4.2L Rover V8 tuning

Charlie_b · Post by **Charlie_b** » Thu Oct 15, 2009 6:47 pm

I'm planning on embarking on a bit of project to try and get a bit more power out of the rover V8 I currently have. At the moment I haven't touched it and is running as standard. Its a 4.2L Rover V8 from a range rover classic.

I'm running it with fuel injection which I'm planning to keep although I'll probably change the ECU/intake for something a little more racey.

Anyway, before I go and spend any money I want to know if its really worth it, as for a few thousand pounds a newer more modern engine could be purchased from a breakers such as a jag V8 or ford lincoln V8 etc.

Anyway, my first thoughts are remap/ecu upgrade such as an emerald system and a bit of work to the air intake. I don't really have much of an issue with this as I've had a bit of experience from previous projects. I may go for throttle bodies, bike throttle bodies or a twin plenum if I can find one.

What I'm not up to speed on is rover V8 internals. In fact, I'm bascially a complete newbie to the rover v8. Here's my thoughts:

First off, the compression ratio of the 4.2 is very low at 8.35:1 (I think - I'm sure you will know more than me) and so I'm thinking of increasing that to somewhere around 10:1. However, I've not seen any pistons with such a high ratio - has anyone any experience with this?

Next would be ARP bolts although I don't think these are too difficult to get hold of, I'm sure I've seen them on the RPi and real steal websites.
A complete new set of bearings, I have no idea what I would go for here.

Cams and timing gear - Ideally I don't want to go too far with this as I'm using the car for weekends/trackdays and really aggressive cams just become a bit of a pain on normal road driving. I was thinking along the lines of 285 degree overlap - again, any advice here?

Those are my thoughts and estimate that would set me back in the region of £700. Do you think its worth it and do you have any other advice?

(I'm likely to do it anyway as I just enjoy fiddling with engines!)

landrovernuts · Post by **landrovernuts** » Thu Oct 15, 2009 7:24 pm

Just for your interest I am more than happy with my 4.2, but often thought about going down the 4.6 route, however when I thought about the money, I am sticking with my 4.2.

The spec of my engine is:-
72 mm throttle body
45 mm trumpets
ported inlet and matched to heads
heads are V8D stage 3 big valve heads
cam kent 218
block decked by V8D to raise compression to 9.75
pistons pocketed
rotating assembly balanced
ARP studs
fuel injection set up by Mark Adams on the rolling road at Power Engineering and was 282bhp at the flywheel at 5100 RPM(1998) obviously alot less at the wheels of a landy, and probably alot less now with current miles.
Exhaust is standard EFI manifolds ported and flowed into standard EFI manifolds, but at the time of rolling road time was JE Dakar manifolds, downpipes and Y going to standard back end.
As for reliability, no problems todate and current mileage well past 200K.

The 4.2 according to some has some issues with the cranks breaking etc, but I take as I find and with some money spent produces very good power. I am sure with Emerald etc more is possible. I did see a race 4.2 engine with emerald for sale a while ago boasting 330 bhp. You pay your money you get your power, however there are cheaper engines out there that produce that power out the box, but then you already have a 4.2!

Toby

Charlie_b · Post by **Charlie_b** » Thu Oct 15, 2009 7:44 pm

I see you went down the route of machining the block to increase the compression ratio - Where did you get that done?

my other thought is that you had to have modded pistons anyway so what what were the advantages over just getting higher compression pocketed pistons (or is this more of an availability thing?)

282bhp? That would be fantastic!

landrovernuts · Post by **landrovernuts** » Thu Oct 15, 2009 8:00 pm

Hello

V8 Developments did all the machine work. (Not sure if they did it or they had it done) As for the pistons, I understand pistons for the 4.2 are very limited and yes standard 4.2's are low compression (8.25 to 1 I belive) how ever my engine was built using composite gaskets which reduce compression even more and this was all completed at V8 D recommendations. I must point out this was 1998, so there may be other better ways now.
There is another post about 4.2 pistons that suggests using 3.9 pistons machined down, that may be easier and cheaper.

Toby

CastleMGBV8 · Post by **CastleMGBV8** » Thu Oct 15, 2009 11:04 pm

Hey 4.2 engines are getting like buses, you dont see one for ages and then they all come along at once.

Standard 4.2 comp ratio 8.94/1.

Depending how far the pistons are down the bore machining the decks could yield 9.5 to possibly 10/1

Toby,

Thats a very healthy output from your 4.2 I was only expecting 260 from my 4.35 engine in a similar state of tune, albeit with an edlbrock 500 and Performer manifold, but that combo is good to flow enough for 280+BHP

For a decent increase in power then heads are the place to start and depending on the heads spec then a cam that can take advantage of the increased flow potential. Improvements to the induction system will then offer more gains.

Kevin.

landrovernuts · Post by **landrovernuts** » Fri Oct 16, 2009 6:00 am

Hello

Yes, that was a healthy power output that did supprise me, as I was only expecting about 250 to 260 at the most. When it was on the rollers before Mark Adams performed the on engine, it was only 220 bhp, just shows the value of having the injection set up correctly. I do remember at the time that this was not cheap! Also at the time the ignition system was played with and cannot recommend Magnecour leads highly enough!

Yes the pistons are 8.84 to 1 and not 8.25 as I said before, however Ray at V8D said I was running 9.75 to 1 now, however compressions are uniformly low (142 to 150 psi) compared to a friends healthy 3.9 (another engine I built) which is between 180 and 190 psi.

I have transferred the engine from the original vehicle and fitted a weber 500 and edlebrock manifold, which I found a total disaster. When a friend eventually got all the electrics sorted in the new vehicle, we replaced the injection and could not belive the difference.

Toby

landrovernuts · Post by **landrovernuts** » Fri Oct 16, 2009 6:32 am

Sorry, that was not meant to be a dig at weber/edlebrock 500 carbs, as I think the issue was that I could not get it set up right and found the engine drank alot more fuel. I found the setting up to be a comprimise all the time, despite having the needle and spring kit. The out of the box settings as recommended by RIP were shocking and the hot starting despite having a fuel return and an insulating spacer was terrible! I even made/modified some needles that were shipped from the States as they were not included in the kit.

I see on the forum many people use them to good effect, so fear it was my application and the way my carb was set up. At the time my my engine sruggled to pull 5th (It is high geared), but now with the EFI back on pulls 5th easy and from 1000 rpm.

Toby

sidecar · Post by **sidecar** » Fri Oct 16, 2009 9:08 am

landrovernuts wrote:Sorry, that was not meant to be a dig at weber/edlebrock 500 carbs, as I think the issue was that I could not get it set up right and found the engine drank alot more fuel. I found the setting up to be a comprimise all the time, despite having the needle and spring kit. The out of the box settings as recommended by RIP were shocking and the hot starting despite having a fuel return and an insulating spacer was terrible! I even made/modified some needles that were shipped from the States as they were not included in the kit.

I see on the forum many people use them to good effect, so fear it was my application and the way my carb was set up. At the time my my engine sruggled to pull 5th (It is high geared), but now with the EFI back on pulls 5th easy and from 1000 rpm.

Toby

I agree with you that the webber 500 is no good out of the box for 90% of engines and I don't think that RPI's setup is very good either!

Really the only decent way to set the carb up is with a lambda probe and about one days road testing and fiddling about. I think that doing it this way could be better than a rolling road session as it's more "real world" plus setting up the cruise etc I suspect is not that easy on a set of rollers that can not hold a steady load. (Rollers tend to be inertia jobbies).

Cobratone won't like this but I'm actually quite pleased with my engine, it is a 4.6 with a carb and yet is only 15-18 odd BHP less than Tony's 4.8 which has MASSIVE throttle bodies! (I think my cam is more hairy than this and there are other differences so it not a great comparison)

Looking at the size of his throttle bodies I reckon that 2 or 3 of them combined would out flow my whole carb!

My lump made 282 BHP on the rollers but the WOT was quite rich at around 11:1, I've now leaned it off to around 12.5:1 so I think my motor should be putting out 285 BHP. It also pulls top gear from around 1200-1400 RPM which ain't bad for a carb. (The car is light though being a Cobra replica).

Pete

CastleMGBV8 · Post by **CastleMGBV8** » Fri Oct 16, 2009 1:34 pm

Pete,

I was wondering where you had been, I can second that an edelbrock 500 carb can be made to work very well.

With my recalibration with your able assistance the engine performs perfectly and I now have reservations regarding fitting the EFi system that I have, only that it may take some time to get it to actually run better than it does at the moment.

I'm not saying EFI isn't better, because the tunablity has got to be more flexible and to have the ignition fully mapped would also be an advantage.

I just seem to have got lucky with the carb calibration and the distributor recurve at the first attempt.

PS the mod for the performer manifold has solved the stat not opening problem, but the engine is still getting a little hot in traffic so will need to look at airflow efficiency through the rad, or possibly a bigger/better rad may be required.

Kevin.

sidecar · Post by **sidecar** » Fri Oct 16, 2009 2:05 pm

CastleMGBV8 wrote:Pete,

I was wondering where you had been, I can second that an edelbrock 500 carb can be made to work very well.

With my recalibration with your able assistance the engine performs perfectly and I now have reservations regarding fitting the EFi system that I have, only that it may take some time to get it to actually run better than it does at the moment.

I'm not saying EFI isn't better, because the tunablity has got to be more flexible and to have the ignition fully mapped would also be an advantage.

I just seem to have got lucky with the carb calibration and the distributor recurve at the first attempt.

PS the mod for the performer manifold has solved the stat not opening problem, but the engine is still getting a little hot in traffic so will need to look at airflow efficiency through the rad, or possibly a bigger/better rad may be required.

Kevin.

Hi Kev,

I've been "lurking" about!

What ya mean "luck".....your carb and dizzy works because of the thousands of hours I've spent experimenting with mine and then posting up the results!

By the way, I've now drilled the counter weights for the air control flappy valve in order to lighten them. It made a fair bit of difference to the low and mid range "grunt" but I did have to fiddle about with the accelerator pump a bit along with the size of the hole in the weights. I did the mod because I noticed that a 600 carb made more low down torque than the 500 carb when the car was on the rollers, I think that the larger primaries of the 600 were allowing the engine to breath better at low RPM. When the 500 was re-fitted the primaries were a bit too small but there was not enough airflow to move the flappy air valve even though the secondary butterflies were open. The 600 had other issues that I could not resolve, the engine would nearly stall if I braked hard, I checked the float heights and even turned my 500 into a 600 by swapping the boosters, in the end I gave up with the 600.

I was telling MantaV8 about the drilling mod when he then showed me a document on the web written by Federal Mogal where drilling of the weights is mentioned!!!!

I think that the mod could work for your engine, being a 4.35, but I think that anyone with a 3.5 would need to go carefully with the hole size.

Anyway with regards to your temp, what stat have you got fitted? I run a 74 degree stat. My lump runs at 75-80, it goes to 82 in traffic at which point the fan kicks in. (Yep I've read the whole chapter in Des's book on cracked blocks....82 max will do me just fine!)

I only run a sierra 2.3 diesel rad fitted up side down (don't ask!), the system uses a header tank rather than an expansion tank. My rad fan is a 14" pacet set to suck, it is quite powerful, it could probably suck the car along at 5 mph! (Pulls about 12 amps)

Regards,

Pete

CastleMGBV8 · Post by **CastleMGBV8** » Fri Oct 16, 2009 7:35 pm

Pete,

You just shrunk my engine! it a 4.35 (94.89mm x 77mm.) the stat is 78 deg. the standard MGBV8 is 82 deg.

I'm going to try setting the fan cut in temp a little lower and look at making a duct to seal off the bottom of the rad to prevent hot air being recirculated which could be whats causing the problem in traffic.

If that does not cure it may have look for a larger or more efficient Rad, seen some Aluminium rads on e-bay which are unbelieably cheap, they start from around £85.00 and do look very nice, anyone bought one?

Kevin.

sidecar · Post by **sidecar** » Fri Oct 16, 2009 8:10 pm

CastleMGBV8 wrote:Pete,

You just shrunk my engine! it a 4.35 (94.89mm x 77mm.) the stat is 78 deg. the standard MGBV8 is 82 deg.

I'm going to try setting the fan cut in temp a little lower and look at making a duct to seal off the bottom of the rad to prevent hot air being recirculated which could be whats causing the problem in traffic.

If that does not cure it may have look for a larger or more efficient Rad, seen some Aluminium rads on e-bay which are unbelieably cheap, they start from around £85.00 and do look very nice, anyone bought one?

Kevin.

Hi Kev,

I can see how you mis-understood me, I've re-written the sentence in question.

I know your engine is a 4.35 which I think is big enough to benefit from the flappy valve mod. The reference to 3.5 lumps was in case anyone else was thinking about doing the same mod.

I'd still try a lower temp stat if I was you, they only cost a few quid, I think V8 tuner sells them.

Cheers,

Pete

Cobratone · Post by **Cobratone** » Sat Oct 17, 2009 1:14 am

sidecar wrote:Cobratone won't like this but I'm actually quite pleased with my engine, it is a 4.6 with a carb and yet is only 15-18 odd BHP less than Tony's 4.8 which has MASSIVE throttle bodies! (I think my cam is more hairy than this and there are other differences so it not a great comparison)

your cam is a LOT hairier than mine Pete, but that doesn't detract from all the good work you've done with your engine, it's a credit to you

sidecar · Post by **sidecar** » Sat Oct 17, 2009 7:29 am

Cobratone wrote:
sidecar wrote:Cobratone won't like this but I'm actually quite pleased with my engine, it is a 4.6 with a carb and yet is only 15-18 odd BHP less than Tony's 4.8 which has MASSIVE throttle bodies! (I think my cam is more hairy than this and there are other differences so it not a great comparison)

your cam is a LOT hairier than mine Pete, but that doesn't detract from all the good work you've done with your engine, it's a credit to you

Cheers mate!

That's why I think that there is still a load of power to be got out of your engine. Having said that I can understand why you are starting again, eg. 350 BHP is really right at the top end of what an RV8 can deliver (well a "normal" one costing "normal" money). Yet 350 BHP is just a middle of the road figure for a stroked SBC.

Its still a shame that you are defecting over to the darkside!

Pete

Cobratone · Post by **Cobratone** » Sat Oct 17, 2009 10:02 am

Thinking of selling the cobra with the original albeit enlarged and flowed efi system and keeping the jenvey throttle bodies for the chevy engine

Decisions, decisions