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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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