Ok, folks, I'm tring to locate my wits end. I'm close. Here's a
little puzzle for those who have seen the light! The only light I've
seen lately was manufactured by lucas...
As some of you know, my TR6 has idled like a dog plopper ever since I
rebuilt the engine 3 years ago. It runs great on the highway, but it
just hasn't had that smooth six cylinder purr at idle... The engine
rebuild consisted of everything, new pistons (.020 over), new cam with
a bit more lift (mild street cam), rebuilt head (at the shop), mondo
$$$ of machine work, etc, etc, etc...
Tim Pettenati (hi Tim!), Glenn Mapes (hi Glenn!), and Lawrence "what
time is it" Buja, all came by last week to bash on the TR with the
idle of DOOM. Tim twiddled with the carbs a bit, and we actually got
the car to run a little bit better. But not to satisfaction. The car
has always had a "rich" smell at idle, but the plugs would say
otherwise. The plugs might be a bit on the lean side, with no carbon,
or oil fouling. It uses just a little oil, but nothing significant.
The occasional miss or stumble continued to persist.
I had not done a compression test after the rebuild until last night.
The test was done with the engine warm, all the plugs removed, and
throttles wide open. Here are the results:
DRY WET(a bit of oil) COMMENT
--- --- -------
#1 100 115 Not sure why the jump with the oil
#2 90 90
#3 80 90
#4 85 90
#5 95 100
#6 105 110
Before the rebuild the numbers were around 120! Note that #1 & #6 are
the highest, following with #2 and #5, then #3 & #4 after that. This
corresponds to the way the pistons rise with regards to the crank.
Kinda interesting eh? At first I though I was using the gauge
incorrectly, so I tried it on my jeep. I got a reading of 130 on a
so-so warm engine with plugs installed. *sigh* I guess it's not the
gauge.
What might be the problem? Here are some ideas of my own....
Could it be possible that I did not correctly degree my cam, when I
installed it? Could the problem be that an intake valve stays open
too long, so that some fuel/mixture goes back into intake? Actually,
the car has backfired through the carbs, but only when it's cold and
the choke is on, and it's very rare, but it did do it last night.
Humm....
Does anyone know of a trick I can use to tell if the cam its correct
timing slot without removing the timing cover? I should be able to
tell something with the rocker cover removed and watch the valves in
relation to the timing marks.
What further testing can I do?
I'm thinking that I'll remove the rocker shaft and try the compression
test again. Of course, this mean that there will be no intake valve
opening, and it will just compress the air available in the cylinder.
If the compression goes up, then I've got a valve timing problem. If
it stays the same, I know nothing more. If it goes lower, I'll know
that my valves are really well sealed. :-)
A leak down test might prove something too. If the valves are
leaking, or perhaps a ring. The thing is, that all this work was done
on the car, so all these parts are either remanufactured or new.
Humm...
Perhaps my machine shop overbored the block. But I'd think I'd be
burning oil like a 2 cycle if that was the case. It does burn oil,
but only about a quart every 2000 miles. Humm...
I would really like to get these numbers up to some reasonable
pressures. I'll pull the head, timing cover, or whatever I need to do,
to get this sucker right. It's a mission! I will not let lucas win!
I will not replace my electrics! (It's already got an electronic
ignition) :-) Any comments, suggestions, or buyers are welcome. :-)
Cheers,
-Scotty "has anyone seen my watch?" Paisley
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