Checking on Timing set

The biggest contributor to longer engine life today is the over drive transmission.
The lower cruise rpm reduces wear, just look at tractor trailers, a million miles on the original engine happens quite often, nice slow cruise rpm around 1800, but TONS of torque

 

Mark, check this out. Semi-truck with loaded trailer - 17 tons to 40 tons. Pulling all the weight and still getting million miles out of the engine, amazing. Vet

 

1 inch slack on the timing chain. How many degrees would that be?? when you set balancer mark to 0* and than turn counter clockwise to see when the rotor starts to move. So if i measure 1 inch from the 0* on the timing tab to let's say 10* on the timing tab i can translate the 1 inch slack to 10 degrees? (If the balancer mark which i am moving counter clockwise stops there because of movement rotor at 10* degrees)

 

I don't believe mine is too worn but never had cover off.

 

My stock 71 always rattled under load before I hotrodded it up a bit... 8 point whatever compression stock, regular low lead fuel, stock timing, qjunk carb, etc, rebuilt it at 95k miles. Bad valve seats, everything else, etc. I suspected rattle from vacuum advance. Disconnect it and rattle will probably go away.
Something to try.....

 

If your timing mark is steady it is okay. Easy check for chain slack is turn balancer mark to 0* (with a wrench) on timing tab. Remove distributor cap and when you turn counter clockwise look when the rotor starts to move and stop turning immediately. Now look where the balancer mark is at the timing tab, at which number or maybe even out of scale. That is your chain slack.

 

I checked the slop in the chain by turning the crank back and forth observing slightest rotor movement. Seems like about 8-9* of crank movement before rotor begins to flinch. I should probably compare to my fresh 350 chain slop.

 

When you check initial timing and the mark is steady you should be fine.

 

Wow, 1 inch of slack sounds crazy. I measured mine at 1/4".

 

Looks like you have a double roller timing chain.
I would think that would never stretch to 1 inch. Lol

 

That is the chain slack PLUS the gear slack between distributor gear and the drive gear on the cam core. The distributor gear slack is--usually--not very much; and is generally discounted. OTOH, some engines do have issues with distributor gear wear, or perhaps the "sacrificial" bronze gear is used, in which case the gears had better be examined so the wrong diagnosis isn't made.

That's toward the upper end of what I consider acceptable. It's beyond acceptable if there's a strong bias towards ultimate performance--a race engine, for example.

According to the service manual, you measure from the chain pushed towards the gears to the chain pulled away from the gears. Your "1/4" inch likely becomes 1/2 inch.

 

ALL chains stretch.
Double rollers stretch less than the factory type link chain.

 

here is how much mine stretched before cam change and I used the distributor movement by moving the engine forward then moving backwards to see how much on timing mark.

 

Mine is similar to yours, good to go

 

How much would 8* - 9* slack be in inches?

 

No slop. I used a broken in .005 oversize chain/gearset for an align honed main, on a stock main blk. Fit real nice. Already stretched so this is where it's gunna stay.

 

With the stock balancer circumference of 21.2”
9 degrees of slack equals .53 inches or just over 1/2”

 

Thanks. And the manual says 1" that would seem as way too much. That would be 18 degrees which is far out of scale. You would not be able to set initial with that amount of slack.

 

The 1/4" was total, so 1/8" in either direction

 

Too bad there isn't an easy gear drive solution.