the rebuild but since I had already overspent I didn't care either way. I just wanted a reliable unit and he said the bottom end was fine.

Re the fan, Messerschmitt 109 pilots customarily painted their spinners so as to confuse the enemy (us!) and since I am a student of WWII aviation, I thought it would be a fun thing to do. I contemplated a spiral but, since I was doing the painting, that seemed a bit advanced.

I obtained NOS FI lines (for the 6 cyls only) on ebay really cheaply - the other lines seemed OK so all I did was replated the fittings with them still attd to the plastic lines. A buddy with a 512 BB Ferrari did the same to his CIS system w/o issue. Certainly, braided steel lines would be better but it seemed at the time quite exp to do.

CIS system - the gas we have today really plays havoc with CIS. The alcohol compromises the plating and the water that the gas attracts corrodes the naked metal. Plan here is to use avgas with pump gas to reduce the alcohol content and also to use Stabil all the time.

Anybody recommend an MSD ignition and if so why?
Rob

[casor]

Couple more things.....

Not obvious from the photos are the bronze Oilite bushings that I had a machinist buddy machine to both fit the throttle plate on the engine and the shaft for the bellcrank assembly. Likewise, I did the same for the bellcrank linkage that hangs off the side of the transmission. I could not find metric sized bushings, so I needed to have these things machined to fit. The bushings were interference press fit into both the throttle plate and the trans bellcrank. The result is a very free moving, but a no play throttle linkage.

The plastic bushings available simply did not work. These fit the shaft OK when it was not installed on the throttle plate, but once installed with a slight press fit, they wound up binding the shaft. No good. In essence, the things were too soft and had a high coefficient of friction.

Note that on the trans side of the engine, I plugged the two CIS decel valve ports - hard to see. Eliminating the decel valve eliminated quite a bit of ugly plumbing.

The valve covers are powder coated bright silver and I painted the "Porsche" nomenclature with red epoxy after sanding lightly.

To mount the clamps for the spark plug wires, I pressed in a couple of rubber "well nuts" into the existing holes in the fiberglass shroud. These compress when you thread a screw in them and are very secure.

Rob

[Steve RSM]

I thought mine was coming out pretty clean until I looked at your pictures. Awesome.

[casor]

Steve - thank you for the comment! If you knew how much cleaning, and plating and powder coating and parts searching went in to just this lump, not to mention the money, you would faint. A labor of love - perfectionists lead very frustrated lives. If I can be of any help with yours let me know.
Rob

[euro911sc]

Very nice work, Rob. I thought the Messerschmitts had a spiral pattern on the nose cone? Not a half'n half?

[casor]

Euro - thanks for the comments and great to hear from a Luftwaffe enthusiast! There were many variations on the spinners on Luftwaffe aircraft. Yes, there were alot of spiral jobs but there were also many 1/2 and 1/2 of diff colors and even 1/3 and 2/3's. Attd is a photo of the Bf-109G in the Speyer Tech Mus just south of Frankfurt. This thing is a work of art......
Rob

Thanks for the post!!

[cay-ahe]

Looks great! Nice work.

[andster]

That is a beautiful engine. I am doing similar work. Where do you get porsche decals (i.e. on your fan housing strap)? Also, how did you plate the fittings and is it expensive?

[casor]

The sticker PN is 93000651000 and is avail from our host - note that there is a 20% m/u since it comes from Germany.

The hardware was gold-CAD plated and yes it is expensive to do. Plus the parts must be degreased and cleaned up before sending them to the plater. I degreased the parts with lacquer thinner and then ran them through a rock tumbler with abrasive stones and sand. Some I glass beaded and some of the common nuts and bolts were replaced with stock items from Wurth if the originals were too bad to be saved.

FYI, do not throw away anything -and I mean anything - until the car is back on the road so that new parts can be matched up against the bad ones.

Rob