Timing chain

[57 lima bean]

How many degrees of crank rotation(slop)before you should look at replacing the chain.This is a 351m in a 90 F250 truck.

[shady]

I don't know, but the local garage I hung out at changed a lot of them. I had one jump with only 70k on it. I would say it depends on miles & if it has nylon teeth.
I have never seen a 1990 with a modified, I think they were all FI 351 windsors. they usually had all steel gears, at least the ones I saw. original motor?

[Lenz]

I had a chain jump on a 302 in a bronco.  Was pulling a trailer with it gone camping and out of town, flat out quit.  I yanked dizzy and advanced it a tooth, ran stronger than ever, the chain jump must have advanced the cam (maybe where Ford wanted to put it in the first place?).  Three weeks later it puked the chain for good (I wasn't about to give up driving it, ran too good).  Moral of the story, if you think it's sloppy it probably is.  'Specially like Shady said if there are nylon teeth involved. 

[57 lima bean]

Thank you guy's.Just less than 6 degrees was the find so I feel I'm good to go.Original engine with 100K.Are you of the mind set that a standard transmission may be harder on a chain?

[Lenz]

Don't know about the transmission but the operator and tune are certainly players.  If it's cold blooded and you get it to where it backfires due to lack of choke, etc., that surely stresses worn components.  Your find of <6 degrees seems safe enough (to me anyway).  I'd think that's pretty close to what you'd expect for a 100K engine.

[FirstEliminator]

   Back in the day, I used to read a lot of Pontiac info. I remember one of the engine builders drilling a small hole in the freeze plug to squirt a constant stream of oil at the timing chain. How does the timing chain normally receive lubrication? Is it just oil mist or oil slung off the crank for supply?
   There aren't many miles on the 351w that I am working on now. I can say there is noticeable stretch in the chain. Not enough to say it needs to be replaced, but it's not as tight as a new chain. This is a "true-roller" double roller timing chain set.
I'd suspect the nylon style timing sets don't require as much oil as a double roller which is why they go over 100K miles. With the double roller being all metal it seems like it needs more than splash lubrication.  While writing this I kinda talked myself into fabbing-up something to drip oil on the chain. Any recommendations on what location of the chain would be the best to apply the oil? Or, am I simply wasting my time?

  thanks,
      Mark

[Heo]

Long time since i built a SBF. But as i remember it
you have to mount the front cambearing below the
block surface a couple of hundreds of an inch to get
an "oil leak".To lube the thrust plate and timing chain.
And there is a grove in the thrust plate that directs
the oil out on the gear and to the chain
Thats how i remember it....but 20 years since i built one