Rover V8 performance

[GGRR 4555]

Hey Guys,

I picked up a 99 discover 1 that has had a 4.6 swapped in after the original 4.0 died. I checked the numbers on the block and it is indeed a 4.6.

The rig was very slow when I bought it. Since then I put 33" tires on it and over geared the hell out of it to try and pick up some performance. It now has 4.43 GBR gears and it slightly better to drive than the old 31's and stock gears.

Anyway, how slow is this thing supposed to be? It barely holds highway speeds and downshifting yields almost no noticeable acceleration on slight grades. The rover has a new fuel pump, fuel filter, air filter, and oil. It doesn't smoke, passes smog, doesn't drag the brakes or have any obvious flaws.

I just don't know if it is supposed to drive like this or if it is way down on power. Any thoughts?

 

[A4L7E3X]

A 4.6 should go pretty well, it wont be like a modern LS but it should be better than you are describing. I have a 3.9 turning 32"s through an auto and 3.54 gears and its no rocket but I can tow a trailer full of firewood up a hill at 100 Km/h... well, most hills.

Start with the basics, i'm guessing that you have checked compression, made sure the plugs and leads are OK, checked fuel pressure, etc etc. Normal basic tune up stuff?

The distributor on Rover V8s is notoriously lazy, you have to run like 10 to 12 degrees of initial advance to get any reasonable performance. Make sure that the mechanical advance is working too, its pretty easy to break the nylon clip inside the dizzy when you pull the rotor button off, and then you can jam up the mechanical advance. Vacuum advance diaphragms go bad too, but this will affect economy more than performance.
A lot of people rave about aftermarket dizzys (ICE, Scorcher, D.U.I etc.) on rover V8s because the factory advance curve is so lazy. You can alter it with different springs and weights if you are feeling adventurous. Upgrading to Bosch ignition components is also fairly common and simple, but this is considered more of a reliability mod than a performance mod.

Getting a bit deeper into the engine the Rover V8s like to eat camshafts. You would be amazed just how well they will start and run with a totally worn out cam, but the performance will obviously suffer. A new cam and a set of lifters can be had for pretty cheap though.

Cam timing can also be an issue, from either a worn chain or just cheap shitty components that don't line up where they should. The factory procedure when installing the cam is just a "line up the dots" deal, but people have reported very wide swings in the actual position. Adjustable cam timing gears are available.

Hope that helps.

 

[GGRR 4555]

A 4.6 should go pretty well, it wont be like a modern LS but it should be better than you are describing. I have a 3.9 turning 32"s through an auto and 3.54 gears and its no rocket but I can tow a trailer full of firewood up a hill at 100 Km/h... well, most hills
Start with the basics, i'm guessing that you have checked compression, made sure the plugs and leads are OK, checked fuel pressure, etc etc. Normal basic tune up stuff?

The distributor on Rover V8s is notoriously lazy, you have to run like 10 to 12 degrees of initial advance to get any reasonable performance. Make sure that the mechanical advance is working too, its pretty easy to break the nylon clip inside the dizzy when you pull the rotor button off, and then you can jam up the mechanical advance. Vacuum advance diaphragms go bad too, but this will affect economy more than performance.
A lot of people rave about aftermarket dizzys (ICE, Scorcher, D.U.I etc.) on rover V8s because the factory advance curve is so lazy. You can alter it with different springs and weights if you are feeling adventurous. Upgrading to Bosch ignition components is also fairly common and simple, but this is considered more of a reliability mod than a performance mod.

Getting a bit deeper into the engine the Rover V8s like to eat camshafts. You would be amazed just how well they will start and run with a totally worn out cam, but the performance will obviously suffer. A new cam and a set of lifters can be had for pretty cheap though.

Cam timing can also be an issue, from either a worn chain or just cheap shitty components that don't line up where they should. The factory procedure when installing the cam is just a "line up the dots" deal, but people have reported very wide swings in the actual position. Adjustable cam timing gears are available.

Hope that helps.

Thank you for the intel! Should I just put a timing light on it and run through the rpm to see if the timing curve is correct? What should I be looking for?

 

[Dougal]

If everything is factory fresh it's about 220hp through a 4sp slushbox. 15 years later a lot of those horses will have escaped and you've got a lot more rolling resistance than stock. Cam wear also reduces valve lift.

High flowing heads and high compression pistons will help it hugely if you're going that far.

 

[A4L7E3X]

Thank you for the intel! Should I just put a timing light on it and run through the rpm to see if the timing curve is correct? What should I be looking for?

For a basic check up on the timing:
Pull the vacuum advance hose off and check timing at idle - with a stock Rover distributor id probably start at 10 degrees BTDC, this sounds like a lot when the factory spec is 0 Degrees (atleast on some emissions engines) but they don't give much mechanical advance so the total timing is still pretty reasonable. My 3.9 is at 12 degrees BTDC static timing and never pings, and I run it on regular unleaded.

You can check the mechanical advance with the timing light by slowly sweeping the rpm and watching the timing light. The front pulley will only have marks up to maybe 12 degrees, so unless you have a dial back timing light it will be a little bit of guestimation, but basically it should start to advance around 1200 rpm and gradually but consistently keep advancing to around 3500 - 4000 RPM. Total advance will depend on the distributor, but I think most Rover stockers only give you like 15 degrees of mechanical advance. FYI the 3500 - 4000 RPM total advance is the "problem" with stock distributors, most performance distributors will bring in the total timing by 2500 - 3000, and give closer to 20 degrees of mechanical advance.

Finally you can check the vacuum advance is working. Basically just apply some vacuum to the hose and watch if it advances up. You can do this with a mighty-vac, by plugging the hose into manifold vacuum, or just by sucking on the end of it if you don't mind the taste of greasy rubber... full vacuum (around 20 inches) should give you about 10 to 15 degrees of advance.

If at any point you notice the timing is bouncing around there is a problem, its not uncommon for the gap between the reluctor wheel and the magnetic pick up to be too wide causing erratic timing. I think the spec is a 0.10mm gap?? But I would double check this before adjusting it.