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.