To helicoil or not to helicoil...(cam caps)

otakar wrote:

In all the earlier KZ900/1000 FSMs they were listed at 104 lb/in (8.67lb/ft). In the later books it is listed as the outrageous 12lb/ft. I have no idea why they changed it. i have always used 100 in/lb until one time that I attempted the 12 lb/ft (144 lb/in), at which time I had to buy a Helicoil kit.

They changed the torque spec when they changed the bolt type in 79. 7 - 8 ft.lbs is plenty.

Don't know why they changed the bolt type though. Maybe bolts were breaking on the assembly line or something. Never really could find a specific reason.

Torque is based on bolt size, engagement, and pitch. The weakest link here is the Aluminum head and not the bolt. I would have thought that they were smart enough to know that. But to increase the torque rating by 40% is idiotic.

otakar wrote:

Torque is based on bolt size, engagement, and pitch. The weakest link here is the Aluminum head and not the bolt. I would have thought that they were smart enough to know that. But to increase the torque rating by 40% is idiotic.

Smart as they are, we all figure we can do better so we modify what the engineers do..... human nature. We all want a better mouse trap. Sometimes we even succeed

What I notice is a variance in castings. Not just the heads but the cases as well.

You can hear the difference in castings when the heads are resurfaced.

You can see the difference when media blasting.

Some are harder than others. I expect some accept cut threads better than others as a result.

The parkerizing is a process to protect against corrosion.
Perhaps corrosion was a cause for the threads being weakened and in their educated opinion, the parkerized bolts would cure that.

Why they decided on torqe increase is still a mystery though.

auggiedog wrote:

They did say that the proper torque for these bolts is 90 inch#/ 7.5 Ft#, not the 9ft# as stated in the shop manual.

just the other day I was torqing the caps on my gpz1100 ...
I torqued them down slowly, starting from 5 ft lb. and went up 1 ft lb at a time...

ended up stopping at 7 ..... it just felt right.

12 ft lb. was a red flag as soon as i saw it in the manual... common sense is a good thing.

You should go to 8 lb/ft.

otakar wrote:

You should go to 8 lb/ft.

I'm scared.... :laugh:

maybe next time I do the valves...

You're smart to stay at 7 ft lb. It does no good to overdo it as they won't ever come loose, so why risk the stripping? I've stripped them at less than 7 ft lb on well worn engines. Exhausts will strip every time if you go too far.

8 lb/ft is what the earlier torque specs were before they went to the 12 lb/ft idiocy. 84 oz/in is a bit low.

Get yourself a tube of this. Poke every 6mm bolt in the end of the tube to coat the threads before you install it. Works like a charm. Coat at least 50% of the threaded length.

I use this stuff every day and don't strip out bolt holes. Also works nice for cam bearing insert lube.

For everything else I use this

I've used lubri-plate before. Good Stuff!
To tell the truth, I have never used a torque wrench!
I have a ratchet, that I cut down to 3 inches.
I have used this for 30 years so far! I guess I have learned a feel for the final tightness for the cam cap bolts!
But I also have done all holes with heli-coil if I ever had to do one of them on a head.
All new, why not, once you get the right kit. Heli-coils are cheap. after you have the correct drill bit and tap!

my 30 year opinion! Never had a failure! Drag Race and Street!

RonKZ650 wrote:

Exhausts will strip every time if you go too far.

Exhaust studs? or the nuts holding the collars...?

I never put a torque wrench on them... just tight'n by hand... then usually crank the nuts down a tad more... after the engine gets hot..


another thought... instead of oil or grease on the threads, anyone use blue loctite?