another head question

[sax player]

i have a twin plenum 3.5 in the stag breathing through a larger afm Flapper type. fast road cam. and standard 3.5 vitesse heads developing a confirmed 220 can i get 250 from stage 2 or 3 heads? who is the best people to go to? or should i go larger engine and aim for 300[/img]

[CastleMGBV8]

That sounds like a nicely set up engine, the vitesse spec heads have all the basic stage one mods and on a 3.5 you will loose bottom end drivability by going futher on the heads, so if the car is for road use only I would leave it as it is.

Kevin.

[kiwicar]

As you have 220 on that spec I would leave well alone, it must be working well together with eveything matching, change one thing ant it will probably make less power. To get to 250 on a 3.5 on the road you are looking at a cam change (probably solid), well matched heads to cam manifold matched to heads, good headers and all the fine details sorted (or your called Ian Stewart).
Mike

[sax player]

Thank you for the input.however i still dont understand why giving a better air flow into the chambers can havean adverse efect.
shaum

[RoverP6B]

If you enlarge the ports on the head to improve the gas flow, then it is my understanding that this will only have a noticable effect at higher engine speeds, say 4000 plus.

For driving around the streets, how often are you revving beyind 4000 rpm?

Below that sort of level, with a larger cross sectional port area, the same volume of gas now occupying a larger area travels slower, so you lose the level of torque down low, shifting it further up the rev range, so you need to use more throttle for the same road speed. Drivability and throttle reponse are now less than ideal, but at higher speeds, you will be flying.

It is all about compromise.

Kevin and Mike know infinitely more about high power Rover V8s than most, so I would certainly consider their advise carefully.

Ron.

[CastleMGBV8]

If your car is for road use then I would definitely leave it as it is, the trade off of having a liitle more power at the top end will end up as a net loss in drivability, the whole point of old fashioned V8's is torque and that's what pushes you down the road.

If you talk to engine tuners they will naturally try and sell you their products, but the end result will probably dissapoint.

If you really want more power then I would suggest you look for a 3.9 half engine to rebuild they are quite cheap now and can be had for a £100.00 +

Also you say fast rtoad cam, do you know what it is?

kevin.

[sax player]

Ok thanks once again but i want more power. So is it feesable to stroke the engine and fit new heads? will the standard sump take the extra throw?
The cam and followers, came from an australian Co if i remember right . Have not had time to look for the paper work
For interest here is the car at leman comes in at 30 sec, worth turning the vol up, really pissed off the etype when i passed him.
Appreciate your comments on the power topic and have a lot more questions
Shaun
http://uk.youtube.com/watch?v=NoDEeRmDu2M

[CastleMGBV8]

Not really cost effective to stroke a small bore 3.5 engine.

It really depends a lot on what you are prepared to spend.

On a small budget you could build a 3.9 and upgrade the heads with a set of big valves and possibly a hotter cam which a bigger engine can handle, that will give you more BHP and torque, to go further would cost quite a bit more. You can buy new build and modified rover engines from £3500 - £10,000 and more, all depends on what you want and are prepared to spend.

Don't know the weight of a Stag but presume it's not that light. you should bear that in mind when selecting a different cam

Kevin.