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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: 81_Chevy on January 10, 2013, 02:35:01 pm
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okay so i have a real werid situation for ya'll. so i replaced my intake manifold gaskets because i had a leak and i put the distributor back in and connected everything back up, etc. when i went to time my engine i hooked the timing light up and the mark on the balancer was showing up at about the 10 o clock position. the timing tab is that the 2 o clock position. i have it timed right now so that it will run but i dont think its right. the engine is a goodwrench 350 from about 2002 - 2004 ish. the balencer is the orginal that came on the truck in 81. im thinking that between the years they may have moved the timing tab over? im not really sure, and i have no otherway of timing the engine except by ear and right now im looking to squeeze every bit of mpg out of it. has anybody had this problem before? do they make timing tabs that bolt on to the timing chain cover?
thanks in advance
-Nic
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Sounds like the outer ring slipped.. Common for a balancer that is 30 years old.
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There were two different timing tabs used.
I've seen my share of balancers that slipped from age.
Your not alone this is a common problem. My engine has the wrong timing tab/balancer combination on it now. It was put together with timing tape that is long gone now. Once I get mine roadworthy that will be another project so I can finish tuning my carb.
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In 1976 GM moved the location of the timing tab on the 350 about 12 degrees CCW.
Prior to 76 the tab was at about the 2 o'clock position. Starting in 76 model year the tab was moved to the 12 o'clock position (behind the water pump).
This change in tab location neccesitated a realignment of the timing mark (i.e. the scribed line on the outer rim of the harmonic balancer) a similar number of degrees.
That changed the radial relationship between the keyway and the timing mark. Pre 1976 the keyway and the outer mark lined up. After 76 the timing mark is 12 degrees CCW out of alignment with the center line of the keyway.
Since you have a balancer from the 80's (which has the mark in the same position as what would come stock on 2000 era engine) - this is not your issue. But the following may help.
As previously suggested, check that the rubber damper hasn't lost it's bond to the outer mass or inner hub. If it has, the relationship between the keyway and timing mark can be lost. When that happens, a timing light is useless.
Long story short, since your balancer is of the newer design the keyway and mark should be about 12 degrees out of alignment as shown below. This shows a late model balancer on an engine with an early timing cover. The drawn-in arrow points to the hub keyway on one end and to where the timing mark would be on an early SBC. The actual mark is what you would find on a post 76 balancer - like yours should be:
Sorry, I can't post images. Go read this link:
http://67-72chevytrucks.com/vboard/showthread.php?p=5354090#post5354090
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okay so what your saying is that i have the wrong timing chain cover? if so im still confused about why my mark would be around 10 o clock. im guess that it slipped off the outside of the balencer, but after school today i will double check where the mark is located with a timing light.
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the mark is located at the 12 o clock position. but i still have another question, when my dad put the engine in in about 2003 why would it have the wrong TC cover on it? it came with it from goodwrench. confusing :o
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I'm starting to think that you stabbed your distributor wrong - i.e. a tooth off. Check like this:
Trace the wire that goes from the #1 spark plug to the cap. Using a Sharpie, mark the post that it connects to - and also make a make on the distributor in line with that post.
Pull the wires from the distributor cap and move them aside. Release the cap and set it aside.
Pull the #1 spark plug.
Bring the #1 piston to TDC on compression stroke. You can click it to TDC with the starter. Or use a 5/8" 6 point socket on the balancer to crankshaft bolt and jack it over to TDC. Whichever way you do it, it doesn't need to be exact - but get it close.
Now, with the #1 piston at TDC on compression stroke - look at the distributor/rotor. The rotor should be pointing at the mark that you made on the distributor base (that lines up with the #1 post on the cap). Again, it doesn't need to be exact, but it should be close.
If you are a tooth off on the cam gear to distributor gear relationship, the rotor will be pointing closer to either the #8 or #2 post.
If this is the case, remove the distributor clamp and re-stab the distributor.
Use the mark that you made with the Sharpie as a reference point. As the distributor drops in and meshes with the cam gear it will rotate CW. Knowing this, you should have the rotor pointing at about the #3 cylinder before you drop it in. As it drops in and rotates, it should finally settle in with the rotor pointing at the mark.