Author Topic: Re-torque head bolts? (Read 8839 times)

UncleErnie · **on:** January 24, 2009, 04:37:27 am

On old BMW's, you re-torque the head bolts before checking the valves.
Didn't see anything in the book, but I would assume I should re-torquie at 500 miles?

clamp · **Reply #1 on:** January 24, 2009, 07:43:52 am

Any overhead valves with push rods would be affected by tightening the head, theoretically.

I would be extremely careful in torquing RE stuff. Infact I would not use a torque wrench but hand feel. The engine is alluminium and not very good at that.

Personally speaking if there is nothing wrong I would advise you not to.

UncleErnie · **Reply #2 on:** January 24, 2009, 12:48:54 pm

Different philosophies, I guess. I don't know about the newer BMW's, but the older ones have an aluminium engine and I was taught to RE-torque by backing the bolts off a 1/4 turn and then re-tighten to spec. Possibly one of the reasons BMW engines lasted longer then other bikes of the time?
I recently re-torqued the heads on my 75 Honda, and the leaks went away.
I've heard that it also depends on what kind of bolt is used. Just thought I'd get more info...

clamp · **Reply #3 on:** January 24, 2009, 01:39:37 pm

Sure BMW,--Honda crack em loose and re torque, nothing to worry about but the poor ole Re was made in India.

I did'nt know you had a leak!!

If you must ,--again I would do it by hand feel, its only 7.5:1

UncleErnie · **Reply #4 on:** January 24, 2009, 02:03:28 pm

Holy Cow! The lid on a jar of pickles is torqued down more than that!
No wonder the valve cover gaskets are glued on.

Well, the valves were a little tight. Runs like a champ so far- so I guess if it ain't broke, when in Rome, prevailing wisdom, etc.

ace.cafe · **Reply #5 on:** January 24, 2009, 02:22:15 pm

On the Iron Barrel Bullets, I generally down-rate the torque values by about 10-15%, in order to help avoid stripping the threads in the aluminum alloy.
I've had success using 20 ft/lbs on the head nuts, instead of the specified 24 ft/lbs.

Normally on a Bullet, if you have a leak at the head joint, re-torquing will not solve the problem in most cases. This is because the Bullet uses a spigot that protrudes above the deck of the barrel and mates into a recess in the head. If the spigot is a bit too tall, then the head can't seat low enough to seal the head gasket, and it leaks oil. Further torquing doesn't solve it. Only dressing-down the top of the spigot, or thicker head gasket would help in that circumstance.

This is VERY common in Bullets.

UncleErnie · **Reply #6 on:** January 24, 2009, 04:15:11 pm

Thanks Mr Cafe.

No leaks (yet)- merely preventive maintenance.

Vince · **Reply #7 on:** January 24, 2009, 05:53:52 pm

I re-torque the head at 300 miles, and if possible, again at 1,000 miles. I use a torque wrench and torque exactly to spec. Here's the trick: Use a torque wrench that measures in INCH-LBS to 600 max, not foot -lbs. Convert by multiplying by 12, so 24 ft/lb = 288 in/lb. Most measuring devices are most accurate in the middle of their range. If you use a 100 ft/lb or higher torque wrench it will not be accurate at 24 lbs. I could be high or low by as much as 20%.
I have been turning wrenches for almost 40 years. I ALWAYS use a torque wrench on any critical component such as a cylinder head or bearing cap.

clamp · **Reply #8 on:** January 25, 2009, 01:16:55 am

Pre 60's Rolls Royce did not give torque settings.

As a young man at RR school a kid put his hand up at the back of the class and asked why is that. The waxed mustache teacher standing there rocking on his heels wearing a brilliant white coat scowled at the young man and said.

"If you don't know when a bolt is tight we dont want you working on our engines.

That was 40 years ago ,--I never did buy one.

UncleErnie · **Reply #9 on:** January 25, 2009, 02:01:52 am

That reminds me...
There was an old ad for Rolls Royce with a headline that said, "At 60 mph, the loudest sound in the cabin of this car is the ticking of the clock."
A friend of his at another agency asked permission and used this line for Land Rover;
"At 60 mph, the loudest noise in the cab of the Land Rover is the roar of the engine."

REpozer · **Reply #10 on:** January 25, 2009, 02:39:30 am

I can remember in the 70's when a Chevy 350 was more dependable then the engine in a Rolls. I guess RR is doing fine ( think its owned by BMW)and now Chevy needs a bail out.

clamp · **Reply #11 on:** January 25, 2009, 07:01:28 am

I don't remember ever doing anything on a Roller more than plugs points brake pumps and sometimes tappet blocks (followers).

There was heater actuators brakes and more brakes, compliant suspension, and exhausts which never fitted because they fitted through holes in the Chassis.

The 6 cylinder did head gaskets occassionally -- 39 head studs.

Ive blown 2 chevys--front crank bearing turned and cut off oil to 1 and 4 --Corvette L82 and a mercruiser 228 (chev 304).

If they were similar the price does'nt reflect it ole chap.

REpozer · **Reply #12 on:** January 25, 2009, 08:12:27 am

A buddy of mine had the Corvette engine in his small fishing boat.He insisted on NGK plugs. I was amazed at how much the engine took a beating and used up plugs.

I wonder how a RR auto engine would hold up in marine application ?

clamp · **Reply #13 on:** January 25, 2009, 01:29:37 pm

Any marine engine has to have a marine cam which is similar to a 4 wheel drive vehicle cam = torque.

A marine engine uses water cooling. Overlap of the cams will encourage reversion which is not good when the exhaust is water cooled.

Water cooled exhaust manifolds are not available for the RR 5.3/4 liter or the 6.1/4 liter engines.

rick505 · **Reply #14 on:** January 25, 2009, 02:41:15 pm

Wow, thread went from question on retorque head bolds to Rolls Royce Marine engine.

Vince · **Reply #15 on:** January 25, 2009, 04:52:45 pm

Back to re-torquing. Some things I forgot to mention, Torgue in at least three stages. Don't go to full torque on the first pass. On the Enfield cylinder head start at 8#, then 16, then 24. Go in a star pattern. don't go around in a circle. If you have the time and patience four passes at 6,12,18,24 would be better. Wait 1/2 hour and re-torque to 24 again. Let sit over night, then torque at 24# again. now proceed with the rest of the assembly. The rocker caps are done the same way -an X or star pattern in at least 3 stages with a 1/2 hour wait for a re-torque. you won't need to wait over night for another session.

clamp · **Reply #16 on:** January 26, 2009, 12:53:14 am

Torque is simply measuring the power/force to turn the nut. It does not take into consideration friction for example.

It is paramount importance therefore that the threads are cleaned and oiled with washers all of the same.

Some cars today(my Mazda diesel) requires that you torque to 20lbs or metric equivelent and then after marking with paint, turn 180 degrees disregarding torque and then 180 degrees again.

BUT on some engines the bolts are designed to be stretched and hold the head down hot or cold like an elastic band.

Jag big end bolts are wasted and are similar. If the exceed a certain length they are to be discarded.

Any torquing should be in stages 3 times minimal

UncleErnie · **Reply #17 on:** January 26, 2009, 01:35:45 am

May I assume you both are talking about initial assembly?

I'm merely talking about checking torque prior to checking/adjusting rockers.
As a BMW apprentice, I was taught to back the bolt off a quarter to half turn, and then re-tighten to spec.
HOWEVER- if RE uses the kind made to stretch, then I wouldn't do that.

Came in from a ride today and found a nut at the right-side cylinder base very loose. I fear re-torquing all head bolts may be a good idea. I was going to wait until 2000 miles, but maybe i should do it sooner. ?

Vince · **Reply #18 on:** January 26, 2009, 03:02:12 pm

Do it now!

UncleErnie · **Reply #19 on:** January 26, 2009, 11:34:20 pm

10-4!
Thanks ~

UncleErnie · **Reply #20 on:** January 29, 2009, 05:34:41 pm

For the crowd that has been biting their nails-
One nut was VERY loose and all whee checked to 24 lbs.
Valves were confusing- One place in the manual says to set them to zero tolerance, but there are pictures of a hand using a feeler guage and then I found a spot that says to set them to .01- so that's what I did. The pushrods spun quite freely, but I feel good aout the setting, so I went with that.

Ordered some new rocker cover gaskets and plan to install them next time with something less rock-like (if you know what I mean).
This is interesting getting to know this particular bike. It definitely has it's own eccentricities.