Need some advice for my 912 motor in the 356 Coupe

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Chris Choin
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Need some advice for my 912 motor in the 356 Coupe

#1 Post by Chris Choin » Fri May 18, 2018 5:49 pm

Yup. Dad had put a 1968 912 engine in it.... still has the 741 transmission and obviously kept the larger 912 flywheel in it. That answered why it was making a grinding noise when I turned the engine manually.

Now comes my real issues... I'm on a low budget but can wrench like a madman.

The engine sat for at least 7 years without being fogged so cyl 3-4 rusted on the inside.
I have what looks like one good head. the other has broken fins (3-4 side).
The pistons seem good so far, cleaning them. Number 3 has the only ring problem(rusted)
After pulling Engine from tranny it manually turns now like it's floating in butter...super smooth.
Cylinder's 1 and 2 are smooth, 3 and 4 may be too far gone.

The pistons and cylinders are original Mahle 82.5mm. Should I try to save them? Is it possible?
The pistons are barely worn...

The Flywheel is apparently too big for the 741 transmission. I've been reading Spencer's Perf guide but am confused how to mate it up right. (180mm...200mm)

I'm in the UP of Michigan and if there are any other Porsche's here...they are buried in a barn. I'm all alone on this and people look in wonder cause they have no idea what the car is.

BTW you guys won't believe how I disassembled half of the engine(In car)

More photos to follow. Gotta shrink them down.

Help is much appreciated.
Thanks,
-Chris
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Chris Choin
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Re: Need some advice for my 912 motor in the 356 Coupe

#2 Post by Chris Choin » Fri May 18, 2018 6:06 pm

Some pics.

The Flywheel is a Sachs 02 3082 220 231

The head with broken fins has me really concerned (cyl 3-4). It appears to have been repaired in the past.
The piston pic is my worst one with rusted ring. The others are much better.

I'm open to all critiques... be harsh, be straight with me, I don't care, I need to hear the truth if I'm screwed... lol

Just bought a copy of ABC's and 912's by Harry Pellow.

-Chris
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Phil Planck
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Re: Need some advice for my 912 motor in the 356 Coupe

#3 Post by Phil Planck » Fri May 18, 2018 6:54 pm

Chris
There are some low cost Chinese flywheels that may meet your budget needs. I just helped a friend reinstall a new QSC that a shop had done a poor job installing the seal for. Seal surface did not look good so we put on a Speedi Sleeve. 68 912 heads were problamatic due to air injection to help meet emission standards. I would send them to an expert for evaluation. I have a decent set of NPR p/c s that should get you by for quite a while.
.
Last name rings a bell. Was your dad on the 356 talk or forum?
Im a troll about 1.5 hrs below the bridge. Wife has a good friend in Marquette.
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Martin Benade
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Re: Need some advice for my 912 motor in the 356 Coupe

#4 Post by Martin Benade » Fri May 18, 2018 7:01 pm

Those cylinders are aluminum with a ferrous coating, probably didn't take well to rusting. You can try honing them and see if they clean up nicely, or have bumps or flaked-off areas, neither of which would be OK.

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Chris Choin
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Re: Need some advice for my 912 motor in the 356 Coupe

#5 Post by Chris Choin » Fri May 18, 2018 7:12 pm

Yes Phil, my dad was Gene Choin; a true Porsche fanatic. I started working on this car last summer( after bringing it to Marquette from California. I spent $800 on parts for it before I took a breath... lol. I couldn't bring all the parts he had but mostly enough for the car to be put back together. I had no idea how expensive the parts were for these, it blows my mind, but availability is nice. I don't know if I have to go Chinese... I do have some funds for it. I want some quality parts in it. I just have no idea what flywheel clutch setup would work. I've heard a VW bus one works but that's the word on the internet...ha

Dad really loved these cars so much and I'm hoping to get it running again. I spent a lot of time crammed in the back seat of this car or one of his speedsters when I was young. I've dreamed for years of driving it.

-Chris

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Doug McDonnell
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Re: Need some advice for my 912 motor in the 356 Coupe

#6 Post by Doug McDonnell » Sun May 20, 2018 2:28 pm

Chris What year coupe? Another troll from SW Michigan. 200 mm flywheel would be correct for later S90,C and SC engine. 180mm for the rest but you can use a 180mm flywheel/clutch in later car. You might have to change the disc more frequently but that is theoretical depending on how you drive to a degree.
1965 356C There is never enough time to do it right, but always enough time to do it over.

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Doug McDonnell
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Re: Need some advice for my 912 motor in the 356 Coupe

#7 Post by Doug McDonnell » Sun May 20, 2018 2:50 pm

My 356C outlaw has a 912 engine with 180mm clutch and flywheel and all is good.PO also raced and wanted less rotating mass and used 180mm for that reason.
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Doug McDonnell
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Re: Need some advice for my 912 motor in the 356 Coupe

#8 Post by Doug McDonnell » Sun May 20, 2018 2:54 pm

1965 356C There is never enough time to do it right, but always enough time to do it over.

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Tom Tate
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Re: Need some advice for my 912 motor in the 356 Coupe

#9 Post by Tom Tate » Sun May 20, 2018 4:40 pm

From your description it sounds the engine was put in with the 912 flywheel. If so you'll need to remove it as the outside diameter is too large for the trans case. Hence scraping sound when the engine is turned by hand. The number of teeth makes it incompatible with our starters also. Paper weight for 356 owners.

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Chris Choin
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Re: Need some advice for my 912 motor in the 356 Coupe

#10 Post by Chris Choin » Tue May 29, 2018 2:10 pm

I want to thank you guys so far. Lots of help from you and I appreciate the emails a lot. I have a lot clearer idea how to handle this now. Any further posts or emails are much appreciated too. I'm pretty sure the flywheel has the 912; 109 tooth ring gear welded too far forward so I'm hunting for either a 180mm or 200mm full setup.

I'm gonna need to either purchase a new set of heads and have them rebuilt. One of mine is pretty good and the other has broken fins that probably compromise the head too much. Cue the sad face. I'm guessing I should hunt for '67 heads.
Thanks!

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Doug McDonnell
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Re: Need some advice for my 912 motor in the 356 Coupe

#11 Post by Doug McDonnell » Tue May 29, 2018 3:36 pm

All C /SC and 912 heads have the same valve size. https://porsche356registry.org/article/64 See Greg Bryan's list of favorites here: viewtopic.php?f=1&t=28826&p=146982&hili ... ds#p146982 You will probably want 02 or 03s
1965 356C There is never enough time to do it right, but always enough time to do it over.

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Steve Proctor
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Re: Need some advice for my 912 motor in the 356 Coupe

#12 Post by Steve Proctor » Wed May 30, 2018 4:47 pm

A 180mm flywheel with Kennedy (KEP) 1700 pound clutch works great, even with an 1883cc engine.

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John Lindstrom
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Re: Need some advice for my 912 motor in the 356 Coupe

#13 Post by John Lindstrom » Wed May 30, 2018 10:12 pm

Steve is right, no brainer, go with the Kennedy 180mm and you will be super glad that you did. Also, be sure to get the matching clutch disc that goes with it.

Ask me how I know..

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Chris Choin
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Re: Need some advice for my 912 motor in the 356 Coupe

#14 Post by Chris Choin » Fri Jun 01, 2018 12:30 am

So I take it this one will work with a 180mm Flywheel?

https://vwparts.aircooled.net/180mm-Ken ... kep180.htm
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Doug McDonnell
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Re: Need some advice for my 912 motor in the 356 Coupe

#15 Post by Doug McDonnell » Fri Jun 01, 2018 12:42 am

No you need the 356 one which is 200mm I believe. Vic would know for sure. https://aapistons.com/products/kennedy- ... 0mm-d-25mm
1965 356C There is never enough time to do it right, but always enough time to do it over.

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