Timing cover replacement

Dakar Timm · Thursday at 1:43 PM

Due to the serious leaking of coolant from what I believe was between the block and the timing cover,I removed
The water pump and timing cover .
The coolant passages from the block appear to have been eaten away . I’m familiar with dissimilar metals corroding .
The motor in question is a 318 Polyhead .
Are all the timing covers the same for the small block ? How much deflection is acceptable for the timing chain ?
I figure in for a penny in for a pound .
It appears the gasket no longer had the surface it needed . Thanks

MoparLeo · Thursday at 2:28 PM

Timing chain play ? Really? You are in there, just replace it now. The new tensioners might also fit.

""
Parts That May Be Interchangeable

Crankshaft: An LA 318 or LA 340 crankshaft can be used in the Poly engine.
Timing Cover, Water Pump, Harmonic Balancer: These components can look similar enough to appear interchangeable and may bolt up, though specifications should still be verified for your specific engine.
Early LA Dampers: Some early LA dampers can be used on the Poly. ""

66 Sat · Thursday at 4:29 PM

Don't rely on AI for your answer and you don't need a new Crankshaft so don't know why that's mentioned.

You can use an LA timing cover but there is an extra hole in the poly block that you'll have to plug. Just carefully dremel away the area on the timing cover where the bolt is located on the block and use the factory bolt. The timing tab is also on the wrong side - I have a bolt-on timing tab on the other side on my Poly (refer blue circles for location of hole that needs plugging and incorrect location for timing marks).

I would throw a new Rollmaster or Cloyes timing chain on there, no aftermarket tensioner required - that would be just something else to wear or screw up.

Dakar Timm · Thursday at 4:39 PM

The reason I ask is ,I see no tensioners . Only the chain and sprockets . Supposedly the motor has less than 10,000 miles since a complete rebuild . I have no issues spending whatever is needed to keep this engine on the road .

Dakar Timm · Thursday at 4:46 PM

66 Sat said:
Don't rely on AI for your answer and you don't need a new Crankshaft so don't know why that's mentioned.

You can use an LA timing cover but there is an extra hole in the poly block that you'll have to plug. Just carefully dremel away the area on the timing cover where the bolt is located on the block and use the factory bolt. The timing tab is also on the wrong side - I have a bolt on one on the other side on my Poly (refer blue circles for location of hole that needs plugging and incorrect location for timing marks).

View attachment 1912707
View attachment 1912709
I would throw a new Rollmaster or Cloyes timing chain on there, no aftermarket tensioner required - that would be just something else to wear or screw up.

Thank you . This is exactly the information I was hoping for . The cast timing marks don't create a clearance issue ? I have the bolt on timing bracket . The timing cover is cast '66 ! You would think things would last !

pnora · Thursday at 5:07 PM

Dakar Timm said:
Thank you . This is exactly the information I was hoping for . The cast timing marks don't create a clearance issue ? I have the bolt on timing bracket . The timing cover is cast '66 ! You would think things would last !

That cover is about 60 years old. No doubt run in a neglected motor.

66 Sat · Thursday at 6:06 PM

There are no clearance issues using an LA cover. There is no tensioner from the factory. You don't need one.
@Kern Dog was trying to make one for a 360 build over on A bodies, not sure if he ditched the idea. You have to run a special chain or it digs into the tensioner from memory.

Kern Dog · Thursday at 6:46 PM

I bought a tensioner to use with a 1990 360 roller engine I built in the Spring.
I thought it was a good idea but some guys advised against it. It was OEM in the V6s and it bolts right in place of the standard type camshaft retainer plate but…..
It was designed to be used with a stock type timing chain. The shape of the links in most aftermarket chains supposedly act like a saw against the plastic guide on the tensioner. I ended up cutting the tensioner off.

Dakar Timm · Thursday at 7:48 PM

Sat 66 , I don't know your real name , in the picture of the timing chain you have posted ,is that how tight the chain is supposed to be ?

pnora · Thursday at 7:59 PM

Dakar Timm said:
Sat 66 , I don't know your real name , in the picture of the timing chain you have posted ,is that how tight the chain is supposed to be ?

Read the FSM is illustrates the correct and acceptable timing chain stretch.

66 Sat · Thursday at 8:20 PM

Dakar Timm said:
Sat 66 , I don't know your real name , in the picture of the timing chain you have posted ,is that how tight the chain is supposed to be ?

I didn't measure the stretch - it was a new chain. I know it's tight enough that you put it on both sprockets and then fit them to the front of the block simultaneously - I'm sure it would loosen up some after running for a while. They do make different sized sets if your block has been align bored.

MoparLeo · 2025-09-05T00:49:13-0500

Post #2 was just to show what other la parts may interchange with the poly motor.
Not a recommendation.

Timing cover replacement

Dakar Timm

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MoparLeo

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66 Sat

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Dakar Timm

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Dakar Timm

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pnora

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66 Sat

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Kern Dog

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Dakar Timm

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66 Sat

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MoparLeo

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