tension - timing chain on riviera 1966- engine 425

[cquisuila]

I have removed the cover and accessed at the timing chain

 

How tension is applicated on the chain please ? Because I find it relaxed.

 

Do you have a tip to check this tension without tool please ?

 

Thank you

philip

[telriv]

Phillip,

 

     IF the chain has more than 1/4"-1/2" slack it needs to be replaced.  IF it still has the plastic coated cam gear it's still original & needs to be replaced.

 

ONE VERY IMPORTANT THING.   When you start putting it all back together the balancer bolt needs to be tightened to at least 225ft. lbs.

 

Tom T.

 

 

Edited July 10, 2021 by telriv (see edit history)

[RivNut]

If you can move the crank gear and the distributor’s rotor will not move, it’s time to change gears. 

[XframeFX]

On 7/10/2021 at 9:46 AM, RivNut said:

If you can move the crank gear and the distributor’s rotor will not move, it’s time to change gears. 

I've seen so many of these in GMs of my past where there's a "dead-zone" when rocking the crankshaft back and forth. All of those had the nylon coated cam gear.

When I installed a roller timing set along with a performance camshaft in a SBC TargetMaster crate engine in the early 80's, no dead-zone.

So, could it be that a dead-zone with the nylon gear was a purpose design? Of course with wear, the dead-zone would be alarmingly larger.

 

I appreciate the wisdom shared here. I had this question for quite some time and since this post is on the topic . . . . .

 

Also, are our Nailheads interference engines by design? I've heard of other GM engines with the nylon gear skip a tooth and the only symptom was an engine that no longer ran.

 

Thank-You.

 

[cquisuila]

On 7/10/2021 at 2:26 PM, telriv said:

     IF the chain has more than 1/4"-1/2" slack it needs to be replaced.

Tom T.

 

1/4 OR 1/2 ?

[gungeey]

42 minutes ago, cquisuila said:

1/4 OR 1/2 ?

Right LOL

So if a 1/4"is NFG then a 1/2" must be really no good.

 

earlier someone stated if you turn the crank and the rotor on the distributor moves without delay the chain if fine. Been using that rule of thumb since the 80's, hasn't failed me yet so I,m sticking with it.

[cquisuila]

ok

thank you all !!! for this answers !!🙂

[Seafoam65]

When I did the timing chain and gears on my car I had to toss the first timing set that I bought

because the new chain was loose. I purchased a different brand and it was very very tight. If you

put the new chain on and it isn't tight, try another brand.

[arnulfo de l.a.]

Had same experience as SEAFOAM65 when i changed mine. Very very tight

[XframeFX]

There's no mention what type timing chain set where 'tight' and 'slack' was experienced. The OE style inverted tooth or roller type. From previous communications, "tight" applies to the latter for sure.

6 hours ago, Seafoam65 said:

If you

put the new chain on and it isn't tight, try another brand.

So, was there any Brand name on the packaging for roller sets? Vendors for our Nailheads source them from somewhere.

For replacement, a roller set recommended over the OE style?

For OE style, there's Cloyes, Melling (same?) and Engine Tech (made-in-China?)

[telriv]

For a quality set Cloyes or Melling. AS stated Eng. Tech is likely made in China, BUT then again they could ALL be made in China with everything seemingly being sourced from Chine.

I recently put a double roller set with a 9 keyway crank gear so the cam could be degreed in. The cam gear was thinner than the stock gear by 1/4" which  made the fuel pump eccentric rattle around like there was a knock in the engine BUT it was coming from the front which when listened with a stecascope sounded like a fuel pump was rattleing. Replaced the pump & it was still there. Had to pull the t/c cover off again & make up a 1/4"spacer to put between the cam & the cam spocket.

I wasn't a happy camper.

 

Tom T.