How much Bhp is headwork worth ?

9th February 2011, 10:01

I have tried doing searches, but can't find any definitive figures.

What does head work do ?

Who is good for doing it ?

What bhp can you gain on a cammed car ?

I simply cannot fit throttle bodies due to noise restrictions, so i am going to have to look down other avenues to gain a few horses

9th February 2011, 10:20

Why can't you use throttle bodies? I have no problem wiry noise on track days, alot of track Saxo have throttle bodies.

9th February 2011, 10:24

Quote:

Originally Posted by AndySAXO

Why can't you use throttle bodies? I have no problem wiry noise on track days, alot of track Saxo have throttle bodies.

Guessing here, but i think he means when he goes to croft.
Most Croft trackdays are now 88db static and the car must have an induction noise similar to that of the car as standard, also with ITB's the exhaust db will be up.

9th February 2011, 10:26

Quote:

Originally Posted by AndySAXO

Why can't you use throttle bodies? I have no problem wiry noise on track days, alot of track Saxo have throttle bodies.

88 db static test limit (which will be ok)& 85 db driveby on the exit of a full throttle 3rd gear corner (which maybe a problem).

9th February 2011, 10:27

you are best off going for a turbo conversion then. 175bhp with stock noise output.

9th February 2011, 11:59

Also wondered the OPs question

9th February 2011, 12:10

Quote:

Originally Posted by Steve

Guessing here, but i think he means when he goes to croft.
Most Croft trackdays are now 88db static and the car must have an induction noise similar to that of the car as standard, also with ITB's the exhaust db will be up.

few days this years coming up were its 105db but price is well over 200 quid

9th February 2011, 12:16

there is no definative figure.

You will get varied outputs depending on how its all matched. EG valve size, and the work done to match the cam profile you are using.

QEP used to do good heads (having done alot of work with pumaracing) although i believe matt is now just selling parts and not doing any engine work which is a shame.

Sandy could put you in touch with his head guy or john could.

9th February 2011, 12:38

Quote:

Originally Posted by Ryan

there is no definative figure.

You will get varied outputs depending on how its all matched. EG valve size, and the work done to match the cam profile you are using.

QEP used to do good heads (having done alot of work with pumaracing) although i believe matt is now just selling parts and not doing any engine work which is a shame.

Sandy could put you in touch with his head guy or john could.

A rough guess at a power & torque figure ?

9th February 2011, 12:44

On just a canned engine would add massively maybe few extra, but it not all about bigger is better.

Pm sandy brown would explain alot to you.

10th February 2011, 07:51

Quote:

Originally Posted by Ryan

there is no definative figure

Sandy could put you in touch with his head guy

I've been doing all my own heads for the last two years.

True there is no definitive figure and actual power increases, if you want to just focus on that, aren't likely to be massive on a low-medium spec engine. The headwork needs to be optimised for the engine spec to produce the best results, one size fits all or stage1, 2 etc is not how serious people approach it. The size and shape of the ports, valve choice, chamber work are all factors that will greatly influence the results on any particular engine, there is not a definitive head that will work well in all cases and this is particularly where alot of flowbench developed heads fall down and CNC profiled heads can be very limiting in that respect too.
Taking all that into account, it's best to approach someone that can give you a good overall spec that is known to achieve what you are setting out to do. That's unlikely to be me in your case, because almost all of my development is based around ITB induction for NA engines. Otherwise you're taking a chance and if noise really is that critical to you, then maybe as has been said, FI might be a better route. Single inlet NA tuning is very limiting and still about as noisy as rear facing TBs under load from the outside.

10th February 2011, 11:54

What sort of price ranges are there for head work? I no thats a bit of a grey question but like port and polish, how much are you looking at to have that done

10th February 2011, 13:06

It depends very much on the work done, different people prioritise different work. For example some will replace valve guides as a matter of course; but the guides in these heads are very good quality and rarely need replacement IMO. Also the type of seat cutting. Some will not re-cut seats, some will hand cut them with stones and/or Mira manual cutter, others use machine cutting, such as Serdi. Quality varies in all cases. Likewise the valves may be left alone and just lapped, or maybe profiled and re-ground or replaced. Head face may be just scuffed off, fly cut or surface ground.

A simple throat tidy and shining up the ports, which is largely a cosmetic job, may only be around £300. If you're paying someone experienced and proven to properly reshape the ports optimally, properly precision cut the seats, tidy the chambers, put a good precise finish on the head face and the valves; which I regard as the minimum standard, lower limit for good work around £600-650, but the sky's the upper limit. Good quality single piece valves will add around £350, some people will insist on spring change and maybe the guides, maybe oversizing the inserts for bigger valves (I've seen genuine 200bhp on standard valves, but there are several ways to achieve your objectives).

10th February 2011, 13:11

agree ^

a rough port clean up, i.e. cleaning up whats already there does not really see any major advantage, apart from looking shiny. £300 seems reasonable, it still takes a long time. unfortunately if somethings shiny, people automatically think its good.

a good proper job as sandy says (port reshaping/sizing to match the engine needs etc) will start at £600. thats before any additional work such as valve seats, valvework etc.

as an example, my full race turbo head by terry dolphin, including valvetrain, larger valve seats, one piece stainless valves, cams etc, stands me in well over £2000.

headwork is pretty much "open cheque book"

- colin.

10th February 2011, 13:48

I agree with nearly everything posted above --but bang per buck --changing your cams is the first and biggest improvement you will get for money spent.
fit a proper plenim and filter system to t/bodies and you should not have a problem with noise level at normal rpm levels,but if you are wanting to run 8k+ then it will be harder,but not impossible to comply --depending on the lenim and filtration system