At last we left our hero, disturbed that his rockers were off. This
was due to long pushrods. Even though I was able to adjust the valve
lash, the pushrod would spank the underside of the rocker, giving us
unpredictiable running results.
Yesterday, I spent the afternoon at a friend's machine shop. There we
shortened new pushrods the same amount that I milled off the head,
minus the difference from the stock pushrods. (.145 thou) My pushrods
came from TRF, and in fact were only .005 shorter than my stock ones.
Other preshortened pushrods are shorter than the ones I created last
night. It's nice to have correct rocker geometry. BTW, I took some
guestimate measurements with my dial indicator, and it looked like I
need to cut them exactly .145 to get the rockers parallel at 50% lift
of the cam. Just as it should be. At least something measures up!
Shorting the pushrods was easy once we gained the courage to cut
through the tube. It was a long way in, and we were a bit timid about
taking too much off. But once we saw the blue coating on the pushrod
end, it was easy from there. Thanks to Nick for the shortening
advice!!! Pushing them together with a 12 ton press was nice too.
Much better than smacking them with a hammer and piece of wood.
The first few weren't quite as accurate as the last, but most are
within plus or minus .004.
Ok, I got her running around 9:45pm last eve. Here's the scoop.
She's MUCH happier with the shorter pushrods. In fact, it made more
of a difference than I thought it would. However...
There's still a miss. (WARNING! theories about to be unleashed) After
running it a bit, I took it out for a spin in the rain, top down of
course. It misses under load until I get it up to 2500 rpm. You know
the sound, "baaaa baaaa baa ba ba ba ba varrrooom"!!!! At this point,
it starts to pull quite hard, and the corners of my mouth start
drifting to the top of my ears. There are potential good things under
the bonnet! After the quick spin, I came back to the garage and
checked the timing. It was rock solid, at 4 BTDC. This is with the
vacuum retard installed. I then checked all the wires with the timing
light looking for a difference in the flash of the light. I was
looking to see if my miss was ignition related... I couldn't discern a
difference between the flash on all cylinders, so for the time being,
I'll rule out the ignition as my miss problem.
Humm. Back to basics. I need a couple of things to run.
Compression: I've got compression... (140-145 on all cyls), however, I
haven't checked it with the new pushrods installed.
Cam Timing: It's dialed in perfect. Checked it three times now.
Spark: Got that.
Spark Timing: Got that. (Good enough for now, I think)
Fuel/Air... Humm. fuel... I'll check the fancy O2 sensors I put in
this thing. Both front and back read around .85 -> .875, which is a
rich condition. I've included the voltage table for your enjoyment!
Voltage Lambda Ratio Comment
0.050 1.25 18:1 Lean misfire limit
0.100 1.07 15:1 Max. MPG point
0.400 1.0 14:1 Stoichiometric
0.870 0.9 12.6:1 Max. power point
0.920 0.8 11:1 Over-rich
1.000 0.7 10:1 Rich misfire limit
See "http://home.sn.no/home/egilk/t_tune.html#lambda"; for more info.
The .85 voltage condition was with both carbs leaned all the way out.
The O2 sensors read over .9 with then needle in the rich position.
Can my miss be related to this condition? Unfortunately, I couldn't
read the volt meter in the cockpit last night while running, so I
can't comment on that. Even though the table says I'm at max power,
I'm sure I won't pass emissions with this miss in her. Heck it
wouldn't pass with a 12:1 mixture without a miss either.
I recall reading somewhere that on the ZS, the rough fuel/air mixture
is done with the float level. Unless someone has a better idea, I
think I'll remove the carbs, and check the float levels, and lower the
float a millimeter, or maybe set it to stock if they are set to high.
I'm told these O2 sensors are more sensitive in the midrange, so
perhaps I have more adjustment in my needles than I think. That or
they are worn out. :-( BTW, I pushed the choke levers down to ensure
that they are off. Unless they are leaking (both equally) I'd assume
the float levels are off.
I also found a vacuum leak. But I plugged that and still have the
identical miss.
As for the low oil pressure... I removed the pressure relief valve,
and guess what. There are grooves etched on the plunger, and the
spring is worn as well. Both could stand replacing, and there is no
pressure that I can feel when I screw the valve into the block. I may
have located my problem. :-) New parts will be ordered today.
Anyway, we're off to the Mountains for the long weekend, so the TR
will have to wait till next week to get everything sorted out. I hope
I get it all running and happy before my temp tags expire... again...
Thanks for all the support, tips and assistance!!!
Cheers,
-Scotty '75TR6
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