sticky clutch

[Richard Crawley]

Have you got the plain dowels as well, or are these instead of Richard?

 

The engine does not have dowels fitted as standard so someone must have fitted them at some time but they should work just as well providing the bell housing was correctly centralized when they were drilled & fitted!

 

My engine has always had the 2 dowel bolts fitted, one either side. They are a very snug fit in the associated holes & installation procedure is to hang the bell housing on the 2 top studs immediately below the head, tap the 2 dowel bolts in with a hammer, pull the housing up to the block on these & then fit the remaining blots which all have clearance holes.

[rob wilsher]

Thanks to all who have made suggestions.

 

It looks as if a gearbox clutch mechanism sort out is required.

Can someone explain exactly what dowel bolts are and what do they look like?

I guess that even if they were original spec, they may have disappeared during restorations and overhauls or are they a permanent fixture on the bell housing or block flange?

 

Thanks again

 

Rob

[Tom Fremont]

Can someone explain exactly what dowel bolts are and what do they look like?

 

Never seen one of these in the flesh ( since 1976 when I got started with them ). Others can inform us the details of the originals. Fortunately you can use 11/32" drill bits for the purpose - they just fit the clearance holes for the 5/16" screws which predominate in the bolt circle. Just push them through in (2) places opposite each other once all bolts are loosened. Once they go in, re-tighten all remaining screws, then finally replace the drills with bolts.

 

The theory is this: supposedly the clearance between the bearing carrier and the quill is ~ 0.015". The clearance holes in the bell housing are oversized by 0.03125" ( = 1/32" ). Hence the screws alone cannot provide the necessary alignment to center the quill with respect to the flywheel. Successive removal and replacement of the 'box only increases the clearance in the 'box holes as they're soft and easily enlarged by dragging the steel threads of the screws across them.

 

This method relies upon the accuracy of the original holes - so far no disappointments

[foster461]

Thanks to all who have made suggestions.

 

It looks as if a gearbox clutch mechanism sort out is required.

Can someone explain exactly what dowel bolts are and what do they look like?

I guess that even if they were original spec, they may have disappeared during restorations and overhauls or are they a permanent fixture on the bell housing or block flange?

 

Thanks again

 

Rob

 

They are not really bolts, they are just dowels. They fit at the 2 oclock and 8 oclock locations and they are just long enough to fit flush with the rear plate and the bellhousing flange, maybe a little under an inch. Their only role is alignment since threaded bolts have too much slop. I did a test. I used bolts at these locations and found I could rotate the gearbox 10 degrees in either direction. With the dowels in place the gearbox had no movement and can be bolted up in this aligned position. Moss US sells them for a buck fifty each and as Tom describes you can use drill bits instead to keep things aligned while you bolt it up.

 

 

Stan

[Richard Crawley]

They are not really bolts, they are just dowels.

 

Sorry to disagree; the original assembly used 2 dowel bolts, there are no sleeves & these must be an after market fitting as far as I’m aware.

 

Bolts have a portion of their shank left unthreaded as opposed to set screws which don’t, ie. the thread goes all the way up to the underside of the head. The hole for a dowel or location bolt is drilled dead size & not a clearance fit as is normal.

 

Ordinary bolts (& set screws) are manufactured using rolled stock bar so the shank is always slightly undersize. For very accurate location, dowel bolts (machine bolts) are made from machined stock bar, ground to size so their unthreaded shank is a specific size, usually a light interfearance fit for a standard drill size.

 

Having explained that, the TR seems to use stock size bolts for the dowels & they look like 3/8” UNF to me but it’s awhile ago since they were out last time! So I guess that either the 2 holes were drilled slightly undersize to give an interference fit with the standard bolt (special drills are probably cheaper than machine bolts in production terms) or it was not considered critical so they left them with the few though clearance a stock drill would give.

 

I’ve also checked the location of the bolts on my car & looking from the front of the engine they are 10 O’clock & (strangely!) 4 O’clock; or put another way – ignoring the 3 studs at the top of the engine the L/H one is the 2nd fixing down & the R/H one is the 4th fixing down.

[jonlar]

10 o'clock and 4 o'clock or 2 o'clock and 8 o'clock - just depends whether you look from the engine or gearbox side!

[Richard Crawley]

10 o'clock and 4 o'clock or 2 o'clock and 8 o'clock - just depends whether you look from the engine or gearbox side!

 

Your right!

[marvmul]

My 1972 TR6 has 2 dowels as described, and I have seen 2 other sixes with these dowels. It's hard to believe that so many owners or garages have fitted these dowels instead of temporaly drill bits i.e.. If they are not original, perhaps Triumph took the initiative to retrofit the dowels via the Triumph garages?

[Richard Crawley]

The point is that if dowel bolts are used, you don't need temporary drill bits as a guide or fit after market dowel pins. I can't say weather or not Triumph dealers retro fitted dowels although I would think it unlikely. It does seem a little strange that few other cars are being reported with the original bolts still in place & that both owners, & some specialists for that matter, seem unaware that these bolts even exist. Perhaps Triumph just decided not to fit them anymore at some point in the cars build history & used 5/16 UNF all round!

 

All I can add is that I’m 99% certain my car is totally original; it was just over 3 years old when I bought it in 1975, had not had any major work of any sort (or even much minor work) done in that time, had only covered 42K miles & came with a known history. I’ve also seen the same dowel bolts on a friends TR5 many years ago.

[jerrytr5]

Crikey, this is a bit of a marathon post ain't it?

For what it's worth, every Triumph I've ever owned or worked on which includes Herald, Spitfire, Saloon, GT6, TR ad infinitum has always had dowels fitted. What are the rest of you doing with them, throwing them away because they're not threaded?

[Tom Fremont]

Crikey, this is a bit of a marathon post ain't it?

 

TR owners are not easily convinced

I at least came by the trait honestly ( doubting Thomas )

[Guest harry dent]

Come to the conclusion that Annular clutch kits are just too fussy on set up and reverting back to normal set up.Am fitting modded carrier and Koyo release bearing with sintered longer bearings on the bell housing to crosshaft.Further pinning as well as hardened pin to fork assembly.I am confident all will now be well.

Harry.

Edited March 27, 2006 by harry dent

[marvmul]

The point is that if dowel bolts are used, you don't need temporary drill bits as a guide or fit after market dowel pins. I can't say weather or not Triumph dealers retro fitted dowels although I would think it unlikely. It does seem a little strange that few other cars are being reported with the original bolts still in place & that both owners, & some specialists for that matter, seem unaware that these bolts even exist. Perhaps Triumph just decided not to fit them anymore at some point in the cars build history & used 5/16 UNF all round!

 

All I can add is that I’m 99% certain my car is totally original; it was just over 3 years old when I bought it in 1975, had not had any major work of any sort (or even much minor work) done in that time, had only covered 42K miles & came with a known history. I’ve also seen the same dowel bolts on a friends TR5 many years ago.

The dowels fitted to my car are not bolts , but short pieces of rod, fitted in the engine flange and sticking out to the rear by about 1/4" to slot into the gearbox flange which has two drillings with the same diameter.

[Guest nco]

Hi Harry,

 

Try the bronze bearing carrier as well! They are not pinned to the clutch fork but I dont think that makes two much of a difference. If anything, it helps the bearing wear and evens the wear on the carrier from the fork pins.

 

Triumph fitted them to the ealier TRs but swapped them to steel to reduce cost.

 

You can get them from Revington. I fitted one to my TR6 last year (have done about 2K miles since) and there doesnt appear to be a problem.

 

Roger Williams book (How to improve TR6) page 49 has a picture of one!

 

Neil

[Guest harry dent]

Hi Neil,

Yes, as part of the modded kit the bronze carrier is also being fitted.Thanks anyway.This is what this forum is all about.Not one person knows everything and a problem shared is a problem halved.

Harry.

[Guest harry dent]

Apart from an ignition problem,all is now well.

Harry.