Poor running and loss of power.

[Kev888]

Stag: Problem – July 2025.

1. Car is a 1974 manual with O/D; owned by present member since 1980, current mileage 125,000, VERY reliable car.
2. Engine is fitted with Piranha (optical) contactless electronic ignition: has run for years with no problems.
3. Trouble started ~2 months ago; the car had not been used for a couple of months, which is a little unusual for me, certainly during the non-winter months.
4. Appeared to be occasional hesitation on running, perhaps just when cold the first time used, or maybe on and off during the day?
5. Initial ‘gut instinct’ was perhaps the engine advance/retard, so oiled the advance/retard in the distributor (through the centre oiling point): this seemed to ensure that the problem only arose with the engine cold, during the first mile or so, again – occasional hesitation when running although cannot recall whether it was only when accelerating or running on an open throttle. Seemed to pick up OK virtually immediately, including if throttle opened.
6. Checked the carburettor diaphragms at the same time as oiling the A/R; as far as I could see they were OK but have been in for a good many years.
7. Next couple of times used the car ran in a similar manner – OK when warmed up but the very occasional hesitation – almost momentary loss of power – once or twice in the first mile or so. However, had a suspicion that the torque was down a shade. Led me to think electrics, so…
8. Replaced the coil. Engine started and ran fine in the garage, but of course not under load (Tuesday).
9. Next time used (Friday), seemed to be fine but then had the very momentary power-loss blip when running, this time when warmed up.
10. Did some further tests on this journey:
    1. Heavily accelerated 30-50mph in 4^th: acceleration slower than usual in this test location,
    2. Applied mid-level of throttle in 4^th O/D from ~25mph/1,000 rpm (not my usual way of driving, although it will normally accelerate with gentle throttle on the flat from this speed): loss of power occurred so dropped out of O/D. Appeared low on torque.
    3. Held up at roadworks, went to move away and engine stalled but restarted immediately. However, power seemed to be down, needing more revs to move off. Also needed this higher power level to start off at the next junction two or three miles up the road.
    4. It appeared that my test in (a) above may have worsened the trouble, but it was perhaps not likely to correct itself anyway.
    5. On arriving home, lifted bonnet and checked the carburettor dashpots: seemed to have enough oil in although I put some more in. Blipped throttle but little or no obvious lifting of the dashpot tops. However, on pushing each in turn down to screw the top back in, the engine revs dropped (and stalled on the first one, second one I opened the throttle a bit first; never tried this before though so unable to comment as to whether this was usual behaviour or not).
    6. Blipped engine on the throttle a couple of times: normally an instantaneous increase in the revs but this time none, and I think even a drop in the revs.
11. Other observations & Notes:
    1. Normally would expect to hear the fuel pump ticking immediately before starting up from cold, although not necessarily always in the warmer weather if the car had been used recently. No sound on Friday.
    2. Filled up with petrol (just under 8 gallons) on the Friday prior to 9(e) above, so fresh petrol in the tank.

---

Although I have one or two ideas (such as replacing the carburettor diaphragms), and the problem may also be down to other carb internal problems, I would welcome any thoughts and suggestions.

The carbs have hardly been touched - certainly during my ownership (45 years, 85,000 miles in my ownership, 125k miles now on the car); my 'modus operandi' has always been to keep the car running regularly, which has - to date - proved remarkably successful!

Thanks,
Kevin.

[Kev888]

Despite no-one on here coming up with any helpful suggestions I have fortunately managed to now sort out the problem myself. As clearly no-one is interested, though, I shall not bother to share my findings.

[KOY 23]

I think your problem is sleep related:
Post #1. Very long and detailed but I fell asleep part way through.
Post #2. Someone got up too early ðð

[Philip Wardle]

Hi Kevin, over time I've found that people are pretty good about trying to help but may be hesitant to post if they don't know the answer or aren't sure. I'd certainly be interested to know how you fixed the problem?

[trunt]

Agree it was a bit long winded Kevin, and you seemed to have all the right ideas. I just could not think of anything else to add.. you had them covered.

[richardthestag]

Sorry Kevin, I did start to read but too much text, bad spacing for reading with my 58 year old eyes from laptop or phone and I just got distracted elsewhere. So I think to summarise your original post;

Triumph v8 a little down on power

doesn't run as sweet nor as powerfully as it used to.

Lots of tests done but most noticeably carbs not touched in 45 years.

Conclusion:
Blimey they have done well and to think there are some who say stroms are crap
Sort the carbs out, the throttle spindle seals will be dead, the float chamber is possibly full of crud. the carb pistons are probably not running as they should. they will be leaking air in all over the place. Diaphragms would be a good start.