How to prevent oil leaks on a new engine build

[roymartian]

In process of having and rebuilding my 25hp, really keen to make this a good job and wanted to get any tips on prevent oil leaks from;

1. Barrels to case ?

I have large copper crush rings in old gasket set, only ever used paper before ?
Make sure case surface is machined flat ?

2. Heads to barrels ?

3. Pushrod tubes ?

4. Should you re-tighten heads and after how long for new engine ?

Thanks guys,

[sunroof]

My 2 cents worth: I'm pretty sure anyone who builds these engines professionally and has figured out how to get them tight is not going to help here so hopefully you can get some good advice anyway.

Someone who has built thousands of engines over the las 40 years gave me a few tips:

25 and 36 Hp engines have 10 mm studs to hold the heads on while later engines have 8 mm studs. The difference is that 10 mm studs do not stretch during operation and 8 mm studs are designed to stretch. What this means is that the head bolt torque on an old engine will go up as the cylinders and heads expand with heat. I have been told that typically at operating temperature the head bolts on a 25 or 36 hp will go up to ~ 45 ft-lbs. Accordingly, I torque the heads down to 45 ft-lbs and then back them off to what ever they are supposed to be. I have never had to retorque head bolts on a 36 hp yet.


Some case glue around the main bearing studs will prevent seepage through the nuts. Be careful not to block any oil passages.

An old aircraft engine builders trick is to put a silk thread between the case halves when you glue them together.

Don

[xeno]

[splitjunkie]

[roymartian]

Would you recommend using copper crush rings or not ?

[splitjunkie]

If you have the correct ones I would. They could save your life if the head to barrel joint starts leaking.
_________________
Chris

You know, a lot of these scratches will buff right out... Jerry Seinfeld

[txoval]

Go to High Performance section...most are very anal about there engines not leaking in that forum

I use Loctite 518, anaerobic sealant for the case halves and barrels to case (no paper), very high quality and forgiving, only dries when air is not present. Once cured, it is a $&@%# to remove

Loctite thread sealant on the head studs into case, all threaded plugs where oil galley plugs were removed

I use 3M Weatherstrip Adhesive, nickname: Gorilla Snot, on all paper gaskets. Fuel pump, oil screen, generator. Dries extremely quick and doesn't like to come off

No leaks on my 36...

[das20v]

Hondabond HT.

Just to be upfront, I never built any air-cooled VW motors, but did a lot of water-cooled VW's and Hondas. From my experience, I swear by Hondabond.

Did you ever see a Honda leak oil? My dad started using it on his street rods and now all of his buddies use it. You can go to any Honda dealer and get it at the parts counter. Ask for Hondabond HT. It's good to 600°F as well. It's the best silicone sealant I have ever seen and easy to find.

I would imaginee case halves and things like that would be ideal. It's a gray color, and if you look close, it has a pearlescent silver hue (aluminum additive?). Great stuff for stopping a leak.