FT: Frame (Twin) cylinder head brackets

[Robert Watson]

NOOOOOOOOOOOOOOOOOOOOO!

 

[Colin]

Martyn!
Illegitimus non carborundum!
Bastard latin but i'm sure you can work it out

 

[Bill Thomas]

I do mine to 35, To allow for a bit of give in the paper gasket or gaskets if
Compression plate used .
We could be here all night !,
Who says a torque wrench is spot on ?, I have worked in Garages and they have been left in tension for weeks, So everything is + or - a bit ?.

 

[Monkeypants]

I just assembled mine and torqued them to 32...disassemble and retorque?

Absolutely. In the meantime do not turn it over, even accidentally!

Only kidding. If the heads seal and work with 30 ft lbs on the hollow setup, then 32 ought to work fine on the solid setup.
I guess the increase to 40 with the upgrade to solid is still well within safety margins and is a bit less likely to leak.

I recall having similar discussion with one of the the S Cal members. His Rapide has the early hollow studs. I quoted the KTB torque number to him, which at 30 ft lbs is the same as Richardson and the Instruction Sheets. He was horrified at that number and claimed 15 ft lbs would be absolute max for that connection.
After that I felt a bit uneasy about running these at 30, but have had no problems to date.
This was put in perspective recently with a discussion of Norton Commando head bolt torque. Those get the same 30 ft lbs but some are only 3/8" studs threaded about 1/2" into aluminium with a fairly fine 20tpi thread.
Those do let go on occasion, but even the early Vincent type bolt connection must be twice as sturdy as those Norton head studs.

Glen

 

[bmetcalf]

I have the recollection that the lower figure is to keep the quite hollowed out cylinder head from being distorted. ClevTrev very likely has an opinion on this.

 

[delboy]

Absolutely. In the meantime do not turn it over, even accidentally!

Only kidding. If the heads seal and work with 30 ft lbs on the hollow setup, then 32 ought to work fine on the solid setup.
I guess the increase to 40 with the upgrade to solid is still well within safety margins and is a bit less likely to leak.

I recall having similar discussion with one of the the S Cal members. His Rapide has the early hollow studs. I quoted the KTB torque number to him, which at 30 ft lbs is the same as Richardson and the Instruction Sheets. He was horrified at that number and claimed 15 ft lbs would be absolute max for that connection.
After that I felt a bit uneasy about running these at 30, but have had no problems to date.
This was put in perspective recently with a discussion of Norton Commando head bolt torque. Those get the same 30 ft lbs but some are only 3/8" studs threaded about 1/2" into aluminium with a fairly fine 20tpi thread.
Those do let go on occasion, but even the early Vincent type bolt connection must be twice as sturdy as those Norton head studs.

Glen

See article 165, Page 98 in "40 years on"
PEI himself. "..don't use much more than 35 pounds feet on a cold engine".
Nuff sed.
Delboy.

 

[Monkeypants]

See article 165, Page 98 in "40 years on"
PEI himself. "..don't use much more than 35 pounds feet on a cold engine".
Nuff sed.
Delboy.

Not really enough, there are two distinct connection types.

He was probably referring to the most common later type.

Glen

 

[delboy]

Not really enough, there are two connection types.

He was probably referring to the most common later type.

Glen

1951 Riders handbook makes no distinction between bolt types. Some 1300 hollow ones in use by then according to the Paul Richardson list.
It says, "..evenly to 35lb-ft torque."

Also try Page116 of "Tuning for speed".
PEI talks of the hollow bolts and says they "have large nuts but must not be tightened to more than 30 lb-ft torque, otherwise they may break when the cylinder expands. Later pattern solid bolts are not subjected to this restriction, but 35lb-ft is ample when the engine is cold." etc.
If you'll pardon the phrase, -I've never had a blow.

Cheers, Delboy.

 

[vibrac]

this is quite interesting from 10 years ago I haven't looked further but I guess there is plenty more

Tighten the cylinder head

Hello everyone, I'm about the reput my pistons, muffs, cylinder heads on my shadow engine, and tighten the heads at the normal torque of 4.15 kg. I would like to know if it is necessary to retighten my cylinder heads after running a hundred miles with the bike ? Is it necessary as it is...

www.vincentownersclub.co.uk

certainly not 40 more like 30
I will stick with my 32 BUT
Get that 2-3 thou clearance right on the head barrel interface before you start the tightening
Also after a week or so re check with a spanner and spring balance.

 

[Monkeypants]

Here's Paul Richardson, page 44

" Engines up to 1310 are fitted with hollow holding down bolts, inside of which are separate solid bolts which relieve the barrels and heads of stresses. The nuts of these hollow studs should be tightened to 30 lb. ft
If a torque registering wrench is not available, a 1ft. long ring spanner can be used in conjunction with a spring scale."

This is the same info for those early engines as in KTB and in the Instruction Sheets.
I don't doubt more torque could be applied before things let go, but I go by the books on this one.

Glen