Another 911SC Engine Rebuild

[porschedude996]

Hello, after purchasing my 1983 911SC almost two years ago. I’ve been working on getting things presentable. Mostly to feel good about the looks and inspire my hobby. I had all the dents taken out, cleaned trunk, interior, a couple of mods.



I then started on a know problem Transmission, which was a disaster. That’s a different post… I was comfortable rebuilding it, got all the gears, Ring & Pinion, First Gear and Main Shaft, along with all the other gears short Reverse. With the R&P, I would need to have access to the the tools to set it up. I’m confident I could have done it, but couldn’t find a loaner. Adding an LSD.




So while the transmission is off to California Motorsports.



I decided to address the engine oil leaks. No broken head studs, but i’m replacing them for obvious reasons.




So with the Cam Towers removed, took a look at the Cams and Rockers. Well those were pitted on a couple of lobs. And the rockers re-bushed, and the contact surfaces touched up. The Cams and Rockers sent to Dougherty Racing Cams for reconditioning and a 964 grind. Also found the Rocker Shafts were all worn, so new there also.



I pulled the Spray-Bars from the towers to clean them out because of metal floating around. I never saw any metallic glitter when I first drained the oil upon my first service. I did find a chunk of brown hard sealant in the tube.

The valve seals were leaking and decided to have them refurbished. Probably Guides and Seals at the least. The guy I sent them to thinks the valves and springs are serviceable.





So now to the Cylinders and Pistons. I pulled the and the Oil Ring Separators and totally carboned up. I checked the piston to cylinder dimensions and the measure .009”. They are Alusil Cylinders. I elected to buy Mahle Nikasil Euro 9.8:1 compression. They have about .0015 piston to cylinder clearance.

[porschedude996]

I also find the Lt Cam Chain loose. The IMS Gear had a tooth that was chipped about 1/4th of the tooth. Something was floating around in there. So the case was split and the good thing is the bearings look great. No specks lodged in the bearings. They were just a dark gray.





More about Cam Drive components. I’m changing all the Sprockets (6), Chains, Hydraulic Tensioners Update and Chain Wheel Supports, IMS Shaft assembly (Bearing Surface below limits). I bought as an assembly, Shaft, Sprockets, Gear, Bolts, even the cir-clip to prevent the oil shaft coupler in axial position.

I also disassembled the oil pump and saw some scratches in the rotors. I sent that off to Glenn Yee Motorsports. He refurbished, ported and polished. I also got the Updated Relief Valves from Glenn.

So currently i’m pulling all the studs from the Towers and Case to Re-Plate with Zinc and then Yellow Chromate. Hard to believe the piles of hardware on these engines.

The cases are going out to check line bore, through cleaning, and oil squirters. Also sending Connecting Rods. Trying to find a machine shop in So-Cal. Most have moved to Lake Havasu in Arizona.

[mikedsilva]

sounds like you're right on top of it. Should be a nice running motor when you're finished

[Henry Schmidt]

If CMS asks you to locate any parts for the transmission, give me a call.
We have everything you need. Don't forgot to update the tensioner arms.
We have new and rebuilt late model arms as well as out Supertec arms.

[porschedude996]

Originally Posted by mikedsilva

sounds like you're right on top of it. Should be a nice running motor when you're finished

Thanks Mike, i’m going to need to take my wallet to the Emergency Room when i’m done.

Originally Posted by Henry Schmidt

If CMS asks you to locate any parts for the transmission, give me a call.
We have everything you need. Don't forgot to update the tensioner arms.
We have new and rebuilt late model arms as well as out Supertec arms.

Thanks Henry, i’ll definitely give you a call.

[porschedude996]

While extracting the Dilavar head studs i was trying different approaches to apply heat. At first i headed the case next to the stud i was removing and it seemed a bit slow to get the heat up enough. The aluminum case is a great heat sink, or heat sucker in this procedure. Mapp Gas is hotter than butane but it wasn’t enough. So I went to the stud and heated about an 1-1/4” from case. What is remarkable is the stud distortion while heating. After I got all the studs out, I was discussing with the experts here about my removals. Consensus is to never heat the bolt. And use an oxy-acetylene tourch on the case. Now I know…

[porschedude996]

In looking ahead, I found an interesting bit of advice. I rebuilt a ‘72 911T 2.4L engine and the shafts leaked and was looking for a good explanation. I think 18-20 ft-lbs sounds good. I’ll try this and also use the rubber O-Rings, well not a circular cross section, more like a disk. My understanding is these were used in RSR’s.

Link to seals:
https://www.pelicanparts.com/More_Info/990579052.htm?pn=99-0579-052-M820&bc=c&SVSVSI=

[mikedsilva]

Originally Posted by porschedude996

Thanks Mike, i’m going to need to take my wallet to the Emergency Room when i’m done.

Haha! Welcome to the club!

[porschedude996]

Today spoke with Walt at Competition Engineering about him performing some magic on my project. From what he sees over his years in the Porsche world, with regard to 3.0’s & 3.2’s, he rarely sees the need to Line-Bore unless there was something catastrophic. Even with 150,000 miles on the clock.

Same with con-rods, even when going to ARP Bolts with higher clamping forces which in theory may distort the Big End hole. Reconditioning the con-rods is spelled out as necessary in the ARP literature that comes with a set.

He also stated the other end, at the wrist pin, rarely ware out. Previously I measured the wrist pin to con-rod rod clearance with my new wrist pins. I could only detect .001”. It was a less than ideal test rig, so the numbers are not 100%, but coupled with Walt’s knowledge, I feel good about reusing without re-bushing.

Today I applied this knowledge to my BE. I checked the BE of the rods at wrench tight, then at 50ft-lbs (ARP Torque Value), and then at .0095” to .0010” stretch value (ARP Spec). The bore of the BE never changed. The value torque value to get to the stretch .0095”- .0010” is 62ft lbs. So 55 to 62 ft lbs is sufficient to achieve bolt strength, top end of that is maximum bolt strength.

So my con-rods are cleaned and ready to go.

Chipping away one shoebox of parts at a time.

[porschedude996]

I started thinking about the cam tower assembly. I’m going with the dry installation. Maybe some window cleaner on the RSR seals to keep from damage during installation. The last 911 engine I rebuilt, I assembled the followers after head and tower installation. This time i’m assembling on the bench beforehand.

[porschedude996]

Thinking ahead again, my mind is all over the place. In the dozens of engines i’ve built over my years, i’ve always used a special lube on bearings and camshafts. Motor oil on most everything else. I know folks who only use motor oil to lube the bearings, and specialty break-in lubes on a new flat tapet cams. Otherwise only motor oil. The first Chevy Small Block V-8 (327ci) I dunked the piston with rings in a coffee can of 30w. I was the thing back in the day (hate that term, why???).

[porschedude996]

When I purchased my Mahl Piston/Barrel Assemblies, I found them pristinely clean and nicely lubed. I was thinking they were ready to install. For those that have never know the proper way to assemble any IC Engine, the rings are clocked out of alignment with regard to the split of each ring to better hold the exhaust gases in the cylinder and oil in the crankcase. Usually 120 degrees out clocking. So given that, I found the spilt openings to be aligned with each other. So with looking at the top of the piston and the top to the intake direction (Up), i’m going with 1st compression ring at 10:00 o’clockish, 2nd compression ring at 2:00 o’clockish, First Oil Ring Scraper at 8:00 or 9:00 o’clockish, oil ring separator at 12:00 o’clock, and lower scraper at 3:00 or 4:00 o’clockish. I believe that is the preferred installation especially on a horizontally opposed engine to keep oil from worming its way to the combustion chamber and causing smoky startups. Please or correct me if you feel differently.

[porschedude996]

I’ve seen it both ways. Detergent Oil or Non-detergent oil during initial start. An old question on any first fire of a rebuilt engine. Any thoughts from you smarties?

[dannobee]

Years and years ago, I watched a video on a development engine (single cylinder, lab setting) that had a marker applied to the back side of the rings, so that ring movement while running would show up on an x-ray machine. The rings were moving around pretty good. Sometimes as fast as 15-20 rpm, and not always constant, nor even in the same direction, depending on load and engine speed. After watching that, I concluded that being careful with ring clocking wasn't anywhere near as important as we all thought. But looking at any set of worn pistons and rings, you can see the wear as the rings move around the pistons.

[stevie 77 930]

Originally Posted by Henry Schmidt

If CMS asks you to locate any parts for the transmission, give me a call.
We have everything you need. Don't forgot to update the tensioner arms.
We have new and rebuilt late model arms as well as out Supertec arms.

Henry's tensioner arms are the ticket. Seen here with new, tensioners, chains and sprockets.

[porschedude996]

Originally Posted by stevie 77 930

Henry's tensioner arms are the ticket. Seen here with new, tensioners, chains and sprockets.

Hi, thanks for sharing. Do you have any pics of them outside the installation?

[stevie 77 930]

Sorry, no other pictures un-instaled. But here is a one from a long time ago when i did my turbo motor back in 2010.




Simply put, the machined bushing fits the shaft perfectly and when installed with the tensioner, there is a minimum of lateral movement (unlike using a spacer).

[porschedude996]

Originally Posted by stevie 77 930

Sorry, no other pictures un-instaled. But here is a one from a long time ago when i did my turbo motor back in 2010.




Simply put, the machined bushing fits the shaft perfectly and when installed with the tensioner, there is a minimum of lateral movement (unlike using a spacer).

Ohhh, I had that wrong in my head. I was thinking it was the whole arm. What’s he get for the bushings?

[stevie 77 930]

The bushing is integrated into the arm to create the wide idler arm.

[Lowo]

I’m pretty sure this would be a nice motor once you’re done with it