The Fixer

I know you know this Greg, I am curious if anyone has really balanced their 928 motor.

Courtshark

Yes, I need to do something there as well. What's the "passive way"?

James Bailey

when Porsche was building and selling new GTS engines for a bit over $30,000 each.....what do you think ??? The also dyno tested each and every engine any which were 5% underpowered got dismantled to find out WHY same with any that were over !! . Porsche and Mahle also sorted the pistons for size AFTER they were completely finished and marked 3 size groups. They did the same with finished blocks too then matched the pistons and blocks for the best fit.

So yes Porsche paid a lot of attention to details....and they owned a scale or two.

The Fixer

Thanks for this information Mr. Bailey,

I meant those who are building earlier track motors.
I had a feeling these motors would really benefit from being balanced.

I've never had the pleasure of experiencing a GTS,
I drove a white/black GT that was on trade at the local Porsche dealer about 15 years ago. They were asking $25K, the seasoned salesman Eric kept egging me on to tromp on it. Was a very nice car.
Eric has been selling Porsche for over 30 years and really likes 928s, he says they need their maintenance, but if done, will run
forever.

Rob Edwards

Any motor benefits from being balanced. One of the great lessons of 'helping' (in quotations because I'm not sure I actually helped, or was a net-timesuck...) Greg assemble my stroker motor was the amount of time dedicated to balancing, weighing, measuring, etc. I spent an awful lot of time weighing combinations of pistons, ring packs, rods, measuring spring rates and coil bind, etc., etc. Took about half a day to measure all the bores post-Nikasil and assign which piston was going in which bore, with which rod and which set of rod bearings, not to mention the consideration of each piston's dish volume and the respective cylinder's head combustion chamber volume so the compression ratios are consistent across the head. Can't know any of that without actually measuring everything.

You should see his mic/bore gauge/dial gauge/depth gauge collection. Absolute ****. He's also got a digital balance that's good down to 0.01 gram, I think that's probably sufficient for most automotive engine work (?)

The Fixer

Mike,
My '83 is very different in the oil filler area than your track car.

With my '83 i just noticed (as many others have i'm sure) if you look inside the breather pipe on the oil fill lid, it's restricted way down to about 3/8" with a thin bit of material which is dremel'd out to it's maximum of about 7/8" opening very quickly. The outside dia. of the breather part of the oil fill lid is a nom. 1".

The breather on the oil fill lid then goes to the intake via a breather hose like your S4 does. I capped the port on the intake this breather hose connects to and i'm venting the breather on the oil fill lid (which really breaths now) right to air with a Moroso crank case filter/vent used for muscle cars.

I had my 9 year old daughter rev the motor before and after this quick mod and the difference is dramatic, and no more gumming up the intake manifold with oil which can lead to detonation.

MGW-Fla

Could you please post a picture of your set up?

mark kibort

I spent a good deal of time balancing my 928 motors. rods, tip and tail. and of course the entire rotating assembly. all the parts were no more than 1 g off.

but, i think we all know that for our engines, in near stock tune, there is no need to go over 6500rpm, and if you did, the oiling is sub-par for the rod bearings. But, balancing certainly will lower the forces that the bearings see over the life of the engine.

The Fixer

I will when the Moroso filter arrives. I will get the part number for you too, it was the only one i found with the correct size to fit the oil fill lid breather.
Cost about $25.

I figured you guys had to be balacing your motors, thanks for the responces.

And Rob,
do you always work in your garage bare footed?
I have an Artist friend who only paints in the nude too.

Rob Edwards

Duude, this is SoCal, no one wears shoes....

The Fixer

LOL

MGW, sorry no before dremel action pic, didn't plan on posting..
But look inside your oil fill lid breather and you will see how restricted
the breather is, maybe 3/8", open it easily to over 7/8" with a dremel.
This restrictor is only a 1/16" thick and is removed very fast.

Then pick up a vacuum port cap from your local auto parts as your breather hose is no longer needed. (just bought this one from Roger too)

Moroso product is jewel-like, impressed...
Take care MGW, Matt

IcemanG17

I vent the crankcase the exact same way on my 16V racers.....The estate was identical but with a K&N and Casper runs a little factory hose to a simple separator I got from autozone

Version 2.0 of the estate runs into an old Super blue can, with the same K&N on the side....it barely gets 1/16" of oil after racing all day

mark kibort

just run stock! its a built in supercharger!
seriously, this looks like it will make a mess. Scot still runs the stock vent to the "U".

The Fixer

Good to know Brian Thanks
Did you dremel out the tiny restrictor hole?
I wish I took a picture of that tiny hole (no jokes please)
The entrance to the breather that has been enlarged is of the right size to take full
advantage of it being opened up. The wafer thin restrictor seems to be begging
for the dremel to remove it. I really like tinkering with this 928, way more
fun than a 911. This motor runs so darn nice!!!!

You're a funny guy Mark Kilbort!
No mess or oil after spirited street driving. I removed the factory separator and looked down the filler neck of my '83, it's pretty darn dry, not what i had expected.
If it becomes a problem once i track this car in the future I'd rather install a catch can than send it back into my intake.
The restrictor in the oil fill lid breather is probably there to discourage oil ingestion..
Or discourage the intake at high revs from competing for oil. Once opened up to
breathe it should not be fed back into the 'U' imo.
Let the intake cleansing begin..

IcemanG17

I didn't dremel out mine, but will tomorrow..... That is the plan...I will take a before and after pic to show as well....

I found a great video about the "Kibort" effect