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Having rough idle on my TR6 and it runs rough up to 2000 rpm. And it smells a lot from unburned fuel on idle which doesn´t go away whatever adjustments I do on the carbs. I would love to have the engine running real smooth that a straight six can do. I´m more interested in low rev torque than high rev power. It´s got Twin SU HS6, KN filters, open manifold and exhaust and I got papers from 1993 on Engine job: Camshaft, forged pistons, ported exhaust and so on. I guess it´s got early PI camshaft or similar. It´s original an US car which was converted to Lucas PI in England 1993 and now back to carbs because of to much PI problems (it was running rough and smelled a lot with PI too). The question is what camshaft to run for smooth running and nice torque for everyday street riding???? Something else that is a must to change together with a new camshaft?
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TR6 TR6 camshaft options
- Thread starter hakantr6
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TR3driver
Great Pumpkin - R.I.P
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Just a suggestion, before you go to all that work, invest in a degree wheel & dial indicator and find out just what cam you have. An early PI cam might have some lope down low, but shouldn't be nearly as bad as you describe. If that is what's in there, then I think you've got something else going on.
From what I've heard, the later PI camshaft should be a good choice; but that's just hearsay.
From what I've heard, the later PI camshaft should be a good choice; but that's just hearsay.
poolboy
Yoda
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I agree with that. Something else that can indicate a non stock cam would be to hook a Vacuum Gauge up to the intake manifold.
You will have one of these types of fittings available to connect the Vacuum Gauge to.
Although the movement of the needle when the engine is idling will not identify the particular cam, it will indicate the "aggressiveness".
Post a video, so we can have a look.
You will have one of these types of fittings available to connect the Vacuum Gauge to.
Although the movement of the needle when the engine is idling will not identify the particular cam, it will indicate the "aggressiveness".
Post a video, so we can have a look.
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I don't disagree with Randall about the distinct possibility of something else going on, maybe too rich a mixture?, I will throw in to the possibilities. But getting back to the camshaft I have a grind on mine from Delta Camshafts described as low torque, and it lives up to the name, but still pulls strong 5000 rpm or a little more, it is a slightly more conservative grind than the early PI grinds, a similar lift and a little less duration as I recall.
The early PI cam is "stinky" at idle and low speeds, due to the large overlap. It also produces a "rougher" idle. The later cam used on both PI&carb cars would be a better choice if you aren't concerned about a loss of performance in the upper rev. range. Also, the needle selected for the SU carbs might also be contributing to the rich mixture. It sounds like the engine has received some serious (expensive) mods. for performance. Berry
Thanks for the replies, the Engine has good compression and we´ve tried with different needles in the SU carbs with no difference on the idle. My mechanic who is a specialist on these old cars is pretty certain it´s got an early PI cam or one with similar characteristics. Might be an even "wilder" cam. Since it´s a streetcar I´m more interested in the low down torque and that it´s running smooth. Very seldom up at 4-5000 rpm, just some occasional acceleration. So the big question is still which cam to get???
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This may appear too obvious. If you returned to the camshaft Triumph built the engine with, it would give you what you're after. I've only ever driven stock TR6's. While I wouldn't describe the 2.5L six as particularly free revving, it's low end torque is something to enjoy. It pulls so nicely from low rpm's in 4th gear. Smooth idle too.