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Which Torque spec should I use?
#1
Which Torque spec should I use? I have 2000 Mercruiser 7.4 MPI (L29) Gen VI. It is basically the same engine that GM put in the 2500 trucks of the same year. I am replacing the heads due to the PO letting the risers leak salt water over the manifolds and heads. It is straight stock. I purchased both 1037 head gaskets and ES72264 head bolts. The Fel-Pro torque spec for this engine is for TTY bolts 1st 37 ft-lbs, 2nd Bolts 1, 2, 3, 6, 7, 8, 9, 12, 13, 14, 15, 16 turn 150 degrees, 3rd Bolts 4, 5, 10, 11 turn 90 degrees. The Merc service manual is 1st 30 ft-lbs, 2nd 59 ft-lbs, and 3rd 89 ft-lbs for short bolts and 92 ft-lbs for long bolts. Seloc manual 1st 25 ft-lbs, 2nd 40 ft-lbs, and 3rd 85 ft-lbs.

I began the torquing to the Fel-Pro spec thinking you produced the bolts. So I torqued everything to 37 ft-lbs. Then I set my torque wrench to 90 ft-lbs to monitor the 150 degrees and started torquing the first bolt. When I got to 120 degrees the torque wrench clicked and I got cold feet and stopped. On the 2nd bolt again it clicked at 120 degrees. I used Permatex Ultra Slick under the bolt heads and added Aviation Form-A-Gasket Sealant to the threads as Mercruiser specs. At least it is consistent.

And now I see from this thread http://www.felpro-only.com/blog/proper-i...t-y-bolts/ that ES72264 bolts are not TTY.  So, I am confused.
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#2
Hi David,

Thanks you your patience while we gathered information and input from our team. We’ll start with by addressing the torque specs.

Here at Fel-Pro, we design our head bolts to be used in accordance with the directions in the repair manual for automotive versions of engines. In this case, since it’s not an automotive application, it would be best to follow Mercruiser’s torque specs. The Merc and Seloc specs are not that far off from each other in regards to the final torque. The Fel-Pro specs you mentioned, which follow the automotive engine guidelines, use the Torque-to-Angle method of tightening – the ES 72264 bolts are not TTY, but they are torqued by angle which produces similar results, minimizing the variations in clamping load across the cylinder head.

As for your bolts stopping where they did in the torque sequence:
Rotating the bolts another 30 degrees even though your torque wrench clicked off will not break the bolts, it will just continue to stretch them at that point.

However, you mentioned a few things that concerned us. Permatex Ultra Slick is designed for lubing moving parts like bearings, pushrods, etc. – not for lubing head bolts. Engine oil should be used to lube under the heads of the bolts. The lubrication used changes the co-efficient of friction for the initial torque up, which will affect when the torque wrench will click.

The second thing is that you mentioned you applied sealer to the bolt threads. Fel-pro head bolts come with pre-applied sealant on the threads when it is called for, so no additional sealers should have been applied. Mercruiser & Seloc head bolts may come without sealer applied to them – we aren’t sure how they handle it. GM calls for a liquid Teflon sealer to be applied to the head bolts IF a pre-applied sealer is not already applied to the threads.
A click-type torque wrench clicks off based on the friction generated during torqueing. Our concern is by adding the Ultra Slick & sealer to the head bolts, friction was too far reduced and the head bolts may have rotated further than they should have during the initial torque up. This will possibly put the head bolts past their yield point, even though these are torque-to-angle head bolts and not torque-to-yield head bolts.

We recommend for you to remove the bolts from the head you started to torque up and toss them. Since we don’t know where the first 2 head bolts may be in the yield process – better to be safe than sorry. Do this one bolt at a time, following the correct torque sequence so that the sealing load is not completely removed from the head gasket, or the head gasket will need to be replaced as well.

Get one new set of head bolts for that side of the engine. Clean the assembly lube from the heads. Apply engine oil to the head bolt flange area and follow the GM procedure. Apply nothing to the bolt threads. As far as the other side goes, remove all the head bolts. Clean the assembly lube from the head bolts & heads. Wire wheel the bolt threads. Apply a liquid Teflon sealer that is similar to GM 12346004. Apply engine oil to the head bolt flanges. Torque the heads following the procedure. No need to use your torque wrench to verify the torque.
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#3
I just experienced a failure with the ES72264 head bolts.

While following the GM service manual at the pass specs 1st 30 ft-lbs, 2nd 59 ft-lbs, and 3rd 89 ft-lbs for short bolts and 92 ft-lbs for long bolts the 3rd pass felt terrible and like a never ending journey to get the wrench to click off. We were able to click off at 92 ft-lbs for long bolts in sequence 1,2,3 and it felt like we were just waiting for one to snap. We stopped and Googled to find info as these TQ specs are so much higher than any other published BBC general spec, after finding and reading through this thread as well as other info that confirmed the TQ specs as posted above for the L29 engines we continued. This leads us now to a wrench adjustment down to 89 ft-lbs for the first short bolt at sequence #4, and this is where the failure occurred the short bolt at sequence #4 snapped.

The ES72264 box notes these bolts as compatible for 1985-2000 which would be both gen 5 and 6 applications. A Google search for gen 5 gives results of 80 or 85 ft-lbs for both short and long bolts, however I was not able to find where anywhere in the research where anyone noted the spec directly out of a GM service manual. It seems as if there is a good bit of difference between the info available on the tq specs between gen 5 and gen 6.

The parts in question here are all fresh out of machine shop. These bolts were installed out of the box with the factory thread applied sealant only and a dab of straight 30wt engine oil on the bolt head.

HELP...
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#4
(08-05-2018, 07:13 PM) Wrote: I just experienced a failure with the ES72264 head bolts.

While following the GM service manual at the pass specs 1st 30 ft-lbs, 2nd 59 ft-lbs, and 3rd 89 ft-lbs for short bolts and 92 ft-lbs for long bolts the 3rd pass felt terrible and like a never ending journey to get the wrench to click off. We were able to click off at 92 ft-lbs for long bolts in sequence 1,2,3 and it felt like we were just waiting for one to snap. We stopped and Googled to find info as these TQ specs are so much higher than any other published BBC general spec, after finding and reading through this thread as well as other info that confirmed the TQ specs as posted above for the L29 engines we continued. This leads us now to a wrench adjustment down to 89 ft-lbs for the first short bolt at sequence #4, and this is where the failure occurred the short bolt at sequence #4 snapped.

The ES72264 box notes these bolts as compatible for 1985-2000 which would be both gen 5 and 6 applications. A Google search for gen 5 gives results of 80 or 85 ft-lbs for both short and long bolts, however I was not able to find where anywhere in the research where anyone noted the spec directly out of a GM service manual. It seems as if there is a good bit of difference between the info available on the tq specs between gen 5 and gen 6.

The parts in question here are all fresh out of machine shop. These bolts were installed out of the box with the factory thread applied sealant only and a dab of straight 30wt engine oil on the bolt head.

HELP...

Hi,

Without knowing the application, we have to make some guesses here. We believe that you are working on an L29 version BBC which is a Gen VI produced from 1996 -2000 which uses ES 72264.

In searching various applications, one will find a variety of torque specs. Later engines such as the 8.1L BBC use TTY or torque to yield head bolts (ES 72188). Earlier applications use ES 72264 which covers applications from the mid-1960’s to 2000. Everything we find for torque specs that is NOT TTY has the maximum of 80 ft-lbs. We could not find any source that showed a torque spec on the long bolts at 92 ft-lbs. We were also not able to find a TSB stating the head bolt torque from your GM manual had been changed from 92 ft-lbs down to 80 ft-lbs, so we aren't sure why you have the head bolt specs you do have. The original poster is referring to a marine application and we are not sure where the specifications listed in his post are from.

Most of the sources we found for the head bolt torque for a BBC is 75 to 80 ft-lbs on the long bolts and 65 to 68 ft-lbs on the short bolts. This would be the torque spec we would recommend using unless there is a specific application you're working on.

At this point, the head(s) with the broken bolts and over-torqued head bolts need to be removed. Inspect the cylinder block to make sure those threads are still in good condition. Install new head gaskets along with new head bolts to the above torque spec.

Let us know if you have any other questions or concerns!
Reply
#5
To clarify, yes I am working on an L29 version BBC which is a Gen VI produced from 1996 -2000 which uses ES 72264. 

I am following the GM service manual at the pass specs 1st 30 ft-lbs, 2nd 59 ft-lbs, and 3rd 89 ft-lbs for short bolts and 92 ft-lbs for long bolts.  I now wonder if the GM manual notes a dry TQ spec without oil on the bolt head VS the Fel Pro recommendation to lube with oil and then TQ to spec that the original post had in question and if the recommendations in this thread should be re evaluated and updated.


(08-06-2018, 04:31 PM)Support Wrote:
(08-05-2018, 07:13 PM) Wrote: I just experienced a failure with the ES72264 head bolts.

While following the GM service manual at the pass specs 1st 30 ft-lbs, 2nd 59 ft-lbs, and 3rd 89 ft-lbs for short bolts and 92 ft-lbs for long bolts the 3rd pass felt terrible and like a never ending journey to get the wrench to click off.    We were able to click off at 92 ft-lbs for long bolts in sequence 1,2,3 and it felt like we were just waiting for one to snap.  We stopped and Googled to find info as these TQ specs are so much higher than any other published BBC general spec, after finding and reading through this thread as well as other info that confirmed the TQ specs as posted above for the L29 engines we continued. This leads us now to a wrench adjustment down to 89 ft-lbs for the first short bolt at sequence #4, and this is where the failure occurred the short bolt at sequence #4 snapped.

The ES72264 box notes these bolts as compatible for 1985-2000 which would be both gen 5 and 6 applications.  A Google search for gen 5 gives results of 80 or 85 ft-lbs for both short and long bolts, however I was not able to find where anywhere in the research where anyone noted the spec directly out of a GM service manual.  It seems as if there is a good bit of difference between the info available on the tq specs between gen 5 and gen 6.

The parts in question here are all fresh out of machine shop.  These bolts were installed out of the box with the factory thread applied sealant only and a dab of straight 30wt engine oil on the bolt head.

HELP...

Hi,

Without knowing the application, we have to make some guesses here. We believe that you are working on an L29 version BBC which is a Gen VI produced from 1996 -2000 which uses ES 72264.

In searching various applications, one will find a variety of torque specs. Later engines such as the 8.1L BBC use TTY or torque to yield head bolts (ES 72188). Earlier applications use ES 72264 which covers applications from the mid-1960’s to 2000. Everything we find for torque specs that is NOT TTY has the maximum of 80 ft-lbs. We could not find any source that showed a torque spec on the long bolts at 92 ft-lbs. We were also not able to find a TSB stating the head bolt torque from your GM manual had been changed from 92 ft-lbs down to 80 ft-lbs, so we aren't sure why you have the head bolt specs you do have. The original poster is referring to a marine application and we are not sure where the specifications listed in his post are from.

Most of the sources we found for the head bolt torque for a BBC is 75 to 80 ft-lbs on the long bolts and 65 to 68 ft-lbs on the short bolts. This would be the torque spec we would recommend using unless there is a specific application you're working on.

At this point, the head(s) with the broken bolts and over-torqued head bolts need to be removed. Inspect the cylinder block to make sure those threads are still in good condition. Install new head gaskets along with new head bolts to the above torque spec.

Let us know if you have any other questions or concerns!
Reply
#6
(08-06-2018, 10:55 PM) Wrote: To clarify, yes I am working on an L29 version BBC which is a Gen VI produced from 1996 -2000 which uses ES 72264. 

I am following the GM service manual at the pass specs 1st 30 ft-lbs, 2nd 59 ft-lbs, and 3rd 89 ft-lbs for short bolts and 92 ft-lbs for long bolts.  I now wonder if the GM manual notes a dry TQ spec without oil on the bolt head VS the Fel Pro recommendation to lube with oil and then TQ to spec that the original post had in question and if the recommendations in this thread should be re evaluated and updated.

Hi,

Unless otherwise stated, head bolts should always be lightly lubricated. The only application we know of that calls for no lubrication on head bolts is the 4.2L I6 found ing the Chevrolet Trailblazer / GMC Envoy and their other derivatives.

John Gurnig from the Fel-Pro Field Test Garage did some digging - here's what he found:

"After doing some more searching and looking through the various years (1996-2000) torque specs from GM, there is some variation here depending on the year.

For 1996 vehicles, the text states to torque all bolts to 80 ft-lbs. The torque spec chart states to torque all head bolts to 85 ft-lbs.

For 1998 vehicles, the text gives the same specs that you have stated – 89 on the short bolts & 92 on the long bolts. However the specifications page confuses the issue by stating cylinder head replacement uses the same specs as before. For a left bank cylinder head installation, go to 30 ft-lbs, 60 ft-lbs, longs to 92 and shorts to 89. For a right bank installation, go to 30 ft-lbs, 60 ft-lbs, final pass of 85 ft-lbs. then long bolts to 92 ft-lbs and shorts to 89 ft-lbs. Confusing? I’ll say.

For 2000 vehicles, there is a torque to angle procedure.

ALL of these engines get sealer applied to the bolt threads. It is good practice to lube the underside of the bolt head on any head bolt. The lack of lube under the bolt heads will increase friction and cause the torque wrench to click off sooner. However by increasing the friction and causing the wrench to click off early may not apply enough load on the head gaskets. All engines are using the same head gasket.

At this point there are only a couple of things that could be wrong here. The torque wrench is out of calibration and not clicking off when it is supposed to. Or there is a metallurgical issue with the head bolts. Can you send the bolts (broken ones along with good ones) back to us along with the box they came in if possible so that we can make sure the bolts are within specs? The gap between 80/85 ft-lbs to 92 ft-lbs is not that great and the bolts should be able to handle that. Now if you were torqueing the bolts to say 120 ft-lbs instead of 80 ft-lbs, then that would be an issue."

Send us an email to Support@FelPro-Only.com if you are able to send the bolts back to us. We'll address the specifics by email. Make sure to reference your post on the forum as we don't handle general inquiries at that email address.
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#7
Yes, thank you, I have sent an email regarding the matter.

Also, to give an idea where my journey started with this problem is in fact with the 1998 GM Service Manual.

I can also assure all interested that the TQ wrench involved here in my garage is not the issue, in fact a 3/8 drive and 1/2 drive TQ wrench were applied in this process.  

Thanks again.  I have always been a believer that if it says FelPro on the package it is a lifetime long part.  

(08-07-2018, 06:35 PM)Support Wrote:
(08-06-2018, 10:55 PM) Wrote: To clarify, yes I am working on an L29 version BBC which is a Gen VI produced from 1996 -2000 which uses ES 72264. 

I am following the GM service manual at the pass specs 1st 30 ft-lbs, 2nd 59 ft-lbs, and 3rd 89 ft-lbs for short bolts and 92 ft-lbs for long bolts.  I now wonder if the GM manual notes a dry TQ spec without oil on the bolt head VS the Fel Pro recommendation to lube with oil and then TQ to spec that the original post had in question and if the recommendations in this thread should be re evaluated and updated.

Hi,

Unless otherwise stated, head bolts should always be lightly lubricated. The only application we know of that calls for no lubrication on head bolts is the 4.2L I6 found ing the Chevrolet Trailblazer / GMC Envoy and their other derivatives.

John Gurnig from the Fel-Pro Field Test Garage did some digging - here's what he found:

"After doing some more searching and looking through the various years (1996-2000) torque specs from GM, there is some variation here depending on the year.

For 1996 vehicles, the text states to torque all bolts to 80 ft-lbs. The torque spec chart states to torque all head bolts to 85 ft-lbs.

For 1998 vehicles, the text gives the same specs that you have stated – 89 on the short bolts & 92 on the long bolts. However the specifications page confuses the issue by stating cylinder head replacement uses the same specs as before. For a left bank cylinder head installation, go to 30 ft-lbs, 60 ft-lbs, longs to 92 and shorts to 89. For a right bank installation, go to 30 ft-lbs, 60 ft-lbs, final pass of 85 ft-lbs. then long bolts to 92 ft-lbs and shorts to 89 ft-lbs.  Confusing? I’ll say.

For 2000 vehicles, there is a torque to angle procedure.

ALL of these engines get sealer applied to the bolt threads. It is good practice to lube the underside of the bolt head on any head bolt. The lack of lube under the bolt heads will increase friction and cause the torque wrench to click off sooner. However by increasing the friction and causing the wrench to click off early may not apply enough load on the head gaskets. All engines are using the same head gasket.

At this point there are only a couple of things that could be wrong here. The torque wrench is out of calibration and not clicking off when it is supposed to. Or there is a metallurgical issue with the head bolts. Can you send the bolts (broken ones along with good ones) back to us along with the box they came in if possible so that we can make sure the bolts are within specs? The gap between 80/85 ft-lbs to 92 ft-lbs is not that great and the bolts should be able to handle that. Now if you were torqueing the bolts to say 120 ft-lbs instead of 80 ft-lbs, then that would be an issue."

Send us an email to Support@FelPro-Only.com if you are able to send the bolts back to us. We'll address the specifics by email. Make sure to reference your post on the forum as we don't handle general inquiries at that email address.
Reply
#8
(08-08-2018, 02:11 PM) Wrote: Yes, thank you, I have sent an email regarding the matter.

Also, to give an idea where my journey started with this problem is in fact with the 1998 GM Service Manual.

I can also assure all interested that the TQ wrench involved here in my garage is not the issue, in fact a 3/8 drive and 1/2 drive TQ wrench were applied in this process.  

Thanks again.  I have always been a believer that if it says FelPro on the package it is a lifetime long part.  

We have received your email and just replied, we look forward to helping figure out what could be wrong here.

Thank you for the compliment, that is certainly what we strive for!
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