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peterb
07-31-2006, 11:58 PM
I have an 86 with a 351. Engine runs a bit rough at idle... can watch tach bounce a bit and hear it.

According to specs, the timing should be 6degrees at 600 RPM. Not being an engine timing expert, I understand what this should look like with a timing light and decided to check it. Set it up, fired it up, hit it with the light, and it's off... about an inch from the pointer in a counter clockwise direction.

New I had to turn the distributor, took the bolt out, dang thing was stuck beyond belief. One can of penetrating lube, a bit of pounding and 5 days of pulling on a wrench with all my might, I finally broke it free. I was just about to put some heat to the base.

Now that I can turn the dist, I started adjusting it. Checking it again with the gun, turned the engine off, turned the dist, started it again, checked it again.... repeat.... etc. Got it finally heading in the right direction, almost right on and the engine runs like crap. Stalls, coughs, backfires. Runs best, where it was.

Suggestions? Am I doing something wrong?

JimN
08-01-2006, 12:16 AM
Did it sit for a long time? The distributor base needs to be in good contact with the block in order to show stable RPM and this is directly related to the way it runs. The points close and ground through the base and if they don't have a good ground path, the magnetic field in the coil won't be intense enough and neither will the spark. When were the cap, rotor, points, condenser, plugs and wires changes?

Did it overheat recently? Has any major work been done on the motor in the past? Have you done a compression test?

Hoff1
08-01-2006, 08:01 AM
Are you sure it's at 6 degrees before (advanced) and not 6 degree after. I placed a small piece of white tape (white sharpie would work greaat) on the spot where my engine needed to be timed at to aide getting in dialed in, really helps when outside in daylight (TMCno1 provided that trick I believe).

jimmer2880
08-01-2006, 08:12 AM
Are you sure it's at 6 degrees before (advanced) and not 6 degree after. I placed a small piece of white tape (white sharpie would work greaat) on the spot where my engine needed to be timed at to aide getting in dialed in, really helps when outside in daylight (TMCno1 provided that trick I believe).

It would be 6 deg before TDC. However, I would time it closer to 10 deg BTC as long as it doesn't start to ping.

peterb
08-01-2006, 09:14 AM
The boat has run every year and sits from October to May thanks to Michigan winters.

I can't remember ever timing it in the 10yrs I have owned it but it has been in for service once or twice a while back.

Overheated about 4 years ago when the impeller crapped out. Hasn't since.

Now that the distributor turns, it is definately still seated and doesn't appear to be rusty or corroaded around the base.

Last year it wouldn't run at the beginning of the year and I did plugs, points, condensor, wires, cap, rotor and coil. This year it wouldn't start and I did points again. It still ran a bit rough at idle and possibly higher RPM (hard to feel) so I tried the plugs.

It runs, sort of (see other post about "86 stalling at 3000 rpm") and the misfire is not too noticible but I thought the timing should be closer than it is... shouldn't it.

JimN
08-01-2006, 11:28 AM
If the motor box isn't propped open while it sits over the winter, remove the plate with the points mounted on it and check the centrifugal advance springs and weights to ee if they move freely. Also, try another coil wire. For some odd reason, I have replaced quite a few of them on 351 motors that had new wires installed. Check the dwell, too and make sure it's set to spec.

Since it did overheat, check the compression. If the head gasket eroded between cylinders, it'll run the way you described.

peterb
08-01-2006, 11:46 AM
Dwell is something I have never checked nor how to check. What am I looking for, what do I need, and how do I check it, set it, maintain it?

As for wires, I thought about getting a new set and trying that.

JimN
08-01-2006, 11:59 AM
The dwell is set by adjusting the points and there are dwell meters available at a lot of auto parts stores. On a Ford motor, it's usually 26-34, IIRC. To maintain it, you make sure the screw is tight and lube the distributor cam. Personally, and you'll probably see others tell you the same thing, I would replace the points with an electronic ignition module. You'll never have to deal with points again and it's much more reliable.

I would still do the compression test. If there's an AutoZone near you, they loan tools and this is one of the ones they should have.