Mk3 stainless steel head bolts

Hi All,
Some help needed. I purchased 4 new stainless stainless steel head bolts for my mk3. They don’t seem to fit. Strange thing is that they are same size as originals. It’s not the tread that is the issue, they don’t go in far enough to do tread up. Is there a trick here or does it just need some persuasion?

Also can I use bearing grease as I have no anti seize her at the moment.

These are the 4 bolts near the spark plugs.

Thanks

Is the length of the threaded section the same on the new and old bolts or the unthreaded section diameter over size, for this application you can use normal grease but replace with copper grease as soon as it available.

Are you sure they are not binding / gauling? Stainless can do this with frightening ease sometimes.

I think normal grease may dissipate over time , and with heat, and re-torquing, and leave you in danger of seized bolts, so I would definitely use (or replace with) copper grease in this application IMHO.

kommando said:

Is the length of the threaded section the same on the new and old bolts or the unthreaded section diameter over size, for this application you can use normal grease but replace with copper grease as soon as it available.

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Yes they seem to be identical

Fast Eddie said:

Are you sure they are not binding / gauling? Stainless can do this with frightening ease sometimes.

I think normal grease may dissipate over time , and with heat, and re-torquing, and leave you in danger of seized bolts, so I would definitely use (or replace with) copper grease in this application IMHO.

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They just don’t seem to go in, not sure how hard to try

You shouldn’t have to try hard at all, they should go ‘snug’ with little more than your fingers.

Are you trying them dry, or greased?

If dry, it could a binding issue.

If greased, it has to be something else.

Unless you used too much grease, and now have it in the holes, and are ‘hydraulically locking’? Doubtful, but worth sticking something down there to ensure the threaded holes are clear of grease, oil, sealant, etc.

Grease will screw up your torque wrench readings - not something I would want to risk on head bolts (especially true on the four long barrel bolts, which can’t be retorqued easily).

I appreciate this video is ARP trying to promote their own anti-seize product, but look at the difference in readings of the products used!

OK, that’s interesting...

Order for ARP Ultra-Torque about to be placed.

Fast Eddie said:

You shouldn’t have to try hard at all, they should go ‘snug’ with little more than your fingers.

Are you trying them dry, or greased?

If dry, it could a binding issue.

If greased, it has to be something else.

Unless you used too much grease, and now have it in the holes, and are ‘hydraulically locking’? Doubtful, but worth sticking something down there to ensure the threaded holes are clear of grease, oil, sealant, etc.

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So far I have just dipped in engine oil

That should be enough to rule out binding.

I’d check the holes for oil, grease, sealant, etc.

Failing that, there has to be a dimensional issue somewhere.

Fast Eddie said:

That should be enough to rule out binding.

Failing that, there has to be a dimensional issue somewhere.

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Re-check the bolt thread size; 3/8x26tpi can SEEM like 3/8x24tpi.

if you place new bolt against one old bolt head to tail so to speak , then the thread corrugationas should be snug over the whole length... perhaps you have done this and if so apologise..

Are the hardened washers installed under the bolt head?

You can check the thread pitch by using the rear most head fastening nut, the one that comes in from the bottom of the head, near the carbs. The nut is a 3/8-26 and should thread onto the head bolts with fingers. You can also take one of the old bolts and lock the threads together with one of the new ones and look for air space, there shouldn't be any; this does require a bit of judgment whereas threading the old nut on is either go or no-go; try both, it will help you develop judgment.

As others have said the 4 bolts in question (actually 5--the shorter one between the exhaust rocker housings) should all go to the bottom of the threaded portion with the use of fingers only.

To avoid these kinds of issues I recommend that all the threaded holes be chased and the fasteners tested for hand fitting prior to final assembly. British Tools and Fasteners (https://britishfasteners.com) has all the taps and dies for English motorcycles. I recommend 3/8-26. 5/16-26 and 1/4-26 for a basic set and 5/16-22 if you really want to be anal, I am. These aren't overly priced and decent quality and should last an enthusiast a life time (I realize that the term "life-time" doesn't go to far with the bulk of Norton enthusiasts); they will not last more than about 50 pieces in a CNC machining center, however.

Thanks for the help guys, so there was a ring of harden grease at the top that was the issue, still took some wiggle to get in, but once in came out fine. They look great.

The ARP TTF is what I use almost exclusively on my rebuilds and engine along with ARP fasteners for all engine reassembly. They are not inexpensive but well worth the cost IMHO.
The only other lubricant I utilize (other than engine oil obviously) is Ford Motorcraft PTFE XG - 8 grease for some brake applications and other areas that could see a lot of direct water exposure. It is also an excellent cable lubricant.