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

[Memaloose]

I've always replaced the nylon cam gear with a steel one and new chain. The last one I did was on an Olds 455, it was a double tooth set. I wouln't do nylon on anything. The 455 had a lot of slop with only 80,000 miles on a 1972 455.
A buddy had a 402 in a '70 Chevelle, he stripped all the teeth of the cam gear, I installed a '67 Olds 400 to replace the ruined 402.

 

[OldBlueDually]

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.

In my opinion, you are doing here what I feel many would do! That timing set you have your eyes on, sounds perfect for this job.

 

[Octane]

Even if replacing the factory gearset with the plastic oem set, most these old trucks are not driven enough to wear out that second timing set anyway. That said, I always put a solid steel gearset and a single roller chain in anyway. If you are not hotdogging the truck alot, the timing sets last a very long time. My van had original timing set in it, with 120k on it. Worn slap out, chain almost falling off. Timing so far out and varying so much, I couldnt go faster than about 45mph over a 1/4 mile run. Lol. Previous owner must have had a very heavy foot, and the motor was a "sludge" motor too

 

[newguy11]

Re

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....

Recently pulled the 305 from my 1985. This engine had the nylon gear and was pretty sloppy

 

[SirRobyn0]

Even if replacing the factory gearset with the plastic oem set, most these old trucks are not driven enough to wear out that second timing set anyway. That said, I always put a solid steel gearset and a single roller chain in anyway. If you are not hotdogging the truck alot, the timing sets last a very long time. My van had original timing set in it, with 120k on it. Worn slap out, chain almost falling off. Timing so far out and varying so much, I couldnt go faster than about 45mph over a 1/4 mile run. Lol. Previous owner must have had a very heavy foot, and the motor was a "sludge" motor too

My truck is driven quite a bit almost 18K last year. But I don't think my 305 will last until I wear out another timing set. I was about ready to yank the 305 last spring but not being able to get a 350 from my builder for a couple months caused me to chase down and solve my oil consumption / plug fouling issue. Then the plan was to do it this winter when the farm slows down. Then the tranny started acting up. Well my engine money is now going into the tranny. I was thinking of swapping the rear end for a full floater while I had the tranny out, but I've kind of decided replacing the timing chain while it's down is more important than a rear end swap. So that has to continue to wait.... I mean who knows I suppose the 305 could go for many more years, but I really have no idea how many miles are on it. It is in good health though. I think a timing chain is a good investment even if the engine only makes it another few years. At the very least when I'm pulling a hill hauling a load or towing and I turning 3K I'll feel better knowing the timing chain a gear set isn't going to let go.

 

[Octane]

My truck is driven quite a bit almost 18K last year. But I don't think my 305 will last until I wear out another timing set. I was about ready to yank the 305 last spring but not being able to get a 350 from my builder for a couple months caused me to chase down and solve my oil consumption / plug fouling issue. Then the plan was to do it this winter when the farm slows down. Then the tranny started acting up. Well my engine money is now going into the tranny. I was thinking of swapping the rear end for a full floater while I had the tranny out, but I've kind of decided replacing the timing chain while it's down is more important than a rear end swap. So that has to continue to wait.... I mean who knows I suppose the 305 could go for many more years, but I really have no idea how many miles are on it. It is in good health though. I think a timing chain is a good investment even if the engine only makes it another few years. At the very least when I'm pulling a hill hauling a load or towing and I turning 3K I'll feel better knowing the timing chain a gear set isn't going to let go.

We owned these engines back in the era they were first produced. In our experience it was always a good idea to replace the timing sets on them if they had over 100k,especially if the engine was down for other things.Its better to replace than to have to fix bent valves from a timing jump. We used to replace the oil pumps too if we had the engine out, especially then. We called it "building back some dependability into it"

 

[greyghost]

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.

I run a dbl roller in 327 with no issues. just guessing most 305's had a fiber cam gear, with tendencies to start chipping off pcs over 100k miles, low budget buy new stock chain n new all steel cam gear, unless crank gear is severely worn will be ok, gears are cheap and better as new set. shop around for cheapest deal, make sure all steel. Timing issues can be ....odd...how is engine running? with vac. line off and plugged, 6 to 8* intial timing fine, one thing to be aware of is harmonic balancers can spin on rubber, making them useless to set timing.get a crank degree wheel line up keyway slot remark balancer, use a sleeve if pulled off for better seal n replace front seal, check balancer mark with TDC of #1 clockwise n counter clkwise. doing this will also show worn out timing gears.

 

[75gmck25]

If you do end up with a double roller chain you might have to grind the oil plug bosses behind it to get clearance for the wider chain. My truck has the base GMPP replacement 350 engine and the double roller chain (Cloyes?) rubbed on the bosses that stick out behind the chain.

I was able to clearance it by slathering the entire area with axle grease to catch the particles from the grinding, and then using my angle grinder to round off the corners.

 

[SirRobyn0]

We owned these engines back in the era they were first produced. In our experience it was always a good idea to replace the timing sets on them if they had over 100k,especially if the engine was down for other things.Its better to replace than to have to fix bent valves from a timing jump. We used to replace the oil pumps too if we had the engine out, especially then. We called it "building back some dependability into it"

Ya, that's my thing I need it to be reliable and I don't need to be worried about the timing set letting go.

I run a dbl roller in 327 with no issues. just guessing most 305's had a fiber cam gear, with tendencies to start chipping off pcs over 100k miles, low budget buy new stock chain n new all steel cam gear, unless crank gear is severely worn will be ok, gears are cheap and better as new set. shop around for cheapest deal, make sure all steel. Timing issues can be ....odd...how is engine running? with vac. line off and plugged, 6 to 8* intial timing fine, one thing to be aware of is harmonic balancers can spin on rubber, making them useless to set timing.get a crank degree wheel line up keyway slot remark balancer, use a sleeve if pulled off for better seal n replace front seal, check balancer mark with TDC of #1 clockwise n counter clkwise. doing this will also show worn out timing gears.

Engine runs fine. I really don't have any symptoms of a loose timing chain. It does have a propensity to want to ping at higher RPM on regular gas, so when I tow I just drop a tank of premium in. I think I might have said this earlier, but if not here it goes. The PO installed an edelbrock on in, and it runs really good, but I believe the secondaries could do to be a jet size richer. One never knows perhaps replacing the timing chain and tightening up the timing will help. I'm running 6* that's spec. My ESC system is unfortunately inoperative, but that's another story. Like I was saying to Eddie, even if I get in there and find the timing chain nice and tight (which I doubt) but if that did occur I would get piece of mind from replacing it.

If you do end up with a double roller chain you might have to grind the oil plug bosses behind it to get clearance for the wider chain. My truck has the base GMPP replacement 350 engine and the double roller chain (Cloyes?) rubbed on the bosses that stick out behind the chain.

I was able to clearance it by slathering the entire area with axle grease to catch the particles from the grinding, and then using my angle grinder to round off the corners.

Not doing a doubt roller and your post just reinforces that thinking, thanks.

 

[SirRobyn0]

Ok guys I was pretty well set on installing the standard cloyes timing chain, but I opened her up and found this.

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It has some slop but not as bad as I expected. Even more interesting it has GM printed on the cam sprocket. So now I'm thinking I might exchange my non-roller single chain for the double roller. What do you all think?

 

[SirRobyn0]

Additional information. I took a closer look at it, and while I'd still say it's not as bad as I expected it does hand a little bit on the crank sprocket maybe 1/4 of a tooth or so. Still I expected to find this thing about ready to depart.

So my choices are to stick the standard wide non-roller unit in there that I've already purchased or exchange it for a double roller. I'm almost tempted to just stick with the original plan and install the wide non-roller unit in there.

 

[SirRobyn0]

Additional information. I took a closer look at it, and while I'd still say it's not as bad as I expected it does hand a little bit on the crank sprocket maybe 1/4 of a tooth or so. Still I expected to find this thing about ready to depart.

So my choices are to stick the standard wide non-roller unit in there that I've already purchased or exchange it for a double roller. I'm almost tempted to just stick with the original plan and install the wide non-roller unit in there.

Answered my own question. I'm going to reassemble with the stock "wide type" non-roller unit that I already purchased. Reason being is it's a 305 so not like it's any kind of performance engine, and the main goal is to extended the life of the engine. An engine that is of unknown mileage, but most certain has a lot of mileage on it. Unlikely I'll get to work on it until tomorrow, but that is my plan.

 

[DoubleDingo]

I was going to suggest using what you already bought.

 

[SirRobyn0]

I was going to suggest using what you already bought.

I don't know what it is. It's really easy for me to see clearly when I'm talking about someone else's truck or engine but where it comes to my vehicle I will sometimes second guess myself, which really sucks. So I appreciate you saying that.

 

[DoubleDingo]

I don't know what it is. It's really easy for me to see clearly when I'm talking about someone else's truck or engine but where it comes to my vehicle I will sometimes second guess myself, which really sucks. So I appreciate you saying that.

I hear ya, I do the same thing. I hem and haw on stuff, and sometimes it takes months to finally buy something I need and then about as long to install it. I am really trying to get out of that habit.