Chain slack, what is it?, and how is it recognised?

H.G.P. · 02-08-2005, 10:15 PM

1. When installing new chains and new tensioners, (or perhaps examining chains already in use), is there a way to check for chain "slack". When is a chain in slack?

2. Can chain slack be felt by hand, or other measurement?

3. Is chain slack or excessive loosening very visible?

4. Also, for those solid mechanical chain tensioners, how did the early (or current racer who uses them), know how much tension to use?

Thanks.

"We shall be waiting for your answer. The decision rests with you"

RoninLB · 02-09-2005, 12:50 AM

Re-build Experts chew on this one!

H.G.P. · 02-09-2005, 08:08 AM

Quote:

Originally posted by RoninLB
Re-build Experts chew on this one!

I guess I'll first take all the tensioers I have, counting the mechanical one I used for the cam timing, and compare their tension effect on the chains.

So what exactly is happening with these oil filled (or is it "spring" )tensioners?

How would one identify the beginnings of a chain tensioner collapse, if not by some type of finger/hand feel?

RoninLB · 02-09-2005, 09:02 AM

I only know from doing mine and from what I read around here. Great pelicanhead experiences in search.

anyway, from what I can surmise for a heads-up,

With operating eng temp and engine stabilized after 10-15mi+, and then giving a full open throttle wack to 5K+ rpm and then quickly letting off the throttle should stress the tensioner that if I hear a garbage can chain rattle I'll figure the tensioners have one foot on a banana peel and the other in the grave. I'm not sure if this is correct for a long duration heads-up, it's only a "surmise"? This has never been addressed around here afaik.

If you come up with hard info please let me know.

H.G.P. · 02-09-2005, 01:37 PM

I checked with the old tensioner(s) today. The chains are such that I can't hardly get them under the arm.

For those who can relate: After tensioner install, would pulling up the chain, "so far", from the rails, tell something about proper tension? In other words, say I can lift the chain 1/4 inch up from the rail, is this firm enough?

KobaltBlau · 02-09-2005, 02:05 PM

sometimes this is called "stretch", but it's not really stretch, it's where the movement wears shallow grooves in the pins, which adds up to a longer chain. there are tools to measure this on a bicycle, since nearly all bicycle chains have the same pitch (not hte same width. I would think that a chain running in a clean oil bath wouldn't experience much pin grooving, but I really haven't done the homework on this.

This web page illustrating the use of a bicycle chain tool might help you understand what I'm saying. The tool is based on an assumption of the pitch, and shows additional deflection from the pitch specification:

http://www.parktool.com/tools/CC_2BIG.shtml

just to be clear, this tool wouldn't work with a 911 cam chain since it is a different pitch (AFAIK). however, a similar tool could be built with some effort.

KobaltBlau · 02-09-2005, 02:08 PM

it actually looks like you may be talking about tensioner performance which is a different issue, but both are interesting.

H.G.P. · 02-09-2005, 04:13 PM

Quote:

Originally posted by KobaltBlau
it actually looks like you may be talking about tensioner performance which is a different issue, but both are interesting.

Yes, that's what I'm trying to find out. In other words, can you tell that the tensioner is doing it's job, by it's measured tension on chain?

And what would be an "ideal" way to tell if the chain is reflecting correct tension? A certain amt. of flex I can move the chain with my finger/hand from the chain rail (the rail closest to the rail)? Along the same idea, is it possible a tensioner can have too much tension on a chain, if so, how can I tell?

Thanks

H.G.P. · 08:18 AM

1. The timing chains are supposed to always be on the rails (slippers) aren't they?

2. Also, will a brand new chain, effect the cam timing, because the chain has a break in period?