The V8 Owners Forum -

Decided on settling for a Rover V8 powered Dax Rush.

Seems there's a few 3.5 or 3.9 engine cars about, which engine is best in terms of getting the most power from it? Or should I hold out and wait for something with greater capacity?

I know next to nothing about these engines but from what I've seen so far the power output is pretty poor unless they've been tuned. I don't mind spending to get the desired power. Ideally I'd like to keep the engine carburetted, but is fuel injection far better for power? What else is involved in getting the power, just how much does it cost? What parts are required for each specific level of tune and what figures are the result?

Many thanks

I think for headline BHP, carbs can be tuned to match injection figures. However, injection engines will work properly across all throttle / load combinations, and all temperatures etc. etc. I have come to the conclusion that there is no real need for carbs anymore (with the likes of MegaSquirt) unless one has a particular preference for them.

For power, you need cubes. Personally I would go for a 4.6, get it relinered (top-hat liners), and enjoy the thicker crankshaft and better oil pump. You are then pretty much forced into mapped ignition and then you might as well have fuel injection too!

300BHP is realistic without going beserk.

Chris.

Firstly decide what you want to do with the car

Secondly decide how much you want to spend

Do the two equate?

Power costs money, sure it is fun but if you are driving to car shows do you need a 600hp fire breathing monster in a 1200kg car? Would you be.happy trying to keep that in check on a damp drive home?

So I have a GT40 replica at about 1100 kg and I have.a John Eales tuned 3.9 in it and it gives 256hp at 6700. The car goes like poop off a shovel.but try to drive slowly through town and it is not happy below about 1900 rpm.

I had it at a GT40 guru and when I turned up to collect it he had a grin on his face he could not shake off and said he had to apologise about knocking my engine as it was the best pulling car he had driven for ahes. He reckoned it would out accelerate most of the Ford 5l carb fed cars he sees, but he did mention that the ford units were so much smoother low down.

He could not believe that my car only got 256hp as the standard sort of Ford unit is about 350hp, but then mine is fuel injected (Hotwire) as opposed to Holley carb so power delivery up the ref range is more usable?????

Now
Ford engine is about £5000 and my JOhn Eales monster has receipts for about £10000. You can do the maths.

Aaaaannnnnnnnddddd if you go for a Chevvy engine they are even cheaper


So I ask the question again
What do you want to do with a the car?


How much do you want to spend?
Ian

Are you using it for racing only? If not, the headline power output is far less important than how that power is derived throughout the rev range, ie torque curve.
If peak power really is important, look for a different engine that starts out closer to your needs. A much cheaper solution than tuning what is basically an ancient design.

Ian Anderson wrote:Firstly decide what you want to do with the car

Secondly decide how much you want to spend

Do the two equate?

Power costs money, sure it is fun but if you are driving to car shows do you need a 600hp fire breathing monster in a 1200kg car? Would you be.happy trying to keep that in check on a damp drive home?

So I have a GT40 replica at about 1100 kg and I have.a John Eales tuned 3.9 in it and it gives 256hp at 6700. The car goes like poop off a shovel.but try to drive slowly through town and it is not happy below about 1900 rpm.

I had it at a GT40 guru and when I turned up to collect it he had a grin on his face he could not shake off and said he had to apologise about knocking my engine as it was the best pulling car he had driven for ahes. He reckoned it would out accelerate most of the Ford 5l carb fed cars he sees, but he did mention that the ford units were so much smoother low down.

He could not believe that my car only got 256hp as the standard sort of Ford unit is about 350hp, but then mine is fuel injected (Hotwire) as opposed to Holley carb so power delivery up the ref range is more usable?????

Now
Ford engine is about £5000 and my JOhn Eales monster has receipts for about £10000. You can do the maths.

Aaaaannnnnnnnddddd if you go for a Chevvy engine they are even cheaper


So I ask the question again
What do you want to do with a the car?


How much do you want to spend?
Ian

If you go chevy you get 430bhp and a warranty for £5220 though probably a tad more torque than you absolutely need http://shop.partsworldperformance.com/l ... e-19258770
Best regards
Mike

ChrisJC wrote:I think for headline BHP, carbs can be tuned to match injection figures. However, injection engines will work properly across all throttle / load combinations, and all temperatures etc. etc. I have come to the conclusion that there is no real need for carbs anymore (with the likes of MegaSquirt) unless one has a particular preference for them.

For power, you need cubes. Personally I would go for a 4.6, get it relinered (top-hat liners), and enjoy the thicker crankshaft and better oil pump. You are then pretty much forced into mapped ignition and then you might as well have fuel injection too!

300BHP is realistic without going beserk.

Chris.

I like the carb engines simply for the look of them, intake manifold, sound and the lovely chrome air cleaner, though as you say injection more efficent at the job.

So the 4.6 is the stronger engine out of all of the Rover V8's ? Seems most of the pre built Rush's are equipped with 3.5's or 3.9's are these not strong engines and tuning is limited? Forged internals are necessary are much earlier levels of tune? Thanks

kiwicar wrote:

Ian Anderson wrote:Firstly decide what you want to do with the car

Secondly decide how much you want to spend

Do the two equate?

Power costs money, sure it is fun but if you are driving to car shows do you need a 600hp fire breathing monster in a 1200kg car? Would you be.happy trying to keep that in check on a damp drive home?

So I have a GT40 replica at about 1100 kg and I have.a John Eales tuned 3.9 in it and it gives 256hp at 6700. The car goes like poop off a shovel.but try to drive slowly through town and it is not happy below about 1900 rpm.

I had it at a GT40 guru and when I turned up to collect it he had a grin on his face he could not shake off and said he had to apologise about knocking my engine as it was the best pulling car he had driven for ahes. He reckoned it would out accelerate most of the Ford 5l carb fed cars he sees, but he did mention that the ford units were so much smoother low down.

He could not believe that my car only got 256hp as the standard sort of Ford unit is about 350hp, but then mine is fuel injected (Hotwire) as opposed to Holley carb so power delivery up the ref range is more usable?????

Now
Ford engine is about £5000 and my JOhn Eales monster has receipts for about £10000. You can do the maths.

Aaaaannnnnnnnddddd if you go for a Chevvy engine they are even cheaper


So I ask the question again
What do you want to do with a the car?


How much do you want to spend?
Ian

If you go chevy you get 430bhp and a warranty for £5220 though probably a tad more torque than you absolutely need http://shop.partsworldperformance.com/l ... e-19258770
Best regards
Mike

Indeed, it'll certainly have to grunt I'm looking for, and more than needed really. I'm just trying to weigh up options, sadly pockets aren't as deep as I'd like

Interested to know what sort of money is needed to tune the Rover V8 and what I'll get. Most of the pre built Rush's in the classifieds harbour a 3.5 or 3.9

Ian Anderson wrote:Firstly decide what you want to do with the car

Secondly decide how much you want to spend

Do the two equate?

Power costs money, sure it is fun but if you are driving to car shows do you need a 600hp fire breathing monster in a 1200kg car? Would you be.happy trying to keep that in check on a damp drive home?

So I have a GT40 replica at about 1100 kg and I have.a John Eales tuned 3.9 in it and it gives 256hp at 6700. The car goes like poop off a shovel.but try to drive slowly through town and it is not happy below about 1900 rpm.

I had it at a GT40 guru and when I turned up to collect it he had a grin on his face he could not shake off and said he had to apologise about knocking my engine as it was the best pulling car he had driven for ahes. He reckoned it would out accelerate most of the Ford 5l carb fed cars he sees, but he did mention that the ford units were so much smoother low down.

He could not believe that my car only got 256hp as the standard sort of Ford unit is about 350hp, but then mine is fuel injected (Hotwire) as opposed to Holley carb so power delivery up the ref range is more usable?????

Now
Ford engine is about £5000 and my JOhn Eales monster has receipts for about £10000. You can do the maths.

Aaaaannnnnnnnddddd if you go for a Chevvy engine they are even cheaper


So I ask the question again
What do you want to do with a the car?


How much do you want to spend?
Ian

Thanks for the info there Ian

The Rush will be used for fast road, mostly straight line acceleration. I do like the idea of the Chevrolet small block very much but I wondered how much it is to tune the Rover V8 and what I'll get for my money. 10K sounds quite a lot for 256 bhp??

Wet weather doesn't worry me too much, it won't see a great deal of it.

The 3.9 cross-bolted is said to be a good one?
I run an old 3.5 that has the gear oil pump on a stalk, which is part of the timing cover. These are getting rare and worn ones have trouble priming, so it might be worth avoiding this engine. I made mine dry sump to get around this and other problems.
So the later serpentine belt engines with the pump around the crank shaft are going to be better. If you go 4.6 and fit replacement top-hat liners it's maybe as good as it gets?

The Seer wrote:

ChrisJC wrote:I think for headline BHP, carbs can be tuned to match injection figures. However, injection engines will work properly across all throttle / load combinations, and all temperatures etc. etc. I have come to the conclusion that there is no real need for carbs anymore (with the likes of MegaSquirt) unless one has a particular preference for them.

For power, you need cubes. Personally I would go for a 4.6, get it relinered (top-hat liners), and enjoy the thicker crankshaft and better oil pump. You are then pretty much forced into mapped ignition and then you might as well have fuel injection too!

300BHP is realistic without going beserk.

Chris.

I like the carb engines simply for the look of them, intake manifold, sound and the lovely chrome air cleaner, though as you say injection more efficent at the job.

So the 4.6 is the stronger engine out of all of the Rover V8's ? Seems most of the pre built Rush's are equipped with 3.5's or 3.9's are these not strong engines and tuning is limited? Forged internals are necessary are much earlier levels of tune? Thanks

Never seen a standard Rover engine with a chrome air cleaner.

All of the standard Rover units are extremely strong. Of course if you start modifying it so it will rev higher than designed, it can break. Same as any engine.

So as the decades rolled by, Rover continuously beefed the V8 up. Roughly in order:
Improved registration of main bearing caps
Improved registration of main bearing caps again, thickened webs across 'V'
Went to 3.9 by boring it out.
Made crankshaft journals larger, fitted cross bolts to main bearing caps, reduced number of head bolts (which improves head sealing!!), went to crank driven oil pump. Called the 3.9 4 litres!, and introduced 4.6l. Fully mapped ignition and fuelling.

Their only cockup was the boring out made the block too thin, so any engine greater than 3.5l is prone to cracking the block behind the liner. The fix is top-hat liners.

The Range Rover P38 engines are the last, so have all the fixes. The only non factory fix is the top-hat liner repair, which will cost you between £1K and £1.5K depending on supplier.

The 4.6 Range Rover engine is 225BHP stock, easily tuneable to 250BHP with a modest cam upgrade. There is also spades of torque, so it will definitely feel blindingly fast, none of this revving a 2.0l up to 6K just to pull away.

Chris.

The 4.6 can be made to push out 300 BHP but all aspects of the engine have to be right, the heads will need gas flowing and bigger valves fitted, you need a decent inlet system, a decent cam, a decent exhaust and a decent ignition system. Other area's of expense would include a good gearbox too. It is not cheap when you add up the total cost but the overall package is good and light. I think that weight is something that you need to consider in a 7 type clone, a heavy lump could make the car a bit of a pig!

If 300 BHP is not enough (it wasn't for me) then a 100 BHP NOS system certainly can put a smile on your face!

Hi Seer, do you know how much power you're after? The Dax Rush is a pretty light car so the power to weight is gonna be pretty damn good whatever engine option you go for.

You don't need to spend anywhere near £10k for a 250-260 bhp 3.9
Mine is in this range and only cost just over a grand. The spec is;

3.9 interim block
Crower 50233 cam
Isky Hi-Rev lifters
TVR standard valve ported heads w/dual valve springs
Ported Inlet Manifold
Carbon Inlet Trumpets
71mm Plenum
Megasquirt 2 for Fuel & Sparks


As has been said above, think about what sort of power delivery you want. I've had quite a few RV8 TVRs and the 5ltr unit for instance has diesel like power delivery with a huge shot of torque off idle and not a great deal past 5000 rpm. This would be utter crap to drive in a ~600kg Dax as you wouldn't be able to use much throttle without lighting up the tyres in every gear. A 3.9 or 4.2 with nice progressive power delivery upto 6000 or 6500 rpm would be much more suitable.

ChrisJC wrote:So as the decades rolled by, Rover continuously beefed the V8 up. Roughly in order:
Improved registration of main bearing caps
Improved registration of main bearing caps again, thickened webs across 'V'
Went to 3.9 by boring it out.
Made crankshaft journals larger, fitted cross bolts to main bearing caps, reduced number of head bolts (which improves head sealing!!), went to crank driven oil pump. Called the 3.9 4 litres!, and introduced 4.6l. Fully mapped ignition and fuelling.

Their only cockup was the boring out made the block too thin, so any engine greater than 3.5l is prone to cracking the block behind the liner. The fix is top-hat liners.

The Range Rover P38 engines are the last, so have all the fixes. The only non factory fix is the top-hat liner repair, which will cost you between £1K and £1.5K depending on supplier.

The 4.6 Range Rover engine is 225BHP stock, easily tuneable to 250BHP with a modest cam upgrade. There is also spades of torque, so it will definitely feel blindingly fast, none of this revving a 2.0l up to 6K just to pull away.

Chris.

Hmm. Obviously if you enlarge a well designed engine you'll have to strengthen it. But you're sort of suggesting it was beefed up because it in some way needed it?
IMHO, many of the changes were made for Range Rover applications - and aren't necessarily a good thing for car applications. The 'Thor' being a prime example. As the RR got heavier, more torque was necessary. However, in a light sports car it can be a PITA.

Although a matter of opinion I contend that the RV8 was not well designed, particularly in its earlier guises. You could break the crankshaft by revving a cold engine, and main bearing caps used to fall off (although you wouldn't necessarily notice).
Project 'Iceberg' (the Diesel project with Perkins) failed because the block wasn't stiff enough. They cast iron components within the block to try to stiffen it.
All the tin head gasket engines leak. Fortunately it doesn't mean water loss, but it does mean combustion products in the oil, and a necessity to change the oil frequently. The switch to 10-bolt heads and composite gaskets finally fixed that.
I believe that Rover only made changes because they had to as the warranty situation demanded it.

You are right however that Range Rovers do stress the engine more, and expose its weaknesses more readily. This is why I think that one of the latest engines is the best because if it is good enough for a Range Rover, it will be bullet proof in a kitcar!

Chris.