I have an 89 F250 w/ the 460 and about 89,000 miles. Is there a recommended interval to change the timing chain?

Thanks,

ERF

 

No, never heard of one.

 

You can eaily check your timing chain wear. The gears and the chain wear and stretch over use. The gears installed by the factory, if aluminum with plastic teeth, were soft, designed to eliminate noises. The teeth often fell off, and the aluminum wore down, retarding the camshaft timing.

The chain accumulates all this wear. The following is an easy check to determine the amount of slack, slop or wear, in your timing chain.

It is not necessary to remove any components as long as you can see the timing marks clearly. It can be done with one person, but a second person can be helpful if the distributor cannot be easily seen while turning the crankshaft from the front of the engine. This test cannot tell if a chain has jumped; it can, however, tell you if there is enough slop in the chain to have let it jumped.

Tools: Breaker Bar with socket to fit the front crankshaft bolt

1. Mark the TDC or 0 mark on the damper clearly. Ensure the rest of the timing marks can be clearly seen; clean them if necessary. You may find it useful to scrape a little chalk over them to highlight them.
2. Remove the distributor cap and place it out of the way. You must be able to see the rotor while turning the engine with the breaker bar. It usually is not necessary to remove the spark plugs, but some high compression engines may require it to get an accurate reading.
3. Turn the engine in its normal rotational direction until the TDC or 0 mark is lined up with the pointer.
4. IMPORTANT: Do NOT turn the crank backwards just to line it up. Doing so will give erroneous results. You MUST rotate the crank in ONE direction only. If you overshoot, just go around again. This is where it may be helpful to remove the plugs.
5. Once the TDC and 0 marks are lined up and while watching the rotor, rotate the crank in the opposite direction. When the rotor begins to turn, STOP. It may help to have a helper push against the rotor's direction of rotation. (Remember, it will be going backwards at this point.) They can feel it begin to move more accurately than you can see it begin to move.
6. Note the value of the timing mark the pointer is indicating. It will be BTC, because you went in reverse of normal rotation.
7. This value is the amount of slop your timing chain has in degrees of rotation. Anything less than 10 is safe, but performance begins to fall off after 5.
8. If you have anything over 25, STOP driving that motor and get the chain and gears replaced!

 

Thanks for the info.

-ERF

 

i remember checking my friends blazer- 32 degrees- i told him i was amazed it still ran
as for interval- id change it between 130,000 and 150,000 miles just for the peace of mind... closer to 130 if youre doing alot of towing and/or rodding on it much, closer to 150 if youre easy on it, but as banjo said the best way is to check for slop and see when it actually needs to be changed.

 

I checked mine yesterday, it has 8 degrees of slop at 94,000 miles. Hopefully the performance will get a little boost with a new set.