Boxerworks.com

I would check the breather too - you may have had a pressure build up in the crank case.

Some joker plugging one of the mufflers has been known to blow the seal it too , but you wold probably notice that---.

Roy Gavin wrote: Some joker plugging one of the mufflers has been known to blow the seal it too , but you wold probably notice that---

Blocking (or restricting) the exhaust won't blow out seals.
That's how engine (jackman) brakes work.

Jake brakes work by lifting the exhaust valves releasing compression not by blocking the flow. Oil seals still wouldn't be effected.

robtg wrote:Jake brakes work by lifting the exhaust valves releasing compression not by blocking the flow. Oil seals still wouldn't be effected.

My mistake , wrong terminology, I was confusing 'jake brake' with 'exhaust brake'.
Exhaust brakes block the exhaust, jake brakes don't.
Neither will blow out engine oil seals.
http://en.wikipedia.org/wiki/Engine_braking

Might have just been a coincidence, but I bought a cheap SS 2 in 1 header for the 75/7 at a swap meet.

Wasnt finished , both front pipes had the same , err , backward projection, and the tailpipe was overlong too.

Cut it to size and fitted it , started her up , and after a minuite or so wondering what the xxxx was wrong the header blow off - there was no connection between either side. Presumably the intention was to cut the hole with a in pipe cutter, but they never got that far.

Put the origonal system back on and noticed a pool of oil under the gear box, and automatically assumed that the cause of the blown seal was excessive crankcase pressure, caused by the blocked exhaust port.

But as I say it might just have been a coincidence, or maybe the truck engines with exhaust brakes also have a upgraded breather system to cope with any excess blowby.

Roy Gavin wrote: But as I say it might just have been a coincidence, or maybe the truck engines with exhaust brakes also have a upgraded breather system to cope with any excess blowby.

That could very well be, I don't think it simply a question of blocking the exhaust.

FTR -
I misspoke in my last post: A TOTALLY blocked exhaust could very well have caused your seal to blow out,
I meant that a partially blocked (as in restrictive) exhaust shouldn't.
Exhaust brakes restrict exhaust flow, they don't totally block it.

thought I had read about the crank having to be held from moving forward and something falling out of place?
Frank in florida

mefrank11 wrote:thought I had read about the crank having to be held from moving forward and something falling out of place?
Frank in florida

Yeah, that's the thrust washer/bearing. That shouldn't cause these symptoms as far as I can imagine.

You have to block the crank (at the front) when you go into the rear-main-seal..as in removing the clutch, flywheel, etc.
BE careful that you notice the location of the flywheel for correct-timing when you put it all back together.

Has the original poster made a 2nd post? Or is someone here working with them to fix this?