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another ls400 timing question. - cam relate

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Old 06-12-14, 05:37 PM   #1
Tiagz
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Default another ls400 timing question. - cam relate

is it possible for the cams to be one rotation off when doing the timing belt on a LS where the belt has snapped and there is no reference point?


I would hate to start it up and have it a rotation off. Maybe I am overthinking this.


will just lining up the marks on the sprocket be good enough?
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Old 06-12-14, 05:52 PM   #2
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What year is your car? If it is a 95-00 ( Interference ) a snapped belt more than likely damaged something. 89-94 ( Non-Interference ) not so much. Either way you want to line up both cams and the crank to TDC or 50 degrees past TDC ( Top Dead Center ) before you start the car or it will not run well. Here's a good post to help you get them line up again.

Original thread Post #39
http://www.clublexus.com/forums/ls40...tml?styleid=14

Quote:
Originally Posted by dashan View Post
I got this from Tundra forum
http://www.tundrasolutions.com/forum.../t-205548.html
The Q
dpr64
01-08-2011, 12:48 AM
Say if I were to work on my 2000 V8 Tundra and the timing belt is OFF and the cam marks are mixed up and the crankshaft mark is unknown and not lined up. Could I possibly just align the crankshaft at '0' top dead center (compression or exhaust stroke unknown) and just adjust the cam timing marks so that they now align with the marks, would everything workout okay? Or would I still have to know if the crank was on a compression or exhaust stroke?

Will rotating the crank around a few times or the cams a few times without the belt on damage each other?
The Answer:
kovawa
01-11-2011, 11:44 AM
The white mark on the crank dampener indicates "top dead center" for the number 1 cylinder only. The camshafts position, relative to crankshaft position, determines whether or not the pistons are on their intake, compression, power, or exhaust strokes.Since each piston reaches it's own TDC once per crankshaft revolution, 1 piston out of 8 is at TDC for every 45 degrees of crankshaft rotation. If you need to realign the camshafts to the crank..... be aware that the toyota V8 is an interference engine. Valve damage will occur if you rotate the crank without using caution. The following is the safest way to realign the timing belt without risking major damage to the engine.
1. remove the spark plugs, this step will allow you to turn the engine by hand and let you feel for any piston to valve contact.
2. Gently turn the crank to 22.5 degrees BTDC ( before top dead center ) or ATDC (after top dead center). This position will assure that none of the 8 pistons is at TDC, which reduces the chances of piston to valve contact.
3.Realign the camshaft pullies to the respective timing marks.
4. Rotate the crankshaft back to TDC.
5. Install the timing belt on the engine.
6. Rotate the engine by hand a few times and double check the belt alignment.
7. Reinstall the spark plugs.
Provided that you put everything else back together correctly during the reinstall phase, your engine should run fine.
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Old 06-12-14, 06:08 PM   #3
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perfect information thanks a lot


My car is a 91 and I guess really easy I was over thinking since the cams rotate twice per crank they needed to be on a certain turn or else the wrong valves would be opening. Intake instead of exhaust ex.

if that's the case it will be pretty quick to get the new belt on
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Old 06-12-14, 07:04 PM   #4
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Your welcome and I hope you get it figured out. That post helped me more than any other advive when rotating the cams on a cam seal job.
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Old 06-13-14, 04:11 PM   #5
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Although I am gonna cry.

Basically this is the second belt i've done in the last week...

I was 99..5% complete on re installation when one of the screws for the passenger side coil fell into the belt. I chased after it with my my extendable magnet and then I rotated the engine over by hand both directions several times assuming if it was indeed in the belt it would come off.. I then got impatient and wanted to verify I installed the belt correctly - I had.

BUT

Heard the weirdest metal on metal noise ever to come out of a vehicle and I immedietly shut it off came to find my brand new belt shredded.

Today after finding a new belt for only 24$locally - Lucky (Federal Mogul brand not mitsuboshi but looks quality.)
I got the timing cover off and found two pieces of aluminum... turns out that is the timing belt guide.

And where it broke off is now sharp and jagged as hell so I am grinding it all down and smooth I don't believe the belt is going to flap or jump teeth without this guide but it sucks I am rebuilding this LS for my brother it's sat in our garage for the past six years and its becoming apparent she doesn't want to be driven and then if it does decide to jump a tooth means I will be redoing the timing belt for a 3rd time. At least I will have it down in 3 hours flat lmao.


For anyone following the LEXLS timing belt guide.

Don't take the radiator out unless you want to make another job for yourself, have a friend break the harmonic balancer loose while you block the flex plate with a chisel - BAM just saved you two hours. (only reason rad was removed was so impact could fit.)

Last edited by Tiagz; 06-13-14 at 04:19 PM..
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Old 06-13-14, 06:08 PM   #6
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Tiagz - one correction. The camshafts rotate at 1/2 the crankshaft speed, not 2X.
This means that you have to get the crankshaft at the correct TDC - the one at the end of the compression stroke (when both valves are closed), not the one at the end of the exhaust stroke (where both valves are open due to overlap).
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Old 06-13-14, 07:35 PM   #7
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I don't think there's enough room to pull the alternator forward with the radiator in there. Plus you don't want to accidentally damage the radiator when removing other parts.
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Old 06-15-14, 07:10 PM   #8
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Have the alternator moved forward with rad in and timing belt accessible as we speak.

Gene I realize that I was just over thinking it.. it is really simple to align the marks as long as your harmonic balancer hasn't shifted. Even so I made marks of my own and rotated the crank 4x and the marks stayed true.

as for the guides that broke off. finally biting the bullet and getting a mig welder and then purchasing the special wire for aluminum and I will just weld the guides back in place. I was going to fabricate my own and then use 2 bolts to retain each guide.. but that meant tapping the crankcase and areas of the timing cover and welding will be so much quicker and less destructive

+ Custom exhaust work down the road can happen asap
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Old 06-15-14, 07:10 PM
 
 
 
 
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