Timing Hole In Crank Sprocket Not Lining Up

[choco 0]

I bought a new cam and wanted to get the timing right with a vernier and dti gauge. Because i have a thin Cometics headgasket i wanted to check the exhaust cam too, so started with finding TDC. When i turned the crank to 90' BTDC and wanted to lock the crank i noticed the hole didnt line up (i know the pulley can slip, so measured without it). I measured a TDC a few times to be certain i got it right. When i positioned the crank so the cutout in the crank sprocket and block lined up, there is about 7mm difference in height between piston 1 and 2, confirming there is something wrong. I ended up using the timing hole in the exhaust pulley (only have one vernier) and put the intake at 108'. Needless to say it runs like sh*t. Anybody knows how it is possible the pistons are not levelled at 90' BTDC, is it possible the crank sprocket moved?

[Tom Fenton 1,541]

(i know the pulley can slip,

 

is it possible the crank sprocket moved?

Have you not answered your own question here?

[choco 0]

No. The pulley and sprocket (the round thing the pulley is attached to) are 2 different things. I know the pulley can slip because of the rubber, don't know if it's possible for the sprocket to slip.

[welshpug 1,657]

no, its on a woodruff key.

[petert 586]

XU9J4/XU10J4 or XU10J4R/RS?

[choco 0]

XU9j4. Am really lost on how this can happen.

[Anthony 1,003]

I can't see how it can slip - the centre piece is a solid bit of metal aligned using a woodruff key on the Mi16, and you don't even need the outer pulley part attached.

 

Apologies if I'm teaching you to suck eggs, but did you check that the alloy end plate (bit that holds that crank seal) with the slot for the pin wasn't damaged? They get broken when people try and lock the crank pulley using the pin, and when broken will allow the pin to slide in when it's not aligned.

 

The later J4R and RS engines with the bonded pulley can and do slip.

[choco 0]

I can't see how it can slip - the centre piece is a solid bit of metal aligned using a woodruff key on the Mi16, and you don't even need the outer pulley part attached.

 

Apologies if I'm teaching you to suck eggs, but did you check that the alloy end plate (bit that holds that crank seal) with the slot for the pin wasn't damaged? They get broken when people try and lock the crank pulley using the pin, and when broken will allow the pin to slide in when it's not aligned.

 

The later J4R and RS engines with the bonded pulley can and do slip.

The end plate is not broken. When the pistons are 100% level (90' before TDC;measured) a pin wouldn't be able to go in. The slot on the crank sprocket is about half a cm counter clockwise from the slot on the plate/engine.

 

Car was running ok on standard pulleys, could be a little down on power, but not backfiring or anything. I will try to put the exhaust cam on 114' before the measured TDC, and see if it runs well. Right now it's about 0,5 a tooth retarded because i used the standard hole in combination with the lined up crank, and the inlet was measured from TDC, not using the pin holes.

Edited July 11, 2017 by choco

[welshpug 1,657]

check the woodruff key is present and intact.

[dcc 855]

Check for woodruff key, retime bottom end, retime cams to suit. Recently timed up a gti6 which had bottom pulley slip, but afaik on the petrols its only an xu10j4rs pulley which is harmonic (rubber centre) and slips.

 

Even that was fairly easy to do tbh.

 

Sounds like you're not in the right location with the lower timing pin

[TAG 25 1 Cars]

Post up some photos, we can see what's what then.

[wicked 103 3 Cars]

The end plate is not broken. When the pistons are 100% level (90' before TDC;measured) a pin wouldn't be able to go in. The slot on the crank sprocket is about half a cm counter clockwise from the slot on the plate/engine.

 

 

What makes you think the slot is exactly at 90 degrees from TDC?

[welshpug 1,657]

its not, its at 70 degrees, I think we have found the problem, user error!

Edited July 12, 2017 by welshpug

[choco 0]

From what i read here on the forum, the pinned position on the 1.9 mi16 engine should be 90 degrees BTDC, and the pistons should be level. Anyway, it is now Found the culprit, the woodruff key. It looked very abused. Got a new one and everything lines up perfect now. I'll try to add pictures of the misalignment and the damaged key. http://s557.photobucket.com/user/chocopower26/library/?view=recent&page=1

Edited July 12, 2017 by choco

[petert 586]

Good work. Imagine if all the pistons were flat at 70 deg BTDC? When the pin is in the slot they're definitely at 90 deg before or after TDC.

Edited July 12, 2017 by petert

[wicked 103 3 Cars]

Good work. Imagine if all the pistons were flat at 70 deg BTDC? When the pin is in the slot they're definitely at 90 deg before or after TDC.

 

Of course they need to be flat at 90 deg BTDC, but their is no real need to have the lock hole exactly at 90 degrees. If it would be at 80 deg BTDC (and pistons not flat), it would still be safe to swap the cambelt.

But good to know that it is exactly 90 degrees. Didn't know that...

[welshpug 1,657]

When pinned the pistons are exactly half way but the pin hole is at 70 degrees from the woodruff key.

Edited July 13, 2017 by welshpug

[petert 586]

Pinning at 90 Deg allows you to set up the cam timing on either phase of crank. Any other number and they'd only be one position in 720 deg.