uprated v8 camshaft
- Thread starter shiner1
- Start date
its ok changing cam-real steel do a selection (Viper Hurricane)-even a standard one-however -now some will disagree---to get the most from the 3.5/3.9 you need ported heads and edelbrock inlet manifold and either edelbrock 4 barrel or holley 4 barrel carb
Have driven a few v8 p6's and to be honest s/u carbs are lacking---am not alone in the fact ask any knowledgeable person and they will agree
Have driven a few v8 p6's and to be honest s/u carbs are lacking---am not alone in the fact ask any knowledgeable person and they will agree
Hi Symes (and shiner 1)
The problem with changing a cam for a different profile is that you are trading one sort of power against another. You can have lots of top end power and no low rev grunt or all low rev grunt and no top end power. But you can't have both! If you don't agree with the compromise Rover have chosen then by all means try a different cam. But don't expect to get something for nothing - it will change the way your car behaves in a manner dependent on how radical a change you make. In particular, if you have an automatic, it could well make it undriveable - automatics rely on lots of low down power. You need advice from someone that knows what they are doing! Tell us how you want the car to behave and we can tell you which cam to use.
Incidentally, the 3.9 cam that most of us use to "uprate" our engines almost certainly reduces maximum power. But it gives oodles of low down power.
I agree wholeheartedly with symes that the achilles heel of tuning a Rover V8 is the inability of the heads to flow gas. There's only a very limited amount you can do about that without resorting to a complete new head casting such as the Merlin heads.
However I take grave exception to Syme's antipathy to the SU. The trouble is, very few people ever bother to find out what an SU can really do. They assume the factory setting is the only one. Go and find someone who understands the SU and start playing around with needles and piston springs. Then you'll not be so keen on splashing loads of wonga on a 4 barrel!
Chris
The problem with changing a cam for a different profile is that you are trading one sort of power against another. You can have lots of top end power and no low rev grunt or all low rev grunt and no top end power. But you can't have both! If you don't agree with the compromise Rover have chosen then by all means try a different cam. But don't expect to get something for nothing - it will change the way your car behaves in a manner dependent on how radical a change you make. In particular, if you have an automatic, it could well make it undriveable - automatics rely on lots of low down power. You need advice from someone that knows what they are doing! Tell us how you want the car to behave and we can tell you which cam to use.
Incidentally, the 3.9 cam that most of us use to "uprate" our engines almost certainly reduces maximum power. But it gives oodles of low down power.
I agree wholeheartedly with symes that the achilles heel of tuning a Rover V8 is the inability of the heads to flow gas. There's only a very limited amount you can do about that without resorting to a complete new head casting such as the Merlin heads.
However I take grave exception to Syme's antipathy to the SU. The trouble is, very few people ever bother to find out what an SU can really do. They assume the factory setting is the only one. Go and find someone who understands the SU and start playing around with needles and piston springs. Then you'll not be so keen on splashing loads of wonga on a 4 barrel!
Chris
unstable load
Well-Known Member
On the subject of 4 barrels, is there any advantage to fitting a 4 carb Boxer mainfold?
Or, even the 4 Weber swan neck at a pinch?
4 "barrels" but not the same thing.....
Or, even the 4 Weber swan neck at a pinch?
4 "barrels" but not the same thing.....
I always think that the key to tuning an engine is to start with the basics and work outwards. So get the combustion chamber shape right first, then move on to the valve throat area, then to the inlet and exhaust tracts etc. Carbs are pretty far down my list of must do's. Only if you've got all of the top items right does it become worth spending loads of wonga on carbs. Then there's really only one ultimate answer and that's individual throttle body injection direct into the inlet ports - ie 8 of them. Anything less than that is some degree of a compromise. But ANY attention is only worth the effort if you've got all the rest right first
The other approach to tuning is to analyse the inadequacies of what you have in front of you based on the approach above. Then look at you're ideal list and pick out items that give you quick low cost wins. For the V8 as installed in the P6, there are three extremely obvious ones. First is to sort out the air induction filtering - do as I did within the existing filter housing (Lucky Breathes Easy)or fit conical filters direct to the carb elbows. Second is the exhaust manifold, which to coin a phrase needs rodding out! I fitted a much larger manifold and system. And third is to get some bigger valves into the combustion chamber care of a set of SD1 or later heads. But try not to drop the compression ratio if you can help it!
There! Tuning on a budget in one easy paragraph! Whatever mods you decide on, you'll need to set up the resulting engine system on a rolling road, whether you have SU's, 4 barrels or injetion! Factory or carb manufacturers settings will no longer be suitable!
Chris
The other approach to tuning is to analyse the inadequacies of what you have in front of you based on the approach above. Then look at you're ideal list and pick out items that give you quick low cost wins. For the V8 as installed in the P6, there are three extremely obvious ones. First is to sort out the air induction filtering - do as I did within the existing filter housing (Lucky Breathes Easy)or fit conical filters direct to the carb elbows. Second is the exhaust manifold, which to coin a phrase needs rodding out! I fitted a much larger manifold and system. And third is to get some bigger valves into the combustion chamber care of a set of SD1 or later heads. But try not to drop the compression ratio if you can help it!
There! Tuning on a budget in one easy paragraph! Whatever mods you decide on, you'll need to set up the resulting engine system on a rolling road, whether you have SU's, 4 barrels or injetion! Factory or carb manufacturers settings will no longer be suitable!
Chris
colnerov
Well-Known Member
Hi, in some respects the choice of carb is down to your driving style and requirements. If you want
to 'plant' the throttle and get instant response then a fixed jet with an accelerator pump will suit.
If your style is to squeeze the throttle and use the torque then an SU is the one. SU's only supply
the petrol that the engine needs, a fixed jet squirts petrol down the throat to go off the line. So
economy Vs power is another consideration. One of the present trends in engine modding is to fit
'bike' carbs which are the same principle as SU's and Stromberg's. So you pays your money.. and all
that. Boxer manifolds are apparently a git to set up and the power gains/cost ratio is debatable.
Colin
to 'plant' the throttle and get instant response then a fixed jet with an accelerator pump will suit.
If your style is to squeeze the throttle and use the torque then an SU is the one. SU's only supply
the petrol that the engine needs, a fixed jet squirts petrol down the throat to go off the line. So
economy Vs power is another consideration. One of the present trends in engine modding is to fit
'bike' carbs which are the same principle as SU's and Stromberg's. So you pays your money.. and all
that. Boxer manifolds are apparently a git to set up and the power gains/cost ratio is debatable.
Colin
rockdemon said:
'They say' that the Hotwire EFI(14CUX)system fitted with a MegaQuirt ECU is perfect for fuelling the RV8s. One can play with the mapping to suit any modifications that have been made. I've been a bit slow in trying a MegaSquirt ECU on my hotwire EFI, as it took me an age to get the thing running correctly with the standard ECU. I think MegaSquirt would've saved me a lot of time, and had given me better results...hey ho :roll:
my so called problem with s/u carbs is the restrictive inlet manifold--the best for performance is a dual plane----and rover manifold is a compromise at best as originally that engine had a rochester 4 barrel--which was not available to UK-----speak to anyone who knows anything about p6 history will tell you--the prototypes had 4 barrel carbs-but nobody in uk understood them-----so as Rover were unable to break contract with s/u--thats what they used---
so yes i dont like su carbs due to restrictive inlet and honestly to believe you can gain any performance from them is laughable
have a 3500 sat in garage with ported heads roller rockers edelbrock inlet and holley 4 barrel along with viper hurricane cam and rhoads pump up lifters---bet that kicks a damn sight more power than if it had su and standard inlet- manifold
so yes i dont like su carbs due to restrictive inlet and honestly to believe you can gain any performance from them is laughable
have a 3500 sat in garage with ported heads roller rockers edelbrock inlet and holley 4 barrel along with viper hurricane cam and rhoads pump up lifters---bet that kicks a damn sight more power than if it had su and standard inlet- manifold
Absolutelu agree, Symes, about your engine giving a lot of poke. But the key phrase is ported heads. The manifold as per Rover is not one you'd choose, but it's well up to the job of even ported heads. I just can't see the point of spending loads of wonga on a set of different carbs and manifold, when the same wonga, in fact quite a lot less, would have bought an injection manifold and megasquirt which will leave your set up for dead in all respects - especially economy.
I don't pretend that the SU's will outperform injection, but they are a fair match for the 4 barrel option, and since you have to spend money to get to the latter, I'd rather spend it on something that is really going to improve performance. For instance a set of Merlin heads.
Chris
I don't pretend that the SU's will outperform injection, but they are a fair match for the 4 barrel option, and since you have to spend money to get to the latter, I'd rather spend it on something that is really going to improve performance. For instance a set of Merlin heads.
Chris
symes wrote,...
Hello Symes,
The Rover manifold is a dual plane design :wink:
I don't argue that there are better dual plane manifold designs that will liberate more power from the RV8, but what came standard on the P6B does quite an acceptable job. As far as torque delivery is concerned, the Rover manifold and the SU carburettors will certainly take some beating, and when all is said and done, torque is really the king.
Just one reference to SU carbs and performance. The Jaguar e-type ran SU carburettors on their 4.2 litre 6 cylinder engine. The car would run to 60mph in 7.00 seconds flat and reach a top speed of 152 mph. Not bad going in anyone's language you would have to agree.
Ron.
Hello Symes,
The Rover manifold is a dual plane design :wink:
I don't argue that there are better dual plane manifold designs that will liberate more power from the RV8, but what came standard on the P6B does quite an acceptable job. As far as torque delivery is concerned, the Rover manifold and the SU carburettors will certainly take some beating, and when all is said and done, torque is really the king.
Just one reference to SU carbs and performance. The Jaguar e-type ran SU carburettors on their 4.2 litre 6 cylinder engine. The car would run to 60mph in 7.00 seconds flat and reach a top speed of 152 mph. Not bad going in anyone's language you would have to agree.
Ron.
yes I know about jags-restored a few 20+years ago as a living--but am on about carb and manifold in relation to performanceSydneyRoverP6B said:
and 7 seconds is relatively slow-my rat p6 does it in 5.2 and also E type can do 152--if you tweek them
my daily car is an Omega 3.0 litre 24 valve v6 that has fuel injection and I fitted lpg----am thinking of injection and lpg on my 3.5 v8-as lpg is 69pence a litre compared to £1.33 per litre of petrol mmmmm
He must know a short cut :wink:
Ron.
Ron.
300ci and Nitrous-hidden bottle in boot---car is useless on corners but in a straight line----wow---am putting v8 in a ford consul-making a gasser--so now you know
I more into drag racing than classics-anyone seen my p6 rat will tell you----damn quick -its this one-in case you do not know
I more into drag racing than classics-anyone seen my p6 rat will tell you----damn quick -its this one-in case you do not know
unstable load
Well-Known Member
Lubbley jubbley!symes said:
