912 engine in a 356

[MMW]

My 356 has an engine # that is from a 1968 912. When looking for parts or tech info such as valve clearance etc. do I use the 912 # or are these engines the same engine just different years? I know mine is not a stock engine & has been modified but other than that I don't know what's in it.
_________________
Mic McWilliams
1959 356 coupe
Missing the original engine 72488
Anybody have it?

[Bub]

Go with the 912 specs when ordering parts- the engines are very similar, but a huge amount of sensitive parts are different and NOT interchangeable. Also, 356 parts are about 5X the price!
_________________

[MMW]

Next question, is it possible to use a 912 case with 356 parts? Can the heads be 356's. Do the heads have #'s I can look up? Sorry for what is most likely dumb questions but I'm trying to learn as much as possible about what I have & I'm new to working on air-cooled engines.

A little background on my motor. It was built sometime in the late seventies & stored until the mid ninties when it was installed. No one remembers what went into it just rumors. Supposedly it had the "best" stuff. Rumors say it has a roller crank, big pistons, custom cam, possible head work. On the outside it has a pair of 48ida's & a header set up. It runs really well.
_________________
Mic McWilliams
1959 356 coupe
Missing the original engine 72488
Anybody have it?

[Bub]

Yep, you can easily use a 912 case with a 356 setup, and it's not uncommon.
The heads will interchange also, but the rocker arms were changed a few times, along with the nuts that hold the heads on, etc..there are different length pushrods and some have different ends specific to early/late rock feet or lifters. The heads have part #'s cast into them under the rocker arm assemblies.
As far as your engine-- you'll never know what in it until you look, and why bother if it runs great. if it runs REALLY good then it's probably stock, since those special internals are hard to set up and cost a HUGE amount of money. There are really only a handful of people left that are really educated and qualified to build a roller bearing 912 engine- and I think they rarely advise people do that. It's no more reliable (probably the opposite) and very very expensive with not much benefit. There are a variety of cam grinds and pistons etc..
_________________

[ensys]

MMW:

Unless you are an incredibly lucky person by nature, you really ought to open it up some to see what kind of pig is in that poke.

At the very least, you should verify that they were lying about the roller crank, because if they were'nt and if it isn't shot already, it soon will be in road car use.

Give yourself a big break and start some investigative work. Pulling the sump plate is an small and easy start and will let you id the crank and rods and the conditions inside the case (including the gunk in the bottom and around the magnet). Of course, it will not tell you if the rods match or the weight is the same. And you will not be able to check the type or condition of the cam or lifters...

Pull the valve covers and you can see which lifter rig and pushrod type is present. Its not much, but its better than nothing.

You won't want to hear this but the smart thing is to gird your grid and pull that puppy apart and rebuild it. Its the only way you can be certain of anything.

The lesson here is that the wise fellow always figures a rebuild into the price he pays for a "mystery motor".

Good luck.
_________________
Keep 'em flying...

S.J.Szabo

[MMW]

Thanks for the info. I had the sump plate off not long ago & did look inside & it was spotless. Didn't know what else to look for. I've since read that a plain bearing crank should look rough & dark like a casting. A roller crank would look shiny like machined. I'll definitely look next time I pull the sump cover.

I plan on checking the valve adjustment in the near future as it sounds like it might have a loose one. At least if it was a small block chevy that is the sound I hear. Not bad just a slight tap. When I do that I'll look for numbers & take a few pics.
_________________
Mic McWilliams
1959 356 coupe
Missing the original engine 72488
Anybody have it?

[r39o]

I have done this 912 616/xx engine in a 356 trick.

Nothing to get excited about.

The ONLY truly custom part is the cover behind the engine pulley. It needs a two more dimples in it to cover the engine case cover. That is because of the mounts for the 912 engine bar.

What your REALLY need is the little Porsche specs book which tells you the dimensions of the internal parts.

You build it by the spec book not by what some one tells you.

So your BEST bet is to yank it apart and mark things as you go.

Then assemble and measure just like any other Porsche engine build.

Now in my youth when I basically built engines from parts we had laying around I could only go by inspection. You have to measure and remeasure all the time anyways.

If you feel afraid of this, then let some one with knowledge do it.

I never was afraid, we had too much of the junk laying around.

Times are different and that old junk is gold now, so some people think it is some sort of magic.

No magic.....

[MMW]

There is a number cast into the heads in between the intake pushrods. It is 101/7 & then under it is an H. Does this help identify anything?


_________________
Mic McWilliams
1959 356 coupe
Missing the original engine 72488
Anybody have it?

[ensys]

Mr. McWilliams:

I gotta say that this initial probe does not bode well for the validity of the "rumors" that came with the engine.

First, those are the older, cast iron, rocker assemblies. Of the two possibilities, this is not the best.

From here on out its a crapshoot as to what parts the engine was actually built with.... and how.....

Do what you feel comfortable with, but realize that if its just "dump some oil in it and its down the road", the wisest course would be to treat it like it was built with crap by monkeys.


The casting date is usually (on these early heads) in the format of number/dots in a circle, probably under the rockers.


I mean this: If you don't crack it open; Good Luck.

Or...... you could take the time to educate yourself a bit with Elfrink or Mr. Pellow's "Secrets".....
_________________
Keep 'em flying...

S.J.Szabo

[Jon Schmid]

"...roller bearing 912 engine"? Since when? Just curious.
Jon

[MMW]

[356JAEGER]

[ensys]

Mr. McWilliams:

I can see your point. Still, unknown conditions can lead to surprising results, as the dowels have demonstrated (which remains a most peculiar incident). I would still council gentle demand and a low rev limit.... It'll improve the odds of a longer life.
_________________
Keep 'em flying...

S.J.Szabo