420 timing mark help

[SM90]

Hey Guys,

New to the forums and really in need of some help. My girlfriends 98 GS blew the head gasket a while ago and we finally go around to replacing it. I ordered the following;

Gates Timing Belt Kit ( Belt, water pump, idler pulleys)
Top end gasket kit with the MLS head gasket
New Plunger Tensioner
New Head Bolts

Anyway I have a good bit of mechanical experience but pretty much all 2 stroke engines ( dirt bikes & snowmobiles) and push rod V8s, never did a DOHC motor before. I got the top end apart and head pulled fairly quick and easy, cleaned everything, reassembled and I'm currently at getting the timing belt properly set.

Now, before removing the belt as I did my tear down, I set my crank pulley at exactly TDC, crank pulley mark and the one on the block were perfectly aligned. My cams however were like this (timing marks were close but) the intake cam was slightly above parallel to the head, and the exhaust cam was slightly below parallel to the head. The were say just shy of a tooth apart.

So I set my cam pulleys perfectly aligned, crank pulley 1/2 tooth BTDC and put the belt on, torqued the plunger tensioner, pin slid in and out perfectly, and turned the motor over twice, with no interference.

When I stop with the crank pulley timing marks perfectly aligned, my cam marks were off, almost exactly as much, (maybe just a little bit more) then they were before I pulled the original belt.

I have read 20-30 links about timing these motors, and ive seen several times people say the marks never align perfectly.

Here is a picture of how my cams currently sit, you can see the marks are about a tooth out, and this looks exactly how it was when I started. Is this way to far off, am I right, what do you think???

Thanks for the help, I really need to get this car back on the road asap as we are sharing my car, and I want to just get this thing finished, I got laid off from my job Monday as well so its been a rough week, hoping to finish so I can drink a few this weekend.

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[dsmcrzy]

Those timing marks should be ALOT closer. If the head was milled they won't quite line up but they won't be that far off. Here is a link to how they should look:

2GNT.com - Cam_Gear_Install

It is definetly tricky to get the belt on there right and alot harder doing it in the car than having the engine out on a stand.

 

[Silver99OZ]

It took me quite a few times when doing mine, the first few times it kept coming out half a tooth off, but eventually I was able to get it perfect. If your doing this alone I suggest you get a second set of hands. I tried three times by myself and thats when it came out half tooth off. With the help of my dads friend we got it first try.

The method I found that works best is to have one person place wrenches on each cam gear to hold and move them to help get the belt on. Then have the second person wrap the belt on starting at the crank and working around counter clockwise. When putting the belt around the cam gears hold the exhaust cam gear perfectly strait and then when you get to the intake cam gear you will most likely have to move it clockwise just a tad to get the belt on it so that there is not any slack in the belt between gears.

To ensure that the cams are perfectly aligned you should be able to hold a ruler up up to the center of the cam bolts and the marks should match the line of the ruler.

 

[SM90]

The head wasn't decked or anything, just removed, cleaned and reinstalled.

The gates kit came with one idler pulley, and then the other pulley was the tensioner style pulley, the one where you adjust the pulley its self to set the tension . I called the guys I bought the parts from and they sent me another idler pulley, as I would still like to you the plunger style tensioner that it had from factory. Could this be a problem, I feel like the belt should still be the same?

Also, once I get the belt around all the pulleys, and go to adjust the slack, as soon as we put the 21lbs of tension on the belt, it moves my crank pulley from the 1/2 tooth btdc, to a half tooth after tdc. Im guessing I don't want that to happen?

Thanks guys

 

[Silver99OZ]

You will want to keep it at tdc. Also, you dont want the cams gears to move at all when taking out the slack. You will still want to have someone hold them with wreches so that they stay lined up. I know its a pain in the ass, I have been through it once before and I am getting ready to replace my head gasket within the next few weeks so I will have to do this once again. It may take you fifteen times, but you should be able to get all three marks to line up perfectly and be able to turn the engine over two times and have them still perfect.

 

[dsmcrzy]

The crack gear will move from 1/2 tooth BTDC to right on TDC it shouldn't move any further past. Make sure you do get a second set of hands it will help with the cam gear and for applying the 21 ft lbs to the tensioner.

Like stated above it may take a few times to get it especially if this is your first time doing it. Also makes sure you turn the engine over by hand several times to confirm the timing marks keep lining up right. Nothing worst than having to take it all back apart again if its set wrong.

 

[SM90]

Me and my friend have tried this several times now and each time we get really close, but not perfect. I don't know any past history on the car, if the head was decked or anything along those lines, but each time we do it we get the same result.

When both marks on the cams are perfectly aligned, the crank pulley is just a hair shy of TDC, maybe an 1/8 of a tooth or so.

When the crank marks are perfectly aligned, the cam marks are say a 1/4 to a 1/3 tooth apart.

Ive looked at the engine for quite awhile and there's no way we can make it better by moving either cam or crank a tooth in either direction, so I feel were definetly correct there, moving anything a tooth will only make us worse.

Does getting the marks to be truly perfect really come down to getting the belt tensioned properly? Again, I know the marks cant get any closer by adjusting a tooth to the belt, so why are my marks still a smidge off? Does getting it perfectly rely on nothing moving even a hair when setting the tension?

Also, as mentioned before, our marks are much closer now, then they were before I removed the belt that was already there, and the car ran good then.

Thanks again, really appreciate the help.

 

[dsmcrzy]

The cams should not move at all when setting tension. The crack should be 1/2 tooth BTDC. When you apply the tension it will move the crank gear to TDC.

How close are you now? The marks should line up perfect and shouldn't be off anymore than the link I posted above. Are they off more than that?

 

[bullettdsm]

Also, as mentioned before, our marks are much closer now, then they were before I removed the belt that was already there, and the car ran good then.

Thanks again, really appreciate the help.

I suspect that you are probably there now. Maybe just being too critical because of what happened in the past. Obviously a pic helps.

 

[rough]

Have this same problem, first time car would not run, second time car runs fine, but seem's cammed, so i'm sure i'm still off 1/2 tooth of some sort. I'm driving it now, it will die in reverse sometime, and never did that before. Not looking forward to round 3

Wish there was a video out there of a complete walk through of the timing's, might have to make one myself "If I can get the timing dead on"

 

[oldag98]

I swapped cam gears, belt, and mechanical tensioner a couple of weeks ago. I had the same problem when done. For me, I had looked at the picture of how everything should line up when done, rotated everything a bit to the left, maybe an 1/8th of an inch, installed the belt and when tightened, the marks lined up perfectly. I took several attempts to get everything to line up correctly. I had to use the stock gears to line everything up, matched the gear markings to the new gears, and then installed them set on 0, If anything is off, your performance will suffer. Once you get the cam timing back to where it should be, you can then tune with the gears. This is a tedious and time consuming operation until you have done it a few times. It gets easier the more you do it.