advice please

[monaco]

Chaps 1) Could anyone tell me if after a chim has been decatted it should sound like it is blowing from the manifold, mine had a little hole in the manifold and so was take off for repair and removal of the pre cats, the hole was welded and it was found that the cats had already been removed. it still sounds blowy from around the Y bit but no leaks can be found ?? 2)the car is a 4.0HC Chim, it sounds very lumpy on idle ( but idle is very steady around 1000rpm )and runs uneven below 2000rpm, but after about 3500rpm it pulls like a steam train. I have no idea if the car has been modified in the past as it was purchased without history, hence the need for some advice. the uneven idle may not be helping the blowing sound either, almost sounds like misfire below 2000rpm Any help or advice would be most grateful.

[Leadfoot]

Time for some new plugs & leads?

[thegamekeeper]

Did you bolt the manifold to a jig when welding it. If not it is most likely to have distorted due to the expansion and contraction from the heat generated from welding and could therefore be blowing from the face between the head and the manifold, quite probably from the underside where it is not easy to see. Remove and look for black witness marks of gas passing

[monaco]

leadfoot What plugs and leads would you suggest ? I understand that magnecor leads are good, any other suggestions chaps ? I need to get it sorted, it's cr@p around town.

[GreenV8S]

If it comes in with a kick at about 3500 rpm I'd suspect the ECU is running in 'limp' mode. There are a bazzillian possible causes but a duff lambda sensor is pretty high on the list. Tracking down the actual cause isn't easy especially if you don't know the history of the car, there are endless ways to mask problems by fiddling with the fuel pressure, idle settings, throttle pot etc. You might want to have Tower View or similar give the car a thorough going over, it will probably save you money in the long run. Cheers, Peter Humphries (and a green V8S)

quote:Chaps 1) Could anyone tell me if after a chim has been decatted it should sound like it is blowing from the manifold, mine had a little hole in the manifold and so was take off for repair and removal of the pre cats, the hole was welded and it was found that the cats had already been removed. it still sounds blowy from around the Y bit but no leaks can be found ?? 2)the car is a 4.0HC Chim, it sounds very lumpy on idle ( but idle is very steady around 1000rpm )and runs uneven below 2000rpm, but after about 3500rpm it pulls like a steam train. I have no idea if the car has been modified in the past as it was purchased without history, hence the need for some advice. the uneven idle may not be helping the blowing sound either, almost sounds like misfire below 2000rpm Any help or advice would be most grateful.

[monaco]

Thanks for advice so far. Do you know if there are any good tuners/rolling roads in the north that know tvr's ?, I'm in county durham.

[thegamekeeper]

have you checked for leaking across the manifold/head surface or are you burying your head in the sand

[monaco]

I have had a good look for manifold/head leaks, but it's very hard to tell with everything in place. looks more and more like a total manifold/Y bit strip down. I have spoken to tower view racing and seems it probably shouldn't sound like this even with the cat's removed !! very hard to tell exactly where the blowing/tapping noise is coming from. the search goes on !!