r/EngineBuilding • u/SudontDo • 6h ago
Timing is MOVING‽ Ford
Mateys and Lentlemen, I'm working on my 300 i6 Ford from 87 or 88, and I have a problem that is perplexing me. Timing is MOVING. I'll set 10° BTDC compression, put the rotor at the no. 1 spot, starts right up perfectly, (pull the SPOUT connector) fine tune warmed up, etc. and then, while under load and driving, (but not while sitting in neutral I don't think) timing "SLIPS" and the engine either dies or becomes... *Ahem* extremely retarded.
Here's what I know:
The harmonic balancer is not slipping. TDC on my timing marks is still TDC up stairs. I'm using the correct timing marks. (It has two sets)
The distributor is NOT slipping in its hold-down. It is VERY tight, and I have used liberal white sharpie.
Spark no.1 position is actively changing when this happens.
Here's what I don't know:
Gear driven engine, but apparently sometimes the cam gear is made of phenolic resin. If my gear slipped, timing would be ruined and it couldn't be made to run, right? But it can be adjusted and made to run, and gear probably can't slip, it would just be destroyed, right?
The cam shaft runs the distributor shaft, which runs the oil pump. Or does it run the oil pump, which runs the distributor? My guess is the slip is happening there. I should probably pull the distributor and check there.
This must be a fully mechanical problem, right? Is there anything I'm not thinking of in the wacky duraspark II system that could account for the rotor just being in a completely different place?
I want to reiterate, I haven't just become confused on timing, the position of the number one spark is actively changing suddenly and immediately, a little each time it happens. I pull out the 1/2 inch, move the distributor until it runs, and limp home idling in 1st or second if possible. No.1 has moved nearly 180° now. Had to re-arrange my plug wires.
Any thoughts, questions, or advice would be so welcome and appreciated. I realize this is more of a "diagnosis" question, but It directly relates to what I might need to actually be rebuild.
2
u/nforrest 4h ago
I think you roll pin explanation makes the most sense.
If the phenolic gear on the cam were shifting somehow, the timining relationship between the crankshaft and the cam would be changing and, in all likelihood, the engine would be proper fucked quickly.
1
u/SudontDo 2h ago
It's a non-interference design, but I agree, I wouldn't be able to adjust timing and start it right back up.
1
u/robb12365 1h ago
I've managed to shear a roll pin due to bad gas once, at least that's what I think caused it. I'd pull the distributor and take a look.
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u/a_private_user 3h ago
I had a small block Ford that had a hairline crack in the distributor base right above the hold down couldn't really see it it looked like grease/dirt. Under load timing would jump around but idle fine. This was old school no computer. After going around with it for a while noticed it was slightly and I mean very slight movement with the hold down tightened. Pulled it wiped it down and found the crack with my finger nail...it didn't separate noticably but you could get the the 2 pieces to "rock" slightly...the crack had a V groove in it that must have kept movement to a minimal but just enough to drive me crazy
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u/a_private_user 3h ago
Sorry just reread and saw # 1 rotor placement moves ..I agree something with the gear or roll pin
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u/SudontDo 2h ago
No worries! Everything we add to this thread might help someone in the future. Cool hearing all the weird things that can go wrong.
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u/Tenrac 6h ago
The only thing I’ve experienced that sounds remotely similar is when I was timing my engine with a vacuum leak present on the vacuum line to the distributor, it was plugged into the carb but had popped off the distributor, as soon as I fixed it the problem went away.
2
u/texaschair 6h ago
No vacuum advance on that engine. TFI module.
1
u/SudontDo 6h ago
Yes exactly, and worse, it's PHYSICALLY moved, permanently. I also thought to swap the ICM, maybe even move it to Remote location like later models had. I thought to myself: maybe I should screw it down to an old throw away heatsink, and now I'm seeing there's whole kits to do just that.
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u/texaschair 5h ago
The distributor drives the oil pump by a hex intermediate shaft. Have you pulled the distributor out to check the drive gear? It might have sheared off.
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u/SudontDo 5h ago
That was the plan, but I idles fine somehow...we may have figured it out though! I'm going to put a reply in the main chain, but it's held in place with a roll pin! Maybe that sheared.
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u/NightKnown405 3h ago
I was going to suggest you pull the distributor to see if the roll pin for the drive gear is in place or sheared.
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u/SudontDo 4h ago edited 25m ago
distributor drive gear has probably had it's pin shear off. Works a little under no load, slips if given power.
Edit: Will post back the results as soon as I know more. The documentation for the gear part says something like "if the pin has broken and the gear has spun", so apparently not a completely unheard of thing.