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thirdtriumph
thirdtriumph
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Re: t120 Cylinder head dilemma
kevin #714299 11/08/17 6:53 pm
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Originally Posted by kevin roberts
just making it a hot rod isnt enough to mess up the motor. my old 72 T120 has the big bore, big valves, way too stiff springs (oops), and a higher lift cam, and it's stayed together for 30 years that way with the head off for a valve job once.

i think the metal particles you found indicate some dirty assembly in its history, and that will certainly cause difficulties.


Thanks Kevin,
The particles were all magnetic too, only evidence is the divots in the valve tips. The left intake being the worst, the others had a corresponding amount or lack of debris. I wouldn't be surprised if they started the motor dry, no assembly lube.


'68 Bonnie, '70 TR6r
'74 CL360
trail 70's and minitrails
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Re: t120 Cylinder head dilemma
slofut #714305 11/08/17 7:51 pm
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Bill/Kev, I've no problem with hotrods, but we know that you need to have a good idea of what you're doing, otherwise things end up working against each other.

My only hotrod experience was with a TR65. I had done a little experimenting on my own T120, with supposedly tuned length exhausts and just a little 2" manifold extension on the inlet, which actually made it fly. My bud with the TR was so impressed, he asked me to do similar but more.

So with T140 splayed head, all the usual dural bits, TT pipes/short traditional megas (67" total) my lathe owning pal turned up 8" manifold extensions, with bells totalling 14" valve to end (I was aiming for boost at 6500). It was quite something, with the bells out behind legs.

It was less than ideal at low revs, though it started easily, but was the proverbial "off the shovel".

He was having a good tustle with a big duke when the bottom blew out of it, post-mortem examination showed a split crank oil seal, sad!

Kev, I took the trouble to reply to your request to revisit stuff about Concentric float needles, it is on the triple forum, where you asked for it, you may not have noticed?

Back to Bill, sorry for the diversion, if ALL the particles are magnetic, that is a lot of material that can only derive from valve, spring, adjuster end, bottom collar. Can you use a magnet to see if the valve etc are ferrous? If you still have the debris, would be good to put it in a dish of petrol and see if a magnet takes it all. I cannot believe that amount of material has come from those divots, but it must have come from somewhere upstairs. Yet it may not matter, as that was from the engine the head was on previously.

Kev do you have any thoughts on the ideas I gave previously? Do you use non-captive lower spring collars? Dave

Re: t120 Cylinder head dilemma
slofut #714333 11/09/17 12:43 am
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DOPE
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lol dave i'm living in my truck for a month with only a telephone for net access and driving 400 or 500 miles per day, so im going to miss all sorts of things . i'll go look for the stuff on the needles. . i get a day off at the end of the week and i'll try to catch up.

btw, some mushroom valve adjusters are reported to have their heads break off. i was thinking that maybe that's what chewed up the tip of that valve.


every day you do not take a chance is a day of your life that you will never get back.
Re: t120 Cylinder head dilemma
slofut #714444 11/10/17 2:15 am
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Found pics of the rocker boxes that came off this head! Hadn't thought of it before but the guy WAS parting out his bike and had the rest of the engine bits on eBay.

[Linked Image]

One thing for sure, it was a flat tracker and a badass bike!

[Linked Image]
[Linked Image]
[Linked Image]
The box with the gasket looks to be the intake side and the tip of the left side rocker certainly corresponds with the valve on my head. Suspect looking tappets to me. Obviously a hard 100 or less than 200 miles if he raced it. Is looks like it was a super nice bike with seriously expensive bits, I'll bet it hauled ass!

https://www.eBay.com/sch/john_fende...e=1&rt=nc&_trksid=p2046732.m1684




'68 Bonnie, '70 TR6r
'74 CL360
trail 70's and minitrails
Re: t120 Cylinder head dilemma
slofut #714627 11/11/17 4:10 pm
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Hi Bill,
Much of this is a post mortem of another person's engine, without all the body parts on the slab. However, I think it interesting to glean as much as possible, as it may help with your decisions of how you proceed with your head.

From your latest pics, as best I can see, the tips of the valve adjusters look reasonable, they can get much worse and still work ok. On that basis alone, I see no reason for them causing so much wear on the valve tips in such short miles. Actually I think that slightly worn adjuster tips are kinder on the valves, once the perfect point contact has smoothed slightly.

I also doubt that oil supply in the top end is responsible for the valve tip divots, whichever way the rocker spindle washers were assembled, there would be enough oil up there to keep a Triumph topend ok for thousands of miles.
In fact, if you look at the pic of the exhaust rocker box, the oil holes in the pushrod balls can be clearly seen. Unfortunately, the gasket on the inlet box makes it difficult to tell if they are present also. But assuming they are, this is the setup Triumph used since Moses until the rocker arms changed to having no drilling to the pushrod ball. I think the old setup was great, providing oil splatter/mist upward from the pushrod cups throughout the rocker box, without too much to get down the inlet guides.
You should check your own rockers for that drilling, as if its not present, you should change your rocker washer assembly to that described by Jubee, and ideally the shafts too, because without the pushrod cup action doing the spraying it needs the slot in the end of the rocker to provide the splatter, hence the need for a plain washer adjacent. A poorer mechanism I think, but cheaper to implement I'm sure.

The one thing I noticed regarding the rocker arms is that 3 were of similar origin, except for the left inlet, which is clearly a different shape, much cruder in profile than the 3 more "sculpted" ones. I have only seen that "ugly" shape in late models, so it may have been a later rocker without the feed to the pushrod ball. If so, with the standard washer setup, there would have been less oil splatter in that valve chamber than intended.
Even so, the wear is extreme for the mileage.
Who knows what valve clearances were being used? Any beating on those valve tips would just be magnified manifold with cams/springs ++.
And maybe an oiltank without a restriction in the return outlet?

Unless they sold elsewhere, I noticed the only significant part of the engine not in the eBay listing was barrels and pistons.

In conclusion (eventually!) I am convinced that heavy valve springs and components have caused the rapid wear on the valve tips, and the DAMNING wear grooves in the valve well.

None of this post mortem guesswork really affects you. Just check that valve protrusion is roughly similar to another head (or ask maybe JohnH here, valve geometry being my concern), check what you've got rocker-wise, the head is reasonably flat (say within 10 thou), fine lap the seats and shove in std spring components, I think that you will be fine.

All the best Dave

Re: t120 Cylinder head dilemma
slofut #714629 11/11/17 4:12 pm
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Oh and by the way, what on earth are those rocker feed nuts all about?

Re: t120 Cylinder head dilemma
koan58 #714637 11/11/17 4:49 pm
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Originally Posted by koan58
Oh and by the way, what on earth are those rocker feed nuts all about?



He’s solved the bottoming-out problem anyway!



Amateur Loctite enthusiast.
Re: t120 Cylinder head dilemma
triton thrasher #714641 11/11/17 5:02 pm
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TT - please elaborate!

Re: t120 Cylinder head dilemma
koan58 #714653 11/11/17 7:00 pm
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Originally Posted by koan58
TT - please elaborate!


They made those union nuts in different depths and some of mine have required thick copper washers or the shaft hit against the inside of the nut before the washers were nipped up.


Amateur Loctite enthusiast.
Re: t120 Cylinder head dilemma
slofut #714657 11/11/17 7:27 pm
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I still don't understand what they were for?

Re: t120 Cylinder head dilemma
slofut #714658 11/11/17 7:50 pm
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Yes they look a bit silly.


[Linked Image]


Amateur Loctite enthusiast.
Re: t120 Cylinder head dilemma
slofut #714659 11/11/17 8:28 pm
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Weird, anyone got any ideas?

Re: t120 Cylinder head dilemma
koan58 #714867 11/13/17 1:04 pm
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Originally Posted by koan58
Hi Bill,
Much of this is a post mortem of another person's engine, without all the body parts on the slab. However, I think it interesting to glean as much as possible, as it may help with your decisions of how you proceed with your head.

From your latest pics, as best I can see, the tips of the valve adjusters look reasonable, they can get much worse and still work ok. On that basis alone, I see no reason for them causing so much wear on the valve tips in such short miles. Actually I think that slightly worn adjuster tips are kinder on the valves, once the perfect point contact has smoothed slightly.

I also doubt that oil supply in the top end is responsible for the valve tip divots, whichever way the rocker spindle washers were assembled, there would be enough oil up there to keep a Triumph topend ok for thousands of miles.
In fact, if you look at the pic of the exhaust rocker box, the oil holes in the pushrod balls can be clearly seen. Unfortunately, the gasket on the inlet box makes it difficult to tell if they are present also. But assuming they are, this is the setup Triumph used since Moses until the rocker arms changed to having no drilling to the pushrod ball. I think the old setup was great, providing oil splatter/mist upward from the pushrod cups throughout the rocker box, without too much to get down the inlet guides.
You should check your own rockers for that drilling, as if its not present, you should change your rocker washer assembly to that described by Jubee, and ideally the shafts too, because without the pushrod cup action doing the spraying it needs the slot in the end of the rocker to provide the splatter, hence the need for a plain washer adjacent. A poorer mechanism I think, but cheaper to implement I'm sure.

The one thing I noticed regarding the rocker arms is that 3 were of similar origin, except for the left inlet, which is clearly a different shape, much cruder in profile than the 3 more "sculpted" ones. I have only seen that "ugly" shape in late models, so it may have been a later rocker without the feed to the pushrod ball. If so, with the standard washer setup, there would have been less oil splatter in that valve chamber than intended.
Even so, the wear is extreme for the mileage.
Who knows what valve clearances were being used? Any beating on those valve tips would just be magnified manifold with cams/springs ++.
And maybe an oiltank without a restriction in the return outlet?

Unless they sold elsewhere, I noticed the only significant part of the engine not in the eBay listing was barrels and pistons.

In conclusion (eventually!) I am convinced that heavy valve springs and components have caused the rapid wear on the valve tips, and the DAMNING wear grooves in the valve well.

None of this post mortem guesswork really affects you. Just check that valve protrusion is roughly similar to another head (or ask maybe JohnH here, valve geometry being my concern), check what you've got rocker-wise, the head is reasonably flat (say within 10 thou), fine lap the seats and shove in std spring components, I think that you will be fine.

All the best Dave


Thanks so much Dave for the detailed help. Hopefully I'll be able to get the head off my bike this week and dig in.


'68 Bonnie, '70 TR6r
'74 CL360
trail 70's and minitrails
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