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2long

TR-2 Lump and Box - And a problem needing help!

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OK, rebuilt engine and box almost ready to install, but there is an issue. Upon reassembly, the mechanic says that there is not enough clearance to adjust valves. Says that the head and/or block has been skimmed to the point where there is no adjustment room between pushrods, valves and rocker. The low port head was just skimmed 14 thousandths, and it had been skimmed at least once before. First concern is if this is really unusual. Options to get correct geometry: (1) Add a 1 mm thicker headgasket (very costly - 130 pounds); (2) add pedestal shims below the rocker assembly; (3) shave off the bottom of the rocker arm; or (4) shorten pushrods. I am thinking adding pedestal shims is the best option (Moss UK has them), but this whole issue makes me nervous so any input or suggestions are really appreciated.

 

Next issue is head stud torque. Manual says 100-105 ft. pounds. Mechanic says that at 90 foot pounds it feels like it is getting close to stretching threads (not sure if he means the threads of the studs or the threads in the block), so he is wondering if he can leave it at that. General consensus so far is that the full 105 foot pounds are necessary to seat the liners on the figure of 8 gaskets, but I don't really know. I did make sure there is the correct clearance of liners above the block. The head studs were checked beforehand and three poor looking ones replaced, while ones that looked good were reused. I am pretty confident the mechanic knows how to tell if the studs can be reused. How likely is it that I will damage threads down in the block? Sorry for so much text, but I really want to get this right.

 

Cheers

 

Dan

 

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Edited by 2long

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Not an expert but.......

 

I would be checking the height of the pedestals and the pushrod length against known correct ones.

 

Are pushrods for low port shorter than for high port??

 

If so you may have later pushrods. Using shims may allow you to get valve clearances but not necessarily with the correct geometry. Has the engine ever ran with these components??

 

There should be no problem torquing up the head studs to the correct figure.....I would take the studs out and see what the issue is....if they are weak then they will surely let go in use.

 

 

Dick.

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Hi Dan,

Paul in Canada had an issue with a stripped stud thread in the head. This was easily heli-coiled. Stronger than previous.

You need the full torque. Is the torque wrench reading correctly.

 

Roger

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Dan,

 

I note you have new lifters, but there is no mention of new pushrods in your parts list - presumably you have reutilised the old pushrods ?

 

Has your builder checked the depth to which the rod sits in the lifter ? There have been known issues with these 838-250 items in the past. You need to know that all are equal, and that they match the old units.

 

Bear in mind also that whilst the lifters are the same in low and high port engines, the rods and the pedestals are not . . . . .

 

Cheers,

 

Alec

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Thanks for the comments. I have utilized the original pushrods with the original head, so it ran with this set up before (although the lifters are new). I am pretty sure that it is a matter of the head having lost too much metal. So I am hoping rocker arm pedestal shims will work, without messing up the geometry. Moss UK has the shims and so I am hoping my situation is what the shims are made to address.

 

Cheers

 

Dan

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Hi Dan ~

 

I torqued my TR3 block to 100 ft/lbs as per the service manual with no ill effects.

 

Regards ~

 

Tom.

Edited by Fireman049

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Dan, You should torque the head up to the recommended settings (100-105 ft. lbs) if the studs/nuts strip now it's far better than having problems later. Don't forget that you will need to retorque the head after the engine has done around 500 miles.

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To follow up on the thread, it seems as if .115 inches has been shaved off the head over time, which is quite a bit. Original head thickness was 3.330 inches, and it is now 3.215. Why could I adjust the valves before the engine was taken apart? Because the previous cam had been ground, which offset the head shaving. So with new valves and a new stock cam, the valve adjustment was lost. My solution is to do a combination of things - a thicker head gasket (.087 inches solid copper instead of the standard .040 inches) to avoid overly high engine compression, and a shim below the rocker pedestal.

 

For the head studs, consensus was to torque it to the manual specs, which has now resulted in stud failure. So new studs will be used. I think it was actually a good thing to discover poor studs this way, rather than having them fail during operation. I will let everyone know how (or if) it goes.

 

Cheers

 

Dan

Edited by 2long

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Dan,

 

Sorry to hear of your problems, all resulting from previous rebuilds.

 

Then to cap it all, not good to have cylinder head stud failure, also I think not a common thing to happen

 

I would be interested to learn - was it a single stud that failed or did more give up?

 

Also were did the break occur - at the juction with the top of the block?

 

Did any of the stud / studs have signs of corrosion at the junction with the top of the block - I found several like this with quite heavy pitting and replaced then with sound S/H studs just in case.

 

You have not said that the broken stud / studs wil be a problem to remove - so maybe the break was higher up the stud?

 

Regards, Richard

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Dan, if a head stud has pulled out of a thread in the block, I've seen that failure before and as Bob Smith said, it's best discovered now, rather than having to remove the apron and engine again.

 

The correct 100 - 105 ft lbs torque is important to get a good water seal around the liners and figure of 8 gaskets.

 

Consider using better quality ARP head studs and nuts, or at least always use new nuts, as the threads stretch after the first use.due to the torque applied. Another option I've seen is using longer nuts with more threads.

 

Pedestal shims are commonly used to restore valve rocker geometry, after heads/blocks are shaved.. The rockers should be horizontal at about half way towards opening each valve, so the top of the valve stems wear evenly.

 

Regards,

 

Viv.

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Hi 2Long,

I shimmed my rocker towers with bits cut from a toffee tin.That was 5 years ago and it runs fine.

Regards

RogerB

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Well, to update on the thread I have surmounted the latest two obstacles. A thicker solid copper head gasket (.084 inches instead of .040 standard) was used, along with pedesttal shims, and the valve adjustment is now properly within the range of the adjustment screw. And, with new studs and stud nuts, the head is torqued to 100-105 ft pounds without any stretching or other problems.

 

Now the moment of truth will soon arrive, when the rebuilt engine, rebuilt transmission, rebuilt overdrive, recored radiator, and replaced chrome trim ring (that is the subject of another thread, and why the engine ended up getting pulled in the first place!) are fired up in the next week or so. So much to go wrong, but sometimes you have to just trust in the fact that it is a Triumph and not a finiky italian job.

 

Cheers

 

Dan

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