Technical How can you test to see if timing chain needs to be replaced?

Is there a test you can perform to see if a timing chain needs to be replaced?
The engine is a small block 350 Chevy with HEI ignition. The motor is early 80's vintage, true mileage unknown and also unknown if timing chain has been replaced in earlier years. The engine misfires at 1400 - 1800 RPMs. The distributor is brand new.
Thanks!

 

I've always thought if the timing stayed where it was supposed to........... could pop off the dizzy cap, turn the crank pulley back and forth to see how much play before the rotor moves.

 

The only real way to check is to pull the timing cover and check the chain.

A miss can be caused by may things not just timing and distributer.

 

put a breaker bar on the crank bolt, rock the crank back and forth a little, you should be able to feel the slop in it. I don't know what the maximum allowable slop is...have fun!

 

One problem that we have is that there is no way to explain what you and I feel for.

 

With the engine not running (!) and key 'off', rock the crankshaft forward and backward, you can feel the slack in the chain. Any more than 5 degrees (clockwise to counter clockwise at the timing mark) and you have a loose chain and/or plastic teeth worn on the cam sprocket. 10 degrees and hurry and pull the cover...20 degrees or more?
The engine 'wasn't running when parked'!

I disconnected a 911T Porsche chain and tied a new chain onto the end with an Alfa Romeo master link, feeding it onto the cam sprockets as I turned the engine with a remote starter.
Two Porsche 'techs' (LOL) asked me how I dared such a feat! I told them it was just to check if the old one was stretched.
Blank 'deer-in-the-headlights' stares...

 

You can watch for rotor movement.

But I'd bet the coil is flakey and causing it to break up.

 

Phtt
Just look for a little hole on the timing cover where it's been slapping.

 

This was the one in my Chevy 350 when I was taking it apart. Supposedly 60k miles and I ran it in a stock car for 6 races, pulled it to 6300 RPMs quite a bit.

 

Not a lot of useful answers here so far. Bob is pointing you in the right direction you want to look at how much the chain can be deflected on the "pull" side. The amount depends on if it is a link style chain or roller chain, the max is less on a roller chain IMO, because the roller has more inherent flexibility.
A stock link style chain in a small block chevy or ford, you shouldn't be able to deflect it more than 1/2". Take a straight edge, lay it along the outside of the chain on the "pull" side, and push it in in the center of the run between the two gears. If you can deflect it more than 1/2" from the straight edge, its hashed, IMO. In other words, I probably would have replaced Bobs example above. Its a little hard to tell by looking at an internet photo, but that looks close to the limit, if a timing chain skips when you are beating on something, you stand a good chance of kissing the whole engine goodbye. A roller chain should be a little tighter, much more than 3/8 is getting iffy.
The reason I specify sbc or ford, they are more or less the same difference between gears, if the run between gears is longer, like a small block mopar for instance, naturally it will deflect a little more.
Most guys will change the gears whenever they change the chain, if the teeth look "hooked" at all, DEFINATELY replace the gears.

 

The simple way to get a pretty good idea is others already said is to rock the crank back and forth while watching the rotor to see how may degrees of movement you have on the crank before the cam and distributor. You don't want to try that on OHC engines but works on most US V8 engines that have a timing chain setup. That can give you the indication of yup I need to pull it apart and change the timing chain or it looks like it's good for a few more miles.

 

That's not a test brother, that's a tear down and inspection.

The symptom he has is "misfire at 1400-1800 Rpm"
I'm more than reasonably certain a stretched timing chain won't be one of top or most likely causes.

 

Well, he asked how to tell if a timing chain is hashed, he got the correct answer. I agree 100% its not whats causing his miss, but I don't play the "internet trouble shooter" game, its a suckers bet and pure guesswork, I leave that for the other guys.
I also made an error in y original post, you measure the slack side, not the pull side, I was trying to edit it when my power went out for a couple minutes!

 

Vicky, you should know me by now, I don't DO "half-assed".

 

No he didn't ask that question.
But You correctly and quite thouroghly answered a different question.
So I guess we are still at "not a lot of useful answers here "?

 

The "look for the hole in the timing cover" answer is pretty useful

 

Thanks for all the replies so far! This is a project I'm working on with my bf and his 47 Ford. I'm the technical information gatherer and apprentice wrench.

 

Uh, really?

 

LOL I had a Buick 6 once in a '64 Wagon that the chain was so loose you could actually hear it rubbing on the cover. I ran it until it was spitting oil and I had to replace the cover, I figured that while I had the cover off I may as well replace the chain. I am not sure that the chain was wore completely out, but I didn't want to pull the cover twice.

 

Well let's see - to me they are different.
You know I love you brother

He asked for a diagnostic procedure - "A test" specifically.
"Is there a test,,,,,, to see if,,,,,,
Because he now can not see ??? (the timing chain)
Since he's experiencing a symptom , the vehicle is together and fully operational.

Apparently there is a diagnostic test but not quite a good enough one with solid results.
An inspection is the only way to warrant if the tear down for the inspection was needed.

or perhaps it really is

"How to tell if the timing is hashed" (worn) ?

Drain the coolant, remove shroud, fan, radiator, accessories, water pump, pull the balancer, drop oil pan, remove timing cover and then , Once the front of the engine is torn down,,,,
the inspection procedure goes like "this" look for "that" and if "then" do the "other" as well. Correct as can be. Now, If your in that far you might as well change the damn timing set no matter what.

Once you get the engine torn down that far we are just 10 mins away from our next "what cam" thread.
And since the pan is off what about the oil pump? Water pump? Those items are too cheap not to do at that point right? Yes the timing cover can be fought into the pan and over the pins and then drive in a new seal but I ain't redoing it when it leaks.

Most useful answer, look for the hole in timing cover.

 

I used to have a Pontiac Grand Prix with a 400 in it. it always idled bad and just didn't run right. the way I tested the chain was to do powerstands until the tire popped. after I put a different tire on it and did some more powerstands the chain broke and I mucked up the valves. the new chain did not fix the bent valves.

so I say go do powerstands and if it does not break your problem lies elsewhere.

 

ah

 

ah and SOMETIMES with a timing light on ... the line can jump around some ...

 

Its the only way to KNOW if a timing chain is hashed.
Here is a short list of some of the possible mechanical causes of the timing moving around, in no particular order. 1) excessive cam end play, 2) breaker plate not stable 3) worn bushings in distributor 4) hashed vacuum advance unit 5)worn timing chain 6) worn distributor gear 7) worn cam gear 8) oil pump problems. Hardly what I would call a conclusive test for a worn timing chain, is it? I know, I know, my methods aren't usually suitably "shade tree'. But they ARE usually accurate. I learned a long time ago to "quit f*cking around, and do it right". What can I say?
As far as the "hole in the timing chain cover diagnosis, that's pretty late in the game. Just run it to 7000 a couple times, then do a compression test. The holes with no compression are the ones that have the valves that bent when the chain skipped a couple teeth.

Shit I see while I was adding that last bit, ratfink posted the same method!!

 

FWIW, a similar method will work if you are not sure if that noise from the rear axle is a bad u-joint, or a couple broken gear teeth.

 

This answer from porknbeaner is the correct way to check for a worn timing chain.
If you believe the timing chain is causing your misfire, put that idea further down the list of possibilities.
I'd look at the coil, as my first suspect.

 

just buy one of these ---- to solve the TC dilemma...
http://www.ebay.com/itm/like/191453625866?lpid=82&chn=ps&ul_noapp=true

 

Turn the crank in the direction of rotation watch the rotor when you see it move , reverse rotation of the crank watch to see rotor move . When you see it move , if crank moves more than 6 degrees , chain is sloppy . Doesn't mean it will not run , it may for many miles . Just not as best as it could . If it is OEM gears chances are plastic covering on sprocket teeth are shot and need replaced with new chain and metal only gears .


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wrench or wench ? LOL, no disrespect intended. He is a lucky guy to have you as apprentice/tech assistant !