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Old 08-22-2021, 10:27 AM
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Back "in the day" the Tempest 4 cylinder timing chain was the "hot ticket",

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  #22  
Old 08-22-2021, 10:32 AM
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FWIW, I own 2 chevy trucks with the 6.5 turbo diesels in them. When you change water pumps the timing chain is exposed in them, and you can clearly see what condition it's in during the operation. I last changed the waterpump on one of the trucks in 2017. The engine is right around 265.000 miles at that time. The timing chain was nice and tight with no slop in it whatsoever. It is a roller timing chain and I was amazed at it's condition.

A diesel engine is infinitely tougher on timing components than a gas engine is because of the nature of a diesel engine the crank is always speeding up and slowing down just due to the design of an engine with 22 to 1 compression ratio. Watch the fan belt on a diesel at idle, and you can see the harmonics at work.

The 6.5 diesels will snap a crank in short order if the rubber in the harmonic balancer goes bad, they are known for this short coming if you don't catch the failure of the balancer right away, the crank will break. I don't have any idea of what material the roller chains in these engines are made from, but it's apparently a lot better design and material than we currently get for our Pontiac engines.

That said, the 195 4 cylinder Pontiac also had terrible harmonics, and Pontiac engineers used the link type chain that was a hybrid hardened link style chain that would last in that application, and also interchanged with the V8 Pontiac engines. I still own a 428 that I purchased the 4 cylinder chain from GM back in the late 70s when they were still available from GM. I haven't looked at it for decades, but it's still in the race car engine that is fully assembled that came out of the 69 GP stock car in my signature pictures. I'll have to tear into it at some time to see how it held up in a race application.

I'd really like to find out why the 6.5 diesel timing chains I mentioned have held up so well, and are a roller chain too...........

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Old 08-22-2021, 10:33 AM
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Yeh wonít be long they will tell you nylon was the best. True rollers have been around for years and you donít hear stories of them failing a lot?


Last edited by grandam1979; 08-22-2021 at 10:40 AM.
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Old 08-22-2021, 02:17 PM
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It's been said that Grumpy Jenkins used the nylon sprockets on his race motors.. He said he liked the cam retard at high RPMS.

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Old 08-22-2021, 03:54 PM
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Originally Posted by grandam1979 View Post
Yeh wonít be long they will tell you nylon was the best. True rollers have been around for years and you donít hear stories of them failing a lot?
No doubt. Ive been using roller chains for decades. Thousands of miles and thousands of drag strip passes. Never had one fail or get too sloppy. I tried a stock type "morse chain" once. It sucked. Worn out in a few thousand miles.

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Old 08-23-2021, 07:27 AM
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"It's been said that Grumpy Jenkins used the nylon sprockets on his race motors.. He said he liked the cam retard at high RPMS."

They were used for the benefits of constant tooth contact (less spark scatter) and they tend to absorb some harmonics between the crank and camshaft. It was sort of a "hot ticket" and a secret little "trick" some racers did WAY back in the day before other ignition timing methods became popular like crank triggers and such.

Another power saver was running LOW volume oil pumps with lower pressure. High volume/pressure pumps (Chevy for example) rob power from the assembly and are not needed for 99.9 percent of the applications they end up in.

I've had HORRIBLE luck with any sort of roller timing set and even knocked a Rollmaster out of the 455 I built back in 2000. It did well for quite a while, then without warning it got loose and started slapping around one night at the track. The car slowed WAY down and I was getting some noise from the front of the engine. I pulled the engine never once thinking the timing set was the issue but that is all that was wrong with it.

I only used the Rollmaster instead of the link belt sets I'd been using here since the 1970's because the company supplying it told me they were bulletproof and I liked the ease of moving the cam around.......NEVER again will one go into one of my engines.......FWIW........

This topic is like many others out there with some muddy-water. Without exception every single high mileage engine I've had brought here where some sort of double roller chain was used in the last build showed a BUTT-TON of slack in it, but none had completely failed.

I rebuilt a 1991 Chevy 350 some years back with over 250,000 miles on it and the little 5/8" wide stock Morse timing set was fine. It had a little slack it in but could have been put back in service. I think if a little 5/8" wide Morse set will go that far without issues a 3/4" wide version will power one of these engines 20,000 miles or so over the next 30 years.

What folks need to realize is that there are quite few different levels of roller timing sets out there, and IF you go that direction for sure I'd look on the top-shelf vs the bottom one. The higher end stuff will have steel billet sprockets not cheap cast iron ones. The chains will be seamless with rollers that aren't "fixed" and actually have a bearing surface that moves around in use. The biggest benefit then becomes the ease of moving the cam around. Even with that said IF you can grinder is doing his job correctly the cam should be coming up in the right position in the first place. The last half dozen engines I did here did NOT require the cam to be moved at all, but I've had a few over the years that were off as much as 5 degrees, so never assume anything with this sort of thing.......

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  #27  
Old 08-23-2021, 07:59 AM
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Also worth mentioning is making sure to drill a hole in your front oil gallery plug to ensure plenty of oil gets on the chain.

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Old 08-23-2021, 08:53 AM
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Keep in mind if you use the Morse timing set you will need off-set cam keys to degree in the cam

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  #29  
Old 08-23-2021, 09:02 AM
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Originally Posted by JSchmitz View Post
Also worth mentioning is making sure to drill a hole in your front oil gallery plug to ensure plenty of oil gets on the chain.
Interesting, I have never heard of doing that. Is that something I should do??

Dave

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Old 08-23-2021, 09:08 AM
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Interesting, I have never heard of doing that. Is that something I should do??

Dave
Absolutely! Drill about a .060" hole in a plug behind the top sprocket so it shoots oil on the back of it. Especially important at idle.

  #31  
Old 08-23-2021, 09:11 AM
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No, there's no way to control the size of the hole, and drilling into the standard galley plugs that are pressed in are a disaster waiting to happen.

The correct way to do it is by using a pre-drilled pipe fitting and tap the block, but that's a little more complicated once the engine is assembled.

Trying to drill a hole in one of the threaded plugs is not fun, and still can't control the size well. Also need to be careful the front plugs don't protrude into the galley too far, or use a taller plug, which can restrict flow.

Best to buy a setup of plugs with the 2 plugs that are drilled and install them when the engine is being assembled. The second plug with a hole is the one by the dizzy.

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  #32  
Old 08-23-2021, 09:26 AM
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Quote:
Originally Posted by HWYSTR455 View Post
No, there's no way to control the size of the hole, and drilling into the standard galley plugs that are pressed in are a disaster waiting to happen.

The correct way to do it is by using a pre-drilled pipe fitting and tap the block, but that's a little more complicated once the engine is assembled.

Trying to drill a hole in one of the threaded plugs is not fun, and still can't control the size well. Also need to be careful the front plugs don't protrude into the galley too far, or use a taller plug, which can restrict flow.

Best to buy a setup of plugs with the 2 plugs that are drilled and install them when the engine is being assembled. The second plug with a hole is the one by the dizzy.

.
I never said to do it on the engine and didn't pretend to outline the whole proper procedure. I just said that it's a good practice. I don't understand your contention that you can't control the size of the hole. I'm a machinist. I can do this no problem. It's not rocket science. But, YES, do your home work before attempting this modification.


Last edited by JSchmitz; 08-23-2021 at 09:33 AM.
  #33  
Old 08-23-2021, 09:32 AM
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I never said to do it on the engine and didn't pretend to outline the whole proper procedure. I just said that it's a good practice. I don't understand your contention that you can't control the size of the hole. I'm a machinist. I can do this no problem. It's not rocket science.
I was replying to dhcarguy, know what you meant by your post, which you posted while I was typing. Being a machinist, I'm certain it's cake for you to drill a hole, but think about someone in a garage with a hand drill trying to do it, and, without clarification that it's a threaded plug.

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  #34  
Old 08-23-2021, 09:37 AM
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Quote:
Originally Posted by HWYSTR455 View Post
I was replying to dhcarguy, know what you meant by your post, which you posted while I was typing. Being a machinist, I'm certain it's cake for you to drill a hole, but think about someone in a garage with a hand drill trying to do it, and, without clarification that it's a threaded plug.

.
Ok. LOL! I digress...

  #35  
Old 08-23-2021, 09:39 AM
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The front plug I thought was supposed to be .030?

https://butlerperformance.com/i-2498...pio-pp475.html

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  #36  
Old 08-23-2021, 09:44 AM
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More on the subject:

http://www.forums.maxperformanceinc....d.php?t=745067

https://forums.maxperformanceinc.com...d.php?t=815591

https://forums.maxperformanceinc.com...d.php?t=632286


.

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  #37  
Old 08-23-2021, 10:33 AM
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Quote:
Originally Posted by HWYSTR455 View Post
The front plug I thought was supposed to be .030?

https://butlerperformance.com/i-2498...pio-pp475.html

.
It could be .030". I was guesstimating at .060". Probably shouldn't have done that.

  #38  
Old 08-23-2021, 10:58 AM
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I dug a little and got side tracked, but have seen others using between .025-.065, which makes me wonder what the sizes H-O kit used.

There are many that offer the plugs pre-drilled, many don't list the size for the front one, but the rear one I've seen many .040 sized.

I have a bunch of the H-O ones, and some I pulled from cores, but haven't measured them yet. Was also trying to dig up my H-O catalog from the day, but haven't tried too hard looking for it.


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  #39  
Old 08-23-2021, 11:02 AM
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no comment on the ability to drill a .030 hole by the average machanic.. Hardest part is wondering why the drill chuck will NOT hold it...lol Wrap the end of the drill with masking tape...then insert into the drill chuck. Don't forget to be-burr the hole.
I have no comments on the timing chain stuff as I have been mildon gear drive for 30+ yrs.

  #40  
Old 08-23-2021, 11:48 AM
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You guys understand that drilling holes in oil gallery plugs at the front of the engine has NOTHING--absolutely NOTHING to do with lube on the timing chain?

The lil' holes in the oil plugs are to bleed air out of the gallery at start-up, so the hydraulic lifters don't tick.

There's press-in cup plugs with holes drilled in them direct from Chevrolet. Melling sells replacements. If they can do it, I don't know why we can't.
https://www.summitracing.com/parts/mel-mpc-52v

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