Cylinder Head Bolts

johnr9q@yahoo.com

johnr9q@yahoo.com

Senior Member
I want to change my cylinder head nuts to Stainless Steel. Can I replace one at a time and not have to worry about compromising the head gasket? I want to do this for appearance.
 
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Stainless cylinder head studs (not bolts, they are studs with external nuts) are not common at all. Typically if one is to change to new studs you use hardened steel studs and zinc plated nuts without washers. But there should be no reason to change the studs if you don't remove the head, and yes, you will likely destroy the head gasket seal if you do so. You could back off the nuts one at a time, replace the nut and then retorque that nut before starting on the next one. I would avoid stainless nuts but instead use the original type zinc-plated steel. The nuts are a special shape with machined mating surface, while a "standard" stainless nut does not have that machined mating surface.
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Normally, to change studs, one would remove the cylinder head to improve "access" to the studs. Doing all (if that is your plan) you would be advised to remove.

It is possible - perhaps - to do a single stud by grabbing the exposed thread, twisting, and hoping for the best.

Better than vice-grips would be a tool designed for stud removal. Such as below. Generally I imagine these would want more than the 10 or 12 exposed threads above the head in place.

https://www.autozone.com/p/duralast-stud-extracting-tool-80-001/1266645?


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These are best used with an impact wrench - although it can be used "by hand."

They will "upset" the thread where the jaws grab - but it has been my experience that the threads are still "usable" despite the upset.

My first impression is that stainless studs have no strength advantage to the usual head stud, and may be a step down in strength (in exchange for corrosion resistance.)

Joe K
 
alexiskai said:
New cad-plated nuts will look exactly like SS nuts. If you use SS nuts there's a risk of galling unless you use a nickel-based antiseize lubricant.
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I think this is the way to go. Do them one nut at a time and you should be fine. New plated steel nuts are often Grade 8 hardened, and I'm not aware of any stainless nuts with that level of hardness. In addition, stainless on carbon steel is known for galling (although not to the extent of stainless on stainless).

Having said that, max recommended torque for a dry 7/16-20 stainless fastener is in the 400 in-lb (33 ft-lb) range, so I'd be reluctant to tighten to the 45-50 ft-lb the head nuts require. (Grade 8 fasteners max recommended torque is on the order of 50 ft-lb).
 
I always liked acorn nuts. Google acorn nuts. You can buy them chrome plated.

Depending on the grade, stainless is not as strong as grade 5 steel nuts. Plus stainless has a tendency to gall and bind to the studs, making them hard to remove.

You can probably get by replacing them one at a time. Torque to 55 foot-pounds. Torque again after a heat cycle. Then measure the compression and look for oil in the water or water in the oil to see if you have a leak.
 
Don't do it. Stainless will not hold the torque. Don't go for the shinola crap. Just put new plated steel nuts on. One at a time. Studs and nuts are either grade 5 or 8. I use grade 8. Stainless is like grade 3.
 
I used over 100 7/16 grade 8 rustless steel,(thats what they called it) in an accordian cider press.Made for the aerospace and food processing industries.Over 10 years ago they were $28.each in quantities under 100,and around $12.each in quantities over 100.
 
Y-Blockhead said:
Nut Depot has S/S nuts but they are graded in corrosion resistance, not grade 5 or 8. I don't think I would use them for heads. https://boltdepot.com/Product-Details?product=5263
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Thanks, Y-B. Yes, 316, 308 and other SS alloy bolts and nuts are widely available, but I was interested in the assertion that they are available hardened to Grade 8. I've not heard of that hardness grading system being applied to stainless steel, and that has not been my experience over the years in various industries. But I'm always interested in learning something new.
 
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