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Thu Jan 28, 2010 6:54 am

My 912 engine build is slowly coming together.
Engine size is 1904 cc hbp will be around 130. Hopefully.

Is it needed to change the 8 6mm dowels for 8 8 mm ones?
Or are they sufficient as they are???

Car will be streed driven.

Sat Jan 30, 2010 6:56 am

How is this done, who makes the pistons and barrels ? I've seen reference to this before but never an explanation.

Thanks, Curt...

Sun Jan 31, 2010 12:10 pm

dsrtfox wrote: How is this done, who makes the pistons and barrels ? I've seen reference to this before but never an explanation.

Thanks, Curt...

VW barrels wich is turned down at the base and shortened.
Also modifed the stud pattern holes so it fits the porsche block.

flat top pistons turned in lathe to have a small dome.

Sun Jan 31, 2010 3:52 pm

You have enough meat on the crank to use larger dowel pins?

Mon Feb 01, 2010 12:51 am

60ragtop wrote: You have enough meat on the crank to use larger dowel pins?

Yes, but the question is if it is needed?

Mon Feb 01, 2010 2:02 am

bcrazy wrote:

VW barrels wich is turned down at the base and shortened.
Also modifed the stud pattern holes so it fits the porsche block.

flat top pistons turned in lathe to have a small dome.

interested in this 8)

Got any photos ?

Mon Feb 01, 2010 5:59 am

atomman1 wrote: bcrazy wrote:

VW barrels wich is turned down at the base and shortened.
Also modifed the stud pattern holes so it fits the porsche block.

flat top pistons turned in lathe to have a small dome.

interested in this 8)

Got any photos ?

I can post some pictures of the barrels soon, but unfortunately the guy that did my piston who is an experienced machinist (but not an engine guy) misunderstood what he was suppesed to do, and destroyed my pistons...

So i need to decide if i am going to buy new ones or just go for the 86 mm slip in that fits without modifications.

Basically what i intendend to do is to shorten the cylinders so they fit. The holes for the head bolts need widening. The piston was supposed to be machine down around the perimeter 2mm, leaving a top ring height of 4 mm. This should have been 4 mm in towards the center of the piston, and then gradually angled towards a diameter of 67 mm.

My machinist did it all wrong and machined a flat part 3 mm down and 11 mm wide all around the piston, this reduced the crwon thickness to 2 mm in some places, so the pistons are useless.

Mon Feb 01, 2010 6:04 am

i was thinking of doing this when my 912 went bang.

I looked at the price of 1720 barrels and pistons and because i am used to VW prices nearly fell over :lol:

i was thinking of finding some VW Barrels and pistons and doing what you have done but ended up buying 1720's from the states when the dollar was week.

What size barrels and pistons did you use ?

Mon Feb 01, 2010 7:48 am

90.5 mm B stroker pistons.

What else did you do to your 912 motor?

Mon Feb 01, 2010 11:14 am

Just 1720 B and P's was gonna put a cam in it but kept with the standard in the end.

It also needed new bearings and i also measured everthing to check it was in tolerance , valve guides etc..
Cleaned up the heads and ported and matched them to the manifolds,

So its pretty standard really, i did have it on the dyno before it blew up and when it comes back from the paint shop i plan to put it back on the dyno and see what HP its makeing now.

Mon Feb 01, 2010 2:08 pm

atomman1 wrote: Just 1720 B and P's was gonna put a cam in it but kept with the standard in the end.

It also needed new bearings and i also measured everthing to check it was in tolerance , valve guides etc..
Cleaned up the heads and ported and matched them to the manifolds,

So its pretty standard really, i did have it on the dyno before it blew up and when it comes back from the paint shop i plan to put it back on the dyno and see what HP its makeing now.

Ok, what did it make before it blew up?
What happened?

Tue Feb 02, 2010 2:03 am

it was making 86hp @ the wheels before the compresion went on 2 cylinders.

some of the rings had had broken and this had caused the land on the pistons to break, so it wasn't to bad,but needed new pistons, it was caused by the oil cooler being all clogged up from the sound deadning getting sucked into the fan and that side of the engine getting hot.

here's a pic of the damage

and heres the new ones

I scrapped all the old sound deadning off now and cleaned up the oil cooler and also had it pressure tested before rebiulding the engine.

Tue Feb 02, 2010 7:55 am

Larger dowels not required.

Tue Feb 02, 2010 10:04 am

Only time I have needed bigger dowels is when a gland nut came loose and beat the dowel holes into ovals. Stock should be fine...