On Sep 8, 4:47 pm, jdhar...@[EMAIL PROTECTED]
wrote:
> On Sep 8, 3:37 pm, Stude <midl...@[EMAIL PROTECTED]
> wrote:
>
>
>
>
>
> > On Sep 8, 1:11 am, jdhar...@[EMAIL PROTECTED]
wrote:
>
> > > Hi,
>
> > > I'm working with a friend on his 1931 Marmon 88 straight-8 engine.
He
> > > pulled the fully functional engine about a year ago, had the whole
> > > thing miked out, replaced all the parts that needed it etc. in prep
> > > for a rebuild to fix leaks and generally restore the engine. The
> > > engine is now all back together, and we can get it to turn over and
> > > run under its own power, but are having some serious complications
> > > with timing it properly.
>
> > > The problem we're running into is somewhat complicated and very
> > > confusing, so I will explain it in detail in the hopes that we get
> > > some useful advice.
>
> > > 1. The distributor worked perfectly in the car before the engine
tear-
> > > down. It's a dual-point distributor, and he's getting his
> > > synchronization equipment ready to double-check, but it was
> > > synchronized when the thing was taken apart and hasn't been touched
> > > since.
>
> > > 2. We have verified that the cam and crank are timed correctly. They
> > > were installed to spec using the embossed teeth on the timing gears
to
> > > align them for the installation of the timing chain, and we have
> > > verified that at Cyl. No. 1 TDC (hereafter referred to simply as
TDC)
> > > the intake valve begins to open at exactly TDC on the intake stroke,
> > > which is exactly as the Marmon manual (which he has, correct to his
> > > year and model) specifies.
>
> > > 3. We have verified the firing order against the Marmon manual. I
> > > believe, off the top of my head, that it is 1-6-2-5-8-3-7-4, but
can't
> > > confirm this- he has the book since it took him about 20 years to
find
> > > one in good condition. In any case, we have verified that the
> > > distributor cap is wired correctly in that order.
>
> > > 4. We have verified that the distributor sparks Cylinder No. 1 at
just
> > > before TDC on the power stroke- in other words, we have statically
> > > timed the engine to two flywheel teeth BTDC for the power stroke
> > > according to the spec in the manual. We've verified that we're not
180
> > > degrees out of time (of course, the engine wouldn't run at all if we
> > > were, but we checked anyway).
>
> > > So, the problem:
>
> > > We can get the engine to start and run on its own. The starter motor
> > > labours intensely to turn the thing over at correct static time, and
> > > it barely starts and runs very ragged with *lots* of partially-
> > > combusted gas in the form of black smoke in the exhaust. This is
> > > frustrating but could be attributed to any number of things, but the
> > > odd thing is: if we loosen the distributor bracket and *RETARD* the
> > > timing by approximately 30 degrees of distributor rotation, which
> > > corresponds (unless I'm mistaken) to 60 degrees ATDC, the engine
runs
> > > much smoother and cleaner, and the starter turns it over easily
> > > instead of labouring. That's as far as we can retard the timing
before
> > > the condenser hits the retard arm spring screw and we can't turn it
> > > any more. I would normally think that we should get better
performance
> > > out of the engine by advancing the timing, albeit at the cost of
> > > hotter and less reliable valves.
>
> > > Additionally, the more we choke the carb, the easier the thing is to
> > > start and the better it runs, even with the throttle wide open it
runs
> > > better if we partially block the air intake.
>
> > > The two "shots in the dark" we're going to take next time we drive
the
> > > 50 miles to where the engine currently lives are a) checking the
> > > timing with a dynamic timing light to see if it's fla****ng TDC when
we
> > > retard the distributor way past where we think TDC should be, and b)
> > > checking the synchronization on the points.
>
> > > Any ideas on what could be causing this? The distance between us and
> > > the engine makes it inconvenient to go back and forth a lot, so we'd
> > > appreciate any tips on things to look for when we try again after
the
> > > weekend.
>
> > > Jon Harvey
>
> > It's a quickie and unlikely, but I would stick a probe into cylinder
> > #1 and make sure that it was sticking up the highest when the
> > (flywheel?) pointer said that it should be.
> > In other words, is "TDC" on the timing gauge the same as with the
> > piston itself?
>
> Thanks Stude, and that's a good thought. We checked that at least it
> was beginning compression when it's supposed to via the puff test
> (kleenex on top of the plug hole) but we didn't try a probe. We'll do
> that.
Let's hope thet the sparkplug is above the piston, not the valves <g>
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