How tight should a timing chain be?

I have a used rollmaster 9-way timing set that I was going to re-use. According to the generic instructions on their site, with 3/8" of slack in the chain it's recommended to use a line-bore set. My block has recently been line honed. So I got the .005" rollmaster set from TA. The new set is very difficult to get on. I had to use a wooden handle from a hammer to pry to 2 gears apart to get the sprocket on; I couldn't assemble it with just hand pressure. It seems tight. Now I have 1/4" slack using just thumb and finger moving the chain with just a little effort.

I watched the David Vizard video about timing chain slack in which a tight setup with 1/16" of slack lost 11+ HP (out of 475) on a SBC vs a looser setup with what looks like 1/4" slack. He also mentions that the ignition timing jumps around more with an even looser setup.

Not looking to gain the last couple hp but instead am more concerned about longevity. Any comments?

 

My take is all new chains will only get slightly looser, never tighter. You can check the push / pull slack thru the fuel pump hole after some use.
Yes, too loose and the timing isn't rock solid.

 

I've not had a chain be that hard to get on and off.....
I.find on my buick it easier if the cam is 180 out to set the chain and gear on then spin the cam around........it seem to allow the gear to come on and off easier and since it only lines up 1 way can mess it up.

Here are 2 recent short video of a 502 stk single roller chain with about 500 hrs to new......that chain was killing the timing setup. On the new chainni was pushing about twice as hard as the old.

I've never seemed to get life out of my roll masters I wanted. Never had a direct issue I can pin to them though......they always seem much looser than I wanted to see when I got back in there



https://youtube.com/shorts/Iq51Tgu2y-w?feature=share

 

I've actually used a .005 oversize chainset that was used and stretched already on a non-align honed block and it fit just perfect!.

 

The chains I use are Rollmaster and ProGear. Very nice pieces. I’ve had a Rollmaster in one of my solid roller engines for 20 years,daily-driven and raced. I had bought a spare way back when I built the engine,but it is still in the package because the first one never got sloppy yet.

 

They should have a small amount of slack when new since I believe they will tighten some during initial break-in. If there is no slack you risk eating the front cam bearing. The stock nylon coated aluminum even if tight won't hurt the cam bearing since the nylon is softer.

 

You will be fine, they stretch out fairly quickly. Not uncommon to have to have some help to get the chain on our engines, I have a meathod that uses some leverage to get the sprocket on the top gear.. it's part of how our stuff is designed..

JW

 

Looks like you really had to move that cam to get it dialed in.

 

That was I believe one of the 1st 350
TA rollers, ground by Erson, and it was one full tooth off. Mike told me it happens, and it did. Was a pita and add'l degreeing to figure that one out.

 

I've had to jump 1 teeth then retard on the crank to get the numbers right b4 on rollmasters

 

I wish it was the Rollmaster, Cloyes in my case, but it was used on previous build with Lunati cam and was fine.

 

So I have never changed timing gear myself, but I am about to do it myself so I have stumbled across a few videos on the subject. This seems like a neat method for getting the chain on [at around 26 minutes]:


Here is a guy who can present a rather convincing argument on the risk of having a too tight timing chain:


He argues that he has seen engine blocks cracking due to too tight chains and possibly a bit of runout in the timing mechanisms.

 

A man told me years ago:
Don't believe anything you hear and only half of what you see!

 

My Rollmaster cam gear is VERY tight to get seated on the cam in my 350, chain seems ok as far as slack, not real tight, not sloppy, I call it good
In multiple tear downs I haven’t noticed any wear or the chain getting sloppy, I don’t worry about it.

 

Since this is a timing chain discussion, I've looked into Rollmaster and they do not make any chains. They are supplied with either a Iwis or Jwis. Some other brand sets may have Rolon, which seem to have good reviews, even tho made in India.
Another can of worms....

 

I decided to take a little more scientific approach to the chain tension. I messaged Rollmaster tech and they replied that all line bore sets were oversized only in the crank gear. The top sprocket and chain are all the same. Using the oversized crank gear was out of the question as it is too big and makes chain installation nearly impossible. So I mixed and matched the upper sprockets and chains. Using a fish pull scale and a metal rule, I measured the play with 3 lbs of pull. Combination of old sprocket and new chain gave me about 1/4" of slack. Which to me seems fine. The upper gear will pop on using only finger pressure. The pic is using the old chain which has about 5/16" play.

 

So something to try to figure out when a block is lone bored......is how much did the crank truely.move up.

It the process only moved the crank up a few thousand going to a .005 setup would make the setup tight.

I had a block where we put billet caps on the mains.....they needed bored in, bobb set it up to barely hit the block saddle and take most out of the caps that were undersized to begin with.......this allowed the aline hone to finish the sizing and not take much out of the block and not need a timing set to be oversized even though it was line bored and honed

 

Guess if the crank gear is larger by .005, that would only be maybe .0025 of movement of the chain down to snug it up?
Yes, if Bobb just fuzzed the block side of main saddle, it should be close to stock dimensions.

 

But what we don't know is how much truly bigger the crank gear is......the set i think is sold listed as line bore by .005

But what does that trans late too??? If the crank now sits a true .005 higher in the block......is the gear only .005 bigger??? Or is it .010??? If the crank moved up by .005 one would need to extend the the gear down by that much to keep the chain the same place.....but down is only half a circle and the gear we also need need to .005 bigger on the other half making it .010 total bigger to make up the size.

If my gret matter hasn't confused me......which its known to lead me on some wild goose chases sometime.

But if the block was line bored but most was cut out ofvthe caps and then one sticks a gear .010 bigger on the crank I could see that snugging a chain right quick

 

I had my 462 line bored and tried to use a TA .005 chain and it was WAY to tight. Wound up using a standard chain and it was perfect. It's all in how you machinsist shades the bore I suppose.