Timing Chain: How Tight Is Too Tight

[Blown & Injected]

Got a .005 under, just like last time, but this timing set feels too tight. I was not sure it was going to fit - had to get tough with it to get it on.

It is a Rollmaster on a turbo Buick so the timing tensioner has been removed.

This time EVERYTHING seems to be tighter than what makes me happy. So how tight is too tight for this V6?

Thanks.

[Ron Miller]

I did the same thing on a BB Chevy. I haven't run the motor yet, so I can't give you any info. I to have thought about how tight is to tight. I'm worried if I run the undersize chain, it might wipe out the number 1 & 2 cam bearing. Hopefully, somebody else will chime in.

[cjperformance]

Ive had some pretty tight chains, enough to make me think about this. This is how i tackle it and it has proved successful.
Fit the chain and turn the crank/cam over several revolutions, install one lifter just with thin oil- the lifter closest to the front whatever engine family it is, put a dial indicator on the lifter, zero the indicator, in most V8 stuff the lifter is around 45deg to the c/line of the chain, so you see less movement at the lifter than any up/down cam movememt(bearing clearance) so i then using hand force only grab under the cam gear and lift it upward(or inline with crank/cam c/line). If doing this i can get the indicator to move at all - i run it, i figure if i can move it basically at all by hand then an oil wedge can definetly get in between cam and bearing on startup when you consider the load the springs and chain drive load puts on the cam trying to force it down onto the can bearing. After half hour run time the chain has some more give anyway.

[novadude]

Craig - have you ever had any tight chains get rejected because they've failed your test? Just curious. I always just assume that if I can get it on the cam gear by hand and get the bolts in, it is probably OK to run, even if it feels really tight.

[MadBill]

Have you verified the under size? Most 0.005" chains are identified with one copper colored link while 0.010" unders have two.

On a related topic, I've never seen a different spec for aluminum vs. iron blocks of the same configuration. Theory would suggest aluminum should have 0.003-0.004" more slack cold.

[Blown & Injected]

Thank you. Just got done taking a look...

I put the dial at 12 o'clock on the chain and lifted on the distributor gear and got the dial to move maybe .002. It is late, gonna put it on the lifter closest to the front and try again tomorrow.

Did not see any different colored links.

Having trouble getting the timing right on this cam - wonder if this chain is causing me some trouble?

[cjperformance]

Craig - have you ever had any tight chains get rejected because they've failed your test? Just curious. I always just assume that if I can get it on the cam gear by hand and get the bolts in, it is probably OK to run, even if it feels really tight.

Yes I've had 4 , maybe 5 chains that i have not wanted to use but these have been almost impossible to fit by hand. I've often had chains i have had to set straight and square and use the cam bolt/bolts to just get the cam gear started and then have oulled on with the bolt/s but im talking socket and screwdriver handle with light hand work, no heavy hauling with a ratchet or spanner and these have been fine, even shown no chain movement with the valve gear in place, after a little run time there is always some movememt.
You would be right in thinking if the chain go's on by hand, it will be fine, it will.

[Dave Koehler]

Having trouble getting the timing right on this cam - wonder if this chain is causing me some trouble?

Nope, that's not it. No such thing as an advanced or retarded chain. Dumb...maybe.

[novadude]

Craig - have you ever had any tight chains get rejected because they've failed your test? Just curious. I always just assume that if I can get it on the cam gear by hand and get the bolts in, it is probably OK to run, even if it feels really tight.

Yes I've had 4 , maybe 5 chains that i have not wanted to use but these have been almost impossible to fit by hand. I've often had chains i have had to set straight and square and use the cam bolt/bolts to just get the cam gear started and then have oulled on with the bolt/s but im talking socket and screwdriver handle with light hand work, no heavy hauling with a ratchet or spanner and these have been fine, even shown no chain movement with the valve gear in place, after a little run time there is always some movememt.
You would be right in thinking if the chain go's on by hand, it will be fine, it will.

Thanks. I was also thinking that the load at the front cam bearings from the valvetrain will be far higher than the load from a tight chain, as long as the cam sprocket can be coerced into place by hand.

[Newold1]

Here is a good time for the "Kiss theory" at work. Obviously on standard type timing CHAINS there has to be little slack on a timing chain set and gears as a group. With the chain and camshaft installed ( no lifters) put a metal straight edge on the chain between the two gears. Then at the midpoint between the gears use a good stiff metal rod or such at that point and mark and measure how far you can push the slack of the chain in. It should be about a !/8-1/4". If it's tighter or looser than that it is either the wrong size chain or a worn out chain or gear set. Obviously there are no exactly perfect timing chain sets and the slack will vary and this is why on a good build you dial in a camshaft to put the opening and closing points where you want them ideally. It's not hard to receive the wrong size chain even when new. A late shift Friday put chain in correct box can and does happen. I as well as others here have experienced this and that's why it should always be one of the items checked and adjusted on a good build especially with line boring of mains and timing chain set changes.

[piston guy]

I had to repair an engine with a "tight" chain. It took out the front cam bearing and main bearing in less than an hour running time TWICE from previous builders. I first put on a new replacement chain and it was too tight. So I ended up using a used chain to get a small amount of "slop". New cam bearings and main bearings and it's still running 6 years later. I can only guess the gears were "big" in diameter.

[BOOT]

Not too much exp messing with chain fitment myself but a car I bought that i later tore down the engine to refresh had a tight chain and wore the front cam bearing, never checked the mains as it was scrap.

[desoto30]

Over the years I have had a few chains that were what I considered very tight to fit by hand. Once installed the created no problems.. I put the tightness down to the slight gear misalignment existing during fitting as the cause of the tightness

[Newold1]

I think unless the engine is equipped with a tensioner like some of the aluminum LS's you need a little slack. Too tight and you can wipe out bearings!

[fastblackracing]

Ive had some pretty tight chains, enough to make me think about this. This is how i tackle it and it has proved successful.
Fit the chain and turn the crank/cam over several revolutions, install one lifter just with thin oil- the lifter closest to the front whatever engine family it is, put a dial indicator on the lifter, zero the indicator, in most V8 stuff the lifter is around 45deg to the c/line of the chain, so you see less movement at the lifter than any up/down cam movememt(bearing clearance) so i then using hand force only grab under the cam gear and lift it upward(or inline with crank/cam c/line). If doing this i can get the indicator to move at all - i run it, i figure if i can move it basically at all by hand then an oil wedge can definetly get in between cam and bearing on startup when you consider the load the springs and chain drive load puts on the cam trying to force it down onto the can bearing. After half hour run time the chain has some more give anyway.

This is a great idea.....Thanks, I learned something new today.