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rover 4.6 - realistic power outputs?
Posted: Fri Mar 14, 2008 6:07 pm
by Seight-V8
hiya all,
this has proberly been done to death.....could couldnt find anything throught the search.
so what are the realistic power outputs for the 4.6 engine.
Just debating changing my tuned 3.5 efi for the 4.6 lump.
But how much gets more horsepower...without going over the top.
There's plenty of figures about but are they true?
If i do decide i dont want to go overboard....just get a reasonable amount of power the the best ££££ value.
thanks for any replies.
scott
Posted: Fri Mar 14, 2008 7:51 pm
by RoverP6B
Everything is relative. It all depends on the application, the transmission type, type and mass of vehicle, etc.
But having said that, a standard 4.6 running the factory camshaft, heads etc has capacity on its side when compared to a 3.5, and there lies the advantage.
Torque, and lots of it!!
Basically, torque gives the car acceleration, hill climbing ability, overtaking ability.
I speak from experience. My 4.6 would run rings around my original 3.5, all due to having substantially more torque, delivered off idle all through the rev range.
Rover engines, especially the big ones, 4.2 litre and above are known for rather poor peak power figures due to the design of the standard heads, but in their favour this very same design favours torque delivery, and lots of it.
As an example of torque vs power from different cars,
during the mid 1990s, the cars doing battle in the Australian Touring car championship were made up largely of Turbo charged Ford Cosworth Sierras, BMWs, and a couple of Holden Commodore 5.0 litre V8s. One team running the latter was the Holden Racing Team, owned at the time by Tom Walkinshaw (TWR). All through the championship on tight power circuits, the Turbo cars had the wood on the 5.0 litre V8s.
Then at the end of the championship, there is Bathurst. A long 1000km race, long straights and plenty of up hill slog. A circuit where torque is king. Here the 5.0 litre V8s come into their own, and at the end of the day, Win Percy and Alan Grice in a TWR commodore cross the finish line first.
Give me torque any day!
Ron.
Posted: Fri Mar 14, 2008 8:01 pm
by sidecar
I've just built a 4.6 lump. Its running V8 Development stage III heads, Edlelbrock performer manifold matched to the heads, 500 carb, Piper 285 cam, CR at 9.95:1,
The preload has been carefully setup using adjustable pushrods
and the ignition is via a DML835 with a modified advance curve.
I would hope to get 285-300 BHP out of it but thats a bit of a guess!
Like other have said its not just peak power that is important, its torque at lower revs that pushes you into the seat when you floor it, the 4.6 has got to score over the 3.5 in that respect.
By the way I used my a lot of 3.5 bits on the 4.6 but there was a fair amount of machining envolved!
Pete
Posted: Sat Mar 15, 2008 9:40 pm
by mgbv8
Sidecar!
My old low comp pre SD1 V8 (factory MGBV8 engine) put out 130bhp at the fly.
I had it balanced and stuck a Typhoon cam + pump down lifters in and lowered the CR with comp head gaskets. Had it fully balanced and stuck on a Weber 500 and she put out 187 at the fly. Stuck a 50 shot of Nos on and she made 257 at the fly.
I'm now running a 4.6 @ 9odd:1 CR with the same type of cam and lifter setup and it goes like stink. I'm expecting at least 250 off gas and 400 with the nitrous on the dyno.