New Timing chain tightness
 

How much space is acceptable between a new hydraulic tensioner with pin installed and the idler arm?

Background:

Upon rebuilding my 2.4 engine I've observed the chains tension appears tighter than I've seen in Wayne's Rebuild book. I have all new sprockets and one piece iwis chains.
I've also measured the links spacing on the new one piece and the old chain, which are the same and have the same number of links. Additionally, I checked a new master link chain and it also measures the same.

I've verified my deck height with a depth gauge to be .050" utilizing a 1.25mm or .050" base gasket. http://forums.pelicanparts.com/uploa...1707602014.jpg

Your 1.25 cylinder base gasket may have something to do with it. Why so thick? Hopefully not several shims stacked, which is not good either.

Were the case halves clipped, spigots milled etc? At end of the day, the deck height sounds about right and I assume all that work was done, neccessitating the use of the thicker base gaskets.

As long as chain isn't bunched up somewhere, it looks about right for brand new. Pull the pin and lets see the tensioner extend and take a photo. That's a shot I'm more familiar with.

But the pin is not pulled out of the tensioner. I’m confused, what is the concern? The timing is the timing and the chain tensioners run within a range of travel, not sure of any pre-pull of the pin dimensions.

Spec for deck height is .040”
Why change it? You r just making it harder on the rings
and inviting detonation

Ian

I'll pull the pin to check.
I'm concerned there isn't enough compression stroke available on the tensioner as I've seen the gap in yellow being Much closer to the top of the cam box. When the engine warms and stretches will this be sufficient or will I begin hearing these chains ?

The deck height is set where it is in order to keep the JE pistons set to 9.5:1

I don't understand why these chains are so much tighter than all others I've seen.... 😕... maybe this is "Ok" .??

Note, as a test and reference I ran a 1.5mm base gasket and there was No slack bn the pinned tensioner and the idler arm- see pichttp://forums.pelicanparts.com/uploa...1707666541.jpg

That’s Too Tight…………
 

Why are you using 1.5 mm base shim? The total travel distance of the tensioner plunger/piston is approximately 11.0 mm between fully extended and the pin installed. A 2~3 mm gap between the idler gear arm and the plunger with the pin installed would be a good starting point for new chains and sprockets.

Tony

IMO, 1.5mm is very little when you look at the geometry. Measure your old tensioner free length and I bet that it is a hole bunch more than you think. You could remove the new tensioner and compress, pull the pin and slowly and controlled let the tensioner extend. That is a whole lot of travel, and oil fed as well.

I took my ild and new and measured the full extension and came up with this.http://forums.pelicanparts.com/uploa...1707680990.jpg

All black and one brown chain guide?
I still think your missing something on the deck height , a real mistake in measuring some where.

Ian

Note, I'm running a 1.25 base gasket, not 1.5
Additionally, regardless of the base thickness the deck height measured with a depth gauge .050" and the solder method at .045, confirmed with an assistant multiple times.

Back to initial question, are these chains too tight?

Waynes book shows the area in yellow with very little gaphttp://forums.pelicanparts.com/uploa...1707690472.jpg

I guess I’m not getting it. The post title is “New Timing Chain Tightness “, and somehow we are jumping to cylinder shims. The design is cam chain tensioner is capable of a huge amount of X axis variables. The geometry of the cylinder base shim/gasket is a whole different subject, but only kinda related. I have not seen a unloaded tension gap dimension in the information I have. Where is this coming from. Are we saying Wayne’s book has a dimension or just a photo? Looking at the photo no slack without the tensioner released seems inconclusive until you release the tension. Also, clarify the chain ramps you have. Brown one should be on the lower right.

I’ve installed all brown ramps when I’ve encountered this situation, with no issues, it will give u more chain slack.

Ramps are installed correctly, 1 brown bottom right.

Maybe this is normal with new chains and sprockets...

Found this:
http://forums.pelicanparts.com/911-engine-rebuilding-forum/331575-when-replace-timing-chain.html

http://forums.pelicanparts.com/uploa...1707760241.jpg

Looks beautiful!

I think you're fine with that amount of clearance. If you want to make them truly bulletproof, you can do the "Jerry Woods Mod" on the pressure fed tensioners. Some people use copper tubing as a spacer, but I prefer using the old copper washers off of the cam housing feed banjo bolts. A couple of them in the tensioner body after removing the plunger will shim up the slack, just in case the oil pressure fed tensioner decides to give up the ghost. (Usually caused by the check valve at the top falling out) Another trick to prevent that is to drill a couple of holes in the body near the check valve, then safety wire the check valve in place.

Question for anyone: I've looked but have not found a spec for the chain length, or measurements across X number of links or pins in my Tech Specs book or other usual places. How does one measure chain wear?

I noticed I can get more out of the tensioner by lifting on the arm.. do I need to pre pressure these tensioners?



Another observation, if the book calls for the cams to be adjusted with the idler arms in a fully pressed position (vice grip) which is more than the tensioners can apply, how then are the cams adequately timed?http://forums.pelicanparts.com/uploa...1707790779.jpg

The main tension the tensioners is applying is spring pressure from the internal spring. You have that plus the little bit from oil pressure.
If you calculate the area of the tensioner and multiply that by the max oil pressure you will see the pressure from oil pressure is not very large. The tensioner really is just a little shock absorber that has a continuous oil feed to bleed out air and a spring to keep some tension on the system.
The oil pressure will blead out air from the upper check valve and the small hole at the top side of the tensioner (circled).

http://forums.pelicanparts.com/uploa...1707800636.jpg

Your pry bar shown is almost guaranteed to put way more force one the system than the tensioner ever will. You only need enough tension to keep the chain from jumping a tooth. This is most needed if the engine is rotated in reverse.

john