timing chain replacement selection advice / what if got after opening it up

[SirRobyn0]

As some of you know I'm about to have my tranny rebuilt. The program is pull it out take it to the builder for rebuilding. While it is out and I'm waiting to get it back I want to knock out a project or two on the truck while it is down. I wanted to do a diff swap, but other things seem to be coming up that is more important. So I'm pretty sure I've got a sloppy timing chain. I don't see the needle bounce when checking the timing, but when I give it some gas with the vacuum advance disconnected before the mechanical advance kicks in I loose a solid 4 degrees of timing. I can't see what else would do that other than a sloppy timing chain. Regardless it's a high mileage 305 so it's probably likely to have some excess slack.

As many of you know I've been a mechanic for a lot of years but I'm not really an engine builder or anything like that. I've always replaced a timing chain with the same type that was already in there. So my question is this. I'm looking at probably getting a cloyes timing set. Standard single roller, or double roller. So the single roller is a much wider gear than the double roller. It would seem like all of the smaller finer teeth in a double roller would be more apt to wear than the wider single roller, but I hear guys praise the double roller. Guy that know school me. I'm open really to whatever you might want to suggest for a timing chain but I am doing a tranny so cost is going to be a factor as well. I'm not stuck to the cloyes brand ether it's just what's available locally and I "Think" they have a decent reputation.

Thanks guys.

 

[fast 99]

Single roller chains seem to hold up better. Have also seen double roller with low miles that were loose. That's what I have seen taking many motors apart.

Unless it will be driven a lot [most of these old trucks aren't] it probably really doesn't matter.

 

[SirRobyn0]

Single roller chains seem to hold up better. Have also seen double roller with low miles that were loose. That's what I have seen taking many motors apart.

Unless it will be driven a lot [most of these old trucks aren't] it probably really doesn't matter.

This is my thinking too that the single roller would hold up better. She's a high mileage 305, and gets driven a lot. I can't image how many more years this engine has in it, at one time I thought I might swap it out this winter but I can't afford to do and engine and tranny the same year on the truck, so I need to get a new timing chain in there and try to keep it going another year or two.

What do you think about the timing backing down 4 degrees on it's own with the vac advance disconnected. Seems like it would be in the chain, what do you think?

 

[fast 99]

Loose chain could cause 4 degrees or:

check both advances and dist drive gear.

 

[SirRobyn0]

Loose chain could cause 4 degrees or:

check both advances and dist drive gear.

Advances are good. I see the drop even with the vac advance disconnected. I've serviced the mechanical advance on the distributor and while it does show signs of wear it is functional. Personally I've never seen a drive gear worn to that point but I was reading about that some last night. Now considering stabbing in a new distributor when I do the rest of the work. I replaced the OE module about a year ago so who knows how many miles are the pick up, the shaft and gear.... Thanks.

 

[fast 99]

agree, gear is a long shot. Have seen more than 4 degrees in a chain.

Actually, the way I checked chain wear was to bring the timing mark up to TDC. Turn the motor back and forth by hand watching for movement of the dist rotor. Have seen much more than 4 degrees before the rotor moved.

 

[Catbox]

How long did they use the nylon upper gears on small blocks?
I know my '72 Chevelle had one.
Then as I was cresting a hill on the freeway, the teeth finally let go and the chain rolled over all of them.

A new double roller went in there.
It still ran after that, but it was never right as I did have to replace a bent pushrod.

I wonder if you might have a nylon upper gear in there....

 

[OldBlueDually]

For a high mileage anything, and for what you are doing I would throw in a stock timing set from a Napa or local auto parts store, I wouldn't concern myself with brand specific unless there is a really good reason (durability, quality, reliability issues..etc.). My experience with Cloyes being installed is really good, below is why I chose that brand. Unsure if this helps or not however

I personally had no choice but to put in a Cloyes brand timing set in my 455 build for my dually to get the cam to actually degree properly. I must say that I am impressed with the quality of the machine work, and the quality of the fit this timing set has.

Here is the set below I originally purchased, and I forget what brand it is (from Comp Cams though). I could not use it because no matter where I set the bottom gear, the degree centerline of the cam was way off, it came out way too far advanced, and way too retarded when each of the 3 keyways were used. This set was also a bit sloppy I thought. Bottom gear had ever so slight play, chain had a minor amount of play.

You must be registered for see images attach

Here is the Cloyes set, which had 9 keyways in the lower gear. This set fit way better too, it felt like a very snug slip fit (near light press fit) to the crank, and cam. The chain also snug, and the tiniest amount of play which should wear in nicely. I was able to degree the cam within 2 degrees advanced/retarded. It came out 1.25 degress advanced using this set. If all Cloyes brand sets are made like this particular one, I would certainly put it into any application. This set did cost more than the above set also though, and more than a stock timing set costs.

You must be registered for see images attach

 

[SirRobyn0]

agree, gear is a long shot. Have seen more than 4 degrees in a chain.

Actually, the way I checked chain wear was to bring the timing mark up to TDC. Turn the motor back and forth by hand watching for movement of the dist rotor. Have seen much more than 4 degrees before the rotor moved.

I think we'd all consider that the right way to check chain wear, I haven't done that, I just have observed the timing thing when setting the timing and verifying advance function. I think with it being high mileage I will more than likely just move forward with replacing the timing set if nothing else for peace of mind. While it takes a little labor a standard timing chain and gear set is $20

How long did they use the nylon upper gears on small blocks?
I know my '72 Chevelle had one.
Then as I was cresting a hill on the freeway, the teeth finally let go and the chain rolled over all of them.

A new double roller went in there.
It still ran after that, but it was never right as I did have to replace a bent pushrod.

I wonder if you might have a nylon upper gear in there....

I have no idea.... As far as I can tell from just googling it there is no definitive answer but basically looks like they ran nylon from about 64 or 65 until the mid-70's. But IDK I'm just repeating roughly what I saw from searching.

For a high mileage anything, and for what you are doing I would throw in a stock timing set from a Napa or local auto parts store, I wouldn't concern myself with brand specific unless there is a really good reason (durability, quality, reliability issues..etc.). My experience with Cloyes being installed is really good, below is why I chose that brand. Unsure if this helps or not however

I personally had no choice but to put in a Cloyes brand timing set in my 455 build for my dually to get the cam to actually degree properly. I must say that I am impressed with the quality of the machine work, and the quality of the fit this timing set has.

Here is the set below I originally purchased, and I forget what brand it is (from Comp Cams though). I could not use it because no matter where I set the bottom gear, the degree centerline of the cam was way off, it came out way too far advanced, and way too retarded when each of the 3 keyways were used. This set was also a bit sloppy I thought. Bottom gear had ever so slight play, chain had a minor amount of play.

You must be registered for see images attach

Here is the Cloyes set, which had 9 keyways in the lower gear. This set fit way better too, it felt like a very snug slip fit (near light press fit) to the crank, and cam. The chain also snug, and the tiniest amount of play which should wear in nicely. I was able to degree the cam within 2 degrees advanced/retarded. It came out 1.25 degress advanced using this set. If all Cloyes brand sets are made like this particular one, I would certainly put it into any application. This set did cost more than the above set also though, and more than a stock timing set costs.

You must be registered for see images attach

I won't be degreeing the cam, just installing a stock gear and chain set, still good info thanks.

 

[85K304SPD]

You will probably need an oil pan gasket as well, or at least some silicone. I think you will have to drop the pan down, at least a little bit to get the timing cover off and on. If your rear main seal is leaking, this would be a good time to fix that too. Also a new front seal and timing cover gasket. Maybe a new water pump and gaskets, while you have it off. New belts while you are that far in. You will need a 3 arm puller too to get the lower gear off.
I would just order a plain single roller chain and gears from ebay, Cloyes is a little overkill for a 305. Just some thoughts...

 

[SirRobyn0]

You will probably need an oil pan gasket as well, or at least some silicone. I think you will have to drop the pan down, at least a little bit to get the timing cover off and on. If your rear main seal is leaking, this would be a good time to fix that too. Also a new front seal and timing cover gasket. Maybe a new water pump and gaskets, while you have it off. New belts while you are that far in. You will need a 3 arm puller too to get the lower gear off.
I would just order a plain single roller chain and gears from ebay, Cloyes is a little overkill for a 305. Just some thoughts...

Good advice. I'm already planning a oil pan & rear main since the tranny will be out. I want to do the belts, but forgot to order them. Water pump is less than a year old. Have the tools I need already. One of the local wholesale places carries Cloyes single roller OEM replacement set which is what I'll be getting. $20 for the set, I'm good with that.

 

[fast 99]

Being a line tech, we always look for easier ways to do something. Pan removal not required. Loosen up the first few pan bolts. After the front cover is removed grind the corners off the cover where it intersects the pan about where the blue lines are. Install the pan end gasket on the cover and cover gasket on the block. A small 3/16th" of RTV on the visible pan and block areas, especially the corners. Use 2 small punches pry the cover down and onto the dowels. Install the cover bolts as usual.

 

[SirRobyn0]

Being a line tech, we always look for easier ways to do something. Pan removal not required. Loosen up the first few pan bolts. After the front cover is removed grind the corners off the cover where it intersects the pan about where the blue lines are. Install the pan end gasket on the cover and cover gasket on the block. A small 3/16th" of RTV on the visible pan and block areas, especially the corners. Use 2 small punches pry the cover down and onto the dowels. Install the cover bolts as usual.

I've done something similar to this method as well, but in the case of my truck the pan gasket isn't leaking but is seeping some, it's a 2wd, so there is no diff to get around and heck it just seems like the easy time to do it.

 

[fast 99]

Pans on 2wd are usually harder. Motor needs to be elevated quite a bit. Take the cap off and remove either the fan or shroud.

 

[SirRobyn0]

Pans on 2wd are usually harder. Motor needs to be elevated quite a bit. Take the cap off and remove either the fan or shroud.

Clearance looked good on an eye ball test but I will keep that in mind if time runs short I may skip the pan gasket. Thanks.