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View Full Version : Adjust Timing on 1990 351 Engine


lakesidelouie
07-24-2010, 11:59 PM
I've done this before, but it's been years. I know how to use the timing light to find the 10 degree mark, but for the life of me, I can't remember what to do next. The engine is backfiring under load, and idle is very low. I think I turned the distributor cap somehow to adjust the timing previously, but can someone jog my memory?

rd1900
07-25-2010, 09:56 AM
yep, loosen the distributor hold down bolt, turn the whole distirbutor a bit the adjust idle timing, and tighten the bolt.

JimN
07-25-2010, 11:40 AM
Points, or electronic ignition? If it has points, make sure they're adjusted correctly. IIRC, the gap should be about .020" and the dwell should be 26-32.

Also, check the dectrifugal advance weights and springs to make sure they can move freely. If they're frozen in place, use PB Blaster to free the weights and replace the springs.

lakesidelouie
07-26-2010, 01:18 PM
Thanks for the input guys.
I decided to let a friend take over the project. When I adjusted the timing yesterday it helped for about an hour, then it began backfiring again and ran poorly under load.

My friend thinks I had a bad install of an electronic ignition last year (the boat has been backfiring ever since). Something about the distributor possibly being reinstalled off-center, so the engine would be firing out of order now causing the back-firing. Hopefully it's an easy fix.

I'm having the gas filters changed out too while he's at it (I don't think they've ever been changed in 20 years I'm ashamed to admit!)

JimN
07-26-2010, 04:40 PM
Thanks for the input guys.
I decided to let a friend take over the project. When I adjusted the timing yesterday it helped for about an hour, then it began backfiring again and ran poorly under load.

My friend thinks I had a bad install of an electronic ignition last year (the boat has been backfiring ever since). Something about the distributor possibly being reinstalled off-center, so the engine would be firing out of order now causing the back-firing. Hopefully it's an easy fix.

I'm having the gas filters changed out too while he's at it (I don't think they've ever been changed in 20 years I'm ashamed to admit!)

I don't know why the distributor needed to be removed for that, last year. It's pretty easy to get at everything while it's on the motor.

However, a Ford distributor has a hex drive that mates with the oil pump and the gear is helical, which means it rotates when it goes in. If the rotor started in the right position when the shaft started to go in, it wasn't when it seated. I'll bet that it's 60 degrees off and once the #1 cylinder is at TDC and the distributor is re-installed & timed, your problems will be over.