Camshaft choice

ChrisJC · Post by **ChrisJC** » Wed Nov 19, 2008 8:22 pm

I'm going to rebuild the 4.6 RV8 in my Landie, to freshen it up, and convert it to MegaJolt. It'll also get a pair of 2" SU's.and a spot of porting. Also I'm going to fit the 4.0 pistons to raise the CR a bit. It runs an auto transmission.

Whilst I'm at it, I fancy a new camshaft. At the moment it's got an RPi Torquemax, which pulls like a train, but I want more!

There seems to be plenty of choice, e.g.:
V8Dev Stealth
RPi Optimax or Piper 270 or Piper 285
RealSteel have various Viper ones.

Any recommendations? Is there anywhere that has a set of dyno graphs showing comparisons?

Chris.

Teesdale_landrover · Post by **Teesdale_landrover** » Wed Nov 19, 2008 8:35 pm

off topic but related, have you ever jetted the carbs to suit the engine. or got an afr readout?
please dont take it the wrong way but i laughed when i first saw a 4.6 on twin su's but anything can be modified to work well

ChrisJC · Post by **ChrisJC** » Wed Nov 19, 2008 9:53 pm

At the moment it runs on LPG only (with 1.75" SU's as throttle bodies). With these new 2" jobbies I'm going to take it to Wilshers rolling road to get them set up properly.

Chris.

bodger · Post by **bodger** » Wed Nov 19, 2008 10:07 pm

are you just using the butterfly part of the carb ?

got any pictures Chris ?

poo slinger · Post by **poo slinger** » Wed Nov 19, 2008 10:20 pm

if the camshaft you are taking out isnot 2 badly worn i will have it if it goes in a 3.9ok.

CastleMGBV8 · Post by **CastleMGBV8** » Thu Nov 20, 2008 12:16 am

Chris,

2" SU's can be lightly modified to flow enough for up to 280BHP Vizard details the mods in one of his books. although I suspect you would need to get the manifold runners opened up to suit the 4.6 engine.

Re the 4.0 pistons I think you will find they will up the compression to approx 11.8/1 which may be a little high, do check as I am only going from memory.

Just found some data 4.0 pistons have a bowl of 13cc.
4.6 pistons have a bowl of 22cc. and that confirms the 11.8/1 figure.

Kevin.

sidecar · Post by **sidecar** » Thu Nov 20, 2008 6:27 am

Back on topic!

I've got a piper 285 (stealth max) from RPI in my 4.6, it goes very well!

I run standard spec (from RPI) lifters and a piper vernier timing set.

Pete

ChrisJC · Post by **ChrisJC** » Thu Nov 20, 2008 8:27 am

Piper 285 - does that require piston cutouts?

Bodger - The carbs are complete, so theoretically it does run on petrol, but there's some issue that I've never bothered to fix.

Kevin - As it runs on LPG 99.99% of the time, the nice high compression should be OK. And for the occasion I do run it on petrol, hopefully I can use the Megajolt to make it tolerable.......

Pooslinger - Not sure if the Torquemax goes in a 3.9, but when I take it out next week I'll number the cam followers so they can be matched back to the cam. PM me an offer if you think it's going to be OK for you.

Any other opinions other than a Piper 285?

Chris.

poo slinger · Post by **poo slinger** » Thu Nov 20, 2008 8:51 am

i will try and find out if it will fit, how old is the cam, miles and what not

bones · Post by **bones** » Thu Nov 20, 2008 9:01 am

you could get hold of Paul at v8 tuner ,hes pretty wise on cams, i told him car and cam i had and described how it would pull away and he got it spot on,

rich

sidecar · Post by **sidecar** » Thu Nov 20, 2008 1:07 pm

ChrisJC wrote:Piper 285 - does that require piston cutouts?

Bodger - The carbs are complete, so theoretically it does run on petrol, but there's some issue that I've never bothered to fix.

Kevin - As it runs on LPG 99.99% of the time, the nice high compression should be OK. And for the occasion I do run it on petrol, hopefully I can use the Megajolt to make it tolerable.......

Pooslinger - Not sure if the Torquemax goes in a 3.9, but when I take it out next week I'll number the cam followers so they can be matched back to the cam. PM me an offer if you think it's going to be OK for you.

Any other opinions other than a Piper 285?

Chris.

My pistons are cut out but whether its required or not I don't know! RPI could tell you what's required.

Paul at V8 Tuner reckons that I could have gone for something a bit hotter as my car is a toy more than anything. (cob rep) Anyway it pulls top from 1500 rpm round to 6k and is "f-in" mental so I'm happy with it!(Loads of other stuff done to it to

).

Pete

landrovernuts · Post by **landrovernuts** » Mon Nov 24, 2008 11:38 am

Interesting to read this thread, I would have thought a piper 285 was a bit peaky for a landy, I would stick to something with a flatter torque curve. Having said that I have a Kent 218 in a 4.2 in a landy and this does not seem to suffer low down torque loss at low speed and am interested to hear any comments on what a Piper 285 is really like in a heavy car with the aerodyamics of a brick. From memory it does not need cut outs in the pistons.

For a short while I ran 2" SU carbs on my 4.2 and have to say apart from the lack of choke performed really well. My engine has a few other modifications however managed a respectful 247bhp with this carb set up. would have stayed with them if I hadn't got a hotwire set up.

Toby

CastleMGBV8 · Post by **CastleMGBV8** » Mon Nov 24, 2008 5:14 pm

landrovernuts wrote:Interesting to read this thread, I would have thought a piper 285 was a bit peaky for a landy, I would stick to something with a flatter torque curve. Having said that I have a Kent 218 in a 4.2 in a landy and this does not seem to suffer low down torque loss at low speed and am interested to hear any comments on what a Piper 285 is really like in a heavy car with the aerodyamics of a brick. From memory it does not need cut outs in the pistons.

For a short while I ran 2" SU carbs on my 4.2 and have to say apart from the lack of choke performed really well. My engine has a few other modifications however managed a respectful 247bhp with this carb set up. would have stayed with them if I hadn't got a hotwire set up.

Toby

Assumably that output was with modded heads if so what is the spec?

Kevin.

landrovernuts · Post by **landrovernuts** » Tue Nov 25, 2008 4:36 pm

V8 Devlopment stage 3 big valve heads, block machined to raise compression to 9.75 to 1, pistons machined with valve cut outs, bottom end balanced, Kent 218 camshaft and fitted with Janspesd manifolds and exhaust which has since been binned in favour of EFI ported manifolds (Much better). The engine was intially built by V8D with hotwire injection with bigger ram pipes, gas flowed and ported inlet manifold and 72 mm throttle, Dakar exhaust manifolds and down pipes - it produced even more power then!

Toby

CastleMGBV8 · Post by **CastleMGBV8** » Tue Nov 25, 2008 6:30 pm

This may proove of interest.

http://www.pistonheads.com/gassing/topi ... 20profiles

Stealth comes ot well as does the real steel typhoon which seems to be a copy of the Crower 50232.

All subject of course to being properly matched to heads, induction, exhaust and ignition systems.

Kevin