45mm inlet and Plenum base inc 72 mm throttle pot.

[Classic Chim]

I have a standard 4.6 bottom end running 38 mm trumpets and inlet etc
Mbe ignition and fuelling
Around
285/295 Bhp
340/345 ft lb torque

Is it worth me replacing the inlet tracts with an enlarged Plenum butterfly to 72 mm 45 mm Bell mouth trumpets and inlet bored to the same then marched to my inlet ports at tother end.
What’s the likely outcome.

Im replacing the lot as a bolt on off system including a new fuel rail so I can keep my original 38 mm set up intact.
It will be re mapped
Anything else I should consider other than porting heads.

Will it be faster at higher revs ?
Will I loose some road manners or bottom end torque ?

Thoughts please chaps.

[trev4]

I think you will need to add big valve heads to make the most of those upgrades. Mat Smith is doing this to a 4.6 at the moment and adding a emerald system, the results on that would give you a good idea.

[carsy]

Alun, i think gains will be minimal certainly not particularly noticeable on the standard heads.

Now if you were having the heads ported etc then i would say yes.

[Classic Chim]

Sure would Trev.

I’ve been told the late 4.6 Rover engines heads had big but not the biggest valves fitted as standard as well as porting being better from the factory but I wouldn’t know if this is true.
By the year 2000 Tvr did very little to the 4.6 engines other than cam change so the heads might need some work to get the best out of the 45 mm base.

[Classic Chim]

Thanks Ian, I’m getting the feeling I’ll be having the heads done : scratchchin:

[SILICONEKID 345HP 12.03]

Classic Chim said:

Thanks Ian, I’m getting the feeling I’ll be having the heads done : scratchchin:

Is it worth it ? My car is probably half a second faster down the strip and probably the same on the road , more importantly its how your car drives and reliability.

My Dad says if its running well leave it alone .

If yoy decide its a keeoer super charge it in the future .

400hp and no need to spebd a fortune on heads and induction .

[Sardonicus]

SILICONEKID 345HP 12.03 said:

Classic Chim said:

Thanks Ian, I’m getting the feeling I’ll be having the heads done : scratchchin:

Is it worth it ? My car is probably half a second faster down the strip and probably the same on the road , more importantly its how your car drives and reliability.

My Dad says if its running well leave it alone .

If yoy decide its a keeoer super charge it in the future .

400hp and no need to spebd a fortune on heads and induction .

Daz has a point Alun your happy with your car

[Matthew Poxon]

My advice would be leave it alone it is working well and spend the money on fuel and trackdays instead.

Yes you might be able to make it a little faster but you do risk undoing all your hard work. Unless you are fancying a little tinker with it.

[macdeb]

Good advice, though I'd save and spend £500 on an oil burning runabout, saves you using the TVR as a daily and you could come over and practice 2-3 times a week!!!

[Classic Chim]

macdeb said:

Good advice, though I'd save and spend £500 on an oil burning runabout, saves you using the TVR as a daily and you could come over and practice 2-3 times a week!!!

Now that’s not such a bad idea,,, the practicing that is

All very good advice.
As I do adore the car you might well be correct in saying leave it well alone.
So with that in mind I’m getting old P38 parts together and then getting some machining done to them rather than disturb my standard set up.
This way I can bolt on off a complete system so reversible and the cost isn’t inhibitive.
Matthew you are correct, I just fancy a play as much as anything.

I’ve got some old junk parts sourced and a Tvr mate is getting them cleaned for me,,,
Watch this space.
They might just sit on my shelf for a year yet.
It’s hardly like the cars slow.
I’m looking for 320 Bhp with 350/60 ft lb torque and have been told that’s entirely possible.

[davelittlewood]

All ears.....

[jojackson4]

Yes don’t do it you know it will pull the scab of the wound that’s nearly healed


Hahahahaha
Get it all together over the year and swap it over next winter

[QBee]

Suggest we get that track day together, all driving each other's cars, as soon as possible.

Try before you buy.....

[jojackson4]

QBee said:

Suggest we get that track day together, all driving each other's cars, as soon as possible.

Try before you buy.....

There’s no way captain R is going around a track in mine

[Classic Chim]

jojackson4 said:

Yes don’t do it you know it will pull the scab of the wound that’s nearly healed


Hahahahaha
Get it all together over the year and swap it over next winter

I like that one.
Yep that’s sort of the plan

[Classic Chim]

davelittlewood said:

All ears.....

Was told with my Ecu it should retain good manners and defo get more power and torque.
I’ve driven a few 5.0 cars and been beat by a load more to know that torque and extra Bhp does show itself especially the Bhp over 4000 revs, I calculated on a fag packet 2/10ths every gear from 2nd onwards over a 1/4 mile, over a full mile it’s a long long way I’d be behind.
I’d like to get the car to a happy medium where me being a driving god I can make up the difference

I’m going to do it in stages, basically a full 45 mm with alloy Bell mouth trumpets, set up with 72 mm butterfly and all matched to my existing headports.

See what it brings.
The heads as we know are the restriction from there on in.
Or I leave it all until next winter and pull the heads,,,, better start saving if that’s the choice!
I want to stay n/a and have something that still looks standard sort of thing.

Big brakes/ great road tyres, the car is now ready for just a bit more power to complete my rocket ship Tvr.

I’ve proved it can eat up the miles and I set out to do that.
It’s everything I asked it to be.

So why change it,,,,,,,, cos we can

And I’m thinking I’ve got to make it my weekend car rather then my truck!
Making it faster suits that aim.

[Classic Chim]

carsy said:

Alun, i think gains will be minimal certainly not particularly noticeable on the standard heads.

Now if you were having the heads ported etc then i would say yes.

I keep reading this and can’t help but think without porting I’m wasting my time, it should all be done in one go.

Yeah sod it, you only live once
Based on what I have and dyno graph information big beads and induction will get me the power I’m missing when up against the 5.0 boys which is very clear and obvious, just runs out of puff over 5000 revs let alone a bit of grunt.

I like my bling in engine bays if done well, part of this is simply to create a polished top end ( if I can do it ) so it looks the part.

Edited by Classic Chim on Monday 29th January 23:20

[Dominic TVRetto]

Classic Chim said:

I’ve been told the late 4.6 Rover engines heads had big but not the biggest valves fitted as standard as well as porting being better from the factory but I wouldn’t know if this is true.

I have heard people say this before, but do not know where this information comes from.

The (in my mind) definitive post on engine specs is Robs post on engine differences - please note the 3rd paragraph describing the two 4.6l derivatives: the standard and the "HC" (which has the 500 valves and enlarged valve throats).

I had these HC heads, and upgraded to the inlet manifold to 44mm with metal bellmouths, plus 71mm butterfly.

With parts, fitting and remapping it cost me around £1000, and netted me 10BHP & torque. No noticeable extra rev range. A classic case of the rather expensive £100/bhp.

I believe the heads were holding back any further gains, so think that you would see less gain than this with your heads.

Conversely, when I upgraded the heads to fully-worked items - everything upstream of the heads was perfectly set-up to maximise the gains, as there were now no bottlenecks, and the engines' power, delivery and character changed substantially.

In short - if you have any restrictions in the system (which in your case is likely to be your heads), you are unlikely to see much meaningful gain, as the whole system has to be upgraded for the extra flow to be realised. All or nothing.

HTH,


Dom

[QBee]

^^^^^^^^^^ This.

I did the 72mm upgrade and loads of others, but was still 30-40 bhp short of the Dazmobile.
My heads were stage 3, so smaller valves, and nothing else I did made a blind bit of difference while that restriction was in the system. It finally dawned on me that until I upgraded my heads at vast expense I couldn’t gain 20-30 bhp, which I would barely notice.

Downgraded from 5 litre to 4.6, added boggo standard Range Rover heads and cam, stuck a hairdryer in the Y piece and added 80 bhp. And frankly it feels quicker, but not ridiculously quicker.

[phazed]

I agree with all the above.

My old 4.6 with a bog standard range Rover engine, typhoon camshaft and 72 mm plenum made 275bhp

Add stage 4 heads, ported manifold, 45mm trumpets, (basically), threw away the cats and it made 320+ the HP.