Reviving Grandpa's '75 911S

[AlexGross]

Hi all, I have been cruising around this site for the past few weeks since I have finally started a rebuild that I have been dreaming of doing for years. In 2002, my grandfather passed away and his daily driver--a Viper Green '75 911S--passed into my hands. It was his daily driver for over 20 years, and he drove it as he should have...enthusiastically. I was only 15 when I got her, and needless to say, I had neither the resources, knowledge, skills, or time to devote to restoring her to a reliable condition. I now have the time, tools, and money to at least get started on bringing gramp's Porsche back to life. Unfortunately, as the car sat unattended for several years in my grandma's garage, it was attacked by mice, time, and the wet weather of the Pacific Northwest. These abusive conditions ruined the already worn interior, most of the vacuum hoses, fuel lines, and undoubtedly didn't help the already leaky engine. So, six months ago I stripped the interior to the bone, dropped the drivetrain, and disassembled the body. After having some of the body panels sand-blasted, I hand stripped the rest of the body and sent it off to the body shop for steel-work and paint. I decided to stay with the original color, and a month ago it was returned to me looking fantastic!

I have now turned my attentions to the drivetrain. It was rebuilt about 30,000 miles ago (new cams, crankshaft, bearings, valves, pistons, cylinders) after an oil pump failure prompted catastrophe. I am hoping that I can avoid tearing into the bottom half of the block, and as it stands now I am planning to replace the stock valve covers with aluminum turbo covers, swap out the restrictive '75 exhaust with 1.5" stainless headers and a 2-1 muffler (it will be a warm weather street car), remove the remnants of the air injection piping, replace the ignition wiring with the Magnecor set I found on Pelican (and new spark plugs), and replace all of the fuel lines and vacuum hoses and fan belt. This is just my preliminary list, and I would appreciate any advice that you all might have to send my way!

I have had one real scare during the breakdown that I would love some advice on. When I went to remove the intake manifold I noticed that one of the two nuts was missing on the 3rd cylinder and that after the mani was removed that there was a small amount of water pooled on top of the thankfully closed valve. The body-shop had steam cleaned the block recently, and I think some water must have gotten in then because there was little to no rust. I cleaned out the port with a cloth and air gun and then hand-cranked then engine with a little engine oil added to the ports. The rest of the valves and ports looked pretty clean (see pictures) but I was wondering if I should get the heads off and take a look.

I was happy to find that all of my head studs seem to be intact (although without case-savers), and that my grandpa had replaced the standard spring loaded tensioners with hydraulic pressure-fed tensioners.

Anyway, I know this was a lengthy first post, but I am excited to get this baby up and running and to get some sagacious advice. Hope you enjoy the pics, and wish me luck...I plan to lay siege to the heat-exchangers this weekend (fingers crossed for no broken HE studs)!

[Walko]

The car looks nice enjoy the slippery slope of Porsche ownership

Michael

[Steve@Rennsport]

Hi Alex,

Well sir, the first I must tell you is what a dynamite color that is and I'm very pleased that you kept it that way. Its a period item that makes your car very distinctive.

JMHO, but I think you are on the right track with everything you've planned and I'd simply add that the key to long-term survival of these magnesium-cased engines is strict control of oil temperature. To that end, you should install the factory optional front oil cooler package, replacing the OEM trombone cooler with a later Carrera radiator-type and fan. This will contain peak oil temps and help prevent head studs from pulling.

Make certain you install a pop-off valve in the airbox to prevent the backfires from cracking the whole thing.

Replace all the rubber suspension bushings, shocks, and perhaps Turbo tie-rods to restore the ride quality & handling.

I hope to see your ride at one of John Walker's swap meets in August.

Hope this helps,

[PFM]

Alex,

I think you will make grandpa proud! Keep us posted it should be a great project with a super history for you.

[eastbay]

I would tear it all the way down and split the case and inspect. If everything is all right it will have only cost you time and gaskets. If anything is wrong, you can fix it and avoid a catastrophe.

[porterdog]

Originally Posted by AlexGross

...Viper Green...

I'm Viper Green with envy!

Hi-res pics required.

[fanaudical]

I'm not sure I'd split the case unless you have indication that it's necessary. These mag cases sometimes warp upon disassembly and don't go back together nicely without line-boring or additional machining...

[Steve@Rennsport]

Originally Posted by fanaudical

I'm not sure I'd split the case unless you have indication that it's necessary. These mag cases sometimes warp upon disassembly and don't go back together nicely without line-boring or additional machining...

Absolutely true.

[AlexGross]

Thanks for the input guys, this is my first rebuild attempt and I'm kind of learning as I go along. I don't think I'm going to split the case, for now I'm just going to remove/clean the camshaft housings and heads...once I get a look at the cylinders and pistons I will decide whether I need to get them worked on. I got about half of the HE nuts off yesterday without destroying any head studs, and am going to go work on the rest of them today.

@Steve: I was thinking about updating the oil cooler, but unfortunately my car doesn't have the trombone oil cooler installed. I was wondering how involved/expensive it would be to run the lines and upgrade to the fan cooled external unit. And as for the August swap meet...I'll put it on my schedule!

@porterdog: I'm glad you like the color, I'm going to roll her outside today and get some pics that will do her justice. I'll get them posted ASAP.

[AlexGross]

Update from the weekend. I attacked the heat exchangers on Saturday after a week of applying penetrating oil to the studs every day. I had read so many cautionary tales about breaking off the exhaust studs that I took every precaution to avoid doing the same. The first one came off with a mere flick of the wrist...the others took some encouragement...but I am happy to say that I somehow avoided breaking any studs and only had one thread out of the block (see pic). Evident in the picture, I have found that my oil return tubes have been hemorrhaging precious oil for some time and will need to be replaced--not a big deal as I am planning to remove the camshaft housings to inspect the heads, valves, cylinders, pistons, etc. Although the engine was rebuilt ~32,000 miles ago, I think that I ought to at least tear down the top end, clean it up and inspect for pitting/corrosion.

Also, on Sunday the wonderful fall weather here in the Pacific North West (primarily rain) finally broke up and I was able to roll her outside for a little photo shoot. In the better lighting I found some issues that I am going to take up with the body shop--namely the front valence fit gap, and some other minor scratches--but overall I am very happy with the finish and fit. Enjoy!


Alex

[notmytarga]

You are embarking on the same project I finished in 2008 when a broken exhaust valve forced the rebuild of the 1975 911S engine in a car I had otherwise finished restoring.

These cars didn't come with the trombone cooler unless equipped with AC. I live in HOT Redding CA and I chose to add the finned oil line setup to a 28 tube brass cooler. Opinions seemed to support that for a 2.7 engine the radiator cooler isn't necessary for non-race use. I can motor about on 100 F days and see temps run up to 180F fast then the thermostat opens, temps drop to 160F then slowly climb no higher than 200F. Before the cooler setup was added to the rebuilt (clean block and attached oil cooler) 220F was easily a problem. In the Pac NW you could likely get away with the extra oil volume and finned lines to a trombone cooler - if you don't add AC or track the car.

The rebuild 30,000 miles ago is a bit suspect because they didn't do headstud inserts and you have all the leaking too. Did they do valve guides? Your list addresses items that would suffer in the oil pump failure but not all the reliability updates. And how do you really know that the inserts weren't done - it is really hard for a novice like me to tell without removing a stud and checking with a magnet.

What is the total mileage on the car? And do you have a rear reflector? The 1975 is a year when they had threaded studs and CAN'T be pried off and left intact. I got really lucky and found a NOS reflector to replace the original that was loosing the reflective paint that I couldn't restore satisfactorily.

Looking good!! I too would want to get it on the road soon. Perhaps drive that engine until other problems require total teardown.

[AlexGross]

@notmytarga: Thanks for the advice on the oil cooler, I think I might spring for a radiator style cooler while I have her torn apart for the winter--while I don't plan on adding A/C or tracking the car right now, I would hate to cut corners now and subsequently regret it during a "spirited" drive through the countryside . As for your questions, the total mileage is 169,497, and during the rebuild at 133,400 miles they did replace the valve guides (both intake and exhaust). The reason that I have asserted that they did not put in case savers or time serts is that I have found no record of them in any of the service records that I found in the car--although the service records only go back to 1987. The complete list of replacements from the 1997 rebuild is:

• Cam Chains
• Ramp Counter Shaft & Sprocket
• Air Intake Boot
• Main Seal
• Cams & Rocker Arms
• Full Gasket Set
• Clutch Assembly (Pressure Plate, Door, Cable)
• Fuel Distributor
• Steering Bearing
• Main, Rod and Cam Bearings
• Pistons & Liners, Intake/Exhaust Guides
• Oil Pump, Cooler and Oil Lines

I will take a closer look at the head studs next time I get a chance and see if I can ascertain whether or not case savers have been installed...And lastly, I think that the mirror had been removed years ago by my grandpa.

One funny thing that I did find (I don't know if it is stock or not) is a dash-mounted radar detector that looks like it came off of a cold-war era submarine.



When I last drove the car, I turned the dial on the back of the device and it emitted a constant high-pitched tone... If anyone knows what it might be, feel free to let me know, and I can get a better picture of it as well.

-Alex

[JeremyD]

check elephant racing for their finned lines. Mine did not come with an external cooler - so I added two - although I did custom for a 3.6 conversion. (Earl's plumbing big mouth oil coolers (-16AN fittings)- ER finned oil lines)

Porsche 911 Oil Cooler kits - Elephant Racing

there is also a company BAT Inc in Sarasota that sells aftermarket coolers.

The key to 2.7 longevity is keeping it from getting hot.

[AlexGross]

Just to clarify the question in my last post: I have tried the gravity/inertia method to separate them (ie. rag on the floor, tapping the housing on stacked 2x4s to get the alternator to drop out Fan Removal Help / Engine Mystery ), I have tapped with a soft hammer, basically anything that I thought wouldn't destroy either the housing or the alternator. Should I try to heat up the housing with a torch like I did to remove the nuts from the exhaust studs, or will that not work with the magnesium like it does with steel? Another thought I had was to take a sheet of plywood or piece of steel large enough to cover the face of the housing, drill a hole in the middle of it for the pulley shaft, and then tighten down the nut on the shaft to use its force to pull the alternator out. Anyway, I know there are many pelicans out there with a great deal more knowledge and know-how than I possess, so I humbly extend my request for your wisdom.

Thanks,

Alex

[flat6pilot]

Getting it pressed out by a machine shop would be the safest. Maybe $10 for them to do it and have them bead blast it while it's there.

[preston_brown]

put a pillow under the alternator and then drop the fan shroud with the alternator face down onto wooden boards. Space them far enough apart to let the alternator fall out. DO NOT pound on the long bolts, they will bend. Trust me.

[tom1394racing]

John Walker's gravity method will work every time. Sometimes gravity needs a little help

Treat the interface surfaces between the alternator and shroud ring with your favorite penetrant and let it soak in overnight

When you are ready to separate the alternator, set up like Preston described but rather than just dropping the shroud ring, you may need to pound it into the wood blocks. Several good smacks will get it started

[AlexGross]

Hey guys, thanks for all the help! I soaked the tight areas with Pentro40 for a few days in a row and then tried the gravity method again. To my delight, after only a few forceful smacks, the alternator slid right out safely landing on the pile of rags. Now its time to clean the housing up for paint and take the alternator to the shop for a rebuild. Also excited to hear that the p202 cam socket and 46mm crows foot I ordered are en route, so I will soon be able to get the rest of the top end torn down and start the fun part...decarbonizing, cleaning, machining, ordering parts, rebuilding, installing, and then--burning rubber . Thanks again for the help, without it I guarantee that I would have some bent bolts, and an alternator still firmly lodged in the fan housing.

Alex

[AlexGross]

So after a lengthy break I have finally started working on the teardown again. I removed the air injection piping, and then started working through the steps in Wayne's book to attempt to get the heads and cam housings off. Everything went relatively smoothly until I tried to remove the cam nut with a Brand-X 46mm crows foot that won't fit into around the nut in the left side chain housing. I am going to go visit my local Porsche garage to see if they will loan me the real tool. I discovered one other thing that caught my attention, and I hope that someone might be able to give me their two cents...
When I removed the internal oil thermostat, a rather ragged and corroded piece of steel was found protruding from its base.



As this is my first 911 engine, I am rather clueless in any sort of diagnostics, and I am just wondering if this is normal or if there is something quite wrong with my thermostat. Thanks for your help guys!

For what it's worth, the cam towers and the chain housing internals looked nice and clean, and I was stoked to get my first glimpse at the guts of this old 2.7.

[AlexGross]

After a prolonged hiatus I have finally made some more progress with my tear-down. I got the correct tools, and then took the weekend to remove the cam towers and heads. This afforded me my first view of the pistons and cylinders and I have some pretty encouraging news. The cylinders are Nikasil (slightly magnetic), and they appear to be in very good shape--there is no pitting or scoring and the cross-hatch hone pattern looks great to my untrained eye. Additionally, the valves (although heavily carbonized) are seated very well, have no cracks or apparent damage, and if machining is deemed necessary, they all have plenty of material to be re-worked.

Nikasil Cross-Hatch:


Right Side P&C's:


Heads/Valves:


With this latest step, I have a few questions that I was hoping that someone might shed some light on for me.

1st: Should I pop the cylinders and pistons out of the block to clean them up, or is it possible to decarbonize the piston heads as they are? The pistons only have 30,000 miles on them, so I imagine that the rings are good, and I would prefer to leave them unperturbed if at all possible.

2nd: Should I send the heads out to be reconditioned or just decarbonize them and clean them? The valves and valve guides were replaced at the same time as the pistons as were the cams and rockers. I think that mechanically everything is probably ok, but I don't know if I can thoroughly clean the cam towers and heads with everything assembled.

3rd: I have been trying to find out if there are case savers installed in this block, but I haven't had any definitive evidence one way or the other yet. None of the head stud nuts were loose, and there was no blow by on the heads...indicating to me that the studs have been tight since the last rebuild.

Here is a picture of what I hope is a case saver or helicoil...any opinions?



Thanks for the advice! I'm really excited to get this baby back together!

Alex