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HELP!! What is the LT1 TDC?

This is a discussion on HELP!! What is the LT1 TDC? within the LT1 forums, part of the Vehicle Specific category; Ok everybody here's the deal, I kind of rebuilt my 93 LT1, New cam, roller rockers, push rods, timing chain ...

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    HELP!! What is the LT1 TDC?

    Ok everybody here's the deal, I kind of rebuilt my 93 LT1, New cam, roller rockers, push rods, timing chain and gear. Now when I put it back together I went by lining up the timing marks on the timing chain and gear on the no#1 piston on TDC, but I was told that the LT1 should be on the no#6 piston TDC when doing this procedure . Can any body help me out and tell me what piston is the engine suppose to be on TDC when lining up the timing marks , Any help would be greatly appreciated. Thanks

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    2004 HEAD/CAM CTS-V 9t8z28's Avatar
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    It is cylinder #1! TRUST ME!

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    Pathelogical Liar BlackLT1Z28's Avatar
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    Just make sure you have the firing order right.

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    who the heck told you #6. you should find that person and slap them really hard.

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    Thanks guys, thats what i thought, I went by the book when redoing my engine so i knew i had it right . Now I did do a little research on this matter and it seems that there is a web site that helps alot about the 4th gen f-body I beleive its called Bfranker and shbox.com it does state that the engine should be on the no#6 piston for TDC I even email with the guy and he assures me that this is correct . I don't know where he got his info but like you guys I agree its suppose to be on the no#1 piston, heck even the repair manuals states this . oh well. Again thanks for the help you guys are great .
    Last edited by predaconssss; 11-10-2006 at 06:17 AM.

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    2004 HEAD/CAM CTS-V 9t8z28's Avatar
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    It sounds like he thinks you are adjusting the rockers.

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    12.36@109 Red on Red WS6's Avatar
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    Quote Originally Posted by predaconssss View Post
    Ok everybody here's the deal, I kind of rebuilt my 93 LT1, New cam, roller rockers, push rods, timing chain and gear. Now when I put it back together I went by lining up the timing marks on the timing chain and gear on the no#1 piston on TDC, but I was told that the LT1 should be on the no#6 piston TDC when doing this procedure . Can any body help me out and tell me what piston is the engine suppose to be on TDC when lining up the timing marks , Any help would be greatly appreciated. Thanks
    Trust me it is a lot better to use #6 TDC but both are correct. Let me explain why. When you have the number 1 cylinder at top dead center you line the timing marks from the crank shaft gear (small gear) in the 12 O'clock & the cam shaft gear (big gear) in the 12 O'clock position. This is an ok method but the timing marks are far away.All the time people get the timing marks off by one tooth.
    Using the #6 at TDC method. Remember this, for every one crank shaft revolution the timing gear moves 180 degrees. So you get the crank shaft gear to #6 TDC the dot will be at 12 O'clock. Then all you do is rotate the cam shaft gear 180 degrees so the timing mark is at 6 O'clock and install the chain. This is a little more accurate because your marks are now only an inch or two away. Here is a diagram showing the timing chain setup at #6 TDC http://shbox.com/ci/sprockets.jpg
    Last edited by Red on Red WS6; 11-10-2006 at 10:14 AM.

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    Pathelogical Liar BlackLT1Z28's Avatar
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    Yeah, that does make sense.
    The 12 and 6 O'clock method would be easier as far as accurate timing.

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    Oh man so I did do something wrong, because what I did I went with the no# 1 TDC and line up the timing marks facing each other which would be the 6 o'clock n 12 o'clock. Damn no wonder when I cranked up the car for the first time it ran like crap. So let me get this straight, at the no#1 TDC both timing marks should have been at the 12 o'clock but, if I want to line up the timing marks at 6 n 12 o'clock the engine needs to be TDC at the no#6 piston. Is this correct. Oh and red on red ws6, man thanks that was the best explanation given to me because i see now how it works and where I went wrong.

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    12.36@109 Red on Red WS6's Avatar
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    Yes your understanding is correct. Sorry to here about it not running right. It is a common mistake that people make. PM me if you need any help.

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    Aright then, back to the drawing board with me to get it done right, I really do appreciate everything fellas you all been great, and yeah thanks red on red ws6 I'll drop you a pm if I have any farther questions it seems you know your stuff. Once again Thanks to everyone.

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    Member Chad97z's Avatar
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    just because it ran bad when you started it, that doesnt means your timing chain or cam is misaligned. Because having 1 out of 16 rocker arms 1/4 of a turn too tight will cause a sticky valve and your engine will misfire on that cylinder. It happened to me when I changed my head gaskets. =) It didn't backfire though.. All it did was lope real bad. One cylinder was esentially not firing because the valve was stuck open and no compression was on my #3 cylinder. So it never backfired, just loped real bad.
    Last edited by Chad97z; 11-14-2006 at 07:16 PM.

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    Quote Originally Posted by predaconssss View Post
    Oh man so I did do something wrong, because what I did I went with the no# 1 TDC and line up the timing marks facing each other which would be the 6 o'clock n 12 o'clock. Damn no wonder when I cranked up the car for the first time it ran like crap. So let me get this straight, at the no#1 TDC both timing marks should have been at the 12 o'clock but, if I want to line up the timing marks at 6 n 12 o'clock the engine needs to be TDC at the no#6 piston. Is this correct. Oh and red on red ws6, man thanks that was the best explanation given to me because i see now how it works and where I went wrong.
    its shouldnt of even started. that would put you 180 out.

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    LT1 Guy
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    Quote Originally Posted by Red on Red WS6 View Post
    Trust me it is a lot better to use #6 TDC but both are correct. Let me explain why. When you have the number 1 cylinder at top dead center you line the timing marks from the crank shaft gear (small gear) in the 12 O'clock & the cam shaft gear (big gear) in the 12 O'clock position. This is an ok method but the timing marks are far away.All the time people get the timing marks off by one tooth.
    Using the #6 at TDC method. Remember this, for every one crank shaft revolution the timing gear moves 180 degrees. So you get the crank shaft gear to #6 TDC the dot will be at 12 O'clock. Then all you do is rotate the cam shaft gear 180 degrees so the timing mark is at 6 O'clock and install the chain. This is a little more accurate because your marks are now only an inch or two away. Here is a diagram showing the timing chain setup at #6 TDC http://shbox.com/ci/sprockets.jpg
    i have read this over and over. i hate to get in to this but i dont want any miss information about. if you rotate the crank gear not hooked to the cam gear like you say then rotate the cam all you are doing is installing the timing set at 12 and 6. 1 turn of the crank with out the cam doesnt put it at #6 it puts it back at #1. then by flipping the cam you change the timing. i looked into this more because i questioned the whole 12 and 12 for #1 tdc. the dowel pin position is what is refrenced in robs site when it says #6 tdc. not the crank position. but because of advance, valve position and pin location in the cap #1 would have already fired. 12 and 12 does nothing more than change the crank from compression stroke to exhaust stroke by changing the valve open and closed positions. the next revolution would be the other. i also contacted comp cams, outlaw motorsports, and lunati. they all asaid the same thing. depending on your cam size duration and lobe seperation you may or maynot lose timing by doing the 12 and 12 install and none of them would recomend it. and dont be confused the car would run probly fine but you would be down from your potential on power.
    Last edited by 96slow6; 12-20-2006 at 08:09 PM.

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    Is your question, where to put the cam as oposed to the crank on #6 top dead center????

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    LT1 Guy
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    read the whole post.i am responding to the original question posted awhile back. the posted started goin in a direction i didnt like so i did a bunch of research about it and got a difinitive awnser so if someone looks it up they get the right info.

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    12.36@109 Red on Red WS6's Avatar
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    Quote Originally Posted by 96slow6 View Post
    i have read this over and over. i hate to get in to this but i dont want any miss information about. if you rotate the crank gear not hooked to the cam gear like you say then rotate the cam all you are doing is installing the timing set at 12 and 6. 1 turn of the crank with out the cam doesnt put it at #6 it puts it back at #1. then by flipping the cam you change the timing. i looked into this more because i questioned the whole 12 and 12 for #1 tdc. the dowel pin position is what is refrenced in robs site when it says #6 tdc. not the crank position. but because of advance, valve position and pin location in the cap #1 would have already fired. 12 and 12 does nothing more than change the crank from compression stroke to exhaust stroke by changing the valve open and closed positions. the next revolution would be the other. i also contacted comp cams, outlaw motorsports, and lunati. they all asaid the same thing. depending on your cam size duration and lobe seperation you may or maynot lose timing by doing the 12 and 12 install and none of them would recomend it. and dont be confused the car would run probly fine but you would be down from your potential on power.

    I think you a looking into this way to much. You are correct, the 12 o'clock position of the crank gear is #1 TDC but it is also TDC for #6. TDC is not referenced by cam position but rather the top of the piston to the top of the block, so regardless crank gear gets set at 12 o'clock. Then take the gears and chain line them up with the cam gear 6 o'clock crank gear 12 o'clock and install and your done. When installed you are at a #6 TDC on the power stroke & #1 TDC Exhaust Stroke.
    I don't think I have given any miss information in my last post or this one. Maybe you just did not understand my explanation. The last 8 engines I have put together I have used this method and never had a problem. If I am wrong please post a link to the sites you referenced explaining it otherwise. Thanks
    Last edited by Red on Red WS6; 12-21-2006 at 02:24 AM.

  18. #18
    LT1 Guy
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    Quote Originally Posted by Red on Red WS6 View Post
    I think you a looking into this way to much. You are correct, the 12 o'clock position of the crank gear is #1 TDC but it is also TDC for #6. TDC is not referenced by cam position but rather the top of the piston to the top of the block, so regardless crank gear gets set at 12 o'clock. Then take the gears and chain line them up with the cam gear 6 o'clock crank gear 12 o'clock and install and your done. When installed you are at a #6 TDC on the power stroke & #1 TDC Exhaust Stroke.
    I don't think I have given any miss information in my last post or this one. Maybe you just did not understand my explanation. The last 8 engines I have put together I have used this method and never had a problem. If I am wrong please post a link to the sites you referenced explaining it otherwise. Thanks
    no worries man. i wasnt saying you were wronge or atleast i wasnt trying to just making sure it was understandable to all. which in hind site i may have made it more complicated. lol. the point is #1 tdc or #6 tdc they are the same crank gear 12 cam gear 6.

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    12.36@109 Red on Red WS6's Avatar
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    Quote Originally Posted by 96slow6 View Post
    no worries man. i wasnt saying you were wronge or atleast i wasnt trying to just making sure it was understandable to all. which in hind site i may have made it more complicated. lol. the point is #1 tdc or #6 tdc they are the same crank gear 12 cam gear 6.
    Gotcha

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