Should I Replace Timing Chain?

[NJBronk]

I am replacing my harmonic balancer and my fuel pump, so I have removed my radiator, fan, pullies, belts, balancer, etc. My engine was "overhauled" under prior ownership and bored .040 over back in 2017. Not sure how many miles on it since (Odometer only reads 2,000 miles - 800 of which are mine since I bought it in January).

At this point I feel like I should probably take the water pump and timing cover off to at least check the chain. I think there are three scenarios:

1) Chain is obviously loose - replace
2) Chain is tight but has nylon gear - leave or replace?
3) Chain is tight and has steel gears - leave alone

What should I do for #2? I try not to replace things that are working just for the sake of it, but have read about issues with the nylon gear breaking apart into the oil pan...

Or Should I leave it well enough alone since I didn't have a problem before...

Or should I just plan on replacing it in any case since I'm in there and they're relatively cheap?

 

[Timmy390]

1. Yes
2. Yes Replace nylon gear teeth get hard and brittle thus break.
3, Leave it alone

Tim

 

[NJBronk]

1. Yes
2. Yes Replace nylon gear teeth get hard and brittle thus break.
3, Leave it alone

Tim

And at this point I should at least check it, right?

I feel like I’m going to have this whole engine apart this winter - I just keep going deeper and deeper…

 

[Timmy390]

And at this point I should at least check it, right?

I feel like I’m going to have this whole engine apart this winter - I just keep going deeper and deeper…

I'm not sure you can even buy nylon timing sets anymore.....but while your in there might as well check. PO's do some crazy stuff......I trust nothing.....

Tim

 

[NJBronk]

Is there anything else I should check/replace while this deep? Oil pan gasket (no leaks that I'm aware of)? I assume front main seal. Anything else? Water pump? the timing cover itself?

 

[NJBronk]

Update - good news is that it’s #3. Steel gears and just about 1/4” of slack when pushing on the chain. I think that’s fine?



At this point I’m also going to drop the oil pan, clean it up, maybe paint it, clean the oil pump pickup screen, and look around a bit under there.

 

[73azbronco]

thats fine.

 

[NJBronk]

thats fine.

Awesome, thanks!

 

[admin]

Good news that found a fairly recent timing gear/chain set in good shape.

But just for future reference...

2. Yes Replace nylon gear teeth get hard and brittle thus break.

Yes, absolutely and without hesitation this. I seized an oil pump leading to a very expensive tow many years ago because some of that brittle nylon broke off the timing gear. A small bit somehow got past my oil pickup screen and wedged into my oil pump, shearing the shaft in two. Bronco still ran, but luckily I noticed the oil pressure drop to zero and stopped driving.

I recently tore down my '68 Mustang 289 for a basic rebuild and it also had the factory timing gear with nylon bits all cracked and falling apart. Just a disaster waiting to happen.