Timing Chain on 03 4.3 - S-10 Forum
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Timing Chain on 03 4.3

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Old 01-25-2011, 05:45 PM   #1
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Timing Chain on 03 4.3

I'm working on replacing the timing chain on my 03 4.3L S10 (216k miles) but when I put the new sprokets on the engine, they won't line up (front/back-timing marks line up fine). Looks like there's a solid 1/16" discrepency. At high rpm, that can put a lot of strain on the chain. Do I need to pull the crank sproket back off and mill off .100"?
Old 01-25-2011, 07:24 PM   #2
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Re: Timing Chain on 03 4.3

what brand of timing set are you using?
is the crankshaft gear fully seated?
Old 01-25-2011, 08:09 PM   #3
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Re: Timing Chain on 03 4.3

I used a sprocket/chain set by S.A. Gear that I ordered from Advance. If the cranshaft sprocket isn't seated down all the way, it might have .010 left to go, can't tell for certain. But that .010 shouldn't be a problem (especially since my gap is over .050.
Old 01-25-2011, 11:30 PM   #4
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Re: Timing Chain on 03 4.3

your crankshaft sprocket is offset, and thus directonal.
about .050" is roughly the amount of the crank gear offset.

if your crank gear isnt nstalled backwards, double check to
make certain you got the correct part # timing set.

i'm usng the S.A. Gear timing set as well.
Old 01-26-2011, 12:13 AM   #5
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Re: Timing Chain on 03 4.3

I'm pretty sure that I got the sprocket mounted right since the shoulder thickness measures +/-.010 from the original (based on how good of a reading you get). Guess I'll have to pull it back off and see what's wrong.
Old 01-28-2011, 09:23 AM   #6
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Re: Timing Chain on 03 4.3

I returned the part to Advance and got another one from Car Quest--much better manufacturing. Also, the gears fit fine. Next time I do this job, I'm buying an air hammer.
Old 02-04-2011, 03:22 PM   #7
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Re: Timing Chain on 03 4.3

New devlopment: I replaced the timing chain because of a P0016 code. However, the code still exists.
Old 02-06-2011, 06:05 PM   #8
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Re: Timing Chain on 03 4.3

a worn distributor gear is also a common cause for a sudden
crank/cam correlation code.

an air hammer? for the crank gear?

a 3-jaw gear puller works great for that.

and just a hammer and and a short extension
do fine for installing them...
Old 02-06-2011, 10:31 PM   #9
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Re: Timing Chain on 03 4.3

Yeah, I used a hammer and PVC pipe but it still took all day to get the crank gear seated. I've come to the same conclusion that my problem is in the distributor. However, I'm not sure that it's a worn gear. I think I might just pull it out and reset it 12 degrees BTDC on the #1 cylinder. Any advice on how to get an accurate read as to what 12 degrees is?
Old 02-07-2011, 02:16 AM   #10
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Re: Timing Chain on 03 4.3

not sure what you mean about setting it at 12 deg.

on 96-laters, you simply bring cyl. 1 to TDC compression stroke,
and make sure the rotor is pointing right at the little arrow
molded in the dist. base with the number "6" on it.
you could wiggle the rotor side-to-side to gauge
how much freeplay it has. shouldnt move more than a couple
degrees.
Old 02-28-2011, 07:04 PM   #11
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Re: Timing Chain on 03 4.3

I also have a 2003 S-10 4.3L with a possible timing issue. Recently took my vehicle to a non gm dealer because it has been sluggish and getting about 3 to 5 miles per gallon less than what i feel is normal for my S10 ZR2(was about 20, now around 15mpg). No codes, no stalling, just sluggish and decreased mpg. The tech at the non gm service station is telling me the timing chain is "1 tooth off running at 6 degrees retarded" and would likely be causing my sluggishness/mpg issue. Since chevrolet replaced the timing chain and associated hardware approximately two years ago, i took the truck back to chevrolet to get their opinion. Chevy service center called me today to advise the timing chain is 7 degrees retarded but still within limits(Chevy says chain can be off by up to 16 degrees) for this engine. The chevy service center advised the trucks "computer" will compensate for the difference. Chevy says no problem with the truck, come pick up your vehicle. Called the non gm tech back and he advised there is very little tolorance for the timing chain(maybe 1 or 2degrees) and the chevy dealer is incorrect regarding computers ability to compensate for 6 degree deviation. Does anyone know who is correct? Anyone know where I might be able to find "printable material" on 4.3L timing chain variances?
Old 02-28-2011, 09:15 PM   #12
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Re: Timing Chain on 03 4.3

I'm not sure what chevy was talking about by saying that the timing chain was retarded (other than to say that it's stupid and a royal pain in the butt to change). If your timing chain is off by a tooth, then it should give you a P0016 code 'CAM/Crank correlation' because the cam and the crank must be within 2 degrees of each other (the 2 degrees is to account for chain stretch over time). Now, it's possible that he was talking about the distributor being off by a tooth, however having the distributor be off by a tooth will still give you a P0016 code. The truck will compensate for a misaligned distributor (as long as the gear is meshed correctly) so that you don't have to worry about throwing off the timing when you repalce the distributor. BTW, my shop manual from GM says that the cam/crank correlation must be within 2 degrees.
Old 02-28-2011, 10:05 PM   #13
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Re: Timing Chain on 03 4.3

not sure how they got it off by 6 "crankshaft" degrees, unless its
"camshaft" degrees they are talking about...

one cam sprocket tooth off equals 6.4 CAMSHAFT degrees,
which equals 12.8 CRANKSHAFT degrees.

there are 56 cam sprocket teeth, 28 crank sprocket teeth.

nonetheless, the dealership is blowing smoke about the computer
being able to "compensate" for it, unless the 4.3 was equipped with
variable valve timing, which it isnt...

even if the PCM did try to alter ign. timing to make the best of the situation,
the cam timing is still off, and the PCM simply cant change that fact...
Old 03-01-2011, 08:46 AM   #14
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Re: Timing Chain on 03 4.3

I am refering to the cam/crank timing chain being off by 6 degrees.

Sounds like you both are saying the NON GM Dealer is correct. The cam/crank can not be off by more than 1 or 2 degrees and there is no way the computer(PCM???) can make up for a 6/7 degree retard difference.

Nukngnir - you mention the shop manual from GM reads the cam/crank correlation must be within 2 degrees. is there any chance i could buy this shop manual from a local book store, pay you to fax me these pages of the manual, take a picture of these pages and post them in the forum?

many thanks for both of your replies.
Old 03-01-2011, 12:59 PM   #15
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Re: Timing Chain on 03 4.3

Mine's digital, but since it's one searchable file, I can't send it to you at 8GB. However, you can easily get one online.
Old 03-01-2011, 03:58 PM   #16
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Re: Timing Chain on 03 4.3

Quote: Originally Posted by nukngnir
Mine's digital, but since it's one searchable file, I can't send it to you at 8GB. However, you can easily get one online.
searching online but can't find anything official. anyone have any clues where i might find the official wording on cam/crank shaft variance? something i might be able to print and bring to the gm dealership.
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