The V8 Owners Forum -

Bet these fetch a good price.....
http://cgi.ebay.co.uk/Rover-v8-ultimate ... dZViewItem

were those heads not owned by somebody on here??? I have seen them before

jesus those valves are massive!

Says they cost over £3500. I wonder what eLSe i could buy with £3500

lol yeah. But still, those heads, 4.6 engine, twin turbos, that could be a beast of a Rover! No valve train on those heads tho. Prob a good job I'm skint

ian.stewart wrote:were those heads not owned by somebody on here??? I have seen them before

They look very similar to the pics posted by Rob from V8 Dev on the old forum. I seem to remember him saying DV had a hand in the developement of those too. Whether they are the same pair or not I don't know but there can't be too many of these out there! I think those heads are only suited to large (5ltr+) rovers really, and to make the kind of power he's talking about valvefloat will have to be overcome.

excuse my ignorance, but what's valve float?

and how can it be prevented (I take it valve float is not a good thing)

Valve float is caused by a combination of engine speed and valve spring resonance, where the springs harmonic frequency mimics the engine speed and does not effectively return the valve to its seat, basically it floats off the seat, there is more to it than valve spring resonance, with valve train weight in the equation too, But this is the reason you have double or triple Valve springs wound at different helixis, shape of wire and strengths to dampen oscillation,

Thats Rob at v8dev's ebay id, those are indeed the heads he had done, I have some pics of them somewhere and posted them on the old forum. The've had the faces machined at an angle to get better port angles (see the head bolt 'oles) and uber valves plus the inlet ports have been welded up so they could be ported upwards.

Bit special they are!

I reckon £850. . . . . .

. . . but no good on a 3.9, even with twin turbos . . ?

Maybe maybe not. The first restriction you're gonna have the old turbo's you're using isn't it?

Not with my low-boost Janspeed set up, I was thinking along the lines of mid-boost (15psi) like Stevieturbo used to run using two T3 turbos.

4.6 + two T3s running ~15psi + Stage III heads = circa 500bhp

Wonder what (if any) the difference would be with the Vizard heads?

Well if Rob's suggestion they still have good airflow at low engien speed then I'm guessing they won't create any more lag than with small ports.

The bigger ports may decrease airspeed and as a consequence the turbo's may take longer to spool, or I'm completely wrong!!

Pro help needed with this one I reckon!!!!

Might be worth buying them for mantlepiece value at least as they're very special.

Well if I did have the money they wouldn't go on my bloody mantle piece that's for sure!

Hi Gav
the main problem with low air speed in a port is low airspeed through the the carb, this is not enough to draw fuel into the airstream and so causes poor air fuel mixture until the flow gets up the charge is "patchy" with some of it lean and some rich (the carb is unable to react to pulsing in the flow and is set up for average flow). The reverse is the case with fuel injection, at low port velocity the mixture is rich (can even start dropping out of suspension in the airflow), and leans out at high velocity. As you have far more accurate mixture control with FI you can better tune this out as you can set a better and more constant compromise, go sequencial injection and you can set the timing of when the injection starts and pretty well tune it out altogether.
Mike