45mm inlet and Plenum base inc 72 mm throttle pot.
Discussion
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.
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.
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.
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.
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 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.
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. Now if you were having the heads ported etc then i would say yes.
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
Sounds like replacing the heavy seats will give me more power (:
Ok forget that then, what bits can I chop off the car
as that’s actually a better way to go.
It’s not just about the ultimate numbers produced but the character and where the power is and I too believe 320Bhp and around 355/360torques is more than enough for a road car.
Trackdays for me are restricted by my power, I know what power it’s got and I also know just a little bit more would be great around our tight short circuits and make it a better experience.
It’s about the only time I’ll be using the gains as it’s more than fast enough for a road car already and I rarely thrash it for the sake of it.
Is it worth doing the heads for a trackday once in a blue moon, not really but on the track day I’ll say it is if I could get that 320, not easy by the sounds of it.
Food for thought.
At no point will I use FI even though that’s the logical way to get big power as I’m not looking for big power.
It’s not something I’m interested in or can really afford right now but port matching and smooth air/fuel flow I am
Thanks for the honest opinions
Very interesting the 72mm Plenum only offering up 2/3hp gain very disappointing.
Ok forget that then, what bits can I chop off the car
as that’s actually a better way to go.
It’s not just about the ultimate numbers produced but the character and where the power is and I too believe 320Bhp and around 355/360torques is more than enough for a road car.
Trackdays for me are restricted by my power, I know what power it’s got and I also know just a little bit more would be great around our tight short circuits and make it a better experience.
It’s about the only time I’ll be using the gains as it’s more than fast enough for a road car already and I rarely thrash it for the sake of it.
Is it worth doing the heads for a trackday once in a blue moon, not really but on the track day I’ll say it is if I could get that 320, not easy by the sounds of it.
Food for thought.
At no point will I use FI even though that’s the logical way to get big power as I’m not looking for big power.
It’s not something I’m interested in or can really afford right now but port matching and smooth air/fuel flow I am
Thanks for the honest opinions
Very interesting the 72mm Plenum only offering up 2/3hp gain very disappointing.
From the replies on this thread I’m sort of wondering if any of it is worth doing.
Daz who has one of the fastest Chims that’s recorded speed time trials is right in saying 1/2 a second is not a lot but forgetting acceleration times for a moment it’s the extra speed over 100 mph where I’d like it to be faster and I need hp to pull it through the air when over 4000 revs in higher gears to achieve that.
I’m basing all this on experience of QBee,Phazed, Ian’s Griff, Daz and Frank and Pete on the strip, all faster than mine. All have higher hp figures but then these cars have higher figures than just about all of us
I couldn’t out drag a Beemer 3 series on track either enoughs enough !
He was quicker in and out the corners, I went home and changed the brakes and the tyres not much later I was so upset. He wouldn’t do it again I’m pretty sure of that
The Beemer had a role cage, full on track car with similar level driver, but still
So these mods do work when done fully and that’s the simple moral of the story, all or nothing.
Might as well pull the heads off next winter if I’m to go down this road.
Might as well add a new vernier timing gear set while I’m there, , that’s just off the top of my head
I might just leave it well alone.
Those that have heard it agree it runs very smoothly and isn’t that really the ultimate goal for most of us.
Daz who has one of the fastest Chims that’s recorded speed time trials is right in saying 1/2 a second is not a lot but forgetting acceleration times for a moment it’s the extra speed over 100 mph where I’d like it to be faster and I need hp to pull it through the air when over 4000 revs in higher gears to achieve that.
I’m basing all this on experience of QBee,Phazed, Ian’s Griff, Daz and Frank and Pete on the strip, all faster than mine. All have higher hp figures but then these cars have higher figures than just about all of us
I couldn’t out drag a Beemer 3 series on track either
enoughs enough ! He was quicker in and out the corners, I went home and changed the brakes and the tyres not much later I was so upset. He wouldn’t do it again I’m pretty sure of that
The Beemer had a role cage, full on track car with similar level driver, but still
So these mods do work when done fully and that’s the simple moral of the story, all or nothing.
Might as well pull the heads off next winter if I’m to go down this road.
Might as well add a new vernier timing gear set while I’m there, , that’s just off the top of my head
I might just leave it well alone.
Those that have heard it agree it runs very smoothly and isn’t that really the ultimate goal for most of us.
SILICONEKID 345HP 12.03 said:
I did not choose my engine , I wanted a 4.6 with standard bits .V8D offered me my engine because some guy put a big depostit down and then pulled out .
All the parts were there ready to be built .
Still dont have a build sheet , gave up in the end .
That’s sAll the parts were there ready to be built .
Still dont have a build sheet , gave up in the end .
t, I’ll swap then you’ll be happy It’s a glorious car altogether
QBee said:
It's a difficult call Alun, as you do have a lovely car that does what it says on the tin and more.
Knowing what I know now, would I turbo my next one? Probably not.
It may have a lot more BHP etc, but it isn't that much faster - as the Dazster says.
That money would have built a swimming pool for the whole family to enjoy.
It’s a funny thing this hp Knowing what I know now, would I turbo my next one? Probably not.
It may have a lot more BHP etc, but it isn't that much faster - as the Dazster says.
That money would have built a swimming pool for the whole family to enjoy.
Unless it’s like 400+ 300 is pretty much as good as 320 as 350 is nigh on as good as 400
Seems the higher you go the less impressed you are. I suppose that’s why Schumacher’s last tlttle winning V10 had 900 hp!
This comes down to two fundermentsl reasons for me
1 I don’t want to get blown off if I do a trackday as I’ll get angry about it, so an inferiority complex
2 because I have a gut feeling freeing up those last few horses at the top end on my engine which even the dyno graph shows it to be restricted would be about right for the car and me. 320 Bhp is not going to be much use on its own but the extra torque combined,,, enough to keep my respectability
Hey it’s all a bit of fun but circuit driving isn’t, that’s serious and the cars got to be fast enough for it or there’s no point.
I’m close to calling it a day with this daily lark,
Car takes on a different meaning depending on how i want to use it
Slowly I’m coming to believe I’ll have to stop putting pointless miles on it,
That day will signify a change in how I get my kicks from it.
Taking it apart and tuning it is just another part of the fun and why I own it as much as I love driving it.
It’s also why I believe it’s the best sportscar out there for ownership interaction with the car.
It’s simple enough for numpties like me
I just need that bit of extra zip at the top end.
Maybe a lightened flywheel could achieve similar
jojackson4 said:
Al as you know I have a very similar setup to Simon with the inlet
And I think it’s a worthwhile thing to do
Yes there is 20 bhp more and it’s something to do when there is st on the tv
Don’t rush it get your bits and bobs together and it will come together Nice
Personally I would not pull the head unless you have to that can be a job for another day
I personally would not bother with the trumpets and just go full bore blended then you could be up to 50mm ish
Get your self a long and shot die grinder tools and have a go your self
Your a rubbing pervert at the best of times this is just hard core rubbing
Have it
Least you got one thing right And I think it’s a worthwhile thing to do
Yes there is 20 bhp more and it’s something to do when there is s
t on the tv Don’t rush it get your bits and bobs together and it will come together Nice
Personally I would not pull the head unless you have to that can be a job for another day
I personally would not bother with the trumpets and just go full bore blended then you could be up to 50mm ish
Get your self a long and shot die grinder tools and have a go your self
Your a rubbing pervert at the best of times this is just hard core rubbing
Have it
This is the plan really. I’m in no position to pull it apart yet anyway.
Blended base, saves a few quid on trumpets but won’t that risk loosing torque ?
I like a to polish me rocket so I think I might have a talent for it
I don’t consider that to expensive,,,, 10 years ago when I had an income to speak of.
Why drive the economy down
A lot of work and some risk goes into head work so it’s not what I’d call profiteering at that price.
And it stays done.
Something as simple as valve seats and getting them accurately installed has its dangers
getting a good seal isn’t as simple as it sounds either.
Good heads are worth there weight in my book
Why drive the economy down
A lot of work and some risk goes into head work so it’s not what I’d call profiteering at that price.
And it stays done.
Something as simple as valve seats and getting them accurately installed has its dangers
getting a good seal isn’t as simple as it sounds either.
Good heads are worth there weight in my book
900T-R said:
The car as I got it, including a subwoofer with amplifier and a big tool bag, came in at 1043.5 kg at Intrax' scales eith about 40% of a tankful left. This was after an engine rebuild that had some rotating weight taken out (crankshaft & flywheel) but otherwise standard. Having said that, it sits on the OZ split rim wheels that are about 3/4 of a kg lighter apiece than the cast Imolas.
The four Intrax spring/shock units weighed 10.2 kg, the Billies that came out weighed 14.5 kg : - 4.3 kg
Skinny spare (?? kg) taken out and replaced with OEM-style air compressor/tyre goo thingy (ca. 1.5 kg)
Std 075 type battery: 14 kg. Odyssey PC950 battery: 9 kg. - 5 kg
Std Lucas starter: 8 kg. Brise axial starter: 2.7 kg. - 5.3 kg.
Old amplifier (Caliber CA-2260): 1.85 kg. New amplifier (Pioneer GM-D1004 Class D): 0.55 kg. - 1.3 kg. More weight saved because of discarded wiring.
Rear subwoofer and 6 x 9 speakers (5.6 kg) replaced with pair of 6 x 9" CDT subs (3.2) kg. - 2.4 kg
Radtec alloy radiator: - ca. 3-4 kg
ACT carbon plenum: - ca. 2 kg
OE exhaust manifolds with dustbin catalyst (?? kg) replaced with ACT manifolds & decat pipes
Etc. As you see, it's relatively easy to shed a couple dozen kg by replacing components with higher specified ones, without deleting any trim or comfort items. Most of the above has been done when stuff needed replacing anyway. None of it sounds significant on its own but it all adds up, especially as lots of it was in the front of the car, outside the wheelbase - which has knock-on effects in being able to retain non-PAS steering and the 'narrow' front tyre size, etc.
That’s a serious weight loss on an already light car. The four Intrax spring/shock units weighed 10.2 kg, the Billies that came out weighed 14.5 kg : - 4.3 kg
Skinny spare (?? kg) taken out and replaced with OEM-style air compressor/tyre goo thingy (ca. 1.5 kg)
Std 075 type battery: 14 kg. Odyssey PC950 battery: 9 kg. - 5 kg
Std Lucas starter: 8 kg. Brise axial starter: 2.7 kg. - 5.3 kg.
Old amplifier (Caliber CA-2260): 1.85 kg. New amplifier (Pioneer GM-D1004 Class D): 0.55 kg. - 1.3 kg. More weight saved because of discarded wiring.
Rear subwoofer and 6 x 9 speakers (5.6 kg) replaced with pair of 6 x 9" CDT subs (3.2) kg. - 2.4 kg
Radtec alloy radiator: - ca. 3-4 kg
ACT carbon plenum: - ca. 2 kg
OE exhaust manifolds with dustbin catalyst (?? kg) replaced with ACT manifolds & decat pipes
Etc. As you see, it's relatively easy to shed a couple dozen kg by replacing components with higher specified ones, without deleting any trim or comfort items. Most of the above has been done when stuff needed replacing anyway. None of it sounds significant on its own but it all adds up, especially as lots of it was in the front of the car, outside the wheelbase - which has knock-on effects in being able to retain non-PAS steering and the 'narrow' front tyre size, etc.
50 odd lb is significant.
More power to weight better cornering and braking ability
That’s quite some achievement
320/350 = fast car
I like it
TUSCAN seats heavier, see I’d have thought the opposite for some reason
Just shows what I know
For the ultimate trackday experience and weight advantage decent race type seats with side restraint are probably a must but day by day I’m not so sure.
Easy enough to swap over though.
It’s all power to weight at the end of the day.
I think I’ll try removing the passenger seat and re set cross weights for a competitive trackday
Just shows what I know
For the ultimate trackday experience and weight advantage decent race type seats with side restraint are probably a must but day by day I’m not so sure.
Easy enough to swap over though.
It’s all power to weight at the end of the day.
I think I’ll try removing the passenger seat and re set cross weights for a competitive trackday
Edited by Classic Chim on Saturday 3rd February 07:24
Going back to heads
Bigger ports and induction = bigger valves = bigger Cam = more overlap and valves being open at the same time for longer.
This is if you are building an engine solely for big power.
This is where my knowledge hits the wall
Purging I think it’s called.
So longer cam duration has both valves open and this can lead to exhaust gases getting drawn back up into the Plenum via the open inlet valve?
The effect must be to dirty the fuel air mixture and cause rough running. This being exasperated at lower revs. Causing it’s own form of shunting.
So you do risk upsetting slow speed manners somewhat if you go for an aggressive cam.
Obvious to some but important to point out.
Cam choice is vital for the characteristics your looking for so a tough decision when used on the road lots.
Bigger ports and induction = bigger valves = bigger Cam = more overlap and valves being open at the same time for longer.
This is if you are building an engine solely for big power.
This is where my knowledge hits the wall
Purging I think it’s called.
So longer cam duration has both valves open and this can lead to exhaust gases getting drawn back up into the Plenum via the open inlet valve?
The effect must be to dirty the fuel air mixture and cause rough running. This being exasperated at lower revs. Causing it’s own form of shunting.
So you do risk upsetting slow speed manners somewhat if you go for an aggressive cam.
Obvious to some but important to point out.
Cam choice is vital for the characteristics your looking for so a tough decision when used on the road lots.
Stands to reason it’s a closely guarded secret in both cases, don’t blame them to be honest.
Peters lack of vacumn pressure at low revs with his big pistons etc and the inevitable purging that goes on, big Cams do big things and not all in a good way if it’s a city burner
On track a fantastic beast.
Peters lack of vacumn pressure at low revs with his big pistons etc and the inevitable purging that goes on, big Cams do big things and not all in a good way if it’s a city burner
On track a fantastic beast.
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