Holiday ride of shame

356 Porsche-related discussions and questions.
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Dan Epperly
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Re: Holiday ride of shame

#151 Post by Dan Epperly »

Steve Turino wrote: Thu Feb 13, 2020 4:33 pm This is an amazingly fascinating and informative thread for someone just embarking on an engine rebuild. Very sorry for your troubles Dan, but thank you none the less.
Thanks Steve, I figure all of us novices need to share our experiences to avoid making the same mistakes or to learn what works and what doesn't.
I will eventually get around to measuring the heads, that should determine whether or not it was the part that failed or the mechanic.
Right now my garage looks like a paint booth...

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Re: Holiday ride of shame

#152 Post by Mike Horton »

Dan, not neccessarily your fault, but you stepped into a trap. These heads and P/C were evidently purpose mated long ago, likely to save the over cut head chamber volumes (yet to be determined), and the custom work, known only to the machinist and the owner then. In truth, the correct use, and suitability of these pieces, to work with each other, is the responsibility of any assembler, and that, may well be the takeaway in this tale. This prior mishmash of various parts, is why my recent S90 build, has taken the betfer part of 2 years, and many hours of research. If it was easy, anyone could do this stuff. Like others here, I laud this thread, and it's teaching value to all. As these cars, and engines age, this issue will become more of a challenge.
You have received great advice here, from some of the most experienced, and current "in the know" folks, who base their council, on fact. We wish you the best of luck, going forward, and that car, from the photo, appears to be well worth the effort.
Mike

Dan Epperly
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Re: Holiday ride of shame

#153 Post by Dan Epperly »

I took the heads to a friends shop and we CCd them. They are 56cc.

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Re: Holiday ride of shame

#154 Post by Mike Horton »

Wes Bender wrote: Wed Nov 13, 2019 9:47 am If an award was given for "Thread of the Year", this would probably be it.
+1
Mike

Dan Epperly
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Re: Holiday ride of shame

#155 Post by Dan Epperly »

Well, I’m back.
Been focused on this for the past 9 months so the 356 engine has sat i the corner collecting dust. I did everything but the metal work on the truck, including doing the body and paint, so it consumed most of my free time.

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Anyway, I assembled the crank and am trying to figure out this whole nutty compression ration And deck height stuff. I’ve read everything on the internet and the domed piston stuff throws me off. I’ll admit math is like Greek too me, so I’m hoping someone can take these numbers and make sense of them in regard to compression ration and if I need to add another copper gasket. Right now I have one copper gasket installed at the base.

Measuring from the flat area of the piston to the top of the cylinder using a straight edge lined up on the dome I get 4.6mm
Measuring from the top of the dome to the top of the cylinder at TDC I get 2.85 mm
Volume of cylinder head is 56cc
Using solder at four points I get a measurement of roughly 1 mm.

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Thanks for any help and your patience.

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Martin Benade
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Re: Holiday ride of shame

#156 Post by Martin Benade »

How wide is the head seating surface?
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Al Zim
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Re: Holiday ride of shame

#157 Post by Al Zim »

I have been around for a million years but realistically pushing 58 around 356 cars. In all the years I have only seen one set of K/S or Mahle 356 engine pistons that were oversize. I have never seen sets from the "factory" (whatever that is or was ) that were oversized but I did not live in California. The factory did make 1700 CC 6.5 to one pistons and cylinders for the industrial engine these were limited to 3,000 or so RPM. So much for that. Even though we have super computers now that are far better than the slide rules and calculators of the 50's++ Porsche (KS and Mahle) produced (and still do) a superior and very reliable piston for the Normal and Super engines. I think the Super/S-90 cam is an excellent compromise for everyday use when attached to a full weight flywheel. The nice thing about using stander parts is when they wear out you can replace them with standard parts. Why haven't you bead blasted your heads to clean them or mention the clearance between the valves and the guides What at the funny marks on the sealing surface of the head?
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Don Gale
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Re: Holiday ride of shame

#158 Post by Don Gale »

Al Zim wrote: Sat Jun 06, 2020 4:31 pm What at the funny marks on the sealing surface of the head?
Circ-interp't on a CNC with an endmill.
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Martin Benade
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Re: Holiday ride of shame

#159 Post by Martin Benade »

Sounds like the words of someone who knows.
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Spencer Harris
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Re: Holiday ride of shame

#160 Post by Spencer Harris »

Beautiful job on the double-cab Dan. Too bad we couldn't shake that single-cab loose up at Poso Flat - maybe next time.
Spencer Harris
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Re: Holiday ride of shame

#161 Post by Dan Epperly »

Hey Spencer, yep, that’s one that got away sadly.

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Re: Holiday ride of shame

#162 Post by Dan Epperly »

Not sure if anyone is following this thread anymore, but for the sake of others I figured I should update because I doubt my experience or lack of is unique.
To recap, this was a project car that came with a complete engine, many new parts, allegedly “blueprinted.” It had a B crank, an unknown new cam, B heads and a NOS set of Mahle 85mm industrial piston and cylinder kit. The crown of the pistons had been machined with a bevel along the edge and the cylinder shortened to increase compression.
I was told the industrials were not good to use in a street car so I bought AA 86 mm pistons and cylinders and assembled it just checking for deck height not knowing what actually the compression was.
Flash forward, well now I know.
I bought a new set of AA big bores. Did the math...or at least AAs on line calculator did. I put in my bore and stroke, the CCs of the combustion chamber (57cc in the head minus 17cc for the dome netting 40cc actual volume) and the deckheight (1.25mm) with one shim (which is what I had originally) And my compression was 10.1!
But hey, it ran for 20k miles.
Doing further research I figure there is no way I can use those big bores with these heads. I noticed Stoddard sells a big bore kit for engines with head volumes as low as 58 cc and a different set for 61cc. So I guess if you are using B normal or super heads or heads that have been cut your choices are narrowed.
This leaves me with the option of replacing my B heads with a set of 912 heads with adequate volume or toss caution to the wind and use the Mahle set I have (which I still need to mock up).
The lesson here is that before you order pistons and cylinders CC your heads.

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Martin Benade
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Re: Holiday ride of shame

#163 Post by Martin Benade »

Unless you have other plans for the 912 heads, this sounds like a perfect time to use them. Build a B-crank C or S.C.
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Pete Indelicato
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Re: Holiday ride of shame

#164 Post by Pete Indelicato »

And as my wife is constantly reminding me--'It's just a hobby", so have fun with it.
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Martin Benade
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Re: Holiday ride of shame

#165 Post by Martin Benade »

My friend was reminded of that by a 13 year old boy as he struggled to start his 1930 s motorcycle, and was getting hopping mad. The kid said “Sir, is having that bike a hobby, that you do for enjoyment?” The conversation has basically improved his life.
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