Author Topic: 351c weird timing problem  (Read 495 times)

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Cyclone03

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351c weird timing problem
« on: April 22, 2022, 11:35:45 PM »
 I will start out by saying this makes no sense….
My friend got his R code 72 Mach one back after 17 years the guy he sold it to put less than 500 miles on it in 17 years!
The previous owner spent a boat load of money to get it running…sort of.

While trouble shooting some odd engine running behavior the timing was checked it’s off scale at about 40deg advance! First thought is damper is slipped. We piston stopped it. At TDC it’s 2 deg advanced 20deg/24deg=2deg.
Anyway….
If you set the damper to 20 and drop the distributor in it will not run. It’s not 180 out.
Pull dist out and rotate rotor one tooth and drop it in it will run,but no way to know what the timing is.
Being gone for 15 years ,IF the timing chain for some reason came off and was reinstalled a tooth off would the engine run and if it did would the timing act like this?
I don’t think it’s a worn chain or slack because if you back the crank up there seems to be only about 5 deg of movement before the rotor moves.
My friend built this engine 20 years ago,it (should) still have the double roller chain he installed dot to dot he has nothing showing the timing cover having been removed. He has a stack of receipts from the previous owner listing every thing done to get the car running.

Any ideas?
Lance H

blykins

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Re: 351c weird timing problem
« Reply #1 on: April 23, 2022, 04:26:46 AM »
Did you check the firing order?  13726548 CCW?  Timing light hooked to correct plug wire?  Not using a dial back light are you?  Factory distributor or MSD?
« Last Edit: April 23, 2022, 06:25:52 AM by blykins »
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Cyclone03

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Re: 351c weird timing problem
« Reply #2 on: April 23, 2022, 07:43:34 AM »
Firing order correct.

Timing light on #1 ,passenger side front.

Pertronics in stock distributor. Swapped in a second one,same results.

Dial back light,tested on engine we pulled the second distributor from.
Lance H

My427stang

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Re: 351c weird timing problem
« Reply #3 on: April 23, 2022, 08:48:25 AM »
So your piston stopped at 20 BTDC and 24 ATDC?  Just checking because if you checked at the small distance between 20 and 24 ATDC, it'd be a slipped balancer or bad pointer and about 20 degrees off

Regardless, still sounds like something funky with the balancer and pointer.   

- I'd likely redo the test with the stop at a different depth. 
- Make sure you are looking at the correct side of the sweep of the balancer to find middle
- When you are finished, put it at TDC and make sure both valves are closed (unless it's a very big cam or crazy ICL, they'll both be closed)

My gut tells me slipped balancer or wrong timing mark, just crossed up test, cam timing won't do what you are seeing.

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Chuck

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Re: 351c weird timing problem
« Reply #4 on: April 23, 2022, 11:46:55 AM »
Everybody should have a cap with a hole drilled at number one for "times" like these. Some though, can't be phased. When things don't seem right, I like to start there.

shady

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Re: 351c weird timing problem
« Reply #5 on: April 25, 2022, 08:29:25 AM »
I had a 73 351c that had a chain jump one tooth on the cam gear and it started and ran fine other than it had no power at all. Was slow to rev even in neutral. Couldn't believe the chain jumped with only 50k miles.
What goes fast doesn't go fast long'
What goes fast takes your money with it.
So I'm slow & broke, what went wrong?

Heo

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Re: 351c weird timing problem
« Reply #6 on: April 25, 2022, 12:35:15 PM »
Ex wife had a Opel 4 cyl that i swaped cam on and i timed the cam one toth wrong. Started fine and run smoth
but totaly gutless uptill about 5000 rpm when it came on like a rocket and pulled like a crazy



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Cyclone03

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Re: 351c weird timing problem
« Reply #7 on: April 26, 2022, 10:43:29 PM »
Update problem solved!

It was the coil!
I’ve never seen a coil act like this. After thinking about it I guess it does. INDICATED timing on the damper showed it needed 30-40 to idle, running the rpm up would show the timing increase then engine would buck like it was pushing against too much timing ,but the coil couldn’t keep up.

Sadly here’s what we did to get there

Zeroed damper
Pulled front cover to check timing set ,all good .
Lashed valves ,solid lifter cam.
Swapped cap,rotor,wires with known good
Replaced plugs
Swapped in no less than 3 distributors all with Pertronics
Gave up for the night.
Next day engine will not start at all!
Smoked a Pertronics
Swapped in a coil….
Fired right up normal timing indications
Took it for several test drives
Adjust vacuum advance can.

All in all a hell of a way to tune up a 72 R code Mach 1.

Drove it some more




Lance H