engine type 546

[Heiner Fees]

During the last few month I assembled the 546 engine *31040 from 1953 . The cylinders and the piston was
new surface plated, also new rings according to the specifications was installed.

I thought it would be great to finished my 546 engine project with a test run on a test bench.
During the first 2h the engine run very well on the test bench. Then we started the power test.
At 4200 rpm we got an extreme pressure in the engine case. The oil was pressed out of the oil breather.
After a short time there was approximately 0,5 liter oil on the floor.
There was no abnormal smoke from the exhaust. The exhaust values was good.
At OT we tested the pressure loss on every cylinder. The values on all cylinders was very homogeneous by 7-9%.
At cylinder 1 the spark plug was black the other 3 was perfect clean and white.
We changed the oil and optimized die oil level but no change.

What could be the reason?
Heiner

[Jim Karaba]

Don't know the answer but that is one awesome test stand.

[Ron LaDow]

Heiner,
There really isn't anyplace for the pressure to come from besides the chambers. Your static tests may be fine, buy at speed and under load, you have blowby.
But one other comment; you might run it a bit more; new engines do seal-up and you might just find that to be the case.

[George Walling]

I'm no Porsche engine building expert or novice but I would suspect that the rings have not seated properly or yet. Some rings take more time to seat and also it is possible that the rings were not properly positioned on the pistons when installed in the cylinders. There is not a lot of places for the crank case to get pressurized other than blow by. I hope this helps and good luck getting the problem solved.

[Alan Hall]

I agree it sounds like the rings are not seated. What material were the cylinders re-coated with? Also what type of rings did you use?
You also said the #1 plug was black, was it sooty black or oil fouled black?
Alan

[David Jones]

Blow by due to rings not sealing. A friend built a Vee engine with nickasil cylinders and after 3 seasons of similar problems he gave up trying to use them. It is apparently due to the ring material not being compatible with the nikasil coating. He never found a ring combo that would seat reliably. His problem was similar in that the engine would run fine under low load conditions but as an example running at Road America it smoked badly and lost power on the long straights. Find some rings that will bed in and you will be OK.

[Heiner Fees]

Hi Alan,
the cylinders were coated with Nicasil and the pistons with MOS2.
The sparc plug was sooty black and not oily.
Heiner

[James Davies]

These look like the original 546 Mahle pistons and cylinders? Did you source new rings for them?

[Heiner Fees]

we installed new rings according to the specifications.
on top of the piston we integrated a small grove see the picture
Heiner

[Heiner Fees]

this are orignal Mahle cylinder
Heiner

[Alan Hall]

Heiner,

The original chrome plating on the cylinders required a soft iron cast ring set, which is hard to find in the 80mm original size for the 1500 engine as most vendors are now using multi-part steel oil rings. I don't know what type of ring is recommended for Nicasil coated cylinders, but you can probably get that information from the people who did the coating. It looks in your photos that you found a set with one piece oil rings, so hopefully they are compatible with the Nicasil.

Not sure what the small groove in the top of the piston is for.

At this point I think Ron's idea of putting some more run time on the engine to see if the rings will seat is probably the best course of action. Probably want to change the oil and adjust the valves again before you run it anymore.

Alan

[Alan Hall]

Heiner,
A couple other thoughts....what piston/cylinder clearance did you end up with on the Nicasil coating? Also what was the ring gap?

[Heiner Fees]

I do not know the exactely clearance between piston and cylinder. My order was between 0.015 - 0.025 mm for the new plating. The gap between the both end of rings was 0.2 mm.
Heiner

[Jacques Lefriant]

Hi Heiner
I would think it would seal after a while since it looks like you have the right rings. I would address the following while you have the engine apart.
1. make sure you use vented valve covers not 912 ones
2. hone your cylinders with a diamond hone and get the proper cross hatch.
3. if you look at later VW engines they have a vented baffle that goes under the generator stand possibly the majority of the oil was slung out. When i run my engines on my dyno I vent the engine with a hose that goes into a clear plastic vented container that i can monitor. racing rules require a catch tank so as not to dump on the track.
j

[Alan Hall]

Heiner,

Jacques' post reminded me of the baffle part that Wolfsburg West sells for the early crankcase. I have never used one, but it might be worth a try.
Link is:
http://www.wolfsburgwest.com/cart/Detai ... =111115450

Alan