Now that I've looked at the piston closer, there's erosion in the area of
the combustion chamber. There's a fairly sharp line the shape of the
chamber, and the aluminum is rough. It looks like some strange form of
detonation. The edge of the piston in that area is rounded and eroded--it
let the heat get right to the ring. Probably what I'm seeing is three days
of racing with mild detonation in the hottest cylinder. I should have
spent the extra three bucks a gallon and run race gas. Oh well, I saved at
least thirty bucks towards the $500 worth of parts I'll need.
-----Original Message-----
From: kas kastner [mailto:kaskas@cox.net]
Sent: Wednesday, September 03, 2003 2:05 PM
To: Bill Babcock
Subject: Re: Stuck piston
I gotta comment on this Bill. You know the old cry of "block pressure".
What happens when you don't have much is the water overheats around the
exhaust valves and it sure can detonate although normally you'd also see
over heating of the water.
On another vein, the water circulation can be helped by reducing the holes
in the front of the head or block so that more water goes to the rear.
There were some engines that I have actually blocked off a few of the
holes in the front of the block so that more water went to the back. That
is not an unusual practice.
I did a test once with a hose and blew the water into the block to see
where it went and most went to the front of the block, the closest point
to the pump.
----- Original Message -----
From: "Bill Babcock" <BillB@bnj.com>
To: "'Friends of Triumph '" <fot@autox.team.net>
Sent: Tuesday, September 02, 2003 9:40 PM
Subject: Stuck piston
> Peyote lost power on the last lap of the last race at the columbia
> river classic last weekend, and started blowing oil out of the catch
> tank. Oh no, methinks, the number four piston stuck.
>
> Yup.
>
> Actually looks like the edge of the piston greatly overheated near the
> exhaust port. No clear sign of detonation though. Anyway, I have a
> growing collection of #4 pistons and liners. Any ideas out there? I
> have a water line from the heater connection to the rear freeze plug,
> I've opened the holes in the gasket and "ported" the head and liner
> area to get lots of water to it. I'm running out of ideas.
>
> I probably shouldn't have been running pump gas (92), though I never
> heard any detonation and the head I'm running has been barely
> shaved--probably only .020". Still, with 87.5mm pistons it's probably
> 9.5-1 or thereabouts. I should cc it.
>
> Time to stick on the high compression head anyway. I needed an extra
> ten HP last weekend. There was a big Healy in my class (a 3000) that
> could pull me on the straight and then was too squirrely in the
> corners to pass. I needed to outbrake him on the entrance to the
> infield and have the whole twisty section to make it stick, but I
> couldn't stay close enough. That meant the Pooper would inevitably get
> me also--he's a tiny bit faster down the straight and nearly as fast
> in the big corners--it's only the fiddly stuff where Peyote has an
> advantage, and the Healy held me back. I finished second once, third
> twice and DNF'ed the last race (though I could have taken the checker
> third just coasting--fourth place was quite a ways behind).
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