Big valve head
Discussion
Benefits are more draw as the valves are big, same with the ports.
If it has known quality valve springs fitted probably worth a grand surely as having a set of heads reconditioned to stage 3 is around £1500 at least I think.
Only any good if your compression ratio is tip top to start with. Valves re lapped so should give you a good seal.
You’d want to know how much has been skimmed off them for reference too I’d have thought for that kinda money.
Probably a bargain at £700 so maybe worth a punt.
Others will advise hopefully.
If it has known quality valve springs fitted probably worth a grand surely as having a set of heads reconditioned to stage 3 is around £1500 at least I think.
Only any good if your compression ratio is tip top to start with. Valves re lapped so should give you a good seal.
You’d want to know how much has been skimmed off them for reference too I’d have thought for that kinda money.
Probably a bargain at £700 so maybe worth a punt.
Others will advise hopefully.
This is a long topic, and I could do with a little more info about your engine, but will try to do my best. I am assuming you have a 4.0, 4.3 non-BV or 4.6 as the 5l and 4.3BV both already have BV heads.
Remember that BV heads are all about removing the restriction of gas flow, and higher flow is achieved by extra capacity or higher engine speed.
Just plonking them on an otherwise standard set up will not result in supercar results, as the will be other restrictions on the system and your engine will not be set up to operate efficiently at the higher speeds needed to produce the flow these BV heads are optimised for.
Firstly - are these heads TVR/TVR aftermarket or other (eg SD1 aftermarket)? Reason being that non-TVR-world BVs can be smaller than TVR BVs (TVR BVs equate to non-TVR-world "Ultra Big Valves", measuring ~43mm inlet ~37mm exhaust).
The valves are only one part of the head, and to get full benefit the ports, throats, valve guides etc will all have been worked on to optimise gas flow at every point through the head.
I have seen TVR 5L or 4.3l heads, or aftermarket heads of a similar quality secondhand for around £1000 FYI.
In order to make the most from these you will need to remove the other restrictions both intake and exhaust side - smooth bore intake/elbow, air flow meter enlargement/removal if going above ~280bhp, 71/72mm throttle body mod, 44mm trumpets/intake manifold upgrade if 4.6l, and removal of at least 1 set of cats if present.
You will ideally want to upgrade to a higher performance cam (if you haven't already) to improve engine breathing higher up the rev range to produce the higher flow your heads are optimised for.
However - with the exception of (I believe) the MC1 cam, these all require fly cut pistons so check it you have these. Also double valve springs, but I believe all TVR RV8s have these as "standard"...?
Effects vary for every cam, but if you keep the standard cam there is a good chance you may see the torque hang on for longer, or the whole torque curve move up by a few hundred RPM - but you won't get the same improvement as upgrading to a cam designed for higher rpm.
Finally you will need to remap your fuelling (at minimum) for the new characteristics of the setup (even if all you have done is upgrade the heads and nothing else) - although fuelling and ignition would be preferable - as the extra performance comes from the extra air/fuel going through the heads rather than the heads themselves if you see what I mean...
Hope this helps,
Dom
Remember that BV heads are all about removing the restriction of gas flow, and higher flow is achieved by extra capacity or higher engine speed.
Just plonking them on an otherwise standard set up will not result in supercar results, as the will be other restrictions on the system and your engine will not be set up to operate efficiently at the higher speeds needed to produce the flow these BV heads are optimised for.
Firstly - are these heads TVR/TVR aftermarket or other (eg SD1 aftermarket)? Reason being that non-TVR-world BVs can be smaller than TVR BVs (TVR BVs equate to non-TVR-world "Ultra Big Valves", measuring ~43mm inlet ~37mm exhaust).
The valves are only one part of the head, and to get full benefit the ports, throats, valve guides etc will all have been worked on to optimise gas flow at every point through the head.
I have seen TVR 5L or 4.3l heads, or aftermarket heads of a similar quality secondhand for around £1000 FYI.
In order to make the most from these you will need to remove the other restrictions both intake and exhaust side - smooth bore intake/elbow, air flow meter enlargement/removal if going above ~280bhp, 71/72mm throttle body mod, 44mm trumpets/intake manifold upgrade if 4.6l, and removal of at least 1 set of cats if present.
You will ideally want to upgrade to a higher performance cam (if you haven't already) to improve engine breathing higher up the rev range to produce the higher flow your heads are optimised for.
However - with the exception of (I believe) the MC1 cam, these all require fly cut pistons so check it you have these. Also double valve springs, but I believe all TVR RV8s have these as "standard"...?
Effects vary for every cam, but if you keep the standard cam there is a good chance you may see the torque hang on for longer, or the whole torque curve move up by a few hundred RPM - but you won't get the same improvement as upgrading to a cam designed for higher rpm.
Finally you will need to remap your fuelling (at minimum) for the new characteristics of the setup (even if all you have done is upgrade the heads and nothing else) - although fuelling and ignition would be preferable - as the extra performance comes from the extra air/fuel going through the heads rather than the heads themselves if you see what I mean...
Hope this helps,
Dom
Difficult to quantify the torque/bhp increases you would see as this will depend on a host of factors - engine size, how many of the above mods you do etc but the results of doing it all are extremely worthwhile and will totally change the car in both power and delivery.
Pulling figures out the air it could be anywhere between 10bhp-50bhp (heads only on a 4l, through to all mods listed done on a 4.6) - but these are just illustrative...
Something just as important but often overlooked is the effect on the available rev range this can have - I gained an extra 1000 usable revs before I need to change gear, than I had before - leaving I can stay in gear and have more torque at the wheels at those speeds where I had to change up before.
This can give extremely desirable performance benefits itself, as well as giving a more sports car like character to the engine and an extra dimension to the RV8 sound at those engine speeds.
Pulling figures out the air it could be anywhere between 10bhp-50bhp (heads only on a 4l, through to all mods listed done on a 4.6) - but these are just illustrative...
Something just as important but often overlooked is the effect on the available rev range this can have - I gained an extra 1000 usable revs before I need to change gear, than I had before - leaving I can stay in gear and have more torque at the wheels at those speeds where I had to change up before.
This can give extremely desirable performance benefits itself, as well as giving a more sports car like character to the engine and an extra dimension to the RV8 sound at those engine speeds.
Just seen the eBay listing -
Don't know if you are a 4l or 4.6l but the combustion chambers are different sizes for these 2 engines IIRC think the 4.6 needs somewhere in region of 28cc..?
Also just double check head bolt pattern to make sure will fit yours as believe head bolts pattern changed at some point for the 4l..?
Someone here will be able to correct me and give more specific info....
Don't know if you are a 4l or 4.6l but the combustion chambers are different sizes for these 2 engines IIRC think the 4.6 needs somewhere in region of 28cc..?
Also just double check head bolt pattern to make sure will fit yours as believe head bolts pattern changed at some point for the 4l..?
Someone here will be able to correct me and give more specific info....
The ports don't look like they have been worked much to me, someone more knowledgeable maybe able to pass judgement on this.
I would personally rather buy from someone who knows what they are doing with items like this.
A decent set of Stage 3 heads is around £1300.
http://www.v8developments.co.uk/technical/head_por...
I would personally rather buy from someone who knows what they are doing with items like this.
A decent set of Stage 3 heads is around £1300.
http://www.v8developments.co.uk/technical/head_por...
SILICONEKID 345HP 12.03 said:
Turbo it then you won't need new heads .
Turbo's also benefit from BV heads. You can't just shove in boost without a care as it can proper cock things up.The 450 engine (4.6) has big valve heads but no porting. IIRC.
28cc heads are the later 10 bolt. Earlier (much) 14 bolt are 32cc again, IIRC.
SILICONEKID 345HP 12.03 said:
How much do stage 4 heads cost ?
These are what I have and you must too.http://www.v8developments.co.uk/products/heads/dom...
In reality Daz, there isn't any more power to be had from your engine unless you spend a lot on money on TBs, lightened fly and a hairier cam.
Mine has about another 40 bhp and a shed more torque but it has had more money, (and the extra half a litre) thrown at it.
Do all that and you will loose a little drivability as well.
I’ve gone round in circles and ended up thinking drivability is one of the most important things to retain.
My Triumph Thruxton had been converted from efi back to carbs and it was a lot faster and even put on a dyno when setting up.
It was really good but hard to go from off throttle to light throttle without a sudden gush of fuel and too much initial acceleration, in a corner not what you want, nearly every bike I owned as a youth did this to some extent on carbs.
I have the same problem with the Tvr if my throttle is stiff and needs oiling which requires me to push the peddle slightly harder and obviously the throttle opens more than desired so a similar effect and that’s running on a standard Plenum.
What this shows me is when I’m burbling around on 1500 revs just the slightest opening of the throttle supplies more than enough air as I’m using like 5% throttle or a few mm travel at best.
Adding more air at those moments is going to exasperate those sort of problems.
I spoke to the people who built my bike ( Norman Hide’s company ) and they said going back to efi and de tuning the bike would solve the problem and tuned as it was with K&N filter with alloy bell mouth bigger inlet tract and bigger jets they would struggle to improve it as it was.
This was a big part of why I sold the bike as I wasn’t about to de tune it, better to let someone else enjoy doing something with it. Something that ruins or adds stress to everyday driving can stop you using a vehicle.
It’s a fine balance.
It might well be that twin throttle pots are in fact better at delivering air at these very light throttle openings for all I know so keep up the good work whoever does these mods and keep telling us of your experiences.
It appears to be a minefield out there, you do one thing and it opens up a whole new can of worms to get the full potential out of it, the old girl goes well, starts first time, every time and doesn't shunt so I think I'll leave her alone until some problems arise and I need things sorted.
Cheers Mark
Cheers Mark
It's not so much a minefield - just more like trying to get more water through a multi-section hosepipe 
You can't just make 1 section bigger and expect twice the amount of water to come out the end - all the sections have to be enlarged, or the water will still be restricted by the remaining bottlenecks...
(As an extremely simplified analogy!)
Hth
You can't just make 1 section bigger and expect twice the amount of water to come out the end - all the sections have to be enlarged, or the water will still be restricted by the remaining bottlenecks...
(As an extremely simplified analogy!)
Hth
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