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Old 12-20-2004, 03:45 AM
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Timing sbc corvette timing at 12o clock on both gears?

[1985 corvette with stock engine]Ok, now i've been going back and forth with people for the past week about what the proper timing marks are supposed to be at top dead center for my engine. Most people are of the mindset that the 2 timing marks on the gears are supposed to be facing each other and others say both at 12 o clock. A speed shop i got in touch with told me it doesn't matter ,that either will work. Something about the fact that the cam turns half as much as the crank....i didn't get it. Anyway, I attached the page out of my Haynes manual for corvettes 1984 thru 1996., and as you will see, it states that from1984 to 1991 the timing marks are both at 12 o clock and from 1992 and up they face each other. Now i don't know why or if a corvette is different for some reason but i can't proceed until i get a definite answer on this. You're probably going to need to magnify the attachment. rick
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Old 12-20-2004, 04:52 AM
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On your 85 put them both at 12 o'clock.The 92 Model year was the LT1 motor.
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Old 12-20-2004, 06:34 AM
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When both are at 12 oclock, you are firing #1 cylinder....

When they are facing each other, you are firing #6 cylinder..........
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Old 12-20-2004, 08:25 AM
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All chevy v/8s are the same. Marks facing each other insures that the timing is correct, 12;o clock is where the dist goes on # 1.

Troy
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Old 12-20-2004, 08:45 AM
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timing marks

All Chevy engines arent the same. As a previous post mentioned, apparently the LT-1 engine is timed differently from the bread and butter small blocks. All the manuals I have show the small block Chevy being timed with the Cam gear at 6 oclock and crank gear at 12 oclock. And this would set the engine for timing on #1 cylinder. I am not a Chevy officianado so Im not totally up to speed on the nuances of the LT-1.

My books also show #1 spark plug terminal on the distributor as being at 7 oclock as well. But Ive been told that other books show #1 to be at the 4 oclock postition.

The manuals I have range from 1968-1984, for the GM stuff.
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Old 12-20-2004, 10:35 AM
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When the crank mark is at 12 and the cam is at 6, it is the begining of the intake stroke. The piston must go down and back up (compression) and fire. That puts the cam mark at the 12 position.

Put the cam in at 12 and 6, turn the crank 1 turn and put the distributer in to face the #1 terminal.....

On the cap, the #1 usually faces the #1 cylinder or at about 5 oclock.................

There, is everone confused?.....Us Chevy guys do it in our sleep.....................
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Old 12-20-2004, 10:57 AM
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Setting up the gearing at 12 and 6 probably helps with more accurate valve timing as visually it would be easier to see any errors (it being off a few degrees) with the timing marks being that close.

BTW 85vette, I have done a cam setup on a 1985 Chevy Corvette. About to do it again too with a differet cam. The first time we set it at 12 and 6.
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Old 12-20-2004, 11:11 AM
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Quote:
Originally posted by troy-curt
All chevy v/8s are the same. Marks facing each other insures that the timing is correct, 12;o clock is where the dist goes on # 1.

Troy
Actually by the book #1 on the cap is at 7;00 oclock. But as long as the rotor is pointing to the # 1 terminal it makes no difference where it is.

Does anyone know where the dist. points to on a LT1?

Troy

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Old 12-20-2004, 12:25 PM
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cam timing

troy-curt, as the very famous and infamous Stock Car Racer, Curtis Turner once said, " If you dont hit the wall once in a while, ya aint going fast enough".
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Old 12-20-2004, 02:38 PM
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Aren't the LT1 distributors driven off the front end of the camshaft. Their Optispark system I think. I would think they use some sort of keyway that would always center the timing in the correct position for the cam/dist relation.
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Old 12-20-2004, 04:16 PM
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And I have hit the wall a few times.

Troy
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Old 12-20-2004, 05:07 PM
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Hitting the wall

troy, welcome to the club.
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Old 12-20-2004, 09:57 PM
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Why is it that i can't get a straight answer on this subject? Seems like everyone just gives excuses why the manual says to time it at 12 and12 and seem to implie that that should be disreguarded for this or that reason. If thats not the correct way to set up my engine then why do they say (right next to the illustration for 84 to 91) that 92 and up timing marks face each other? Wouldn't they just say ALL sbc's are timed facing each other? There has to be a good reason and it isn't for putting the distributor in only. If you look at the attachment you'll see it's the procedure for installing timing chain, gears, distributor, and the onset of valve adjustment. Boy, for chevy builders there's only 2 guys that recognized this as the legitamate setting for an L98 and they didn't offer any excuses for why it's better to use 6 and 12. Excuse me if i seem pissed off but this is my personal car, i've never been to this point on a sbc before and i'm on hold right now because i want this thing to start right up the first time. Thanks, Rick
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Old 12-20-2004, 11:23 PM
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Quote:
Originally posted by poncho62
When the crank mark is at 12 and the cam is at 6, it is the beginning of the intake stroke. The piston must go down and back up (compression) and fire. That puts the cam mark at the 12 position.

Put the cam in at 12 and 6, turn the crank 1 turn and put the distributer in to face the #1 terminal.....

Your manual is telling you where to have the timing marks when you install the distributer. The same as poncho62 said.

No one is making any excuses, just trying to help you.
Read the posts, and all of the installation instructions for the cam.

Troy
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Old 12-21-2004, 12:31 AM
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Last edited by 85 vette; 12-21-2004 at 01:04 AM.
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