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[omegaV6CD]

Intake camshafts are critical for performance thats why they were used on the st200, later they discovered that the exhaust cam was affecting the torque curve shape and hence they used it on the GSI's. If people are interested i can write a brief post on how each camshaft parameter affects the performance.
Back to the lifters discussion, if the lifter fails you can get this horrible clapping noise but also if it cannot hold pressure you will get severe missfire, also the torsional vibration through the cam will change which might do many things like loosening the cam sprocket.
Now if you have to redo the whole thing to change the faulty tappet you will have to buiy another cambelt kit or at least a belt/ new rocker cover gaskets/ sealant/ crank pulley bolts etc, So unless you are a bodger(i'm sure you are not) It will be false economy not to change them.

[Phil]

Just realised my mate's got one of those Vectras. Didn't realise they made so few!

They did make some Super Tourings with a 2ltr engine, after the ST200 run had come to an end.

The ST200s had an individual MSD build plate in the lower dash

They are the X25XE

[Kevin Wood]

Just realised my mate's got one of those Vectras. Didn't realise they made so few!

They did make some Super Tourings with a 2ltr engine, after the ST200 run had come to an end.

The ST200s had an individual MSD build plate in the lower dash

They are the X25XE

His is certainly a V6 and IIRC it has the build plate too.

Kevin

[JamesV6CDX]

Intake camshafts are critical for performance thats why they were used on the st200, later they discovered that the exhaust cam was affecting the torque curve shape and hence they used it on the GSI's. If people are interested i can write a brief post on how each camshaft parameter affects the performance.
Back to the lifters discussion, if the lifter fails you can get this horrible clapping noise but also if it cannot hold pressure you will get severe missfire, also the torsional vibration through the cam will change which might do many things like loosening the cam sprocket.
Now if you have to redo the whole thing to change the faulty tappet you will have to buiy another cambelt kit or at least a belt/ new rocker cover gaskets/ sealant/ crank pulley bolts etc, So unless you are a bodger(i'm sure you are not) It will be false economy not to change them.

Does that make me a bodger  

[omegaV6CD]

Intake camshafts are critical for performance thats why they were used on the st200, later they discovered that the exhaust cam was affecting the torque curve shape and hence they used it on the GSI's. If people are interested i can write a brief post on how each camshaft parameter affects the performance.
Back to the lifters discussion, if the lifter fails you can get this horrible clapping noise but also if it cannot hold pressure you will get severe missfire, also the torsional vibration through the cam will change which might do many things like loosening the cam sprocket.
Now if you have to redo the whole thing to change the faulty tappet you will have to buiy another cambelt kit or at least a belt/ new rocker cover gaskets/ sealant/ crank pulley bolts etc, So unless you are a bodger(i'm sure you are not) It will be false economy not to change them.

Does that make me a bodger  

Exaactly!!!
Joking aside if i wanted to refer to you as a bodger i would have done it in a direct way and not indirectly, people that know me on here will confirm that i have no problem expressing myself. If you wanna see some proper bodging i will send you some pictures of how i'm going to fix the numberplate on my Wife's Golf.

[JamesV6CDX]

Intake camshafts are critical for performance thats why they were used on the st200, later they discovered that the exhaust cam was affecting the torque curve shape and hence they used it on the GSI's. If people are interested i can write a brief post on how each camshaft parameter affects the performance.
Back to the lifters discussion, if the lifter fails you can get this horrible clapping noise but also if it cannot hold pressure you will get severe missfire, also the torsional vibration through the cam will change which might do many things like loosening the cam sprocket.
Now if you have to redo the whole thing to change the faulty tappet you will have to buiy another cambelt kit or at least a belt/ new rocker cover gaskets/ sealant/ crank pulley bolts etc, So unless you are a bodger(i'm sure you are not) It will be false economy not to change them.

Does that make me a bodger  

Exaactly!!!
Joking aside if i wanted to refer to you as a bodger i would have done it in a direct way and not indirectly, people that know me on here will confirm that i have no problem expressing myself. If you wanna see some proper bodging i will send you some pictures of how i'm going to fix the numberplate on my Wife's Golf.

Some of the things I used to do to my Mk1 fiesta to keep it on the road..... SHOCKING is the only word for it!!

[Markjay]

Performance camshafts will have redesigned cam lobes, which change the timing (typically creating an overlap) and the opening curve (typically opening earlier and closing later to maximise flow), but more crucially they will go deeper to maximise valve opening. This puts more stress on the lifters/tappets so reinforced ones are used on tuned engines.

Also, when engines revs very high (above 7000 rpm) the hydraulic lifters may not be able to respond fast enough, resulting in the cam lobes 'floating' over the tappets, which is why on many race engines the hydraulic lifters are replaced with mechanical ones.

However while the 3.0L cams probably have some of these features that makes them better than the 2.5L ones, they can be described at best as 'mild fast road' and definitely not 'race' cams...

[Kevin Wood]

I would imagine the 2.5 cams just have a little less lift than the 3.0s in order to keep the gas velocity up. This would give the manufacturer a slightly easier time with emissions and fuel economy.

It'll be interesting to do a visual comparison between them. I might even take my DTI along when we do ClarCEs and have a measure.

Kevin

[ClarCE]

I would imagine the 2.5 cams just have a little less lift than the 3.0s in order to keep the gas velocity up. This would give the manufacturer a slightly easier time with emissions and fuel economy.

It'll be interesting to do a visual comparison between them. I might even take my DTI along when we do ClarCEs and have a measure.

Kevin

I'll change that statment:

I think the 3.0 Cams give me the following:

0.8mm more lift
valve open to close duration is 133 degrees from previous 127

this should give me between 15-17 more bhp...

[Kevin Wood]

3.0 Cams give me 0.08mm more lift I think...

Ahh, OK. Not very significant given that the lift is probably 8 - 10 mm. The main difference is probably the duration, then.

Basically on a 2.5 there's less gas to get through the same size valves. All other things being equal the gas will just move more slowly but manufacturers always have their eye on emissions and a slower moving body of gas loses more fuel out of the vapour onto the sides of the inlet manifold and head, etc. This upsets the emissions and fuel economy so they strangle the engine a little by shortening the valve duration or reducing the lift and we're back to a fast moving body of gas and a little less power.


Kevin

[ClarCE]

3.0 Cams give me 0.08mm more lift I think...

Ahh, OK. Not very significant given that the lift is probably 8 - 10 mm. The main difference is probably the duration, then.

Basically on a 2.5 there's less gas to get through the same size valves. All other things being equal the gas will just move more slowly but manufacturers always have their eye on emissions and a slower moving body of gas loses more fuel out of the vapour onto the sides of the inlet manifold and head, etc. This upsets the emissions and fuel economy so they strangle the engine a little by shortening the valve duration or reducing the lift and we're back to a fast moving body of gas and a little less power.


Kevin

I've edited that post - 0.8mm I meant! oops!