V8 Engine Build for a P38

[Henry-b]

Ay up gents!

probably been done to death

The old P38 has a worn out old 4.6 - infrequent oil changes from its previous owners, and a life of towing have taken their toll on the motor, and it is quite slow, it seems to fall on its face above 2800rpm

No misfires or lumpiness it just doesn't pull like it should..


What kind of build would be ideal for an heavy old 4x4 which will be towing a fair bit?

Stock HP is 218hp and 300 lb-ft according to the original specs

Is it possible to get 400 lb'ft out of a 4.6?



H

[ChrisJC]

The 4.6 in my P38 is in good order. I rebuilt it 80,000 miles ago and the only change I made was a mild cam update to take it from 225BHP to 248BHP.

I have to say that seems pretty adequate to me - given how shocking the handling is.

Chris.

[DaveEFI]

Sounds typical of a worn out cam - that tends to suffer first with poor servicing. To get a big increase in torque, you either need a larger engine or forced induction.

[Henry-b]

Well I narrowed my apparent lack of power down to a defective MAF

she picks up quite well now...

Apparently stock the motor has 218hp and 300 lb'ft

Mark Adams offer's a chip to improve performance, i'm guessing they're strangled for emissions reasons the the map "opens them up" anyone had the map?

And finally is camshaft wear guaranteed for the RV8 at around 130k she has had LPG since 2003 however the Oil changes weren't that frequent, however being that LPG doesn't have the impurities that petrol does, would that make any difference to internal wear/conditions?

H

[unstable load]

And finally is camshaft wear guaranteed for the RV8 at around 130k she has had LPG since 2003 however the Oil changes weren't that frequent, however being that LPG doesn't have the impurities that petrol does, would that make any difference to internal wear/conditions?

H

Cam wear is almost always the number 1 thing to look for, assuming the engine has been neglected with oil changes, but if it has been flogged hard AND neglected, then you will be in for the rest of the engine, too.

[DaveEFI]

Well I narrowed my apparent lack of power down to a defective MAF

she picks up quite well now...

Apparently stock the motor has 218hp and 300 lb'ft

Mark Adams offer's a chip to improve performance, i'm guessing they're strangled for emissions reasons the the map "opens them up" anyone had the map?

And finally is camshaft wear guaranteed for the RV8 at around 130k she has had LPG since 2003 however the Oil changes weren't that frequent, however being that LPG doesn't have the impurities that petrol does, would that make any difference to internal wear/conditions?

H

By those figures it is a late P38 with the Thor engine? BMW spent quite a bit of time optimising the RV8 for 4x4 use. The power is reduced over previous versions, but torque improved, due to the longer inlet tract. Before chipping it, I'd make sure it is good health - perhaps check the power output etc on a decent rolling road?

[ChrisJC]

I would think that all the map can do is to richen the mixture up through the mid range as it is highly optimised for economy and emissions rather than outright power.

There is no way that a remap can get any more air into the engine, so all it can do is adjust the mixture a little.

I fitted a different cam to mine (+25BHP) with no other changes, and no remap, and it works fine.

As an side, I also built a 4.6 with ported heads, very high lift cam, high compression pistons, but it is too far outside 'spec' for the Thor system so it does not idle properly at all, and throws a fault code. So I would shy away from going too mad with Thor.

Chris.