Cylinder Head Nuts....No Washers?

As per the Workshop manual there are not supposed to be washers used on the cylinder underside nuts & sleeve nuts. Washers are used on the top side two 5/16" nuts and on the five 3/8" bolts. Is this purely because the underside nuts are in contact with the iron block rather than soft Alu? Any down side to using washers in these locations?

I think you will find there is minimal thread stick out so engagement in the sleeve nuts is not at a premium.

That comes back to the stud length and getting the head in place with the push rod angle. (perhaps) but I did make new longer studs and all have washers including the sleeve nuts and single rear.
When I got my 850 one sleeve nut was missing (fell off ?) so another thanks to Mike Veach in Iowa for sending me two replacements for the post cost only.

Being on iron, they are probably not needed.

My sleeve nuts at first appeared washerless but when cleaning them by wire wheel I found a thick washer/spacer somewhat fused to the end of each sleeve. Not sure if they were factory added or some alteration to ensure studs didn't bottom out inside sleeves whe n torquing. Took some force to dislodge but were not welded.
I too have fitted longer studs and changed to UNF threaded (to go with Helicoils in head). Hoping extra stud length not a problem for fitment, but can trim back if needed. Would like to add washers or short spacer to the rear single nut to help it sit further away from surface, since gives more clearance around fins for better wrenching.

I had to pull the KW push rods right up inside the head with no rockers in place but had no trouble fitting the head, removing it might bee different not that is matters (I would simply remove the studs in situ)

This is a new AN nut which would maybe have engaged half the available thread with the stock stud (and no washer)



These are modified 750 head bolts with 14. 5 mm of thread in the head.





If in doubt and its not broken, modify it anyway.

...if it aint broke, fix it.

gortnipper said:

...if it aint broke, fix it.

Click to expand...

I too have seen different OEM length stud thread length over the production range. However, a bit off the prize?

The nuts on cast iron is a diversion from what I view as WAY more important. The washer quality on the aluminum is drastically more important.
Soft thin hardware store, or missing, washers have caused crushing - squishing on the heads aluminum top surface. It is detected as a visual depression in an original flat counterbored washer pocket and rubbing on the bolt shaft or sticky studs. I have paid very close attention to use the original washers or my own custom made tool steel hard thicker washers.
A bit of cold forming back close to original with a tapered punch allows closer to normal fit of the bolt and clearance for the studs (front 2).

I do the same for my BSA A-10 heads

Like TW, I make longer studs, but starting from std head bolts.
This takes care of the more difficult to make cycle thread end.

Got my head fitted with longer, 3/8" fine UNF threaded studs. Didn't seem to make any real issue for placing head, once I learned to fully stuff the rods up in head, off the rocker perches, rubber-banded to stay. Once head squarely over the block, releasing the rods into the passages gave lots of freedom to then find the studs/holes to proceed.

However a new issue....the UNF threaded 3/8" studs mean a new nut is needed for the rear/center stud...an only ones I have on hand are 9/16 wrench/spanner size....cannot clear the cylinder block fins to tighten nut. I have an ARP 3/8" fine threaded nut on order that uses a 7/16" wrench/spanner size...which is what my original nut was and it was fairly easy to work on/off with my existing 7/16 ring spanner. I drilled out the front long sleeve nuts and fitted 3/8" fine UNF helicoils and they are working great.

you need one of these

850commando said:

you need one of these

Click to expand...

Actually I have the MotionPro spanner clamp to torque wrench drive socket tool. Holds most hand spanners at 90 degrees to torque wrench. Should work on this fastener assuming I have a suitable ring spanner for the nut.

the advantage of the ARP nuts, s that they are a wrench size smaller, disadvantage is that they are 12point. but i used them, and had CNW supply me with the two long nuts for the front....

I made new studs from 750 head bolts so they have the 26 TPI thread for the stock nuts and then a split 3/8 drive clamp for torqueing.

Will the 24 TPI UNF thread make a difference to torque. (or more so pulling on the head thread)

Oddly enough when I saw my first Mk111 yesterday, sure enough that rear stud was well up the nut so a good deal of its thread not used, a washer would only reduce that on a stock stud.

Perhaps to some degree it is all a moot point unless the studs stay anchored in the head and that was most of the reason I made new ones so they used all the available thread in the head (which the stock stud does not)
Its a whole new ball game (imho) when you get to torque them.

My Dad, an engineer by training, said that making a threaded section much longer than 1.5x the stud diameter does not appreciably increase the max load range for the fastner, since the stud will stretch starting in the section nearest the top of the hole. As surrounding material fails, the next section deeper in the hole begins to deform, so no big increase in load is achieved. Using a greater diameter hole/stud will improve load range.

That is all and dandy but the stock AN stud does not have that diameter to thread engagement ratio.
The studs I made are machined to suit each head thread and the head thread (Besides dropping around $300++ on studs and inserts in a courser pitch) was my main concern.
I was in no doubt the brand new AN studs would have pulled out of this brand new cylinder head maybe at first assembly.

If you have made new studs that engage as per the stock stud depth (not use the thread available) and you use a torque wrench on a different TPI be careful is all I will say.

If these were to pull I would have no choice but go to a 16 or so TPI full depth so would make new studs to suit that.

It is plain to see the depth difference here.



These have not moved to date, the four long cylinder cap screws (850) cold settled after eleven days. (before the cylinder head was installed)

I look forward to your thoughts when you are doing the last 30 ft/lb torque wrench pull on those three fasteners.
Maybe the hardened washers actually increase the applied torque because a lot of the friction (galling) has been removed from the fastener in direct contact with the cylinder.

There might be a good reason many just crank them as much as they dare with a ring spanner. (Seat each fastener then give them an equal amount of degree rotation )

Specialty tool #432

I'm using 3/8"-16 UNF (course) thread into helicoils at 5/8" depth in the head...as per J.Comstock's guidance. His video shows this arrangement to hold a bit more than stock, and helicoils were a bit better than the other similar 3/8" thread repair kits tested.

Mr. Comstock's DIY headstud insert load tests:



And another earlier video showing long/short studs in stock holes vs his own insert design:

That makes more sense including the depth which is not even a half inch on the stock 20 TPI stud.

I elected to stay with the stock 20 TPI thread, based on that it seemed better to use all the thread in the head.
Time will tell and was free, just a bit of shed time.

The JC 750 head got his 20 TPI Al/bronze inserts at those studs and as the tests showed (iirc) they will never pull out with the stud thread failing first.

Tornado said:

My Dad, an engineer by training, said that making a threaded section much longer than 1.5x the stud diameter does not appreciably increase the max load range for the fastner, since the stud will stretch starting in the section nearest the top of the hole. As surrounding material fails, the next section deeper in the hole begins to deform, so no big increase in load is achieved. Using a greater diameter hole/stud will improve load range.

Click to expand...

I think that’s correct for similar material (ie steel into steel) but with high spec steel into aluminium I think it’s different.

Tornado said:

I'm using 3/8"-16 UNF (course) thread into helicoils at 5/8" depth in the head...as per J.Comstock's guidance. His video shows this arrangement to hold a bit more than stock, and helicoils were a bit better than the other similar 3/8" thread repair kits tested.

Mr. Comstock's DIY headstud insert load tests:



And another earlier video showing long/short studs in stock holes vs his own insert design:

Click to expand...

Same here, I went the JC advised route with the UNC threaded inserts in the head and matching studs. Very confidence inspiring.

As I’ve said before, cNw and JS offer excellent off the shelf stuff for the whole range of top end fasteners. I used cNw on the 850. But the alloy barrels in the 920 require different. LCRKen helped me out with this, but JS now does it all off the shelf.
The smaller 12 point nuts and bolt heads are a revelation!
I know some folks categorise this as bling, but IMHO it could be more opposite, it’s solid solutions to known problems and well proven in use by JC himself.

Fast Eddie said:

Same here, I went the JC advised route with the UNC threaded inserts in the head and matching studs. Very confidence inspiring.

As I’ve said before, cNw and JS offer excellent off the shelf stuff for the whole range of top end fasteners. I used cNw on the 850. But the alloy barrels in the 920 require different. LCRKen helped me out with this, but JS now does it all off the shelf.
The smaller 12 point nuts and bolt heads are a revelation!
I know some folks categorise this as bling, but IMHO it could be more opposite, it’s solid solutions to known problems and well proven in use by JC himself.

Click to expand...

I've had no clearance issues on the stock head fastners using my existing spanners and sockets. The new UNF studs i've placed in head need different nuts. As mentioned earlier, I took Mr.C's advice and helicoiled the long sleeve nuts to work for UNF fine thread. The rear center nut was already thing walled at 7/16 AF size so didn't want to fit helicoil. Had tried to find a longer coupling nut to use here, thinking extra length would give better clearance at the typical 9/16 or 1/2" AF fastner sizes for 3/8" fine thread. But no luck and may not have given enough clearance. So the ARP's seem a great solution. Except for prolonged shipping times from US (four weeks now from an Amazon retailer).