Rolling Road booked for tomorrow, 97 4Ltr 74 thousand miles
Discussion
rolling road booked for tomorrow, 4Ltr, 1997, 74 thousand miles and original cam!
well i have had the car for a while now still feels like its running ok think i have just got very used to the power. only engine mod's been changing the air induction to a act one with a K&N filter.
Keen to find out how much power it's lost! probably confirm it's time to look at a new cam.
be interested to know what people think a reasonable figure will be? will post up the results when i get them...
some of this is because i keep thinking about supercharging it
well i have had the car for a while now still feels like its running ok think i have just got very used to the power. only engine mod's been changing the air induction to a act one with a K&N filter.
Keen to find out how much power it's lost! probably confirm it's time to look at a new cam.
be interested to know what people think a reasonable figure will be? will post up the results when i get them...
some of this is because i keep thinking about supercharging it
My '99 450 with 74k miles will be getting a trip to the dyno once a year now to monitor the onset of cam wear.
About 3 years ago it produced 276 bhp and the torque peaked at just over 4000 rpm; a month or two ago the bhp had dropped slightly to 264 and the torque peaked just before 4000 rpm. Still a fairly good figure, but the shift of peak torque suggests the cam shaft has started to tire - and presumably the wear will accelerate.
For the sake of £40, I think it's a good way of ensuring that I get the cam changed at the right time: no earlier than necessary.
About 3 years ago it produced 276 bhp and the torque peaked at just over 4000 rpm; a month or two ago the bhp had dropped slightly to 264 and the torque peaked just before 4000 rpm. Still a fairly good figure, but the shift of peak torque suggests the cam shaft has started to tire - and presumably the wear will accelerate.
For the sake of £40, I think it's a good way of ensuring that I get the cam changed at the right time: no earlier than necessary.
Give or take a few ponies due to rolling road and day-to-day variances, I'd expect the following (all corrected back to flywheel):
< 200 bhp Problem
210-215 bhp Average, OK condition and set up
> 225 bhp Exceptionally strong engine, but still well within the realm of possibility for a 4.0
< 200 bhp Problem
210-215 bhp Average, OK condition and set up
> 225 bhp Exceptionally strong engine, but still well within the realm of possibility for a 4.0
Just to give the OP a further point of reference, my 30,000 mile 4.0HC only made an embarrassing 188.3hp at the flywheel when I first bought it 
A full service, a new Stealth cam, an ACT induction kit, an ACT De-Cat Y Piece, pre-cats out & and a set of 250cc Vectra injectors soon had me seeing a healthy jump to 232hp.
The original 30,000 mile TVR 435 (HC/5.0 litre spec) cam we removed actually wasn't as bad as some I've seen, but it did have two visibly worn lobes and others following suit.
At the time I'd also gone down the Mark Adams Tornado chip rout which did give more linear well controlled AFR but very little in the way of any power improvements if any at all.
Add in a well mapped Canems engine management system with wasted spark and she immediately jumped to 250hp, and on LPG too!
What it needs now is a set of decent heads, which I estimate would easily take it to the cloud-cuckoo-land 275hp figure that TVR claimed the 4.0HC made.
But once you've thrown £1000 - £1500 on a set of well ported heads with bigger valves only to make another 25hp or so, it becomes very tempting just to forget fitting better heads altogether in favor of a supercharger that should deliver a far more noticeable 80hp gain.
But that's a £4.5k project in itself so as many have found before me, extracting decent power from the old Rover V8 is not a cheap exercise!
The saving grace is that the current 250hp I'm seeing from my 4.0 litre with standard heads is considered very respectable and because a Chimaera is so light the car still picks up her petticoats & gets along the road very nicely thank you.
The fact it does so at the cost equivalent of 40+mpg on LPG is a nice little bonus too
A full service, a new Stealth cam, an ACT induction kit, an ACT De-Cat Y Piece, pre-cats out & and a set of 250cc Vectra injectors soon had me seeing a healthy jump to 232hp.
The original 30,000 mile TVR 435 (HC/5.0 litre spec) cam we removed actually wasn't as bad as some I've seen, but it did have two visibly worn lobes and others following suit.
At the time I'd also gone down the Mark Adams Tornado chip rout which did give more linear well controlled AFR but very little in the way of any power improvements if any at all.
Add in a well mapped Canems engine management system with wasted spark and she immediately jumped to 250hp, and on LPG too!
What it needs now is a set of decent heads, which I estimate would easily take it to the cloud-cuckoo-land 275hp figure that TVR claimed the 4.0HC made.
But once you've thrown £1000 - £1500 on a set of well ported heads with bigger valves only to make another 25hp or so, it becomes very tempting just to forget fitting better heads altogether in favor of a supercharger that should deliver a far more noticeable 80hp gain.
But that's a £4.5k project in itself so as many have found before me, extracting decent power from the old Rover V8 is not a cheap exercise!
The saving grace is that the current 250hp I'm seeing from my 4.0 litre with standard heads is considered very respectable and because a Chimaera is so light the car still picks up her petticoats & gets along the road very nicely thank you.
The fact it does so at the cost equivalent of 40+mpg on LPG is a nice little bonus too
well successful day i think, max at the engine was 221.9 bhp @ 5,803rpm.
so quite pleased with that, if some one with knowledge of reading the graphs see's anything important of note please let me know.
is the consensus that there hasn't been to much cam ware and that it's not worth replacing yet? i think when i get some time i will take some measurements of the cam ware with a test dial indicator just to make sure and to check for even wear.
only problem now is because it's not down on power, im going to have to look at how to get more.
so quite pleased with that, if some one with knowledge of reading the graphs see's anything important of note please let me know.
is the consensus that there hasn't been to much cam ware and that it's not worth replacing yet? i think when i get some time i will take some measurements of the cam ware with a test dial indicator just to make sure and to check for even wear.
only problem now is because it's not down on power, im going to have to look at how to get more.
There are some good 400s out there. My last one had 240 bhp and 260 or 270 lb and pulled very nicely!
http://www.pistonheads.com/gassing/topic.asp?h=0&a...
http://www.pistonheads.com/gassing/topic.asp?h=0&a...
Good result. Your peak torque is above 4000 rpm, which is where it should be.
Do it again at the same place in a year's time. If the result then is similar, then do it again at the same place in two or three years' time.
I'm firmly of the belief that a dyno run should be a regular thing; whether that's every year or every couple of years depends on the recent trend you've seen. It's the change that's important rather than a single result, IMHO.
For me, it's going to be every year now that the signs of cam wear are evident.
Do it again at the same place in a year's time. If the result then is similar, then do it again at the same place in two or three years' time.
I'm firmly of the belief that a dyno run should be a regular thing; whether that's every year or every couple of years depends on the recent trend you've seen. It's the change that's important rather than a single result, IMHO.
For me, it's going to be every year now that the signs of cam wear are evident.
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