A long essay, background info followed by several engine related
questions.
Just to refresh, the day before Halloween, I left work a bit early and
on the way home I received a smile/wave/thumbs up from a blond in a new
SL. THe next day when I left for work the engine in my car made a
horrible "metallic detonation" sound when rev'ed above about 2K rpm. I'm
rather busy this fall and it was over a week before I finished the
diagnosis and found something wrong. After checking timing, distributor
advance springs, fogging the intakes with water to blow out any carbon
build up (that was the most enjoyable part of the trouble shooting -
aggressive running up the throttle while fogging the throats). Finally
I did a compression check. Cylinder #5 at 40 psi and cyl #6 at 30 psi.
No signs of oil/coolant foaming or oil in the coolant.
I upgraded my Spit bodied GT with a 73 TR6 engine 11 years ago. I
rebuilt the engine including milling 0.135 inch off of the head to bring
the compression up to about 9.3 : 1. Camshaft is an S2 clone from
BPNW. During the engine break in phase, at about 300 miles on the
engine, I got stuck in very slowly creeping traffic and I cooked the
engine. Most of the coolant boiled out before I was able to get a few
hundred feet up the road and onto a side street. I have had 60,000
trouble free miles after that in the past ten years, never again abusing
the engine. Had the head gasket blown in the first year or so, I would
have attributed it to the overheating. I have a difficult time thinking
that the event 60,000 miles ago is the cause - but if not, what else
would cause a blown head gasket? When I fogged the engine I used a
spray bottle on a mist setting so I do not think hydrolocking could be
the culprit for the compression leak.
I have Weber 40DCOE side drafts on this engine. When the same carbs
were mounted on the prior engine (stock 2.0 GT6 engine) there was no
noticeable Weber reversion - that vaporized gasoline smell after the
engine is shut down. I have had a decade to ponder the cause of the
reversion and the only two things different between the GT6 and TR6
engines (other than the displacement) is the compression ratio and the
camshaft (S2 clone vs stock). For the past decade, I park the car in
front of the garage and let the fuel smell dissipate for an hour or more
before driving the car into the garage. Since I have to tear into the
upper end of the engine this winter to fix the head gasket, I figure I
might try to reduce or eliminate the Weber reversion. Does anyone have
any knowledge / experience with this phenomena, what caused it or how
you reduced or eliminated it (short of going back to stock carbs)?
Thanks in advance, back off to digest mode. THis weekend I'll be
limping the car over to my workshop/storage garage - I do not have the
time to get to the head right away and get the car back on the road for
the last few days/weeks of salt free driving (winter is just not that
far away here in Metro Detroit).
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