Timing Chain Stretch?

[mopowers]

As a timing chain stretches with wear over time, does the spark timing advance or retard?

 

[EL5DEMON340]

Retard very slightly.

 

[1967 'cuda]

The chain is driven (pulled) by the crank sprocket. As it stretches over time the camshaft will be slightly late (retarded) in relationship to the crank. The real problem though is the relationship between the crank and cam. Advancing the cam timing moves the valve opening and closing events earlier in the cycle. Since the relationship between the intake and exhaust lobes cannot be changed, advancing or retarding a cam affects both the intake and exhaust valve equally. Also, the most important thing advancing or retarding a camshaft affects for engine power is when it closes the intake valve. For example, if the camshaft is advanced, the intake valve closes sooner. This typically increases cranking compression on a high-duration race cam. The result is more torque and power in the lower rpm ranges. But as the rpms increase, the velocity of the air/fuel charge in the intake ports also increases dramatically and the early intake valve closing hurts power.
On the other hand, if the camshaft is retarded, the intake valve will close later (usually sometime during the compression stroke). As you might expect, this drops cranking compression and hurts low-rpm power. But as rpm increases and cylinder filling is aided by the extreme velocity of the air/fuel charge in the ports, a retarded camshaft will help power.

​

 

[skykeith]

I run the P5007709 chain tensioner in both of my small blocks. I have no way of knowing if it does any good or not, but it does tighten up the chain.

 

[RustyRatRod]

If it really bothers you, run a gear drive. There are some pretty nice and affordable ones out now.

 

[BigBlockMopar]

I recently replaced a 40 year old timingchain set with a cheap new set.
The difference in engine power is very noticable after the ignition timing has been reset aswell again.

If I were to guess how much power/torque the 318 in my car has gained again from this I would want to say 15-20%.

Also, my engine would slowly heat up on the highway when doing 70mph or higher.
Now with the new timingchain set I can cruise at 80 mph again without any significant temp increase.

 

[BillGrissom]

To answer the OP's question, yes it would retard the spark timing, but doesn't matter since you should adjust the spark timing every few years anyway (standard part of a "tune-up"). When the timing chain gets real sloppy, you will see the timing mark jump around erratically. As mentioned, a worn chain will also affect valve timing, which is more significant. That makes the engine run better at high rpm, which is why many racers purposely set the valve timing later (using multi key slots in the gears). I went the other way and set my gears 4 deg advanced for better low-end (mileage) and to allow for future wear.

 

[Abodybomber]

The above post,dead on!

 

[jos51700]

Imma say it again in case the first seven weren't enough.

Retarded.

Oh, yeah, and the timing goes retarded too.

 

[toolmanmike]

To answer the OP's question, yes it would retard the spark timing, but doesn't matter since you should adjust the spark timing every few years anyway (standard part of a "tune-up"). When the timing chain gets real sloppy, you will see the timing mark jump around erratically. As mentioned, a worn chain will also affect valve timing, which is more significant. That makes the engine run better at high rpm, which is why many racers purposely set the valve timing later (using multi key slots in the gears). I went the other way and set my gears 4 deg advanced for better low-end (mileage) and to allow for future wear.

X3. Although my 273 tops out at 5000rpm because of the advanced timing. That's ok though, I don't need to scream it to 6 or 7000 r's. lol