>From: Terry Thompson <firespiter@yahoo.com>
>
>I'm still confused by the mis-timing of my spitfire
>1500.
>
>To reiterate the problem. When I opened the gap on the
>points (as far as .025" from the initial .016"), the
>car would increase idle speed significantly. And my
>car's signature sputter at 3k rpms decreased pretty
>significantly. It turns out that, in effect the larger
>gap was advancing (?) the distributor (i think). This
>was with the static set to 10deg BTDC and plugs gapped
>to .025".
>
A larger gap on the points would cause the points to close
later - retarding the timing (I think). It's OK to increase
the spark plug gap, but I wouldn't mess with the points gap.
I would also use feeler gauges just for an initial setting
and then check it with a dwell meter for more accuracy.
>But adjusting the distributor housing clockwise, moves
>the static and dynamic timing even further out Before
>Tap Dead Center (earlier) in the crank's rotation,
>right? Which I would assume would make the car run
>choppy. (e.g. combustion while the piston is on an
>upstroke). but it doesn't.
>
I've noticed that my spitfires will tolerate incredible amounts
of timing advance and still happily idle although tend to "hunt"
at a steady cruising speed. Not a good idea, since you will probably
have engine damaging pinking which you wouldn't be able to hear
over all the other mechanical noises.
>To be specific, with the gap set correctly to .014"
>and playing with the distributor housing adjustment,
>vacuum port capped and vac advance unattached. I get a
>drastic increase in RPMS around 30 deg BTDC using my
>timing light (this is an estimation since the scale on
>the timing chain cover only goes to 20 deg BTDC).
>
>At 10 deg BTDC (static/dynamic) the car's idle speed
>drops and occasional pops and the signature sputter at
>3K rpms returns. BUT the car seems to have more
>torque. But any further towards ATDC than 10 deg BTDC
>and the engine stumbles and eventually cuts off around
>the 0 deg TDC mark.
>
>Is this normal, or is my 1500 engine possibly have a
>mis-indexed camshaft, sticking valve, worn muffler
>bearing, bent kanutsen valve?
>
A 1500 should idle sweetly with the timing set to TDC.
>Also, putting the timing light on the #4 plug wire, I
>get the crank notch appearing in the same spot in the
>cranks rotation as the #1 ignition. What's with that?
>
The plugs only fire every other engine revolution and the
number 4 fires at the same spot as number 1, but on the
off revolution. 2 and 3 do the same thing, but 180 degrees out.
>Once again, 138-140 lbs. compression across all
>cylinders. New bottom end bearings about 10k miles
>ago. New plug wires, cap, points assembly, condensor,
>rotor, plugs. All above measurements were with the
>vacuum advance unattached and the vacuum port
>sealed/plugged. No hunting idle. No forward/rearward
>movement in the crank (thrust washers in good shape).
>This is a '77 engine with dual carbs. (the sparking
>tips have become slightly tanned in the past 300 miles
>of driving, but are slightly toward the white range).
>Last night I enrichened the carbs a half of a flat.
>
>Trying to figure out why the car increases idle speed
>so far BTDC is making my head hurt. Any ideas?
>
Basically if your timing advances smoothly as engine speed
increases and doesn't jump around, it may not be optimized,
but it shouldn't cause any major driveability problems. I
would set it to spec and look elsewhere (I'm sorry, but I
don't recall the original post describing the problems. Why
do you have a points distributor in a '77?)
Sorry I didn't have any answers, just gave you a little more
to think about! Good luck
Greg Rowe
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