Subject: [TR] Big Blow By -- TR3A

From: Geo Hahn <[email-masked]>
Date: Wed, 15 May 2013 17:31:01 -0700

My TR3A engine is blowing lots of smelly but only slightly visible fumes
out of the breather tube.  Enough that is was clearly noticeable to those
unfortunate enough to be following me when I got on it.  My interpretation
was a massive amount of blow-by from one or more cylinders.

A compression check yielded:

1 - 135#
2 - 140#
3 - 135#
4 - 85#

Adding oil into #4 did not raise compression at all so I thought it
unlikely to be the rings.

A leak down test on #4 sent copious amounts of air out the breather tube.

Took the head off this morning -- no hole in #4 piston and the gasket shows
no noticeable (to my eye) signs of failing around #4 cylinder.

Anyway, head gasket failures I have had have always been either coolant
into the cylinder or combustion products into the coolant -- the rim of the
cylinder is a (relatively) long way from the oil galleys.

I will note that the projection of the liners above the deck is very slight
so I do plan to use 'Randall's Fire Ring' 26awg copper wire enhancement on
the next gasket.

Now my choices -- put an 'improved' head gasket back on, torque the head
down and do another leak-down test or...

Open up the bottom end and push #4 piston out to see what the rings look
like.

Would a broken ring produce the problem & numbers I am seeing?

Is there something else I am completely missing?

Thanks for any advice, guesses or sympathy.

Geo

** [email-masked] **

Archive: http://www.team.net/archive

---

From: "Randall" <[email-masked]>
Date: Wed, 15 May 2013 18:23:15 -0700

Definitely pull #4 piston.  Sounds like a broken ring, or maybe broken
piston to me.

Can't be the head gasket, or there would be coolant involved.

Don't forget to clamp the liners, as you'll most likely have to turn the
crank to get #4 apart.

-- Randall

---

From: Randall <[email-masked]>
Date: Thu, 16 May 2013 18:22:10 +0000

---- Geo Hahn <[email-masked]> wrote: 
> Seems I have only recovered about 1/4 of the missing ring -- makes me
> wonder where the rest went. 

Those pieces on top of the magnet look very thin.  I'm not sure what would do that, but evidently something tore the ring up pretty good.  Perhaps the other pieces got through the gap into the combustion chamber and out the exhaust valve?

> The engine ran so well (even with this problem) that I am inclined to
> address the immediate issue in the most direct way -- I assume that would
> be a used 83mm piston -- rather than pursuing new parts that come is sets
> of 4.

Seems reasonable to me.  I drove a lot of years with a pretty badly damaged cylinder wall, and as you say it ran well enough.  Oil consumption was surprisingly minimal, too.  I think my current TR3 engine blows more oil than that old 3A engine did.

If I find time this weekend, I'll see if there are any usable 83mm pistons that I haven't thrown out yet.  Don't think I saved any rings, but a set of rings is only $40-50.

Randall