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timing chain

fatboyreyn

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Aug 31, 2006
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116
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east coast
Corvette
1986 red
What's the easiest way to check if your timing chain has jumped a tooth, on an 82.
 

wishuwerehere82

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Rochester, NY
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Red '82 Coupe,Sebring Silver '98 Coupe
The sure and accurate way to check is to pull the water pump, harmonic balancer, timing chain cover, and look at the dots on the sprockets. They should be aligned facing each other at Top Dead center
If there's an easier way, I am not aware of it.
 

Jack

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Dec 27, 2000
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Florence, SC (Timmonsville SC)
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71 War Bonnet Yellow VERT 71 BH Blue CPE (SOLD)
First, sbc/bbc rarely jump a tooth and continue to run.

If it jumps a tooth, the chain MUST have a lot of slack in it.

If chain has a lot of slack in it, the timing mark will dance around quite a bit if you put a timing light on it. Also, RPM will be unstable at a given throttle position.

I'd put a timing light on it before I'd pull the cover off.
 

grumpyvette

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Apr 17, 2001
Messages
841
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Loxahatchee, FL, Palm Beach co
checking your timing chain for excessive slack is real fast/easy on the first gen sbc engines
(1) MANUALLY with a breaker bar, rotate the engine in one dirrection,(clockwise looking from front too engine) untill the timing tabs at TDC if you miss and need to reverse dirrection, DON,T ......go around again, to aline it.
(2)once its aligned pull the distributor cap, mark exactly where the rotor points (it doesn,t matter if its 180 out),
(3)now reverse direction on the breaker bars force dirrection,and watch carefully how far you move the timing tab/tdc marks BEFORE the rotor on the distributor moves, more than about 6 degrees indicates a mandatory timing gear replacement up to two-three is fairly normal for an engine with some miles on it, but indicates a good deal of slack,NONE is of course IDEAL
 

HammerDown

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Jan 23, 2003
Messages
470
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Glenolden Pa
Corvette
1981 White/ Red int.
Hmmm... so could the OE plastic tooth gear and chain still be good w/120,000 on it?
Starts fine, idles smooth etc.
Something tells me...I'll be gettin my hands dirty !
 
Joined
Aug 19, 2004
Messages
485
Location
Denver, CO
Corvette
'72 Targa Blue Coupe
Grumpyvette is correct. He knows the deal. Sometimes, you don't even need to pull the cap. Just grab the balancer, rotate one way, and rotate back-you can feel the slack in the chain. Of course, pulling the spark plugs helps, but that's the quick and easy.

To get more detailed, you can pull #1 plug, "bump" to TDC, align mark on damper to zero, then do the breaker bar thing-that will give you more precise "degrees of slop" in the chain.

If you are running a nylon/plastic gear at 120K-that's asking for trouble. Make it go away..;)

Suggest true double roller replacement.

Rick
:gap
Buried in Snow
 

kmacpher

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Joined
Jul 18, 2004
Messages
5
Location
Warren, OH
Corvette
1981 Red
Yea I figured...maybe I'll wait till Spring, kinda chilly in the ol garage now.
Ahh, come on, it's been pretty warm this christmas (although I have got out the the garage- feeling bad that i've ignored her), you could have had this done and over before end of the year.
I did mine with a double rocker when I replaced the cam. The worst CAM i've ever seen, several lobes were gone - I can't believe the engine even operated.
Good luck in the Spring.
 

black_81_vette

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Dec 1, 2002
Messages
295
Location
wisconsin
Corvette
black 81 corvette 4-speed
with that kind of milage if it isnt shot its gotta be close ive seen those gears chewed up on cars with 50k on them! although a cam change would be nice remember the springs will need to be changed as the originals wont stand up to higher lift ect.And dont forget new lifters.
 

HammerDown

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Jan 23, 2003
Messages
470
Location
Glenolden Pa
Corvette
1981 White/ Red int.
Ahh, come on, it's been pretty warm this christmas (although I have got out the the garage- feeling bad that i've ignored her), you could have had this done and over before end of the year.
I did mine with a double rocker when I replaced the cam. The worst CAM i've ever seen, several lobes were gone - I can't believe the engine even operated.
Good luck in the Spring.
If I'm off from work next week I'll jump on it. I'd rather do it outside (more room) then in a small single bay garage. :crazy

Can I be sure a true double roller will fit under the OE timing cover?
Looking in the Summit website now for parts.

PS here's the real stupid part by me:eyerole ...few years back maybe 4-5 and 12,000 milws ago (I) pulled both heads, had them totally rebuilt, valves, guides, springs, even studs. New Cam and lifters. Comp roller rockers...new water pump and hoses.

BUT... I PUT THE OE CHAIN BACK IN...IT LOOKED LIKE NEW.
Now I have that uneasy feeling.
 
Joined
Apr 29, 2001
Messages
2,141
Location
Rio Rancho, NM
Corvette
1981 HD Suspension; ZN1 Option
The sure and accurate way to check is to pull the water pump, harmonic balancer, timing chain cover, and look at the dots on the sprockets. They should be aligned facing each other at Top Dead center
If there's an easier way, I am not aware of it.

Wish is right, and for the most part, there are not many stock sprockets still running out there [perhaps], but one clarification applies here:

The "dots" facing each other is an aftermarket feature.

So if it is the stock sprocket, then you'll surely find the crankshaft sprocket dot at 12 o'clock and the cam sprocket dot at 12 o'clock as well.

One can verify this by ensuring that when the 12 O'Clock dot is aligned at the top for the cam, the cam alignment dowel is positioned to the left side (when looking at the engine from front to rear).

This will position the #6 cylinder top dead center dot at 6 o'clock AND facing the 12 O'clock dot for the crankshaft.

So to recap, in stock configuration, both sprocket dots go at the 12 o'clock position. Also, not all stock sprockets include the #6 cylinder dot.

For aftermarket sprockets (the double-roller chain sprockets for instance), the cam dot faces the crankshaft dot when the crankshaft dot is at 12 o'clock (#1 cylinder top dead center). These sprockets only have one dot on their faces.

The cam dowel position is key in both situations, so use that as your verification step when aligning sprocket dots.

GerryLP:cool
 
Joined
Jan 1, 2002
Messages
7,246
Location
Washington, Michigan
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'67 Marina Blue Convertible
The "dots" facing each other is an aftermarket feature.

Nope - the factory crank and cam sprockets also have the "dots". When the sprockets are "dot-to-dot" (crank dot at 12 o'clock and cam dot at 6 o'clock), the convenient feature for alignment, the engine will be at #6 TDC on the compression stroke. Turn the crank one revolution, and both dots will be at 12 o'clock, and the engine will be at #1 TDC on the compression stroke.

:beer
 

fine69

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Dec 12, 2004
Messages
975
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Maryland / D.C.
Corvette
'69 Convertible Vette; '72 Z28 Camaro Rally Sport
"... look at the dots on the sprockets. They should be aligned facing each other at Top Dead center..."

Are you sure? When putting mine back together again, I believe the dot on each sprocket was at the top position (i.e., 12:00) for Top Dead Center, compression stroke. I'll have to check out my pics again, but I'm pretty certain.
 
Joined
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Messages
2,141
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Rio Rancho, NM
Corvette
1981 HD Suspension; ZN1 Option
Nope - the factory crank and cam sprockets also have the "dots". When the sprockets are "dot-to-dot" (crank dot at 12 o'clock and cam dot at 6 o'clock), the convenient feature for alignment, the engine will be at #6 TDC on the compression stroke. Turn the crank one revolution, and both dots will be at 12 o'clock, and the engine will be at #1 TDC on the compression stroke.

:beer

John,

That is a nifty way to do it for stock cam sprockets. :beer I have always done it the hard way, apparently.

However, I believe that aftermarket cam/sprocket manufacturers state in their instructions to place dot-over-dot while the #1 cylinder is at top-dead-center. They don't include #6 cylinder TDC marks on their sprocket (generally speaking, perhaps there is one brand that does).

I suspect that aftermarket manufacturers chose to place the #1 cylinder at TDC, and then make their cam sprockets to only include a dot at the six o'clock position that would align the cam in its proper position at the #1 TDC. That's what I meant as an aftermarket feature. I recall also that I read an article as well in CH magazine calling it an aftermarket manufacturer's feature, though, perhaps for the same reasons.

Thanks!

GerryLP:cool
 

wishuwerehere82

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Joined
Sep 6, 2003
Messages
2,314
Location
Rochester, NY
Corvette
Red '82 Coupe,Sebring Silver '98 Coupe
If I'm off from work next week I'll jump on it. I'd rather do it outside (more room) then in a small single bay garage. :crazy

Can I be sure a true double roller will fit under the OE timing cover?
Looking in the Summit website now for parts.

PS here's the real stupid part by me:eyerole ...few years back maybe 4-5 and 12,000 milws ago (I) pulled both heads, had them totally rebuilt, valves, guides, springs, even studs. New Cam and lifters. Comp roller rockers...new water pump and hoses.

BUT... I PUT THE OE CHAIN BACK IN...IT LOOKED LIKE NEW.
Now I have that uneasy feeling.
I put a Cloyes double roller in my 82 with no fit problems.
 

wishuwerehere82

Well-known member
Joined
Sep 6, 2003
Messages
2,314
Location
Rochester, NY
Corvette
Red '82 Coupe,Sebring Silver '98 Coupe
Are you sure? When putting mine back together again, I believe the dot on each sprocket was at the top position (i.e., 12:00) for Top Dead Center, compression stroke. I'll have to check out my pics again, but I'm pretty certain.
Whether at #6 or #1 TDC, the dots will not line up if the timing chain has jumped a tooth, and it will be noticable.
In my book, the dots face each other for timing chain and gear replacement.
 

HammerDown

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Jan 23, 2003
Messages
470
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Glenolden Pa
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1981 White/ Red int.

wishuwerehere82

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Joined
Sep 6, 2003
Messages
2,314
Location
Rochester, NY
Corvette
Red '82 Coupe,Sebring Silver '98 Coupe
Thanks for the feedback...I'll be into it tomorrow.
Probably going with Summits true roller set...
http://store.summitracing.com/partd...4294840140+400304+4294892073+115&autoview=sku

or CLoyes
http://store.summitracing.com/partd...4294925046+4294840140+400043+115&autoview=sku

I know someone makes them for Summit, maybe Comp?
My engine shop ordered all of my parts from Summit when they did my valves and bored my cylinders for me. The shipping time was fast. Everything was ready for me to pick up when the block and heads were finished.
I requested the Cloyes set, and they agreed that it would be the best choice.
Timing chain+gears,pistons,rings,bearings,pushrods,cam,lifters,oil pump,gaskets. Everything came in all at once. No backorders.
 
Joined
Jan 1, 2002
Messages
7,246
Location
Washington, Michigan
Corvette
'67 Marina Blue Convertible
John,

That is a nifty way to do it for stock cam sprockets. :beer I have always done it the hard way, apparently.

However, I believe that aftermarket cam/sprocket manufacturers state in their instructions to place dot-over-dot while the #1 cylinder is at top-dead-center. GerryLP:cool

That's correct - when the sprockets are dot-to-dot, #1 WILL be at top dead center, but NOT on the compression stroke. That's why so many distributors get installed 180* out and the engine won't start; you have to turn the crank one revolution from the dot-to-dot position in order to have #1 on the COMPRESSION STROKE.

:beer
 

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