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#863965 11/23/21 4:36 pm
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I have been upgrading my 66 6T engine gradually to the T120 spec, from the crankcase up it is now a T120. I am going to change the worn camshafts this winter with the 70-3134, 70-3325 combination. I have been advised to use 70-3059R followers because they will fit my E5861/E4676 guide blocks and have a "1 1/8 radius" My bike has the (66 only) E6329 exhaust tappet, with the recessed oil hole to match the extra oil feed in the block. I would like to be able to retain that tappet design, if possible.

My questions are:

Does anybody know if the 66 only tappet has a 1 1/8 radius? or if it can be run on a 70-3325 exhaust cam?
Will, there be any adverse effect to just fitting a cam with no oil hole and going back to drip-feed only?

Very grateful for any advice

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Hi Julian
Sorry but I can't help you very much with this, other than let you know the 66 style oil feed exhaust tappet was made as an R style, I have one that I bought mixed in with some other parts.

It's been stamped with a double R....make of that what you will smile
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Hi Julian, My understanding is that the 70-6329 exhaust cam follower, as used in the 6T and TR6 engines was of the 3/4" radius. The 70-6490 followers, used on the '66 T120 models were 1-1/8" radius. Just curious, why the 70-3325 exhaust cam?
-Dave


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Thanks, Dave, 3/4 is helpful I did not know what it was...

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The 70-3325 is an inlet cam, no points drive on the end.

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Hi Dave,
According to Parts Book number 4 I need E4855 for the exhaust, but this seems to be obsolete/unobtainable but I have been led to believe 3325 has the same profile and is a replacement and I believe that the new ones are nitrated?

Julian

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It's both for a pre-unit, but you probably want a 70-9989, which is the E3134 profile nitrided exhaust cam. You can blank off the tappet oil feed with the nitrided cam, so you can use whatever radius follower you wish, the late T120's used an "R" follower, just compare the shape with a 70-3059R, you never know what might have been done to the profile in 50 odd years.

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Thanks that is very interesting I will have a think about that

Julian

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It is my opinion and my experience that on the roads I personally like to ride a Triumph sports (as opposed to a 6T) 650 on, the E3134 profile inlet and E3325 profile exhaust combination is hard to beat. That would be twisty, narrow roads with lots off hills and speed variations.
On more open roads that encourages higher and more consistent speeds, I'd go for an E3134 exhaust cam.
A fitting English idiom would be "horses for courses" I suppose.
The T140/TR7 exhaust cam is basically an E3325 (I don't know what the difference is, if any, possibly a slightly extended ramp) and I've used it on many bikes. There must be loads available from all the engines converted to the E3134 exhaust cam. I have a few myself, very handy they're well made and hardened, and very durable.
Most people I fix bikes for are in their 50s to 70s and their hooligan days are long behind them. They're more than happy with the "slower" exhaust cam, as they get more power and better throttle response at the speeds they actually ride at. I've got a reputation for building fast Triumphs, while many times building them slower...

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The 3325 has 0.296" lift and no ramps, while the 7017 is 0.305" (measured) and has quietening ramps. I'm sure that when timed sensibly, you can get nice characteristics with a 7017 exhaust. Personally, I prefer the ramp cams, the 7016 T140 inlet is not too aggressive with a 3/4" follower, but I'm not sure I'd be able to tell. Anyone who wants a 7017, I have a lot of them!

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Originally Posted by TinkererToo
The 3325 has 0.296" lift and no ramps, while the 7017 is 0.305" (measured) and has quietening ramps. I'm sure that when timed sensibly, you can get nice characteristics with a 7017 exhaust. Personally, I prefer the ramp cams, the 7016 T140 inlet is not too aggressive with a 3/4" follower, but I'm not sure I'd be able to tell. Anyone who wants a 7017, I have a lot of them!
Re the 7017, much as I expected. I've only ever measured them with calipers, plus eyeballed them as being very close to the E3325.
I too like ramp cams, and the 750s are much better as regards clatter than earlier Triumphs. A set of 7017s on a pre-unit would be nice, combined with the later cam wheels, though it would take some modifications to the inlet cam wheel nut.
I have plans to fit a pair of E7016 to a pre-unit together with a 750 kit. I don't ride sensibly ALL the time. cool

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Thanks for all that amazing expertise from all of you. Following the great tip from Tinkerer, I have found the 70-8801 tappet (with an oil hole) (sold to match the 9989), that is perfect for the job. With regard to the cam, I am disappointed because having fitted a new barrel, the correct 66/67 1/32 rebate head, 9:1 pistons, and a pair of brand new 389/203 carbs it still will not exceed 100mph with the standard E4818 cm that I have fitted, but the exhaust note is just pure music with that combination but both cams have almost worn off the chrome now.

Not quite used to this bulletin board threading so sorry if I missed anybody.

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Originally Posted by Julian1966
it still will not exceed 100mph
Julian

How fast will it go in third gear?


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The E4818 is a E3325 form inlet cam, you really want an E3134 form cam in there, something like the 71-0040, which is a nitrided cam, but retaining the breather hole. The 7016 inlet with 3/4" radius is a nice step up from there, but it needs to be modified to use the breather.

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Originally Posted by triton thrasher
Originally Posted by Julian1966
it still will not exceed 100mph
Julian

How fast will it go in third gear?
Most speedos tend to read too high, how accurate is yours? How did you ride? Keep in mind that the speeds they recorded back in the day were with rider prone and wearing tight fitting leathers. If you sit bolt upright, an honest 100 mph isn't bad, especially if you're wearing a bulky suit. If you're a slim guy in swimming trunks, chin on tank, I'd expect better too.


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It’s common to find these bikes overgeared by a big gearbox sprocket, so they can’t reach peak rpm in top. It’s also common to find insufficient fuel flow and/or unsuitable main jets.

I’m the last person (sometimes!) to criticise anyone’s speed-tuning, but this bike sounds like it may be slower than a 1966 6T.


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Just another thought, the pre-‘69 heads had rather soft valve seats, if you have any “pocketing “ of the valves, it will kill the flow into the engine. Of course’ there are many other reasons for poor performance, but the basics matter, something I learned very early on when a workmates ally T100 was miles quicker than my own. He had a father who knew what he was doing.

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I have a GPS speedo very accurate and allows you to dump the cable.

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Yes, it has 20 tooth sprocket, I have a 19 that will be fitted this winter, there is a gearbox issue it that it started jumping into a false neutral at 90 when I checked the main shaft it was worn to the point that it fitted into a new bush without reaming so I left it to get it back on the road for the summer, very interest to learn that you think that may be a problem, in fact, the jumping out of gear was worse with a headwind so I probably should have changed that last time, thanks.

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Well, I am still learning, but the head had new seats and I lapped in tungsten valves and regularly check the pressure in the cylinders, it is well low, but equal, but as it has a new barrel, new pistons, rings valves, and seats, and is not showing white smoke from the pipes and sounds great so I concluded that it must be that cams are for a 6T?

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Tungsten valves, are you sure? Tungsten is very heavy , possibly one of the worst choices for valve material.


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You're probably right about the cams, as long as the seats were done properly, hard to know without seeing them.

Last edited by TinkererToo; 11/25/21 3:31 pm.

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