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Jerry's 912 engine rebuild

I have been in the process of restoring a 67 912 for about 3yrs. Here is a thread on the progress Jerry's 67 912 restore
I have been working very close with Comp Engineering on rebuilding a 67 912 engine I acquired.

This is what I started with



I will try to make this as informative as possible. By the way this is my first engine rebuild but with Walts help from comp I will try to give as much detail as possible.

Stay tuned
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Jerry McAbee
1967 912
1968 912
2002 Tundra 4x4
Old 07-15-2010, 10:16 PM
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Jerry, ever feel like someone is following you?

Still enjoying this journey from afar....

Dion
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1968 912
1974 914-6 3.2 conversion (gone, but never forgotten)
2006 VW Jetta tdi
2009 Subaru Forester
Old 07-16-2010, 04:28 AM
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Glad to see the support I may need it. If any one whats to add or question any thing I post please do. I will do my best to be as accurate as possible I have never claimed to be perfect.

I didn't have much back ground on the engine before I purchased it. I know it had been sitting for 7-8 years. It was converted to 6 volt and it had a s90 flywheel to work in a older VW.

After tear down I found it to be all original. Looks like it had never been rebuilt before.

Original piston and cylinders were worn out with 2 compression rings broke. and a lip on the top of the cylinder bores.




The heads didn't look to bad one of the spark plug treads was bad. I installed a tread insert and really screwed it up. Not cheap to have fixed. Come to find out the heads needed to be rebuilt any way.



Here is a list of parts and condition

Crank good standard
rods rebuild-able
cam reground to 331-s spec
case line bore standard.
flywheel unusable s90
carbs need rebuilt

If you are thinking about do a complete rebuild I would strongly suggest having the inspection and machine work done by a professional Porsche shop like Comp Engineering I know there are other but I have not tried them. With Comp Walt will walk you throw any questions you might have the hole way throw your build.
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Jerry McAbee
1967 912
1968 912
2002 Tundra 4x4
Old 07-18-2010, 05:45 PM
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Lets talk about piston and cylinders.

The japan big bore kits for about 800.00 I was told you have to run a low compression.

The LN are about 2,000 dollars I'm sure they are good

The mahle are about 3,000 and stock bore.

Walt suggested JE race pistons 86mm with 356 cast iron cylinders CE price 1,350 street edition and 1,550 race. Good for 100,000 miles

I purchased a set of 356 cylinder for a fellow pelican 100.00. Walt had a good used set of JE pistons. CE bored, honed and gaped the rings ready to install. I got a nice set of P&Cs for about half the price.


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Jerry McAbee
1967 912
1968 912
2002 Tundra 4x4
Old 07-18-2010, 08:58 PM
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Shasta Design Pistons

You might want to check out Duane Spencer's Shasta Design pistons & cylinders as well

Piston and Cylinder Sets
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Rick Becker
'66 912 since 1977, '68 912 SWT since 1985
PCA 912 & 912E Register Advocate, 912 Registry Member #0001
http://912register.pca.org | www.facebook.com/PCA912Register | Twitter: @PCA912Register
Old 07-18-2010, 09:23 PM
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Head work
As I mentioned before I screwed up one of my heads by putting an thread insert for one of the spark plug holes.
CE is one of the pioneers of welding damaged heads and restoring them to new. Here is some pictures of my head being restored.





Walt and his welder



Me watching














Heads resurfaced with new guides,valves,springs and one spark plug hole repair.
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Jerry McAbee
1967 912
1968 912
2002 Tundra 4x4
Old 07-18-2010, 09:32 PM
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Thanks Rick The 911 forum has tons of info on engine rebuild I would like to see this forum with more on the 912 rebuild.
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Jerry McAbee
1967 912
1968 912
2002 Tundra 4x4
Old 07-18-2010, 09:57 PM
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Rocker assembly

The rockers were usable. CE resurfaced the rocker face. Here is the assemble process

notice the offset of the center bolt on the rocker stand

both sides are assembled the same










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Jerry McAbee
1967 912
1968 912
2002 Tundra 4x4
Old 07-18-2010, 10:43 PM
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Very interesting. Please keep the progress reports coming.
Old 07-21-2010, 08:58 AM
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Cam and Cam gear

The cam that was in the original engine was a standard wide lobe. There was a little pitting on the lobes. Walt suggested a 331s grind. I know there are a lot of different grinds for these cams, I can't tell you the difference. I was told this 331s grind is a good street cam with power from 2000 rpm to 5000 rpm.

original cam



I made some notes about installing the cam gear



Notice the notch in the cam, bolt hole and timing mark in the gear for proper timing and special washers.




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Jerry McAbee
1967 912
1968 912
2002 Tundra 4x4
Old 07-21-2010, 05:21 PM
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Crank and rods

The original crank showed no wear no cracks. Clean and polish was all that was needed.

The rods were re bored,new bushings and balanced.




Notice each rod and cap have matching #s don't get them mixed up. Some of the #s might be ground off so keep them as sets.

When installing the rods on the crank the #s must be on the same side trust me I tried it the rod got stuck, thankfully no damage to the rod or crank.
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Jerry McAbee
1967 912
1968 912
2002 Tundra 4x4
Old 07-21-2010, 06:01 PM
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Crank and rods continued

Crank

Don't forget CLEAN CLEAN CLEAN
Clean everything with acetone and a Qtip. If Qtip comes off dirt clean till Qtip comes off clean. This goes for every mating surface.



Notice the crank holder is just a piece of metal with a hole for the gland nut.

Rods, rod bearings and nuts
The rod nuts can not be reused they must be new.




Install rod bearings on rods keeping the rods and caps as a pair. We used Permatex ultra slick engine assembly lube. Put some lube in the crank oil hole and on bearing surface. Install rods with numbers up on crank rotating rod to evenly distributing oil on rod bearings. Put rod cap on make sure numbers are on the same side. Thread on new nuts. Put all the rods on first then torque to 32.5 lbs per Porsche manual


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Jerry McAbee
1967 912
1968 912
2002 Tundra 4x4

Last edited by Rick Becker; 07-27-2012 at 08:41 AM.. Reason: correction "acetone" rather than "paint thinner" at Jerry's request
Old 07-21-2010, 08:06 PM
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Jerry, it's been a while since I had a 4 or 6 cylinder down to the rods, so thanks for the trip down memory lane. I feel like buying an engine just to rebuild now.

Great job.

Dion
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1974 914-6 3.2 conversion (gone, but never forgotten)
2006 VW Jetta tdi
2009 Subaru Forester
Old 07-22-2010, 04:25 AM
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Sorry its been a while I took a break from the engine to go to a boy scout camp with my son.

Recap
cam is ready
cam followers cleaned and ready
crank with connecting rod are ready
Case machined, line bored, and clean.
Clean all passages with brake cleaner and compressed air.




Next install head studs
With blue lock tight install studs to 141mms. I used a special stud socket but 2 nuts would probably work fine all went in easy.



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1968 912
2002 Tundra 4x4
Old 08-10-2010, 11:19 PM
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Crank case continued

Mount left side case on engine stand. The side the oil cooler mounts to.
Take the #1 bearing and test fit, line up pin hole and scribe with a pencil.






Install # 2 and 3 bearing in case there should be just a little lip on each side. There is a 2mm crush on the bearings when the case is closed.

Install #1 bearing on the end of the crank shaft.

Lube bearing and crank surfaces with engine assembly lube.

Set crank in left half of case. Slightly lift one side of the crank and rotate the #1 bearing till it drops into the pin check pencil marks.

It should look like this

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Jerry McAbee
1967 912
1968 912
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Last edited by Rick Becker; 08-24-2010 at 12:27 AM.. Reason: at the request of Jerry1
Old 08-11-2010, 08:00 PM
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Lets see if we can get the case closed today finally.

Next is the cam followers

Install the followers in the left case(one on stand) uses ultra slick assembly lube liberally.
Use US assembly lube on the flat area that rides on the cam


Install the followers in the right case half add extra US assembly lube on the inside lip. This will hold the followers in place long enough to set the case half together




Install cam

ultra slick on the bearing surface(note the cam rides directly on the case).
Put US assembly lube on all lobes

line up timing marks(note earlier picture)

Time to prep case halfs

We used Locktite 574 on mating surface.
(Don't forget to clean clean clean.)
Only apply to left half of case( except where the cam plug goes on the other case half)
Be careful not to get it on any bearing surface.
After carefully applying a bead of locktite dab it with a little brush. This will insure even distribution







almost ready
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Jerry McAbee
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1968 912
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Old 08-13-2010, 05:05 PM
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Just a little more prep.

Rod holders help hold the rod up and out of the way.

Have all case bolts and nuts ready to go
Make sure the washers have a little bevel for the o-ring to sit in.
Curil- T all o-rings

Check list

All bearing surfaces are lubed
Crank is setted in the bearings flat
Crank and cam gear timing marks are lined up

Almost forgot the cam plug.





Ok lets do this don't fart around you only have 10 to 15 minutes to have all nuts and bolts torqued before the loctite 574 sets up.









Just one more note make sure you rotate the crank occasionally.

Thats it we did it.
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1968 912
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Old 08-13-2010, 08:28 PM
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We torqued all the nuts bolts and acorn nuts to 28 lbs.

Forgot one small detail sorry.
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Jerry McAbee
1967 912
1968 912
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Old 08-13-2010, 08:33 PM
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Using Loctite on the case nuts is really unusual...

Last edited by Barwaut; 08-14-2010 at 04:01 AM..
Old 08-14-2010, 03:56 AM
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Quote:
Originally Posted by Barwaut View Post
Using Loctite on the case nuts is really unusual...
Agreed, but I don't see where he used Loctite on the case nuts.....he used it on the case half.
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1968 912
1974 914-6 3.2 conversion (gone, but never forgotten)
2006 VW Jetta tdi
2009 Subaru Forester
Old 08-14-2010, 09:39 AM
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