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[ClarCE]

Hi all,

As some of you are aware I'm going to be fitting (with help) my 3.0L (excellent condition) cams soon, to my 2.5 V6.

What I wanted to know was what implications that this might have on the future - besides things like fuel economy, I wouldn't be doing this if I was remotely bothered about that sort of thing..

What I am thinking about is increased wear, blowing spark plugs out of the wells and destroying the engine, getting heavily pitted pistons and eventual destruction - these kinds of things.  Engine has 101K on it at the moment, what can I realistically expect to get from it by changing the cams over.

Or

Will it do nothing except use more fuel and make me smile more

Cheers,

Chris.

[Marks DTM Calib]

Remember this.....this engine is pretty much the same as the 3.0 one with the excepetion of the bore and stroke....and Vx sold 2.5V6 power plant with the 3.0 cams fitted in the Vectra GSi......

So its all smiles and no worries...

[tunnie]

Remember this.....this engine is pretty much the same as the 3.0 one with the excepetion of the bore and stroke....and Vx sold 2.5V6 power plant with the 3.0 cams fitted in the Vectra GSi......

So its all smiles and no worries...

Just to hi-jack this thread a bit (sorry Chris)

Mark, can 3.0 cams be fitted to the 2.6? Or do they have to be the 3.2 cams?

Seen a very nice 2.6 MV6 Manual for sale, and if I had the cash would have traded up! I will prob get a 2.6 when I do finally trade up...

I am assuming like the 2.0 / 2.2 the 2.6 is just a stroked 2.5? With a slightly larger bore?

[omegaV6CD]

Hi all,

As some of you are aware I'm going to be fitting (with help) my 3.0L (excellent condition) cams soon, to my 2.5 V6.

What I wanted to know was what implications that this might have on the future - besides things like fuel economy, I wouldn't be doing this if I was remotely bothered about that sort of thing..

What I am thinking about is increased wear, blowing spark plugs out of the wells and destroying the engine, getting heavily pitted pistons and eventual destruction - these kinds of things.  Engine has 101K on it at the moment, what can I realistically expect to get from it by changing the cams over.

Or

Will it do nothing except use more fuel and make me smile more

Cheers,

Chris.

You strictly need new lifters if you want the Job to be a proper one. Other than that you should have absolutely no issues.

[ClarCE]

All sounds good, already smiling more

No worries Tunnie, I do it all the time

Would you worry about the lifters then as Omegav6cd suggests Mark?  I didn't really want to be pulling the head to peices to be honest..

[JamesV6CDX]

All sounds good, already smiling more

No worries Tunnie, I do it all the time

Would you worry about the lifters then as Omegav6cd suggests Mark?  I didn't really want to be pulling the head to peices to be honest..

You won't be pulling the head to peices

Once the cams are out, the lifters just pull upwards

(a suction device helps!)

[Kevin Wood]

Agreed, the lifters would be an easy change with the cams already out but a new set of 24 of them would make this quite an expensive operation.

Kevin

[Kevin Wood]

... but then isn't only one of the cams (Inlet / Exhaust) different between 2.5 / 3.0 in any case .. or did I imagine that?

So presumably one cam and lifters in each bank could stay.


Kevin

[Marks DTM Calib]

Thats true of the older C25XE but, not the X25XE.....as for the lifters.....I would test and clean them......

[ClarCE]

Ok, I have a couple more questions following responses:

1.) When cleaning and testing the lifters are there any seals I need to replace?

2.) Part number for 2.5 V6 Lifters incase when testing I find any broken ones

3.) Part number for 3.0 V6 Lifters as I may just replace the lot if not mega bucks...

Cheers again!

Chris.

[Matchless]

Lifters are the same across all V6 Ecotec engines of the same vintage.
There were some changes around 97/98 which is tied in with a different oil pump which required modified T vents, the lifters also changed to a different construction but that was for reliability, not oil pressure reasons.

When the cams are out you can clean and test the lifters following the guide on here.

Remember when assembling:-
Green sealant under the front cam bearing cap front edges, black sealant in the corners of the camcover seal path but take care to keep the sealant away from the drain holes in the front bearing caps.

[ClarCE]

Lifters are the same across all V6 Ecotec engines of the same vintage.
There were some changes around 97/98 which is tied in with a different oil pump which required modified T vents, the lifters also changed to a different construction but that was for reliability, not oil pressure reasons.

When the cams are out you can clean and test the lifters following the guide on here.

Remember when assembling:-
Green sealant under the front cam bearing cap front edges, black sealant in the corners of the camcover seal path but take care to keep the sealant away from the drain holes in the front bearing caps.

Chances are that mine are of the 'changed' variety then seeing as its a 98 car - if I read what you're saying correctly, there is no difference in the lifters between 2.5 and 3.0 varients..

[Kevin Wood]

When I've thought about changing them in the past on other engines they've been 7 or 8 quid each. Multiply by 24 and it's expensive.

In theory you should change them with the cam. In practice I think if the lifters are in OK condition I'd leave the old ones in. If I were fitting brand new cams I'd treat them to a new set of lifters.

It may be worth giving them a clean because once crud gets into them there is no where for it to go.

How are the lifters at the moment? Do they quieten quickly after an engine start?

I have heard you can planish the top surfaces with some fine wet and dry prior to re-fitting but not sure I could make them any flatter than a set of decent 100k lifters anyway!

Kevin

[ClarCE]

When I've thought about changing them in the past on other engines they've been 7 or 8 quid each. Multiply by 24 and it's expensive.

In theory you should change them with the cam. In practice I think if the lifters are in OK condition I'd leave the old ones in. If I were fitting brand new cams I'd treat them to a new set of lifters.

It may be worth giving them a clean because once crud gets into them there is no where for it to go.

How are the lifters at the moment? Do they quieten quickly after an engine start?

I have heard you can planish the top surfaces with some fine wet and dry prior to re-fitting but not sure I could make them any flatter than a set of decent 100k lifters anyway!

Kevin

Mine is a pretty quiet one I think - there is noise there that I can hear, but its not loud - maybe I just have a couple that are knackered...

Maybe I'll buy five of them and take back what I don't use when attempting this job..

[Ronald_McBurger]

Yeah yeah, you all sound very knowledgable, but has yoiur MV6 got a Homer Simpson that flashes when you brake?

[Marks DTM Calib]

.....and nuts the rear window making you think something is falling off the rear of the car....

[Admin]

Ladies and Gentlemen, Homer has left the car....

[TheBoy]

Ladies and Gentlemen, Homer has left the car....

Good.

I would have refused to get in it

[Marks DTM Calib]

Now [size=16]THATS[/size] worth a drink

[TheBoy]

Who said drink  

 [smiley=beer.gif]

[tunnie]

did someone mention booze?  

Btw as per other post, can 3.0 cams be fitted to a 2.6? or doe they have to be 3.2's?

I am assumiung like the 2.0/2.2 the 2.6 is a stroked 2.5? So 3.0 cams could be used?

[omegaV6CD]

All sounds good, already smiling more

No worries Tunnie, I do it all the time

Would you worry about the lifters then as Omegav6cd suggests Mark?  I didn't really want to be pulling the head to peices to be honest..

It is a fundamental rule that when you change cams you change lifters the reason being that when an engine has run for long time the lifter and the cam have settled to match one another while wearing in. Now if you introduce new cams to old lifters then this process of bedding in will re-occur With the danger of affecting the radius of the lifter(lifters are not flat) and preent them from rotating as they supposed to. if this happens the wear will be accelerated. This is the reason why serious engine manufacturers alwasy Kit these parts together as s[are parts. This is the technical reason, but apart from that it is a damn good idea to do it while at it because at 107k miles you don't know when a lifter will decide to go making your nice engine sound like a flamengo players clapping.

[STMO123]

...and you wont forget to tell your insurance company, will you?

[jonny2112]

I have bought two new lifters as I believe I have some noisy ones and wanted spares in case I couldn't clean or reuse all of the originals. I wasn't aware of the possibility of making the situation actually worse by introducing new items, and I may not bother with it now

BTW local dealer quoted around £16+ each for new lifters, and they only came in sets of 32!!!
I got mine from fleabay for £8 +del but I only bought two.

[omegaV6CD]

...and you wont forget to tell your insurance company, will you?

It is none of their bussiness is it?

[TheBoy]

...and you wont forget to tell your insurance company, will you?

It is none of their bussiness is it?

They will disagree...

[tunnie]

...and you wont forget to tell your insurance company, will you?

It is none of their bussiness is it?

Ohhh yes it is!

A: The car has been modified, and i suspect a question asked when you initally took out the policy was "Is it standard" and now its not.

B: A fairly large performance increase....

So yes technically they should know, if they find out it was modified they don't have to pay out!

[ClarCE]

All sounds good, already smiling more

No worries Tunnie, I do it all the time

Would you worry about the lifters then as Omegav6cd suggests Mark?  I didn't really want to be pulling the head to peices to be honest..

It is a fundamental rule that when you change cams you change lifters the reason being that when an engine has run for long time the lifter and the cam have settled to match one another while wearing in. Now if you introduce new cams to old lifters then this process of bedding in will re-occur With the danger of affecting the radius of the lifter(lifters are not flat) and preent them from rotating as they supposed to. if this happens the wear will be accelerated. This is the reason why serious engine manufacturers alwasy Kit these parts together as s[are parts. This is the technical reason, but apart from that it is a damn good idea to do it while at it because at 107k miles you don't know when a lifter will decide to go making your nice engine sound like a flamengo players clapping.

Hmmm

Based on that advice then, if I've got cams that have been used for star ship mileage, is it going to hurt them using new lifters? Over the lifters that they would have originally worn with?

And - sets of 32??! Looks like I'll be saving for a bit before I put these in, the last thing I want to do is ruin the engine.

[JamesV6CDX]

...and you wont forget to tell your insurance company, will you?

It is none of their bussiness is it?

Ohhh yes it is!

A: The car has been modified, and i suspect a question asked when you initally took out the policy was "Is it standard" and now its not.

B: A fairly large performance increase....

So yes technically they should know, if they find out it was modified they don't have to pay out!

On a scale of 1 - 10

Chances of an insurance assessor.. taking of the cam covers to check out what cams are in a totally standard looking Omega, following an accident?

[JamesV6CDX]

All sounds good, already smiling more

No worries Tunnie, I do it all the time

Would you worry about the lifters then as Omegav6cd suggests Mark?  I didn't really want to be pulling the head to peices to be honest..

It is a fundamental rule that when you change cams you change lifters the reason being that when an engine has run for long time the lifter and the cam have settled to match one another while wearing in. Now if you introduce new cams to old lifters then this process of bedding in will re-occur With the danger of affecting the radius of the lifter(lifters are not flat) and preent them from rotating as they supposed to. if this happens the wear will be accelerated. This is the reason why serious engine manufacturers alwasy Kit these parts together as s[are parts. This is the technical reason, but apart from that it is a damn good idea to do it while at it because at 107k miles you don't know when a lifter will decide to go making your nice engine sound like a flamengo players clapping.

Hmmm

Based on that advice then, if I've got cams that have been used for star ship mileage, is it going to hurt them using new lifters? Over the lifters that they would have originally worn with?

And - sets of 32??! Looks like I'll be saving for a bit before I put these in, the last thing I want to do is ruin the engine.

From what I've heard.. these cams are meant to be in super condition... I think you'll be fine

If your lifters are not noisy.. I would just inspect/clean them as you wish.. and re-fit with the 3.0 cams

Project Elite, a couple of lifters went back in the wrong places... and it's running sweet as a song..

Just put the cams in, and enjoy the right foot

[Markjay]

Valve Lifters (24):

X25XE & X30XE to engine number 08159068 - P/N 9117905 (old P/N - 90 511 241)
X25XE & X30XE from engine number 08159069 - P/N 9117904 (old P/N - 90 542 783)
Y26SE & Y32SE all models - P/N 93 174 076 (old P/N - 9117904)

From EPC.

[Markjay]

[omegaV6CD]

All sounds good, already smiling more

No worries Tunnie, I do it all the time

Would you worry about the lifters then as Omegav6cd suggests Mark?  I didn't really want to be pulling the head to peices to be honest..

It is a fundamental rule that when you change cams you change lifters the reason being that when an engine has run for long time the lifter and the cam have settled to match one another while wearing in. Now if you introduce new cams to old lifters then this process of bedding in will re-occur With the danger of affecting the radius of the lifter(lifters are not flat) and preent them from rotating as they supposed to. if this happens the wear will be accelerated. This is the reason why serious engine manufacturers alwasy Kit these parts together as s[are parts. This is the technical reason, but apart from that it is a damn good idea to do it while at it because at 107k miles you don't know when a lifter will decide to go making your nice engine sound like a flamengo players clapping.

Hmmm

Based on that advice then, if I've got cams that have been used for star ship mileage, is it going to hurt them using new lifters? Over the lifters that they would have originally worn with?

And - sets of 32??! Looks like I'll be saving for a bit before I put these in, the last thing I want to do is ruin the engine.

To answer you question the lifters are the ones that get hurt the cams are usually harder.
If you want to do the job properly fit new lifters.  Trust the professional's advice and you won't loose.
DO NOT FORGET to prelubricate everything with assembly lub.

[JamesV6CDX]

Not arguing for one min about the best practice - I agree this would be to replace the lifters.

It's all very well listinging to the professionals, but is the advise of the professionals always worthwhile, when it involves spending more on a few components than the market value of the car?

If they are £8 each, that makes it £192 just for new lifters

Is it really economical?

[omegaV6CD]

Not arguing for one min about the best practice - I agree this would be to replace the lifters.

It's all very well listinging to the professionals, but is the advise of the professionals always worthwhile, when it involves spending more on a few components than the market value of the car?

If they are £8 each, that makes it £192 just for new lifters

Is it really economical?

Well it depends the way you look at it. When i had my omega i spend 2500pounds on it to have it in the condition i wanted which was very uneconomical but again my reward was 30000faultless miles and 2 Summer round trips to Greece without a single issue and very illegal speeds.
my view is that owning an omega can forgive any expense spent when you think of the depreciation that new cars suffer. Don't get me wrong the old lifters can run perhaps another 100000 miles if you are lucky but i would really be pissed off if a year after all that effort and money spent a lifter decides to fail. I would sacrifice a few nights out for the lifters.

[ClarCE]

So if the lifter fails, what does this cause to happen?  By Failing you mean breaking up? Or the spring breaks and I have to take it to bits to chuck new ones in?

It is a question of making economic sense for me really - i.e does it make economical sense to replace them all now, or will it cost me more in the long run if I leave it...

[JamesV6CDX]

In best practice terms, you should change them all.

My PERSONAL OPINION is that, in economic terms, you don't need to change them, if they are all good and quiet.

I've seen plenty of sucesfull cam changes with the lifters staying in place.

[JamesV6CDX]

Worst case secnario = cams out again to change lifters...

If a lifter fails.. it won't cause any internal damage, apart from a lot of noise

[ClarCE]

Worst case secnario = cams out again to change lifters...

If a lifter fails.. it won't cause any internal damage, apart from a lot of noise

Cheers James - this is what I had hoped - full speed ahead on the cam change

[Phil]

Don't forget the ST200 ONLY had the INLET cams from the X30XE engine, so in theory you only need to change 2 cams and 12 lifters, saving some money and still keeping piece of mind??

[ClarCE]

Don't forget the ST200 ONLY had the INLET cams from the X30XE engine, so in theory you only need to change 2 cams and 12 lifters, saving some money and still keeping piece of mind??

That doesn't sound right to me - my engines X25XE I think what you're saying was the case on the older C25XE - whats the ST200?  Sounds like a Mondeo  

[Phil]

That doesn't sound right to me - my engines X25XE I think what you're saying was the case on the older C25XE - whats the ST200?  Sounds like a Mondeo  

ST200 is the Vectra Super Touring 200, the V6 engined touring car road going replica, commonly mistaken for the GSi which it pre-dates or the SRi on which it was based.

Basically only 38 saloons were made numbered 1-37 and no 50, most were white, one was red and one or two IIRC where black, there was also a one off estate no 0000, in pale blue Arctic Blue. There was NEVER a hatchback version

basically:-

"Swindon race engineering carried out the work on the V6, they tried different cam and ecu set ups but found the MV6 inlet cam was so close to what they needed, they used that instead. The ECU was not changed due to cost reliability and strict emission controls

The pre sales pack, which was written before the car was launched, said it had ecu upgrade and would come with 6 speed box, this was not the case, it also said it would come with 325mm grooved discs but plain 330mm were fitted instead

Full spec over and above the SRi( GSi wasnt available at the time):-
Speedline Mistral 7.5J*17 alloys ET49 5 spoke with full size spare
Steinmetz side skirts
AP LSD
AP lower final drive - 4.45:1
AP road/ race 4 pot brakes with Goodridge braided hoses
X30XE inlet cams
Koni road/ race suspension package, 35mm drop
Recaro front seats with Eurosport motif, matching trim to rear seats and door cards"

And before anyone says, yes MSD did make the final limited run, but Swindon did the origional engine development as they were hevily involved in the BTCC engine development at the time.

The inlet cam upgrade ment the engine produced 200ps (approx 197bhp) hence the reason it was called the ST200.

This year is the 10th anniv. and they are having a big do at Billing.

[ClarCE]

That doesn't sound right to me - my engines X25XE I think what you're saying was the case on the older C25XE - whats the ST200?  Sounds like a Mondeo  

ST200 is the Vectra Super Touring 200, the V6 engined touring car road going replica, commonly mistaken for the GSi which it pre-dates or the SRi on which it was based.

Basically only 38 saloons were made numbered 1-37 and no 50, most were white, one was red and one or two IIRC where black, there was also a one off estate no 0000, in pale blue. There was NEVER a hatchback version

basically:-

"Swindon race engineering carried out the work on the V6, they tried different cam and ecu set ups but found the MV6 inlet cam was so close to what they needed, they used that instead. The ECU was not changed due to cost reliability and strict emission controls

The pre sales pack, which was written before the car was launched, said it had ecu upgrade and would come with 6 speed box, this was not the case, it also said it would come with 325mm grooved discs but plain 330mm were fitted instead

Full spec over and above the SRi( GSi wasnt available at the time):-
Speedline Mistral 7.5J*17 alloys ET49 5 spoke with full size spare
Steinmetz side skirts
AP LSD
AP lower final drive - 4.45:1
AP road/ race 4 pot brakes with Goodridge braided hoses
X30XE inlet cams
Koni road/ race suspension package, 35mm drop
Recaro front seats with Eurosport motif, matching trim to rear seats and door cards"

And before anyone says, yes MSD did make the final limited run, but Swindon did the origional engine development as they were hevily involved in the BTCC engine development at the time.

The inlet cam upgrade ment the engine produced 200ps (approx 197bhp) hence the reason it was called the ST200.

This year is the 10th anniv. and they are having a big do at Billing.

Making more sense now - I was seriously under the impression that you have to change all 4 cams, and indeed thats what I'm now in possesion of - Marks DTM - any comments here?

It just got technical and went over my head  :-?

[Kevin Wood]

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

Didn't Mark say further up the thread that in the early engines it was only the inlet cam that was different but later both were different?

Kevin

[ClarCE]

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

Didn't Mark say further up the thread that in the early engines it was only the inlet cam that was different but later both were different?

Kevin

Yeah I thought he did - but on C25XE so not X25XE - maybe they put the C25XE into some early Vectras - although I thought the Vectra was launched after the Omega - then I don't know really either  :-?

[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!