45mm inlet and Plenum base inc 72 mm throttle pot.
Discussion
I’ve been studying air flow on a basic level for some time now and flow upto and around a valve is very interesting indeed. How the characteristics of the incoming air and fuel change as piston goes down the stroke. High pressure then lower but sucked in more and how it swaps from roof to floor port pick up of the air as it does so.
The fact the runners are tubular going into rectangles just before the heads doesn’t help much.
Hahah, it’s often the opposite wall to the one you think is to be worked but watching plenty of videos of liquid and air through pipes has helped a lot to understand how the air acts in motion and then when it hits a bend.
I noticed how the inlet manifold does have a dish shape on the opposite wall after a corner, air hits it and the dish shaping in the casting chucks it back towards the middle of the port.
The fact the runners are tubular going into rectangles just before the heads doesn’t help much.
Hahah, it’s often the opposite wall to the one you think is to be worked but watching plenty of videos of liquid and air through pipes has helped a lot to understand how the air acts in motion and then when it hits a bend.
I noticed how the inlet manifold does have a dish shape on the opposite wall after a corner, air hits it and the dish shaping in the casting chucks it back towards the middle of the port.
Edited by Classic Chim on Sunday 22 April 19:07
SuperApeInGoodShape, that’s funny enough 
You sound like you’ve done plenty of this work so I Thankyou for your contributions to this thread.
Inlet continuity does worry me a touch but going to 44/45 mm it’s hitting a restriction when it hits the heads rather than before them.
I’m starting to think more about velocity than outright size and keeping a constant flow vital for that end goal.
I have a 5.0 inlet I borrowed here as standard Tvr and it tapers so that's becoming my preferred option but need sizing equipment to do this accurately on my own one.
You sound like you’ve done plenty of this work so I Thankyou for your contributions to this thread.
Inlet continuity does worry me a touch but going to 44/45 mm it’s hitting a restriction when it hits the heads rather than before them.
I’m starting to think more about velocity than outright size and keeping a constant flow vital for that end goal.
I have a 5.0 inlet I borrowed here as standard Tvr and it tapers so that's becoming my preferred option but need sizing equipment to do this accurately on my own one.
The only thing I can say about engine power speculation is go to the drag strip.
Dyno are one thing. The clock something very different and very accurate.
So I did
I raced a Suburu Imprezza with very similar levels of power, he said it was 300 hp and it was only a year old, we were neck and neck.
I did 12.60 1/4 mile on drag radials that rubbed on my arches I did 12.7 on Rainsport road tyres.
I don’t think I’d do the time without the power.
I’ve also raced a great racer and all round top dog in his Chim dyno’d at a different place to mine 325 Bhp and he usually just beats me so if I didn’t have that figure I’d be nowhere near him.
My block is decked and compression marginally higher and use aftermarket Ecu in MBE so get best use of advancing ignition etc.
If the figures are correct or not the times are
Who really knows with these bloody dyno.
Dyno are one thing. The clock something very different and very accurate.
So I did
I raced a Suburu Imprezza with very similar levels of power, he said it was 300 hp and it was only a year old, we were neck and neck.
I did 12.60 1/4 mile on drag radials that rubbed on my arches I did 12.7 on Rainsport road tyres.
I don’t think I’d do the time without the power.
I’ve also raced a great racer and all round top dog in his Chim dyno’d at a different place to mine 325 Bhp and he usually just beats me so if I didn’t have that figure I’d be nowhere near him.
My block is decked and compression marginally higher and use aftermarket Ecu in MBE so get best use of advancing ignition etc.
If the figures are correct or not the times are
Who really knows with these bloody dyno.
QBee said:
Yes, but are your heads, on your car at present, Range Rover or TVR spec, Alun?
I’m trying to avoid the question as I don’t know. As far as I know they are standard Rover heads from late 99 as that’s what I traced the engine date to. The cars march 2000 so that makes sense.
Dom was busy on bigger projects by that date and the Rover engine a thing of the past so as I’m aware no porting just bigger cam got installed.
But he’s a canny lad who keeps his cards close to his chest so unless he can remember what he did I’ll not know until there off the car.
Or he might level with me and tell me to stop wasting my time with these heads but it’s a standard 38 mm 4.6 Rover set up on Standard but very late heads with stock valves as far as I’m aware.
It might seem perverse to some but building a set of heads and getting fully involved in doing it good fun to me.
I want to machine the buggers too
I have a constant battle going on in my head
Leave my car alone or have Dom put the heads on because I like the continuity
Leave my car alone and simply sell these heads to someone who will want the extra power more than I do and sort out Peter.
Put them on and never look back!
If things go as I’d like
I’ll afford to do it all properly and prove there worth on my car on Dom’s rolling road then a real one with a clock.
At that point decide if I want my own to be done or leave them well alone as I do have a a very good car and engine right now that’s fantastically usuable and that’s very important.
Jason has said he can get it to run just as good with the bigger stuff on there so not to worry about it but I might ask him again to be sure.
I nearly bought a model aeroplane last year,, spend more on them than on these heads just crashing every week
Aaaaaarrrhh, what an education can do for you
Saying that I grew up in the Midlands in a fairly well to do household then pop off to Wales to see my family and mates who had 2p to their name yet all had horses or many of them did stabled on the farm, all wild ponies they caught for free.
Nearly all gone now on those hills hear my nans place but those boys I used to be envious of and they could really ride,,,bare back, hard to believe now but the bloody things ran up and down the streets, well there was hardly any cars there even in the 70’s
They all look happy there mate
By the way their talking about you
Saying that I grew up in the Midlands in a fairly well to do household then pop off to Wales to see my family and mates who had 2p to their name yet all had horses or many of them did stabled on the farm, all wild ponies they caught for free.
Nearly all gone now on those hills hear my nans place but those boys I used to be envious of and they could really ride,,,bare back, hard to believe now but the bloody things ran up and down the streets, well there was hardly any cars there even in the 70’s
They all look happy there mate
By the way their talking about you
Alun if you've still got your timing slip from your 1/4 mile sessions you can probably guesstimate if its crank or wheel hp from your 1/4 terminal mph figure.
If a chim really is 2500 - 2550 lbs (with fuel & driver) you'd expect somewhere around 108mph for 254bhp flywheel or 113mph for 300bhp flywheel.
If a chim really is 2500 - 2550 lbs (with fuel & driver) you'd expect somewhere around 108mph for 254bhp flywheel or 113mph for 300bhp flywheel.
Edited by SuperApeInGoodShape on Monday 23 April 14:12
SuperApeInGoodShape said:
Alun if you've still got your timing slip from your 1/4 mile sessions you can probably guesstimate if its crank or wheel hp from your 1/4 terminal mph figure.
If a chim really is 2500 - 2550 lbs you'd expect somewhere around 108mph for 254bhp flywheel or 113mph for 300bhp flywheel.
Very interesting as I’m usually about 110 mph and 108 on my fastest run that was going to be 112 or so based on my 60ft time but I was getting drag. Hot day too. If a chim really is 2500 - 2550 lbs you'd expect somewhere around 108mph for 254bhp flywheel or 113mph for 300bhp flywheel.
I’ve often thought it’s probably about 285/290 at the fly based on driving other Tvr that have been Dyno tested. I was told it was the second highest figures they’d got for that spec engine.
I think the Dyno at Powers is not that far off.
Edited by Classic Chim on Monday 23 April 14:16
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