possible solution to constantly retourqing head bolts

thegnu · Dec 21, 2012

I was just looking over my wifes trike an trying to think of a way to make it a bit more maintence free , specifically its head bolts for some reason they are aways working loose , I have used the sbp head bolt set an double nutted them to help stop them from working loose , to no avail . an had this idea just crush me ..CASTLE NUTS AN COTTER PINS ! any body tried this yet ?
what do ya think guys? its like SO obvious I almost feel a lil stunned that I havent tried it yet . your opinions an collective experince is appreciated.
Gary

2door · Dec 21, 2012

Gary,
First off I'll have to say that I do not have the problem. When I assemble an engine I torque the head bolts/nuts to somewhere in the 120 to 140 inch pound range then run the engine a few times so it reaches operating temperature then 'CHECK' the torque again. Usually it will take a small degree of tightening to get back to the initial torque value and then I forget about the head fasteners.
I've never had one come loose and I've always relied on the stock fasteners except for the chrome acorn nuts which I replace in favor of shouldered hex nuts and one flat washer. No thread locking compounds either.

Second, if you drill the stud to take a cotter pin and a castle nut then you're stuck with that position and if you need to retighten, you're screwed.

Lap the head and the cylinder so the gasket surfaces are absolutely flat then install a new head gasket and torque the fasteners. And one more thing I forgot to mention; while the cylinder head is off I double nut the studs and torque them into the case to the same value as the nuts. Then install the head and give it a try.

Let me know if I'm way off base here.

Tom

thegnu · Dec 21, 2012

Tom , I am at my wits end with that motor , I folow the same proceder as you, my chopper motor check head tourque every so often , the rat has shown no problem an I have 20 miles on it already , but that darn trike grrrrrr, I checked the low end to be sure I wasnt pulling the studs out of the block , double checked the nuts threads ,to be sure they werent worn . lapped the head to be sure it was good an flat before hand, new head gaskets , it just refuses to stay tight . an its always the heads nuts , even went so far as lapping it a second time along with the jug .
I just figured castle nuts could help since your able to keep tightening them by roughly 1/8 turns . your not off base its just normal diagnostic process'. in my op any help here is good help .
Gary

killercanuck · Dec 21, 2012

just curious, is it the nuts coming loose or the stud itself working loose from the block? If they're working loose, castle nuts wouldn't to too much except look cool. Some loc-tite in the case end would help, but god help you if you ever want to get them out cleanly again... Even with blue, it is steel to aluminum remember

(sry Tom, I said the L-T word, but I did warn him

)

But yea, castle nuts are a good idea, I doubt stage-8's would fit without removing huge chunks of fins eh?

hm, maybe stage-8's upside down... I'm over thinking this I think.

thegnu · Dec 21, 2012

yep every time just the nuts , the studs havent moved at all an the threads in the block are fine .
Gary

2door · Dec 21, 2012

I suppose you could give nylon lock nuts a try. The engine isn't going to produce enough heat to compromise them, me thinks. They don't get near as hot as some people claim.

Does this engine seem to have more vibration that your others? I know some do shake pretty bad and that could be why the nuts aren't staying tight but then you'd be having the same issues with all of the fasteners, not just the cylinder head.

You're right about the 1/8th turn, but watch that torque. The aluminum might not like things if you go overboard. Maybe a little less nitro in your next batch of fuel?

Keep us informed, Gary.

Tom

bairdco · Dec 21, 2012

i use nyloc nuts on most of my motors with no problems, the nylon never melts.

like tom, i torque mine down the first time, check them after the first ride, and forget about them. on the rare occasion i've had one loosen up, and i've blown a headgasket or two (not uncommon with the 20 or so motors i've built, rebuilt, modified, sold, etc...) but for the most part, they stay tight.

when i've blown headgaskets, it's usually coming home from working all night at not letting the bike warm up at all when it's cold outside. southern california's usually not a problem, but it does get in the 40's at 5am sometimes. could be a cold weather problem.

also, the stock flat washers are pretty soft, the split lock washers compress and wear out, the aluminum on the head is soft, and the studs on some of the motors are pretty cheesy, and even some of the nuts are a loose fit.

all of this can add up to loose nuts.

i wouldn't go with cotter pins, though. like tom said, now you can't tighten them.

easy fix? carry a small wrench.

thegnu · Dec 22, 2012

It doent seem to vibrate any more than my other motors in some ways it almost runs better , as my methods have improved . so I am yet to try another Idea , while digging through a bucket of old bolts in the garage I found one stainless steel bolt that just happens to be 8mm an the correct length an thread pitch for this motor , so you guessed it the idea of swapping out for proper "head bolts " has come to mind . but think I will try the nyloc nuts first , my concerns with the nylon melting out of them has been relieved , Thank you guys.
so now the question is if I should end up with the stainless bolts in this motor does any one know the best grade ? or should I just go with my gut an get grade 8 stainless bolts.
will keep yall posted as I move through this problem.
Gary

bairdco · Dec 25, 2012

stainless and aluminum are a bad combination. stainless threads on the bolts are sharp, and cut into the soft aluminum. then they seize up.

if you do go that route, use anti-seize on the threads.

i built a motor with grade 8 steel allen bolts instead of studs. finding the correct length is crucial. but as far as i know, it's still working. sold it a while ago.

2door · Dec 25, 2012

This reminds me of an old discussion here some time ago regarding the different threads on the cylinder studs. Every engine I've had has had fine threads in the case and course threads on top where the head nuts are. Some said their studs were threaded the same on both ends. The issue being is that I could not find bolts locally, long enough in fine thread to use as head bolts. They had to be something like 6" long with a 1 thread and everything I found over 4" was course thread, or a 1.25.

My question is why the factories rely on studs and nuts for the heads, intake and exhaust manifolds when they could use bolts instead. I always replace the intake and exhaust studs with Allen head cap screws and that was my intention for the heads but couldn't find the fine thread fasteners. The idea being that using bolts instead of studs and nuts is that you only have one set of threads to be concerned with as opposed to two. Any thoughts?

Tom

locell · Dec 26, 2012

2door said:
This reminds me of an old discussion here some time ago regarding the different threads on the cylinder studs. Every engine I've had has had fine threads in the case and course threads on top where the head nuts are. Some said their studs were threaded the same on both ends. The issue being is that I could not find bolts locally, long enough in fine thread to use as head bolts. They had to be something like 6" long with a 1 thread and everything I found over 4" was course thread, or a 1.25.

My question is why the factories rely on studs and nuts for the heads, intake and exhaust manifolds when they could use bolts instead. I always replace the intake and exhaust studs with Allen head cap screws and that was my intention for the heads but couldn't find the fine thread fasteners. The idea being that using bolts instead of studs and nuts is that you only have one set of threads to be concerned with as opposed to two. Any thoughts?

Tom

for what its worth, I know that a turbo volvo motor uses long bolts, not studs and nuts - perhaps for the same reasons you say

thegnu · Dec 26, 2012

I absolutly agree with you Tom ,1 set of threads to worry about breaks down to 1 possible failure point instead of 2 .
I was going to go with the grade 8 stainless bolts or possibly just steel bolts , on the trikes head because. ANY STEEL bolt in aluminum is a bad thing no matter what you do you will have an electrolytic reaction , but Bairdo does raise a good point the stainless is harder but its also a slippery metal .
Gary

nightcruiser · Dec 26, 2012

IDK if someone has suggested it yet, but blue loctite on the head nuts works well for me....

The first year I rode my bike I had the same problem as you, constantly re torquing the head to keep it tight. Over the winter I pulled her apart and installed upgraded studs and hardware. I used red Loctite on the stud/block junction, and blue Loctite on the stud/nut junction. This year I haven't had to re-torque the head once....

That said, I wouldn't use loctite on the stud/block junction ever with the original kit studs. They are generally pretty crappy and bound to fail, extracting them from the block with loctite on the threads might be a tough job.

RicksRides · Jan 2, 2013

Use copper washers. This is what I used on my 1260cc Kawasaki Dragbike 140+hp never had the problem again. Rick

thegnu · Jan 2, 2013

wow , ya think that kaw has enough hp? ok I will try copper washers first , is there any specific thickness tho?
Gary

RicksRides · Jan 2, 2013

thegnu said:
wow , ya think that kaw has enough hp? ok I will try copper washers first , is there any specific thickness tho?
Gary

I needed all those horses to get down the track @ 150mph It was like riding a launching rocket, Dang, I miss my youth,,lol... a standard thickness washer for the diameter youre using, just nothing really thin. the thing with copper is it soft . the nut will grip it real well and the copper is gonna grip the casing without gouging it

SuperDave · Feb 15, 2013

Grade 8 is the best choice in my opinion. I've replaced all the external screws, studs/nuts and bolts with allen head bolts. Not only does it clean up the looks (and complements the polished covers) they are just superior fasteners. If I could find them in my size & length for the head, I would do those too. Short of grade 8 head bolts, I just roll with the acorns for now. To be honest, they look nice. I too have to retorque the head far too often for my liking. I am considering upgrading the studs. Locktight's a good idea too. I wonder if the factory studs are stretching? I've heard the quality rolling out of China factories is as varied as the tides.

I'm not ashamed to have built my motor for maximum bling. I want something I'm not ashamed to be seen on.

Don't hate me because I get 150 MPG, Hate me because I'm cooler than you! usflg

Kioshk · Feb 15, 2013

The retourque-after-warmup technique has always worked for me. In any case, check out this article on nut-locking:

http://www.roymech.co.uk/Useful_Tables/Screws/Locking.html

Specifically, wire and slotted-nut techniques.

pocdragon · Mar 9, 2013

hello all,

just my 2cents on the topics athand

ive heard that using studs over bolts is better when your removing bits and pieces like intake and exhaust.

the hard sockethead cap screws will bite the aluminum case threads and eventually wear them down.

if you had studs, the threads in aluminum wont move, and wont wear out nearly as quickly, but on the other hand you need clearences to remove things from the protruding studs and you need the good hardware to stay tight

just a thought dnut

2door · Mar 9, 2013

You are absolutely correct about excessive use of the threads. If the engine is to be taken apart time after time, intake and exhaust manifold removed and reinstalled, cylinder and cylinder head removed often, there is the potential for premature thread wear/failure when using steel fasteners in an aluminum casting.

But... unless one is building and riding a bike solely for racing where frequent tear downs are normal and often necessary, why would it be an issue? There really shouldn't be a need to be constantly removing and replacing parts, carburetors, intake/exhaust manifolds etc. Build it right the first time, torque them correctly and re-torque after a few heat cycles then leave things alone. Just my opinion.

Tom

possible solution to constantly retourqing head bolts

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