tegwin
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| posted on 27/1/10 at 02:01 PM |
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Tuning quandry... popping in silencer?
The last time I took my TVR out it was misbehaving....
Its a triumph Straight 6 2.5L engine with twin SU carbs and old style points ignition...
Car was ok for the first bit of my drive, got hot and ran ok, but after a while the car started loosing power... especially under load, the car
juddered and there was deffinate explosions going on in the muffler under my seat.... If I pull the choke back on, the problem went away and the car
ran perfectly again... Drop the choke and it goes bad...
Anyone know what this problem could be? Cant figure out how the choke can effect the running like that... any ideas?
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BenB
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| posted on 27/1/10 at 02:03 PM |
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Isn't popping in the silencer usually an air leak or very lean running?
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blakep82
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| posted on 27/1/10 at 02:06 PM |
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usually an air leak in the exhaust manifold. oxygen burning with unburn fuel in the exhaust
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flak monkey
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| posted on 27/1/10 at 02:21 PM |
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Its running too lean.
Possibly blocked jet or something if it was running OK?
Sera
http://www.motosera.com
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adithorp
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| posted on 27/1/10 at 02:48 PM |
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Sounds like it's drawing air somewhere.
Far more worrying though is the use of the word "muffler"!
adrian
"A witty saying proves nothing" Voltaire
http://jpsc.org.uk/forum/
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tomgregory2000
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| posted on 27/1/10 at 03:02 PM |
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It does sound like it is running lean and when you pull on the choke you are feeding the engine with more fuel, one or more of your jets may be
blocked.
And the popping in the exhaust is usually down to an air leak
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tegwin
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| posted on 27/1/10 at 03:07 PM |
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Hmmm... I guess the air leak would have to be pretty close to the engine on the manifold?... Its just weird the problem only started happening....
Will check the jets and mixtures etc... I guess its possible one of the pistons in the carb is sticking or binding... although I only just cleaned
them up and got the engine running properly...grrr
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Would the last person who leaves the country please switch off the lights and close the door!
www.verticalhorizonsmedia.tv
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cliftyhanger
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| posted on 27/1/10 at 04:01 PM |
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Do the carbs have the "waxstat" jets fitted (they are flat-bottomed, about the diameter of 1p)? If so these can cause th emixture to weken
excessively when they get hot, made worse if there is no carb heat shield fitted (essential on these really)
If this is the case you can remove the waxstat capsule and replace with a 1p! plus the little spacer that is inside the jet, thats the locost way, or
buy new non-waxstat jets and linkages (less locost but tidier). Just a thought, or even my 2p worth
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tegwin
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| posted on 27/1/10 at 06:45 PM |
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They already have the queen in them doing her bit..... so its not the wax stats...
Looks like I need to get it hot and see if I can figure out whats going on... 
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Would the last person who leaves the country please switch off the lights and close the door!
www.verticalhorizonsmedia.tv
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cliftyhanger
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| posted on 27/1/10 at 08:19 PM |
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In which case maybe the oil in the dashpots? too thin allows the damper to rise too fast on acceleration and weaken the mixture.
Also I am assuming you didn't mix the dashpots/pistons during the recent work? And the butterflys all seat well?
Then maybe needle valves?
But sticking jets unusual to cause power loss, and easy to check. Leaks, I use WD40 to trace those.....
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x_flow57
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| posted on 27/1/10 at 08:21 PM |
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quote:
Originally posted by adithorp
Sounds like it's drawing air somewhere.
Far more worrying though is the use of the word "muffler"!
adrian
I agree bigest problem here is that word (muffler) its a silencer/exhaust system. 
But the car has gone lean for some reason or another.
Nick
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NS Dev
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| posted on 27/1/10 at 09:03 PM |
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quote:
Originally posted by tegwin
The last time I took my TVR out it was misbehaving....
Its a triumph Straight 6 2.5L engine with twin SU carbs and old style points ignition...
Car was ok for the first bit of my drive, got hot and ran ok, but after a while the car started loosing power... especially under load, the car
juddered and there was deffinate explosions going on in the muffler under my seat.... If I pull the choke back on, the problem went away and the car
ran perfectly again... Drop the choke and it goes bad...
Anyone know what this problem could be? Cant figure out how the choke can effect the running like that... any ideas?
could be a few things, not necessarily just going lean, though a check over the carbs will be a good start.
I'd have a good look at the distributor as well, it sounds like the timing could be all over the shop, plenty of vacuum (i.e. on choke) might
(if it has vac advance) pull on enough advance to stop the problem. Stick a timing light on it while your checking stuff and see if it wanders at
higher rpm (not just moves as it should, but starts to flutter around)
Retro RWD is the way forward...........automotive fabrication, car restoration, sheetmetal work, engine conversion
retro car restoration and tuning
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tegwin
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| posted on 27/1/10 at 10:03 PM |
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Good call on the dizzy.... I have no idea on the condition of it....ancient like the rest of the car I suspect :p
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Would the last person who leaves the country please switch off the lights and close the door!
www.verticalhorizonsmedia.tv
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boggle
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| posted on 27/1/10 at 10:47 PM |
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plug colour will tell you whats going on in your cylinders....if they are white, then its a lean issue...
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Angel Acevedo
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| posted on 28/1/10 at 04:18 AM |
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Old style ignition.
quote:
Originally posted by tegwin
.... old style points ignition...
Car was ok for the first bit of my drive, got hot and ran ok, but after a while the car started loosing power... especially under load, the car
juddered and there was deffinate explosions going on in the muffler under my seat.... If I pull the choke back on, the problem went away and the car
ran perfectly again... Drop the choke and it goes bad...
Anyone know what this problem could be? Cant figure out how the choke can effect the running like that... any ideas?
Old style points ignitions are known for this,
A lot of stuff to go wrong,
Check:
- Axial play of rotor.
- Points condition, clearance, dust.
- Advance weights rotating points( Fulcrums?)
Dizzy Cover play, New Condenser, Conections well made.
Total advance.....
-Dizzy cover cracking...
May be more, but this should be a good starting point....
Beware of what you wish.. for it may come true....
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