Top Dead Center-Question?

[Ky91Tsi]

I am in the process of rebuild my 1g 6 bolt, and after putting the engine back together with the help of a Haynes manual, I have come to a question I need answered on wether or not my engine is at TDC. If the #1 piston is all the way at the top of it's stroke level with the top of the block, is that TDC, because my crank mark is not pointing to the mark on the block for reference to TDC. But if I put the marks on the crank and blocks together, the #1 piston isnt at the top of the block. So would this be TDC? The piston is just below the top of the block. I can take pic of what I am talking about if needed. Just checking so i dont mess it up.

Thanks.
Richard

 

[steve]

When the piston is at the top of it's stroke that's TDC for the cylinder.

Which crank marks are you using? If it's the one on the bacing plate and front cover then you need to make sure you didn't flip the backing plate. If it's the mark on the harmonic dampner and the timing belt cover then it's possible the outer pulley has shifted on the crank hub.

 

[Ky91Tsi]

So, would this pic here be an example of the engine being at TDC?

http://i48.photobucket.com/albums/f224/mxdawg121/Picture142.jpg

Or would this picture be an example of the #1 Cyl at TDC?

http://i48.photobucket.com/albums/f224/mxdawg121/Picture083.jpg

Sorry for robbing whoevers pictures these were, I just need some clarification on this, so I dont lock my engine up.

Thanks.
Richard

 

[boostedinaz]

http://i48.photobucket.com/albums/f224/mxdawg121/Picture142.jpg

This one.

 

[GTM]

When the piston is at the top of it's stroke that's TDC for the cylinder.

Which crank marks are you using? If it's the one on the bacing plate and front cover then you need to make sure you didn't flip the backing plate. If it's the mark on the harmonic dampner and the timing belt cover then it's possible the outer pulley has shifted on the crank hub.

Steve is correct and if you are not able to get proper results then do suspect the harmonic dampner has started to break. The most you could be off would be 3 degrees which is way more like 15 in the second pict you borrowed.

If you need more accuracy you can use the flywheel ring gear and make a pointer from a tin can or "L" bracket that you bolt to the block. Paint mark with nail polish on any flywheel tooth that corresponds to the pointer when you have established TDC. If you use a dial indicator on the piston you then will be confident within a tooth that you have TDC. This leaves nothing to chance for your pulley and timing marks with a nominal investment in time if you have to fabricate the pointer.

Many years ago it was common practice for mfgs to mark the starter hole and the ring gear because front engine timing marks were not always reliable. You will rarely find this in any book for it's forgotten or unlearned knowledge. If you replaced the ring gear you were required to re-stamp the index marks for TDC and ignition timing. It also is helpful if using vernier adjustment cam timing gears to mark opening and closing positions with different paint colors.

Cheers,
GTM

 

[Ky91Tsi]

Okay, for some clarification, I do not have the crank pulley on yet, I have the spacer from my balance shaft elim kit, the backing plate that has the timing mark on it, and the timing belt pulley, that is it and the retaining nut of course.

Today I just pulled the bolt off and spacer and all that and found my backing plate, the one with the timing mark, was just spining and not on the key on the crank. So I put the spacer on first the the backing plate and tried to get it set to #1 TDC, well somehow even with doing that, its still not coming to #1 TDC looking like this pic:

http://i48.photobucket.com/albums/f2...Picture142.jpg

I tried to see if turning it 180 would help and to no avail, it did not.

What have I done wrong? Did I install the pistons 180* out of time or something? I really need some help on this one, I am wanting to get this thing running again, its only been over a year now.

Thanks for the help so far.

Richard

 

[BUCK]

OR - you may have bent Rod from bad ECU flooding Piston with Gas & thereby bending Rod that tried to compress gas like mine did & therefore #1 wasn;t coming all the way up because Rod was 'short" ... The Crank mark AINT WRONG!

 

[GTM]

Okay, for some clarification, I do not have the crank pulley on yet, I have the spacer from my balance shaft elim kit, the backing plate that has the timing mark on it, and the timing belt pulley, that is it and the retaining nut of course.
...

I'm sorry this just isn't computing in my head. The url for the pict did not show up so don't know what that was supposed to show. I'm still working with a temp hard drive and all my DSM materials are off line. All I can suggest is revert back to the original parts for a temp test to confirm their placement and orientation. There is no way to get pistons and rods 180 out, 1&4 are up and 2&3 are down, rotate 360 and it will still be the same. The crank pulley will only be pointing at the timing mark of the outer cover and there is no way to mistake it's direction. Maybe you can find some other picts online that will help, other than reversing the sprockets and finding some incorrect mark I just can't imgine what you are seeing or doing.

Anyone else??

Cheers,
GTM

 

[Ky91Tsi]

So should I go by the timing mark on the crank pulley itself and not the one on the backing plate that slides onto the crank shaft and over that keyway? Is that what I am doing wrong, cause I am not reading #1 TDC off the actuall crank pulley?

Thanks.

Richard

 

[BUCK]

http://vfaq.com/mods/timingbelt-1G.html

MEMORIZE IT - There will be a Pop Quiz Monday...

1990-1992 Models

 

[Ky91Tsi]

Okay, I read that but that still does not tell me why when I put the timing mark on my backing plate to the pointer on the front case why the #1 piston is not at TDC, but about a 1/2" or more below TDC. What could be causing this, I know the backing plate is on right, because of the keyway in the crankshaft, so I know its not turned out of position. Any other ideas DSM masters? I would appreciate it very much.

 

[Marc91GSX]

Have you tried getting it to TDC without using the mark? Just ignore the mark for now and make sure that your piston reaches the TDC. If your piston is not reaching TDC then you could have other problems such as the wrist pins being too high on the pistons which would cause the piston to sit further down in the block. If you can get it to TDC then tell us how much off the mark is. Also have you checked to see if your crank key is installed properly. I always buy a brand new key everytime I rebuild an engine because it is one less thing I have to worry about.

 

[GTM]

Okay, I read that but that still does not tell me why when I put the timing mark on my backing plate to the pointer on the front case why the #1 piston is not at TDC, but about a 1/2" or more below TDC. What could be causing this, I know the backing plate is on right, because of the keyway in the crankshaft, so I know its not turned out of position. Any other ideas DSM masters? I would appreciate it very much.

Is #1 the only cylr that is not at TDC... where is #4??

What are the chances you have one or more rods in backwards?? I don't know if these are offset rods??? Have parts gotten mixed from other engines or at a machine shop???

I don't think it's a piston issue if you look at the pictures early in the thread, however, installing offset rods backwards could cause this. They won't get longer or shorter but the crank rotation will not be correct. A quick check of oil hole and piston lube may be the quick test.

My money is on this as the answer.

Cheers,
GTM

 

[Ky91Tsi]

I did install a new keyway in the crank, it was done at the machine shop.

Both pistons #1 and #4 both seem to travel to the same identical height in the cylinder, and I can rotate the crank and all 4 cylinders will travel to full stroke and to where it should be. I marked the pistons and rods to the forward direction on engine so there still could be some crazy chance that one is facing wrong direction. I will call mitsu today to fine out if the rods are offset connecting rods.

Thanks for all your time and advice.

Richard

 

[GTM]

I did install a new keyway in the crank, it was done at the machine shop.

Both pistons #1 and #4 both seem to travel to the same identical height in the cylinder, and I can rotate the crank and all 4 cylinders will travel to full stroke and to where it should be. I marked the pistons and rods to the forward direction on engine so there still could be some crazy chance that one is facing wrong direction. I will call mitsu today to fine out if the rods are offset connecting rods.

Thanks for all your time and advice.

Richard

The key and keyway (slot) in the crank are not the problem.

I can't see 1 being out and the other 3 correct if they are offset rods. I believe the factory pistons have an arrow stamped showing forward. If the pan is not on you can pull a rod cap and see where bearing holes, squirt, and crank holes are placed. The squirt holes should line up with crank so it will hit the underside of the piston when they get into position. The front of the engine is the crank pulley end closest to #1 cylr. I just can't imagine what has happened if you are using the old lower sprocket and the same crank.

In your profile you have a good pict of the lower sprocket but no timing mark. I see a small dowell pin but that was all I could see. If you could set the 1&4 pistons to TDC and then show a picture of the timing mark it might be helpful.

Please do call Mitsu and get the correct info. Again I'm not a DSM expert but think in later models they reversed the engine from Left to Right but not sure of this. My point is someone could have confused the front for the rear when installing rods and pistons at a shop.

You really got me going with this one and I'd like to know what is the problem so I can store it in my brain for the next time.

Cheers,
GTM

 

[BUCK]

It's the Keyway if 1 & 4 come to TDC without the Crank Mark matching up - PERIOD.

 

[GTM]

It's the Keyway if 1 & 4 come to TDC without the Crank Mark matching up - PERIOD.

For the life of me I cannot figure how the keyway on the _crank_ can change unless he welded it up and broached a new keyway.

The only only variable would be the keyway in the sprocket/cogged gear which we don't know if he's swapped parts, reversed them end for end etc.

Please bring me up to speed, without the poster's input we can only keep guessing. I should ammend that first statement to exclude a roller crank with a spline fit but you don't find too many of those on DSMs.
........................

Edit:
The poster reported having a problem with the sprocket timing and TDC not aligning. There was some discussion of the crank pulley but nothing was ever confirmed it was on or off registry for he never made a dry run with the front cover temp installed. If we just make sure we are talking about the same parts, which timing mark, there won't be any confusion.

Cheers,
GTM

 

[Ky91Tsi]

Yes, I am having trouble getting the timing mark on the backing plate to line up with the timing mark on the front cover.When it is lined up the #1 cyl still is not at full stroke, it's about a 1/2" away from reaching the top of its stroke. I have reused all my original parts,the only major thing done to the block and engine wise was to install a balance shaft eliminator kit. I installed that using the VFAQ also.

All the arrows on the top of the pistons are facing towards the front case. That is the proper direction, correct?

The timing mark that I am trying to base my engine off of is the one on the backing plate that goes behind the cogged pulley for the tming belt. When it is rotate to what should be #1 TDC, both the #1 and #4 cylinders are still about 1/2" from coming all the way to the top of the block(they are not flush with the top of the engine block).

This photo shows how my engine looks when the timing mark on the backing plate is turned to what should be #1 TDC, is this how TDC should look?

http://www.dsmtuners.com/gallery/files/2/3/7/4/2/P1010055.JPG

Anymore help would be appreciated.

Richard

 

[GTM]

Yes, I am having trouble getting the timing mark on the backing plate to line up with the timing mark on the front cover.
...
The timing mark that I am trying to base my engine off of is the one on the backing plate that goes behind the cogged pulley for the tming belt. When it is rotate to what should be #1 TDC, both the #1 and #4 cylinders are still about 1/2" from coming all the way to the top of the block(they are not flush with the top of the engine block).

This photo shows how my engine looks when the timing mark on the backing plate is turned to what should be #1 TDC, is this how TDC should look?
Anymore help would be appreciated.
Richard

What I/we are not understanding is if the cogged gear on the crank is a replacement. If it is a replacement can it be compared to the original????? We are trying to narrow down where things have gone wrong and this is the major suspect for being the wrong part or mismarked.

You do have the option of using the front cover and the pulley to set the timing, it may be a pain but at some point you need to check one mark against the other to establish which part is incorrect.

Although probably not important when the pistons are 1/2" below TDC which way does the crank need to be turned so they will be at the top of the stroke? I know this has been sitting for a year and not have priority status but this discussion has been going and we are not making progress. Those of us who do try to help would like to solve a problem as quickly as possible so it doesn't drag out for some time. We forget what has been forumlated and our train of thought is broken, thus it becomes more difficult to be effective.

Cheers,
GTM

 

[Ky91Tsi]

No I did not replace the cogged pulley. I am having trouble with the backing plate that goes behind the cogged pulley. I cannot get the timing mark on the backing plate to match up with the #1 and #4 cylinders when they are at TDC. The timing mark is off and the crank must be rotated at least a 1/4 turn to get the #1 piston at TDC where it should be. I am re-using all the parts down on the crank, including pulley and timing belt cogged pulley, the only new thing installed was a spacer that came with my balance shaft eliminator kit, to take place of the pulley that goes on the crank for the balance shaft belt, other than that new spacer everything else is the same as when I took it off. I will try and get some pics to show more in detail what I am talking about tomorrow.

Thanks for your help GTM, and everyone else!

Richard

 

[BUCK]

Any chance you "flopped" the backing Plate? - from the VFAQ I posted about a dozen Posts ago...

15. Once the crank sprocket is off, mark the front of the backing plate and remove it. Then remove and discard balancer belt. (You are marking the front of the backing plate to make sure you put it back on in the right position for proper crank timing. You can mark it by cleaning it off with brakeparts or carb cleaner, then using Witeout or white paint around the timing mark notch - this will make it easy to tell the front from the rear).

 

[GTM]

Any chance you "flopped" the backing Plate? - from the VFAQ I posted about a dozen Posts ago...

15. Once the crank sprocket is off, mark the front of the backing plate and remove it. Then remove and discard balancer belt. (You are marking the front of the backing plate to make sure you put it back on in the right position for proper crank timing. You can mark it by cleaning it off with brakeparts or carb cleaner, then using Witeout or white paint around the timing mark notch - this will make it easy to tell the front from the rear).

Is there any way to identify bolt and contact silhouettes from where it was bolted to the block and the cover attached as a means of establishing the face?

Since I've never been there with a DSM I have no feel for how long it takes to flip it around and try. Looking at the pict I could guess the angle to be close to 45 degrees so flipping would give the 90 he's indicated it's off. It seems to be about the only real possibility given _Ky91Tsi_ last report.

Cheers,
GTM

 

[4WARND]

Any chance you have a 7 bolt back plate on a 6 bolt block ? The difference is about the 1/2" you describe. Borrow another backplate and check it.