Michael Graziano wrote:
[symptoms that coincide with a massive air leak]
You've almost certainly popped something in the intake tract that is
causing a *major* vacuum leak -- no doubt the backfire blew a plug out
of a manifold or a hose off of a connection.
> And
> every once in a while Poof... a big cloud (as in ALOT) of smoke out the
> intake and what seems like other places as well, even out the valve cover.
> Not sure of color (looks white), but smells of gas. ALso frequent
> backfiring (constant little pings, and an occational louder one accompanied
> by lots of black (not blue) smoke.
>
> I thought maybe the timing chain, but the valves are moving when I crank it.
Timing chains rarely fail. 21-year-old rubber hoses eventually *always*
fail.
Go for the easy stuff first.
> That's timing chain driven, correct?
Correct. If the valves are moving, it's not the timing chain.
> Carb seems to be in OK shape. No rips
> in the piston gasket. Never found an intake leak.
You will. Unfortunately, both the safe method and the stupid method for
locating intake leaks require that the car be running. (Both methods:
spray stuff on manifold, hoses, etc and note idle. Safe method: stuff =
carb cleaner, which is noncombustible, and listen for idle to drop.
Stupid method: stuff = starting fluid, which is ether, which is HIGHLY
combustible, and wait for engine RPM to rise. Unfortunately, this often
becomes: spray ether and watch engine bay go FOOM in large, greasy
cloud. I hear it hurts a lot when your eyelashes grow back after being
singed off...)
> I REALLY have no idea what to do next. I'm afraid the whole intake
> backfiring thing has been leading up to this. Maybe my valves are all
> screwed up?
Have you checked your valve clearances recently? Do you know The Rule
of Nine? A yes, followed by a no, to these two questions may point in
another direction.
> I now keep the carb relatively rich, and the choke partly out
> to keep the engine smooth.
Ah -- sounds even more like a big vacuum leak. Understand why? It
means the engine is sucking in so much extra air that you can only get
the car to run with lots of extra gas (carb rich, choke out). And now
whatever it is that *was* just leaking has now popped all the way off
the car, which is why it was running badly, then finally died.
Have you got a gulp valve on the car? That's the most likely culprit.
Plug the hole in the manifold that leads from the gulp valve (may be
called anti-run-on valve, it connects the breather to the carburettor)
and try restarting. You can plug it, for purposes of testing only, with
a double layer of good, high-quality duct tape and a hose clamp. That
will only last a day or two, though. Once, when my gulp valve failed, I
used to keep duct tape in the car with me for emergency roadside
repairs. Eventually I did a permanent repair, but I'd have exactly the
symptoms you describe -- plus the added bonus of a reed-like wheezing
screech as the duct tape vibrated as the air pulses went in past it.
Highly entertaining. :-)
> If I need to pull the head off this damm thing, what should I purchase
> ahead of time (tools, parts) to do it?
Don't do that. Try blocking wherever air is supposed to go from the
gulp valve into the carb/manifold first.
And if you're dead-sure it's the valves, spend $20 on a compression
tester first and see whether you're getting compression in all four
cylinders.
> And what should I read other than the Bentleys and Haynes as prep work?
This list. :-)
Seriously -- no book (that I know of) does even a half-baked job of
teaching how to troubleshoot. I'd be grateful for a recommendation, but
I haven't come across one; it's something that seems to be learned at
the Master's side, or by trial and error, or a little of both.
Troubleshooting a starting problem is generally a case of checking out
these parameters, in this sequence:
1. Is the engine turning over?
2. Am I getting spark? [do you know how to check?]
3. Am I getting gas?
4. Am I getting air?
5. Am I getting *too much* air into the engine?
6. Are these things occurring at the right time?
7. Do I have enough compression?
A "no" answer to any of these will generally point you to why your car
won't start. Based on the times I've had the exact same symptoms you're
describing, I'm fairly sure (as sure as I can be from a distance) that
it's #5.
> I would think I need a new gasket,
> some sort of machinist's straightedge to check for warping, and if all
> seems lost when I get it off, an elephant gun with a dozen or so rounds.
Take a deep breath, relax, don't worry, have a homebrew... Seriously:
the metal parts on these cars are generally robust, easy to work on,
simple to comprehend, and sturdy. In fact, it's that "easy to work on"
phrase that's responsible for more than half the problems I've ever
experienced with British sports cars, my own or friends -- it's so easy
to change things, even if you don't know what you're doing, that things
get changed even when they shouldn't. Knowing what to put *back* is
sometimes the key part of tuning the car.
> Sorry to vent like this, but I seem to be at wits end here. WHat other
> info should I be revealing and any suggestions on what I need to do next?
Just this: with these cars, it's *always* simpler, less drastic, and
cheaper than you think. The trick is to think first, and *then* spend
time and money.
Where do you live? Is there a neighbor/friend on the list who can lean
over your engine bay with you and help point things out to you? That's
still the best way to learn.
But I believe you when you say that you haven't found an intake leak yet
-- and I also believe that when you find it and plug it, the car will
run again. You may then need to redial the carb to compensate for the
proper airflow, but that's another story (and not one for me -- I've
played with Z-S carbs for a grand total of about nine minutes. Swap on
a pair of SUs from a British Spitfire and I'll gladly help you out...)
Best of luck,
--Scott Fisher
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