Forums/Z31P/z31-basics basic-modifications-basic-questions-aka-the-newbie-forum/setting timing
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xanmanz31: (2013-09-27 16:39:41)
so having trouble setting timing belt. when i set my cams and crank to marks the LH cam wants to turn clockwise one tooth when i put the belt on. i counted 40 teeth between cam marks and 43 teeth from LH cam to crank. when i put the belt on the crank sprocket with the marked tooth in the gap right after 43 rubber tooth on the belt the LH cam turns one tooth clockwise. if i try to turn the crank counter clockwise to compensate it puts TDC at 5* instead of 0*. i guess its possible my crank pulley has spun slightly. when i pull sparkplug on cylinder 1 and watch the piston come up as i turn crank 0* puts piston at TDC.
heres a youtube vid of the issue: http: [http://[video=youtube_share;bq7vv73itgQ http://youtu.be/bq7vv73itgQ[/video]] https://youtu.be/bq7vv73itgQ]
G-E: (2013-09-27 17:19:53)
Your cams will have a tendency to spin a little with your rockers bolted down, hard to see, did you loosen them?
As long as your crank sprocket and pulley have clean keyways and woodruffs, they shouldn't move off axis, so the timing marks will be correct
visco: (2013-09-27 18:26:12)
If all the marks line up for TDC, crank and cams, set the belt onto the crank at the correct position, then slip the belt on the right cam with the belt mark lined up properly. Now with a wrench on the left cam move the sprocket until the belt and cam line up with the final belt mark. Two people make this a lot easier to move both into position. Make sure the tensioner is not adding any tension.
Most of the time you need to hold both cams in place with 2 wrench so they don't roll as you getting the belt on. I have also been able to set the belt without the tensioner in place, then slip the tensioner over the stud with the belt in place. This process can be a pain in the ass.
xanmanz31: (2013-09-28 01:54:12)
ok so my rockers are loosened bc i felt there was possibility for bent valves if anything spun out of sync. the keyways look fine on all 3. i swapped cam sprockets from other motor bc the originals had significant dents in keyways from the cam.
i will try putting the belt on clockwise from top to bottom i assume it would help to have rockers tightened down as well. i might tighten RH rockers first then apply belt then tighten LH rockers. i figure if i pull any on the belt to stretch onto LH then RH will be less likely to move. i usually leave tensioner off until last minute.
Twisted`Z: (2013-09-28 21:50:09)
FSM states that the valve covers are to be removed and rocker shafts are to be loosened, allowing, safe, free spin of the camshafts.
Also, when aligning the timing marks, compensate for belt tension. Otherwise, when you go to tighten the tensioner the timing will be off by a tooth or two on the cams. When I did the timing belt on my Z, I set both cams back by one tooth, installed the belt, and tightened the tensioner and as the belt reached proper tension, the marks were just about dead on. (I'll be honest, it took a couple tries to get timing just right.)
Also make sure you get the belt seated properly across the cams or your timing and belt tension will never be right.
xanmanz31: (2013-09-30 03:23:58)
i thought about just setting the "problem cam" back one tooth just havent had a chance to work on it since last time but i figured loosening the rockers couldnt be a bad idea. i feel like years ago when i first did the timing belt i remember the cams spinning out of control from spring pressure. id be afraid id bend a vale from that too.
300zxturboftw: (2013-09-30 16:13:43)
Maybe I'm confused, but if your belt is off one tooth, isn't timing set improperly? I just had rockers loosened. got the marks on the cam gear as close to the timing belt plate cover and threw on the belt marked up with the lines on the belt with the dimple on the cam gears/crank sprocket. the cam gears didn't perfectly match up with the marks on the timing cover, but they were close enough and i had 40/43 teeth in between and the lines on the belt matched up fine with all the gear dimples.
xanmanz31: (2013-10-01 01:38:07)
i see what youre saying as far as the markings on timing cover being a "guide". now if i cant get the belt to go on properly with cams and crank at marks then i set back the amount im off. that way when i put the belt on and it moves everything it "should" pull all into correct position. this is all assuming i live in Z eutopia lol.
i suppose that the crank markings lining up would be most important. the cams have possibility of flex due to cover bending. the crank marking is stationary.
another question would be that for TDC on COMPRESSION stroke wouldnt the lack of tension on the cam and the fact im setting it on mark force it into said stroke? one turn of cam sproket makes one rotation of cam lobe right?
Twisted`Z: (2013-10-04 09:20:00)
Well you don't set the belt on there one tooth off. With the rockers loosened, you would turn the cams clockwise by about a tooth (or however much it takes), put on the belt normally so that the belt markings match with the cam/crank gear markings. (Not the timing cover markings.) Then as you bring the belt to proper tension, it rotates the cams counter clockwise (crankshaft shouldn't move) and the marks on the belt and cams should line up with the marks on the timing cover. That's how I did it, the first time when I had installed the new belt I couldn't quite get the cams to line up just right and the car ran okay but had a power surge at 3500 rpms. After I re-timed the motor using the method I just mentioned, the car ran better, moar power through out the gears and large v-tech-like power surge at 3500 rpms was gone. Car even sounds better. It took me a couple tries as well to find the right spot for the cams before putting on and tightening the belt.
Twisted`Z: (2013-10-04 09:36:01)
You should have the rockers loosened in the first place. It's bad to try to rotate the cams separately from the rest of the system with the rocker arms still applying pressure. If you loosen the rocker arms you can freely spin the camshafts by hand, and there is no chance of the cam snapping out of position and possibly bending a valve.
As long as the crankshaft position is lined up properly, and the cams are lined up properly in correspondence to their TDC markings when the belt is at proper tension you've got it. At a proper TDC all 3 gear markings and belt markings obviously line up, and the distributor rotor should point in the general direction of the fuel pressure regulator on the front of the plenum, or more appropriately the rotor should be dead center over the #1 spark plug contact point inside the distributor cap.
xanmanz31: (2013-10-05 02:29:26)
my issue is that its pulling only the LH cam clockwise when i put belt on with tensioner loose. then when i tighten tension it will pull counterclockwise slightly but not enough to bring back to mark.
[http://[video=youtube_share;kbXqMh_ij84 http://youtu.be/kbXqMh_ij84[/video]] https://youtu.be/kbXqMh_ij84]
shromy: (2013-10-05 16:10:45)
count teeth between the cams and ds cam to crank. If they come out to the numbers listed before in this thread then your good to go. be sure to make 2 full revolutions of the crank to ensure no valve contact, then start it. The marks on the back plate are about worthless.
xanmanz31: (2013-10-05 23:37:19)
yeah ive counted the teeth multiple times. i even marked each tooth with white paint pen to make sure. i also went ahead and flipped the belt so the arrows are facing outward. im trying to get things back together so i can start it. im really not sure what else to do. i know the cam sprockets dont have any play since i replaced the original ones for that reason. all rocker shafts are torqued to spec in multiple stages. i set the crank according to punch on oil pump and gear. i also checked that piston was at top with a straightened coat hanger in plug hole waited for it to reach peak.
most frustrating part is its jut the LH cam everything else lines up as it should.
visco: (2013-10-06 02:11:46)
No longer understand your issue , but line up the punch marks with the belt lines install with everything bet cams and crank , count teeth to assure position, then tension the belt per FSM. Cams can be moved to line up the belt to TDC. I wouldn't roll them 180 deg to do that but to move them back or forward a couple teeth is not an issue
xanmanz31: (2013-10-07 00:49:33)
my issue is that my marks arent lining up. they are very close but i worry that ill have to do it again. ive set it as close as i can feel to exact. my tooth counts are good from cam to cam and from LH to crank. guess all i can do now is wrap it up and cross my fingers. biggest pain is not being able to look at crank marks straight on and using the camera doesnt do well either. as for belt tension i dont have a fish scale or anything to test weight i can push it down in the center and it will go down about 1/4 inch.
Kingman: (2013-10-07 03:51:31)
Way too tight! Do a 90* twist test or put a ruler behind the belt and put 22lbs of force on it and the belt should deflect 1/2". There's tons of thins around the house a guy can compile to work. Being able to only push it down 1/4" is asking for a snapped camshaft. When you can twist the belt 90* without an insane amount of effort, you've got it about right.
As long as the tooth count is correct the timing is set and really if everything isn't lined up absolutely perfectly, and belt tension being correct, it can look a bit off. Tooth count is the most important.
xanmanz31: (2013-10-07 04:04:38)
so with the 90* rule of thumb with the belt horizontal i should be able to turn it perpendicular without too much force? with a ruler i should be able to push down 1/2 inch? should i be able to do this with all spans of the belt? cam to cam cam to crank tensioner to cam?
Twisted`Z: (2013-10-07 11:12:13)
From what I could see in the part of your video that my computer loaded (internet hasn't been fond of youtube lately, only got about half of it). You do know that there is a timing mark on the gear that is on the crank shaft that lines up with a corresponding mark on the oil pump? Properly time the motor with the timing covers and crank pulley off the motor. Make sure that your crankshaft mark lines up. From the video (could've been camera angle) of crank timing gauge, it looks that your crankshaft could go clockwise just a hair. Though those markings on the crankshaft pulley are supposed to be for checking timing on a running engine with a timing light.
Did you pull the intake plenum and remove the driver side valve cover, along with passenger side and loosen the rocker shafts on both heads? It can be done with just passenger side really, but so much easier to get properly timed if both heads have their rockers loosened and cams can free spin.
If it's not quite lining up at proper belt tension, try again. Whatever amount you are off by is how much you need to add/subtract from your cam positions before installing and tightening down the belt, and if your crankshaft timing is really off by a hair or so, adjusting there might also help a bit.
les_joey_paul: (2013-10-07 16:31:23)
I didn't loosen them at all when I timed my car, it was hard to turn the pass side cam into place because of the spring tension, but it did stay there when i installed and tensioned the belt.
visco: (2013-10-07 19:37:55)
Ive done about 8 t belt changes over the past 10 years and I never loosen the cams. If the dimples on the crank and cams( not the marking on the back cover) are at the proper tooth count, that's what you need. I've had several instances where the right or left or both cams rolled. I used a wrench to turn them back to proper position/tooth count to line them all up. Most times I have to hold the wrench while another set of hands slides the belt onto the sprockets. I just did 3 timing belts within the last 4 months. Two times I was able to get the belt on with the correct tooth count without the tensioner installed and then slide the tensioner onto the stud , while keeping the tooth spacing at the proper count. An extra set of hands helps with all of this stuff.
I use a motorcycle drive belt tensioner gauge to apply the 22 lbs of pressure. I also mark the T belt back cover to the 1/2" deflection so I can line it up when I'm pushing on the belt. Never had an issue.
xanmanz31: (2013-10-08 03:26:32)
originally i had to pull the LH head to replace valve seals. yes cams were loose & everything was off. i do know the crank sprocket has the punch mark that lines up with notch on oil pump. i tried to get the crank marks lined first & run the belt from there. in the video i just didnt want to take the pulley off again (lazy). on all three punch marks i have marked them with white paint pen so they stand out more. the crank is the hardest to set since the angle is so poor. i set it by eyeball first then put timing cover and pulley on and adjusted then belt. however when installing belt the crank was able to move just enough to be a pain.