Timing chain too tight?
 

I am building a mild 400 for the street car with leftover parts I have laying around. I installed a double roller timing chain I had laying around. I don't remember why I had it on the shelf. Had to be left over from the race car, Well anyway it seems very tight took a little tapping to get it on. Very little slack. After looking up the cat. number, it is .005 undersized. Do you think this would hurt anything or should I just order a new standard one?

Also it's been years since I installed a fuel pump drive on the timing chain. Is it worth filing the flange to get rid of the slop? It is really loose when I tighten the cam bolt.

Front cam bearing might take offence, might not.

As for the fuel pump eccentric; not worth filing hard steel. As or " Really loose" I forget. Loose sounds about right. think the cam end sticks out a little to assure the Stuck eccentric/Gear/cam nose are fully seated LOOSE eccentric spins loose.

Not good with .005” undersized chain!

You now have likely taken out most all of the needed oil clearance on the crankshaft side of that front cam bearing, and also you have progressively reduced the oil clearance on the top side of the cam bearings on the way back to the rear of the block.

I have measured this once with one of my motors after a slight line hone was done.

I had both a standard and undersized chain and I used my magnetic dial caliper to check how the cam was loaded and in turn rocked from front to rear as I installed both chains.

All I can tell you is that I decided it was far more prudent to go with a looser fitting stock length chain and then did my normal advance the cam 2 degrees thing to compensate for normal chain stretch.

I did not recheck with a degree wheel after I did that, but I guess my normal 2 degree advance ended up being only 1 degree.

As with any type of clearance in a motor it’s better to be a hair too loose then too tight!

You might want to take a look at this video.

https://www.youtube.com/watch?v=0FgWYtAeegM

Stan

Good video..I have a .005 undersize on my engine that seems a little tight. Sounds like I'm putting my other Cloyes on. The Cloyes as mentioned in the video does not seem to stretch or wear. I'm always looking for extra horsepower and may help with engine wear in the process as well.

The undersized are for builds that have had an align bore/hone on the mains. If your build hasn't then....?

I like my timing set on the tighter side as early run time usually loosens it up.

You did not mention what brand and style timing set you are using. People know that I am on here frequently talking up Cloyes timing sets. There is a reason. Cloyes checks the center to center distance on EVERY performance set they sell. 100% of the sets see the fixture, not 1 every 10,000 or whatever. So that's why your -.005 set is actually too tight like it should be on a block that has not been line honed ever or just a very minor touch up. If you have a Cloyes set you are working with, PM me and I can fix you up with a STD new chain only. I have a few. If any other brand, I would be very cautious mixing and matching sprockets and chains. If a flat link chain, absolutely do not run it tight. The only timing chain I have EVER had pull apart and break was a too tight flat link chain on a Buick V-8. It pulled apart at about 1000 miles and did allot of damage. I am not sure I fully understand what is going on with your fuel pump drive. The outer cup, sometimes called the "bearing", does run fairly loose and free without the pump arm pre-loaded on it. Make sure the camshaft nose sticks out past the camshaft sprocket and the inner cup pilots on the cam nose. They used 2 designs at least over the years, both will work. One has a tiny tab that indexes on the camshaft key slot and lines everything up. The more common design has a tab further back that indexes in a dimple in the camshaft sprocket. It is a larger tab. Good luck with it.

Mine was align bore/honed. My timing chain set hasn't loosened up in 4 years. I'm going to check my slack again this spring..and may swap my other set in.

I have a couple of those .005 timing chains too. Bought years ago.

Figured out I might need one on one of the IA2 block builds.

Tom V.

Went thru my notes and I bought the -.005 chain for the race motor when I line honed the mains. Didn't end up needing and put it on the shelf. I did find a used one taken off the race motor hiding in a box and ended up using it. It has a good amount of slack but should be good for a mild build, They both are Cloyes.

As far as the fuel pump eccentric (drive), I just installed it like it is suppose to be, I just don't remember how loose they are. It's been close to 20 years since I put one on. The outside ring that the fuel pump rides on has almost 1/8 of slop in to out. If I push and pull it away from the timing gear it has a good amount of play.

Again, I have some new STD chains only if you want to change it out. Just let me know.

Has camshaft end play been checked? (With a dial indicator). Should be approx .003-.010
Just wondering if cam snout was pulled through the pump eccentric all the way

I hope this is relevant to the discussion about timing chain length. For years (many), I have been under the belief that on the shorter chain sets, the chain was the same and the difference was in the taper of the gears. This affected where the chain rode on the gear and made the chain essentially shorter. I researched this many years ago, because I couldn’t see how they could actually make a chain shorter without taking out a link (this would be waaaay to much) or using shorter links (not practical) This is what I was told by one of the major timing set manufacturers- it’s the gears. Thoughts. Bill

I would like to hear about this also.

So does anyone have both sets of chain and gears on the parts shelf to compare closely for us?

Wow, the Dave Vizard video was good (very sad about his daughter), told me what I've always known about double roller timing sets. I tried a few over the years and they show WAY too much timing bouncing all over the place on the dyno when you follow them with a timing light. He mentions this couple of times but obviously it doesn't hurt power as much as having one too tight and tranfering the torsional stuff between the cam and crank.

Here I use factory timing sets, the good stuff sourced NOS off Ebay and once in a while picked one up at a swap meet. My favorites are the ones with the heat treated steel gears, not cast, but they are difficult to find these days. Aside from being more difficult to move the cam around they will easily outlast the rest of your engine and by design the "smooth" drive and contant tooth contact has a power advantage over any type of roller timing set.........
https://forums.maxperformanceinc.com...1&d=1677499764
https://forums.maxperformanceinc.com...1&d=1677499781

I assembled my engine one time and had a noticably tighter than normal std. chain,

some short time later i chainged the camshaft and i noticed the soft babbit face of the front bearing was displaced and created a small lip that i had to contend with while changing the cam

next time I am in there i intend to change that bearing as i wasnt prepaired at the time and total destruction did not appear to be imminent,

if it was a harder faced race bearing it may of overheated instead of conforming

Cam and split precision bearings in these engines use a film of oil between themselves and the part being supported. In theory there is NEVER any actual metal to metal contact as pressurized oil is used to fill the space between the parts.

It makes sense that IF you were to install a timing set that has downward tension on it you are going to diplace out the oil between the front journal and cam bearing and could have issues in that area.

Same thing with installing a cam that requires some effort to tuirn it. It should turn freely with two fingers or the builder should NOT proceed with the engine build till that problem is corrected. Pontiac engines have enough issues with cam bearings right to start with, so no need to help them out any more with a super-tight timing set.....IMHO......

Never thought about this parameter very much , but it does raise an eyebrow.
Always figured just one or two links were a fraction shorter.

The taper on the gears would be a highly calculated piece of precision.
The gears would have to have special ID on them.

Whichever way any MFG is doing the short set , seems like the un-normal element(s) would have a special marking to differentiate it from normal. Compared to standard.
Thinking out loud

Good Topic. I will have to reconfirm that the Timing Chain I installed on the 455 Engine
was not a .005 chain. Block has never been line-bored. I bought 2 chains years ago.

Tom V.

You have explained this before about factory timing chain sets Cliff. Years ago, I was pondering a double roller set for my car but was talked out of it by an Ex-racer. He said use the factory timing chain and gears because they were made for your engine!! Back then, I knew the parts manager of my local Pontiac dealership and I had him run the part numbers on the national parts line. He found the stock chain and gears at a reasonable price. Even though I wasn't having any issues, I decided to change the timing chain set. The set had been changed prior to my ownership because of the famous Pontiac timing gear failures we're all aware of. Everything looked fine but the chain had a bit of slop in it. I installed the new set and lined up the factory marks that had not changed. Ran beautiful but when I put a timing light on it, the mark was advanced several degrees! I returned it to the stock setting and feared I was off a timing tooth or more. I talked with my racer mechanic again and he said the new chain took up the slack from the old chain and your engine should perform better now. He went on to say the old chain must have been really sloppy. It didn't look like that but must have been. I learned a great deal by doing this work myself and having a seasoned mechanic give me solid advice!!! Cliff is correct, stay with the factory timing chain and gear set!!

I've also taken some critisism for recomending "stock" type timing sets.

EVERYONE, even highy experienced and educated folks still believe that a "double roller" timing set is an upgrade over a USA made 3/4" wide factory type set. I don't consider that to be an accurate statement, but in the big scheme of things it really doesn't matter.

The bad reputation the stock sets get is simply becaused some early versions used a plastic coated top gear that eventually started flaking off teeth and failed. If you don't think the Morse chain is strong split apart nearly any HD 4 x 4 transfer case built in the last 30 years and see what kind of chain they use.......I'll bet it's not a "double roller" variety!.....
https://forums.maxperformanceinc.com...1&d=1677563719

Out of curiosity I called Cloyes yesterday and the tech I spoke to said the shorter set ups offered for motors that have been line bored or honed is all accomplished in the lenght of the chain, never the gears.

How long would it take for one of these chains to loosen up? Most folks degree the cam more advanced for chain stretch.

Agree the plastic coated factory sprockets probably did more for the double roller chain market than any other single item. Also agree some professional racers insist on using a flat link chain set-up even with the plastic sprocket in some cases because of the superior harmonic dampening they claim. I would just add that the QUALITY of the timing set, specifically the chain makes more difference than the design. I know of situations where people have rebuilt transfer cases with drive chains like the one pictured and after less than 10,000 miles the chain was slapping around in the case making aluminum chips and jumping teeth under load. The crappy Chinese chain had stretched out that much. Factory GM/Pontiac timing sets were flat link and had Morse chains = high quality. I would use them without issue. The reinforced chain from the 4-cyl Tempest engine is even better. Used to run them all the time. But try and find these parts today. I am sure there are a few obscure sets out there. Double roller sets same deal. You need a quality chain. IWIS, JWIS, Renold are all high quality chain manufacturers and their brand mark is on the chain links. No name at all, made in China, and Rolon brand made in India, not so much. Choose your parts carefully.

When I bought my last chain I needed a .005 short one. I wanted to buy a Cloyes but their tech told me the sort sets do not get their top Z chain, only std length get them
Rollermaster have gotten a bad rep by some people. But they do use their top IWIS chains on their .005 sets. So that is what I bought from Butler.
We will see how that goes but it was the best one I could find for a line bored block.
If I have any troubles I will go with a Milodon gear drive. People seem to love them.

I don’t have anything to ad to this post but got an interested 3/4 link stock like timing set I got from Cloyes about 6 months ago. The cam gear is billet.

I like those better than the cast iron top sprocket variety but I've never had or seen any issues with either type. I'll add here that there are more failures with double roller timing sets than we hear about or would suspect. I know of two in the the past year or so from board members here but they don't post their experiences about them. One of those failures was similar to the Rollmaster that failed in my own 455 about 20 years ago. Without warning the car started loosing power and slowing WAY down at the track. It also started making a LOT of noise from the front of the engine. I never suspected the Rollmaster timing set in my engine was taking a dump because I had the timing cover off 4 times about a year before it failed to move the cam for ICL street and track testing. At that time the chain was pretty tight with no more than about 3/8" to 1/4" slack in it.

I suspect what happens is that without a tensioning device the chain starts slapping around with great force once it developes a certain amount of slop in it which leads to it failing pretty quickly. This can't/doesn't happen with a Morse chain due to the far different design.

A testimonial for how good the stock type sets are is when I pulled the engine from my dad's 1991 Chevy 3/4 ton HD truck. It had logged over 250,000 miles and running just fine till it broke a ring land in one of the pistons. 1991 was in the transition years for GM going from flat to HR camshafts. His engine to my surprise was a roller block but had a flat cam in it and a dinky little 5/8" wide stock link type timing set in it. It was still in fine shape, not really all that much slack in it considering the mileage and would have went quite a ways further if the piston had self destructed........

Below are the two types I use here. The second pic is the Melling version last time I bought one with the cast iron top sprocket. It still used the good USA made chain, but who knows today what will show up on one.....
https://forums.maxperformanceinc.com...1&d=1677648985
https://forums.maxperformanceinc.com...1&d=1677649137

I have one of those and a Morse on the shelf. I wish you could get them shorter.
Might use one on my IA2. Bet it would be one of the few aftermarket block builds with a stock type chain.