Rebuilding, tuning a thor rv8 discovery 2

[russ1]

Good evening people

I am rebuilding my discovery 2 v8. i use this quite a lot for off road and it has roll cages, winch bumpers etc etc so it is a fair bit heavier thank stock

So when i am rebuilding the engine i might as well do what i can to increase the power,

But am abit unsure whats best route to go, what cam, what to do with heads, is it worth changing away from the standard cast exhaust manifolds, larger throttle body etc

Any sort of help would be great to help find a package that works.

Thanks
Russ

[ChrisJC]

Your best bet is to just increase the capacity of the engine. The easiest option is to get the bottom end from a 4.6 from a P38. The engine management system will auto tune to manage the extra CC's. Provided it's the THOR system.
You are really after more torque than top end power, so going for more than 4.6 would help even further.

Chris.

[kiwicar]

If it were me I might consider a 4.2 rather than a 4.6 or even a 4.8 kit for a small journal crank, if I could find one. But bigger capacity. A basic stage 1 head conversion and a mild cam all would help with long tube headers, but basically more capacity! Is it an auto? I presume so, because you could add a torque converter with a higher stall which would help the off road performance, though not help your fuel economy!
Best regards
Mike

[russ1]

yeah it is a auto, thought about the 4.6 option as i have a p38 bottom end that has had a slipped liner, sure there is no reason why i cant pull the crank and rods and fit them to my block is this true?

been reading up on the 4.0 > 4.6 and theres alot of people saying to swap crank and rods but keep the 4.0 pistons to lift the CR is this worth doing?

cam wise, is the stumpuller still about the best cam for a land rover?

thanks for all your help.

Russ

[kevcon]

Been there done it

Bear with us as Ive just got in from work so if some of this doesnt make sense, dont be afraid to ask.

my spec so far
Disco 2 V8 Auto.
4.6 rods and crank, 4.0 pistons and Rpi Toque max cam. Left the head left standard for now. Running LPG

Really torque now from idle up to about 4000rpm then drops off.
0 to 60 down to around 8.5 to 9 seconds and pulls strongly all the way to the tone and then drops into top and then not much.
think this is to do with the cam but could be fuel. will find out at the weekend.

Was set on the stump puller cam myself, but RS insisted none of their cams where designed to run in the thor engine. So after a lot of phoning around and being told the same, had to settle for Rpi's torque max cam kit.
F@%*&^g pricey (£405) and think I should have gone for their next cam up.

Head work would definitely go for larger valve and opening the ports up as seams a bit breathless.
Inlet manifold is good for torque, but could do with being debired and larger throttle body can alsobe found at JE Engineering.

have found so far that the engine management cope happily and seams to adjust itself at 500 and then the 1000 miles mark.

sorry but have to go now as have to be up again for 6 and the flaming batteries going.
will be back on latter
kev

[Eliot]

larger throttle body etc

Probably not a concern until the engine is breathing much more than it is now.

JE Engineering commented on my manifold page:
"the throttle body has a 68 mm throttle as standard and again, we often take this out, in this case to 71.5 mm. The Thor manifold, when used with either a standard cam or a mildly tuned cam, gives a strong torque peak at around 2,000 rpm, much higher than that achievable with the Lucas plenum design, but even with careful gas-flow work the power is limited. We find it difficult to achieve more than around 280 bhp with this manifold, where a similar amount of effort on a Lucas Plenum manifold will yield 320 bhp (but with less torque below 3,500 rpm'

[ChrisJC]

yeah it is a auto, thought about the 4.6 option as i have a p38 bottom end that has had a slipped liner, sure there is no reason why i cant pull the crank and rods and fit them to my block is this true?

been reading up on the 4.0 > 4.6 and theres alot of people saying to swap crank and rods but keep the 4.0 pistons to lift the CR is this worth doing?

cam wise, is the stumpuller still about the best cam for a land rover?

thanks for all your help.

Russ

I used the TorqueMax cam, and it was pretty good I thought. Since then I've switched to the 270, which isn't as good at the bottom end, but keeps going for longer.

It's worth using the 4.0 pistons on the 4.6 crank + rods if you run LPG. Not sure if it's worth it if you run on petrol.

Chris.

[russ1]

Thanks very much for all your advice. Looks like it may be a call to Rpi for on of there cams then.

With regards to lifters are the anti bleed ones worth the extra or do people just stay with standard.

Kev, are you still using stock 4.0 MAF etc or did you go for the larger 4.6?

Thanks.

[CastleMGBV8]

Russ,

Rather than spend another fortune with RPI for another cam (you can buy cheaper elsewhere) I would be inclined to speak to Peter Burgess re a pair of heads to match your engine spec and requirements.

If you are prepared to sacrifice a little torque at low RPM then you could retard your existing cam by approx 4 degrees with an offset woodruf key from Real Steel which will move the power band higher in the rev range, and with a decent pair of heads will produce a much free'er reving engine with a decent hike in power.

If you want more breathing at the higher rev range then swap the Thor manifold for a Gems one but as mentioned this will reduce bottom end power slightly.

Kevin.

Kevin.

[ChrisJC]

I would say in a heavy Disco, BHP is irrelevant. You want torque, and you want it from idle. This means the right cam, small ports & valves, and CUBES!

Chris.

[russ1]

Am not to fussed about top end power it's more low end am after

I have the 4.6 crank and rods and the 4.0 pistons sorted and just need to put a order in this week for cam lifters etc etc

Are the bleed down lifters worth the money?

Just hope I get the time next weekend to build the engine.

Thanks for all your advice
Russ

[kiwicar]

Hi
blead down lifters are intended to tame a failey long duration high overlap cam, I don't think they are what you want for a discovery. You want a high lift, short duration low overlap cam to maximise low down torque, whilst blead down lifters will reduce overlap, they do it by reducing lift and thereby reduce the duration further, this could cut low down torque by reducing Volumetric efficiency before they "pump up" you would be better off just choosing the right cam in the first place.
Best regards
Mike