Thread: Little help, head bolt spec
05-24-2009, 03:31 AM #1
Little help, head bolt spec
I know I have seen it before but could someone point in the right direction to a thread with the tolerances for reusing the stock head bolts.
05-24-2009, 09:36 AM #2
I wouldnt reuse stock head bolts..JMO..
05-24-2009, 11:33 AM #3
But if u were to use the new stock bolts, I believe it's 22ftlbs 1st, then 120* followed by another 90* The ARP bolts sold in the online store are the best, and are re-usable. 80-90ftlbs depending if u lube w/ oil or moly lube.
05-25-2009, 11:54 PM #4
05-26-2009, 01:41 AM #5
Please don't re-use those...
05-26-2009, 04:30 PM #6
I am confused, for a stock machine the service manual clearly allows reuse of the head bolts up to a stretch limit. So basically, above a certain length you toss them. The following is quote from the service manual:
This assembly uses stretch screws.As the screws have been stretched from the previous installation, it is very important to measure each screw at assembly. If screw is out of specification, replace by a new.
Failure to replace screws and to strictly follow the torque procedure may cause screws to loosen and lead to engine damage.
CYLINDER SCREW M11
SERVICE LIMIT 148.5 mm (5.846 in)
05-26-2009, 05:52 PM #7
It is just really good practice to NOT reuse the head bolts, unless you just really don't want your head to be sealed in the best way possible.
05-27-2009, 12:22 AM #8
05-27-2009, 09:19 PM #9
I decided tonight to measure my head bolts and see how much stretch is remaining in the bolts. Stretch bolts are just another way to preload the head to make sure there is enought load at the face to seal the head to the case. If Bombardier did thier homework right , they should have calculated the bolt length were there was not enough to load the head without risk (plus some safety factor). The stretch in the bolt actually puts an active load on the head kinda like an advanced lock washer because the bolts want to go back to thier original shape.
So, attached are the measurements for my case bolts. As you can see there is an average of greater than 30 thousandths of stretch remaining in the bolts. Does anyone have multiple new bolts they could measure. I used a digital caliper from the tip to the washer and then added the washer thickness for a tip to bottom of head measurement. I would like to see the amount of stretch caused by 1 use. Might help us all decide to reuse or not in the future with these bolts.
My guess is that the rod and rocker bolts are stretched much closer to yield and that is why they cannot be reused. BTW - yea, I know I am wierd. This is kinda interesting though............and less than $80 in bolts everytime you touch your engine .
05-28-2009, 11:24 AM #10
I measured my used stock stretch bolts ... but only measured one new bolt before installing ... had the work almost all done before I realized I was curious about the length of the new bolts. Now I measured from the bolt head to the bolt tip (bypassed the washer) and I used mm. What I found generally was that most of my used bolts measured at or around 148.5mm ... which is beyond re-use according to the manual. I did have 3 that measured less, with one measuring 148 even. The one new bolt I measured came out very close to 148mm also. So, my work was casual, not scientific, but it seemed that three of my bolts could have been reused, while the rest were at or beyond the manual's limit. Mine seem to have stretched approx .5mm after usage, but again, I was more curious than trying to be perfect in measuring.
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