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1 25th June 13:30
bugsy segal
External User
Posts: 1
Default 1969 Chevy 250 Six Cylinder

I just replaced the 250 inline six cylinder engine in my 1969 C10 and
made a mistake in the timing and being a carpenter not a mechanic I am
not sure how to coorect it. Help would be appreciated. I do not know
how to set the distributor so the timing is correct? I have the firing
order and know how to get the number one piston to TDC but that is
about it and it does not run very well and backfires through the
carburetor. Any guidance or where I could find exact instructions
would really be appreciated. The car manuals I have do not give the
information. HELP!!!!!!
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2 25th June 13:31
steve w.
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Posts: 1
Default 1969 Chevy 250 Six Cylinder

Two ways to do this.
Unhook the negative battery cable. Remove the number one plug and turn
the engine over to put number one at TDC on the compression stroke. Move
the engine so that the timing mark on the damper is at about 10 degrees
BTDC. Now you have two options. One requires you to pull the distributor
out and the other will just make you turn it a bit one way or the other.

One : Find the number one plug tower. If I remember right it is the
tower to the left of the vacuum advance pot. (been a while). Make a mark
below that plug tower on the distributor base (piece the cap sets on).
Now pull the cap and see where the rotor tip is actually pointing. Since
it probably won't be pointing at that tower, remove the clamp and pull
the distributor out. Watch how it rotates back as you pull it up. Now
set the rotor tip to that mark you made and back it up like you saw it
rotate when you pulled it out. (usually 1-2 teeth different) Set the
distributor back in and see if the oil pump drive will go in OK. It
probably won't so use a long screwdriver to rotate the oil pump shaft to
a position so that it will. (look at the bottom of the distributor and
move the shaft to match that position as close as possible. Now put the
distributor back in and let it drop all the way down. You should now
have the distributor in the engine, The engine should be at about 10
degrees BTDC, and the rotor tip should be pointing at the mark you made
on the distributor base. Lock it down, Reinstall the cap and check the
firing order on the cap.

Two : Follow the number one plug wire back to the distributor cap. Pull
it off. Remove the distributor cap. Look at where the rotor points. Make
a temporary mark on the distributor base in line with the rotor tip. Put
the cap back on. Look at the mark and see which tower it is closest to.
Mark the center of that tower on the distributor base and take the cap
back off. Loosen the clamp and turn the distributor so the mark you made
is in line with the center of the rotor tip. Lock the clamp back down.
Put the cap back on. If that tower had a plug wire on it take it out and
put the number one plug wire in it's place, that tower is now number one
plug. Pull the rest of the wires and reinstall them following the firing
order using the one you marked and put the number one wire on as the
starting point.

Myself I would use the second method and tag the wire as No. 1. Same
result and easier.

If you followed the steps your engine should now be timed real close to
10 degrees BTDC. It should start and run OK unless there are other
(worn points, bad condenser, bad coil, bad cap)

Use a timing light (with the vacuum line off the advance pot) to set it
exactly. (some were 6 degrees BTDC and others were 10 - 12). To get it
really dialed in get it running good. Fill the tank with whatever grade
gas you intend to use most of the time. Now take it out on the road and
find a hill. Drive up the hill and listen for the engine to start
pinging. No ping is OK but to get the best mileage, loosen the base
clamp and adjust the timing to be 2 degrees more advanced. Try the hill
again, hear any pinging? If no repeat the adjustment of the base
advance. Now hit the hill again. Hear it pinging? If yes you can now
retard the distributor one degree and call it a day. You engine will now
run with the best power and mileage for that grade of fuel.

Oh IF the new engine was installed using an older points distributor I
would suggest finding an HEI unit to fit it. Makes them run much better
and no messing with points. BUT if you install the HEI make sure you
install a new power feed wire to the distributor from the keyswitch. The
factory wire has a resistor wire built in that reduces the voltage to
the points to reduce the amount of power they switch (it helps make the
points last longer) That resistor will also limit the HEI to lower rpm
since it will not be running at full power, that will burn it out quick.

Steve W.

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3 25th June 13:31
External User
Posts: 1
Default 1969 Chevy 250 Six Cylinder

Sounds as simple as being one tooth off of the cam gear to me. I do not
remember, but will the straight sixes run (horribly) with the distributor
180 deg out??
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4 25th June 19:12
big al
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Posts: 1
Default 1969 Chevy 250 Six Cylinder

No engine will run with the distributor 180 out.

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5 25th June 19:13
External User
Posts: 1
Default 1969 Chevy 250 Six Cylinder

I saw an old Ford straight 6 run in school (I remember now what I was
thinking) with the timing WAY off. For some reason I thought it was 180
out, but this happend over 15 years ago now so the facts are skewed...
instructor was a nut job and he was able to start his thing up (it was on a
stand that we used to test carburators that we rebuilt) and then short this
bad boy WITH HIS FINGERS touching all 6 plugs to shut it off. The man
taught Auto electrics too and had a perpetual twitch.....
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6 25th June 19:14
mike powers
External User
Posts: 1
Default 1969 Chevy 250 Six Cylinder

I hope your instructor put his thumb on the block first. I have seen people
do this on model T's but that was
a low voltage magneto ignition. On having the spark 180 out, think about
what is happening when the spark goes off.
You are into the charge part of the cycle. Unless you are very lucky the
intake valve will be open and instant backfire.
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7 26th June 00:57
dwain & bonnie colton
External User
Posts: 1
Default 1969 Chevy 250 Six Cylinder

Turn the dist. counter-clockwise to advance the timing. Keep moving it till
it pings when you hit the throttle, then turn it back about a 1/4"and you
should be fairly close. With a timing lite check it, should be about 10
degrees b-4 top-dead-center...Dwain..
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