The V8 Owners Forum -

I am looking for advice on which way to go I have a tired P5B bottom end with SDI heads which i am lead to believe have been rebuilt an offenhouser 360 manifold and a tired Holley 390 cfm carb, the bottom end rumbles until oil pressure picks up 50 psi cold less than 5 psi hot needs a new water pump original distributor with petronix ignitor & flame thrower coil engine breaths a lot. Want more power dont know wether to rebuild and modify existing, sdi front cover camshaft etc or by an EFI engine

Just buy a 3.9. Will be hotwire injection which is supposed to be pretty good all round, much more power than a 3.5 and common out of range rovers. If you dont want the injection you could just stick your Holley and inlet manifold on the top which will probably make more power than the standard injection (if it is properly set up) and you already have it so wont cost you anything and no headaches!

You might be better with an Eddy 180 manifold than the Offy 360, unless you have tight under bonnet clearance.

TC

Thanks for response what sort of BHP can I expect from a 3.9/4.6 engine. Clearance is not an issue weight is as the engine is mounted behind rear wheels
Mark

V8 Rail wrote:Thanks for response what sort of BHP can I expect from a 3.9/4.6 engine. Clearance is not an issue weight is as the engine is mounted behind rear wheels
Mark

A standard 4.6 lump would make around 230 at a guess but would make a lot of torque. Torque is what pins you to the back of the seat when you floor it so that's good. A 3.5 can be made to produce 230 BHP but on the road they would be like chalk and cheese.

To get more BHP out of the bigger RV8 lumps the heads really need some work as they just don't flow well enough. My Stage III 4.6 makes 280 BHP and 300 ftlbs of torque.

What is the benefit of using a 180 edelbrock manifold against a 360 offenhauser.
Also how difficult is it to do away with the fuel injection and go back to a carb & manifold what wiring mods are involved I already have an electric fuel pump fitted

V8 Rail wrote:What is the benefit of using a 180 edelbrock manifold against a 360 offenhauser.
Also how difficult is it to do away with the fuel injection and go back to a carb & manifold what wiring mods are involved I already have an electric fuel pump fitted

Which manifold you use depends on what use that car is put to.

The eddy 180 has very good fuel distribution, the runners are all a similar length and the angles of them match the angles of the inlet tracks in the heads. This all gives good throttle response, good bottom end, mid range and reasonable top end. The rev range is not bad either.

A 360 manifold may ultimately produce more peak power but can suffer in areas where the eddy does well.

Alot of people consider the eddy 180 to be the best 'all rounder'

As to fitting a carb, well if your current setup uses a dizzy then fitting a carb would be easy in terms of the wiring. Your fuel pump would need to be changed for a low pressure one. I'm not sure that you could use your pump with a regulator as the pressure difference that you require is alot less. The pump may 'complain'

The eddy 180 is a medium rise whereas your 360 is a low riser, the runners are far shorter in the 360 and will not produce as much torque and low down power as the 180, 360's are generally for high revving high bhp motors, or where you dont have enough under-bonnet clearance for a high riser!

Thanks for your responses
Mark

And remember, if you do go 4.6 and carb/dizzy, you will need to change the cam as there is no drive on the 4.6