I am at the point in my engine rebuild where I need to install the timing belt stuff and set it.....I have read several post and I am a little unclear what I can rotate without damaging stuff.
Right now the crankshaft is set so that all pistons are halfway down in the cylinder bore. From what I have read I need to:
1) Rotate both camshafts so that the timing marks are pointing to each other.
....now this is where I am unsure.
2) I need to rotate the crank so that it is a 1/2 tooth before the mark on the oil pump but I am unsure if I will mess up any valves doing this?
If I rotate the crank now will it mess up any valves? With the camshaft marks aligned to each other is it possible to rotate the crank 360 degrees without damaging anything?
Sorry if this has been answered a million times but I was unclear after reading the 420a rebuild manual and I do not want to mess anything up. Thanks in advance.
#95748, "RE: Timing Belt Install Question" In response to Reply # 0
The half-tooth is just a trick because the tensioner will pull the belt forward once you apply tension. It's not mandatory or exact. If you want to read up on the technique, you can search, there are many threads on timing belt alignment.
For me, using binder clips or clamps to hold the timing belt on the cam gears is the most useful trick.
Make sure you also align the crank sprocket and oilpump marks.
#95749, "RE: Timing Belt Install Question" In response to Reply # 1
I have a general idea on how to align the timing...my question is it ok to rotate the crankshaft once the camshafts are aligned but before the timing belt is installed. Will it damage any valves?
#95796, "RE: Timing Belt Install Question" In response to Reply # 5
So what you're saying is that you have the cams aligned and locked, are you allowed to rotate the crank 360º now to align the crank?
My best guess is no. I just did this on a 2.4 GA that broke it's crank sprocket. The manuel said to not rotate the crank once the cams are aligned, for the same reason that you described.
However, what you should be able to do, is rotate it COUNTERclockwise. It sounds like you're really close to the timing marks, but you overshot them a little (on the crank). You'll have to get a bit creative on how you rotate the crank backwards, but it'll happen. How close are you on the marks with the crank? There's no harm in moving the crank backwards (I would say to stay on the safe side less than 90 degrees). I used a vice grip with a towel to grip the crank and move it backwards. (It also helps to have the spark plugs out).
Brian
Red 97 Eclipse GS (420a) MTX Custom Garrett T3 Turbo system Megasquirt w/52 lb/hr injectors & a Walbro 255 Kicker/Alpine Audio (3 amps, 2 subs) 90 Cav 2.2 TBI auto (winter) <- yeah, it's fast
#95800, "RE: Timing Belt Install Question" In response to Reply # 6
Right now the crank is set so that all the pistons are half way down in the bore. Currently the cams are not aligned and I need to rotate them so I can align the marks. I know that it is safe to rotate the cams because the pistons are down in the cylinder. So when I get the cams aligned and locked I will than need to move the crank to align it to the mark on the oil pump. I am not sure how much I need to move the crank thats why I was wondering if the cams are in the "aligned" position would there be any valves stick down that I might damage? If so how might I go about moving the crank to where I need it?
#95807, "RE: Timing Belt Install Question" In response to Reply # 7
Is the crank 90º before or after TDC?
My concern is with cylinders 2+3. If you're at TDC (cylinder 1+4) are at TDC, then all those valves are closed with the cams aligned. However, at the bottom of 2+3's stroke, how much are the exhaust valves open? (I don't know)
If your crank is 90º BEFORE TDC, then align the cams and just turn the crank clockwise, since 1+4 are going up and 2+3 are going down.
If it's 90º AFTER TDC then align the cams and turn the crank COUNTERclockwise, and back them up, since going backwards would result in 1+4 going up and 2+3 going down.
Brian
Red 97 Eclipse GS (420a) MTX Custom Garrett T3 Turbo system Megasquirt w/52 lb/hr injectors & a Walbro 255 Kicker/Alpine Audio (3 amps, 2 subs) 90 Cav 2.2 TBI auto (winter) <- yeah, it's fast
#95809, "RE: Timing Belt Install Question" In response to Reply # 7 Jan-17-06 05:24 AM by DR1665
Originally posted by jam013200 Right now the crank is set so that all the pistons are half way down in the bore. Currently the cams are not aligned and I need to rotate them so I can align the marks.
Okay. This is becoming more difficult than I think it needs to be.
Leave the crank alone.
Turn your cam gears until you feel the valves snap shut. (You will know when this happens. Resistance will increase, then the gear will snap forward.)
Spin the crank whichever direction you want until you get it where it needs to be (I use the half-tooth before the mark method, myself). Make sure the spark plugs are out so you're not building compression and making this job harder than it has to be. If you, by any chance, messed something up, you will feel the pistons touch the valve and can stop immediately. I've never experienced this in the instructions I'm sharing.
Adjust your cam gears to where they need to be.
At this point, you can spin the cam gears around over and over if you need to. You should not encounter any interference.
#95812, "RE: Timing Belt Install Question" In response to Reply # 9
Originally posted by DR1665 At this point, you can spin the cam gears around over and over if you need to. You should not encounter any interference.
You mean with the Cylinder 1 (and 4) at TDC, you can spin the cams without hitting the pistons? I thought we had an interference motor, which would mean that you can't do that.
Brian
Red 97 Eclipse GS (420a) MTX Custom Garrett T3 Turbo system Megasquirt w/52 lb/hr injectors & a Walbro 255 Kicker/Alpine Audio (3 amps, 2 subs) 90 Cav 2.2 TBI auto (winter) <- yeah, it's fast
#95814, "RE: Timing Belt Install Question" In response to Reply # 10
Originally posted by ForceFed420a You mean with the Cylinder 1 (and 4) at TDC, you can spin the cams without hitting the pistons? I thought we had an interference motor, which would mean that you can't do that. Brian
Well, Brian, he said that he had all the pistons halfway up/down.
I would think that, so long as none of the pistons were truly at TDC, you could spin the cams all you wanted. I've honestly never even bothered to check this out. You're not turning anything that fast to begin with, and you'd feel it if you made contact, so I doubt any damage would occur beyond what you get from valves rolling into each other on the work bench.
#95815, "RE: Timing Belt Install Question" In response to Reply # 11
Originally posted by DR1665
Originally posted by ForceFed420a You mean with the Cylinder 1 (and 4) at TDC, you can spin the cams without hitting the pistons? I thought we had an interference motor, which would mean that you can't do that. Brian
Well, Brian, he said that he had all the pistons halfway up/down. I would think that, so long as none of the pistons were truly at TDC, you could spin the cams all you wanted. I've honestly never even bothered to check this out. You're not turning anything that fast to begin with, and you'd feel it if you made contact, so I doubt any damage would occur beyond what you get from valves rolling into each other on the work bench. This is just how I roll.
Brian (right?), I see what you're saying. Assuming the pistons are indeed halfway down, then yes, you certainly could turn the cams as much as you want. However, with the crank at TDC (aligned with the oil pump mark), then rotating the cams (360º) will cause them to hit the pistons. If he truly has it aligned on the crank, then it will truely be at TDC. That's how I interpreted the question.
Here's why I'm being kinda anal. I just had to work on my brother-in-law's Grand am (2.4). His crank sprocket broke and caused the piston/valve collision to bend the valves. I replaced the crank sprocket, timing chain and cleaned the oil pan, and we took it to a mechanic to take the head off and replace the valves (I ran out of time) He took it to the mechanic (who actually called me to talk about the motor) and the mechanic said that the valves were bent, but very slightly. He said it doesn't take much to bend a valve so it doesn't seat. In fact the pistons showed no signs of damage and the valves were just slightly bent.
Here's the kicker, the compression on 2 cylinders was zero.
My point in saying this is that I just went through what can happen if pistons hit valves, and with the cams snapping around like they do, I didn't want him to have a slightly bent valve and having to pull the head off.
Now granted, the motor was running when this happened. Could you do the same damage just turning it yourself? Probably not.
I hope this clarifies where I'm coming from.
Brian
Red 97 Eclipse GS (420a) MTX Custom Garrett T3 Turbo system Megasquirt w/52 lb/hr injectors & a Walbro 255 Kicker/Alpine Audio (3 amps, 2 subs) 90 Cav 2.2 TBI auto (winter) <- yeah, it's fast
#95817, "RE: Timing Belt Install Question" In response to Reply # 12
Originally posted by ForceFed420a Brian (right?)
Haha. Yeah.
Originally posted by ForceFed420a I hope this clarifies where I'm coming from.
Totally. We're both right.
I don't necessarily think that turning the cam gear and having the valve come into contact with the piston is going to bend it (unless someone is really turning the gears with a good deal of force), but it's a definite possibility.
So, as long as no pistons are at TDC, there should be no interference whatsoever.
#95813, "RE: Timing Belt Install Question" In response to Reply # 9
Originally posted by DR1665
Originally posted by jam013200 Right now the crank is set so that all the pistons are half way down in the bore. Currently the cams are not aligned and I need to rotate them so I can align the marks.
Okay. This is becoming more difficult than I think it needs to be. Leave the crank alone. Turn your cam gears until you feel the valves snap shut. (You will know when this happens. Resistance will increase, then the gear will snap forward.) Spin the crank whichever direction you want until you get it where it needs to be (I use the half-tooth before the mark method, myself). Make sure the spark plugs are out so you're not building compression and making this job harder than it has to be. If you, by any chance, messed something up, you will feel the pistons touch the valve and can stop immediately. I've never experienced this in the instructions I'm sharing. Adjust your cam gears to where they need to be. At this point, you can spin the cam gears around over and over if you need to. You should not encounter any interference. Hope this helps.
Well said Brian. Also a trick to turning the crank is to thread the crank pulley bolt back in the crank and use a ratchet or torque wrench to turn the crank. This will make things alot easier.
I wouldnt be too worried about damage when the motor is not running. Set things up per instructions in the Haynes/Chiltons manual then slowly rotate the crank two full revolutions. You'll know if something is out of alignment in which case you start all over.
I used a large flathead screwdriver to hold or bind the cam gears so they could not turn while applying tension to the system. 1/2 a tooth before TDC is a good rule of thumb because when the tensioner takes the slack from the belt the system will turn forward. I had to do this a few times before I got it right. Just be patient and everything should work out!
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