Hi all
I use 89mm venolia pistons with .006 clearance and they seem to give me two
years before I start getting ring trouble, so far twice on cyl 4 where the
comp ratio drops from 165 to 115 and I start throwing oil from the rocker
/valve cover vent straight into the catch tank.
Cyl 2 comp falls to about 130 on my scale at the same time. 1 and 3 sit at 155
Ish. This seems to be the order of wear in my engine and a couple of similar
ones, so pretty consistent I'm told.
This is all due to accelerated ring wear due to heat in the rear of the engine
as others have said and if I let it go too far, scrap pistons as a minimum.
Provided I keep a tab on the comp ratios and measure what I pump out of the
catch tank I can keep track of wear on a relative scale, recognising that if I
do so I won't get a heavy failure. Short of solving the issue finally this is
the only way to deal with it, hence my bi annual refit.
I'm getting two years worth of relatively trouble free running with my steel
crank, venolia pistons and carillo rods. That's about 18000 to 20000 rally
miles, maybe 10000 of those at 5000 rpm and above, 3000 at maximum attack of
6500 to 7500 and above (my counter reads to 6000 so when the beastie stops
accelerating and the noise doesn't get louder I know I'm on the peg).
I can forward the specs of the various bits if anyone else is interested.
Happy days.
Tony
Sent from my iPhone
On 11 Sep 2012, at 16:23, "MadMarx" <tr4racing@googlemail.com> wrote:
> I had the same trouble with Wiseco pistons.
> Maybe they expand a lot.
>
> I run as piston to wall clearance 0.13mm.
>
> Never believe what the piston manufacturer says.
> Won't work on a wet liner Triumph engine.
> The liners deform under heat and getting oval.
> More clearance is needed as normal.
>
> At the current engine I try to install old liners in the same direction
when
> they were installed the first time in hope the deformation is smaller.
>
> Chris
>
>
> -----Urspr|ngliche Nachricht-----
> Von: fot-bounces@autox.team.net [mailto:fot-bounces@autox.team.net] Im
> Auftrag von Robert Blake
> Gesendet: Dienstag, 11. September 2012 17:08
> An: fot@autox.team.net
> Betreff: [Fot] Never be beaten by equipment
>
> Pops and I had a less than excellent weekend at TWS it would true to say
> that we were beaten by equipment, one of us physically.
>
> We just put a new engine
> in Dads #14. The second one since December. We built this one with Wiseco
> pistons, stock liners bored to 87+.005 on 1-3 and +.006 on number 4. This
> resulted in the engine lasting most of the day Friday for test and tune. On
> his last run we did a plug check. We had been trying to dial in his mixture
> all day and moving from a lean condition as evidenced by previous plug cuts
> in the day. After adjusting the mixture, reinstalling the plugs, gapping
> points, and rechecking timing we started the engine to hear a horrible
> clatter from within. Same clatter that dad had heard at the Mitty so we
> feared the worst.
> Later that evening he and Bob Kramer confirmed that #4 piston skirt was
> scuffed again. The same thing happened on the previous engine at the Mitty.
> Oil pressure was great all day (80 psi from 3000rpm up) the water temp
never
> went above normal range.
>
> So other than lack of piston to liner clearance, what causes pistons skirts
> to scuff on the liner? Can a lean mixture on the rear carb cause this
> without showing up as a hot running condition?
>
> On to my
> issue.
>
> My aluminum hood pins broke on the TR3 on the back straight.
> Unfortunately, the passenger hinge snapped but the drivers side did not.
The
> hood bent back and slapped my helmet pretty good (beaten by my equipment).
> Never thought of it that way before. Not pleasant. So I am in search of a
> decent bonnet. It is for a 58 TR3A. I am not too picky but proximity to TX
> is a major consideration.
>
> Info on both issues is appreciated.
>
> Greg
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