Cam for Thor (motronic) P38

dnb · Post by **dnb** » Tue Feb 16, 2016 11:07 am

I need to change the flex plate in my P38 and it seems easier to remove the engine than the gearbox given the equipment I have and the amount of leaks of just about everything the engine has. While it is out I thought it might be a good idea since it's done 110k miles to change the cam and associated parts.

Then the voices started speaking to me. What upgrades are there these days? I understand cam choice for Thor v8s historically has been limited and could be tricky. I found a cam kit claiming 22ftlbs over standard at v8 tuner but it was twice the price of a standard cam kit and I expect even a new std cam will feel like an upgrade...

Thanks

DaveEFI · Post by **DaveEFI** » Tue Feb 16, 2016 1:24 pm

I don't know the Range Rover, but you can change the cam on an SD1 without removing the engine. I'd guess it would be even easier on a larger vehicle.

I also don't know how well the engine management on your engine would adapt to the different fuelling etc needed with a different cam.

My guess is many of these claims for aftermarket cams - even if true - are based on optimised fuelling and ignition timing for that cam.

BMW spent a great deal on time and money updating the RV8 to its Thor guise specifically for 4x4 use. Be odd if a simple cam change improved things by much.

dnb · Post by **dnb** » Tue Feb 16, 2016 2:02 pm

I know the cam can be done with the engine in place. But the flex plate and rear crank oil seal requires either transmission or engine removal. And since the engine requires work and the transmission doesn't it is an easy decision.

As far as I can tell Mark Adams can reprogram the Motronic ecu now so advantage can be taken from an upgrade. The ecu should be adaptable to small changes based on the amount of sensor data it gathers. I expect the engine is at least 20bhp down on standard power with the old cam so it's as far out of spec the other way already...

DaveEFI · Post by **DaveEFI** » Tue Feb 16, 2016 3:25 pm

If it's done a fair few miles, chances are the cam is worn. What I'm not sure is if a different profile one will give you better results.

If it's leaking everywhere, are you sure it's not just down to excess crankcase pressure due to worn rings etc - or a blocked breather system? If that's the reason, changing seals won't much help.

I'm wary of assuming a different profile cam on its own will always give better results.

When the original on my SD1 needed changing, I got a Piper one said to be ideal for both auto and EFI. It wasn't. Changed to a new standard one which was.

ChrisJC · Post by **ChrisJC** » Tue Feb 16, 2016 6:30 pm

I changed to a different cam in my P38 Range Rover (Thor). I can't remember exactly which one, but it was supposed to be +23BHP as I recall. It seems to work perfectly fine!

I removed my engine (for a rebuild), but cocked up the rear crankshaft oil seal. I decided it would be easier to remove the transmission to fix this, which I did. Removing the transmission is much easier than removing the engine, provided you have a car lift and a transmission jack.

Removing the engine could politely be described as a fair bit of work:

Chris.

dnb · Post by **dnb** » Tue Feb 16, 2016 8:06 pm

There is method in the madness. I have no easy access to a lift or a transmission jack but do have a large engine hoist I used for my TVR. I am fairly happy with the breathers and rings so doubt there is too much wrong with the bottom end although I will obviously do a compression test first.

Thanks for the cam info. I am leaning towards keeping it standard at the moment else the costs wI'll escalate to silliness.