big valve head

29th January 2008, 21:30

hey i maybe looking to change to a big valve head as my vts head has a possible hair line crack, just a few questions:

what kind of performance gains am i looking at ?

what head would be best (c2 vts, 307 etc) ?

and...

do they require any modification to make them fit ?

cheers for any help jay.

29th January 2008, 21:35

what is your current spec? no point in going BV on an otherwise standard engine.

29th January 2008, 21:36

Quote:

Originally Posted by vtr_jay

hey i maybe looking to change to a big valve head as my vts head has a possible hair line crack, just a few questions:

what kind of performance gains am i looking at ?

what head would be best (c2 vts, 307 etc) ?

and...

do they require any modification to make them fit ?

cheers for any help jay.

from what i know,
the c2,307 head has 2mm larger inlet valves so would probably b cheaper to buy that and have it ported than pay £700+ for a quality bv head.
the head would need the inlet studs drilling and tapping and you would have to block off a oil return in the block. also im not sure what head gasket you would use but i know the c2,307 has a thinner head gasket.
also youd need to use vts valve springs and followers and you can use vts cams.

just my little input

29th January 2008, 21:37

Quote:

Originally Posted by williamsvts

what is your current spec? no point in going BV on an otherwise standard engine.

and agree with this^^

29th January 2008, 22:17

the current spec is it has kent pt51 cams ,4 brach manifold (4-2-1), de-cat magnex exhaust, raceland induction kit and a remapped ecu.

29th January 2008, 22:38

then wih those mods there would be a gain, but i dont know if i could justify spending over £500 and gaining few bhp, id spend money on brakes, supension unless you have future mods planned?

30th January 2008, 00:23

A "big valve" head won't definatly give you gains, it depends wether the valves in the standard head are producing a restriction to the flow of the gases.

30th January 2008, 08:54

Indeed. I would hazzard a guess that the bigger valves would possibly come into play when you start reaching the 170+ bhp mark. I've seen numerous examples of where VTS's and 106s with 708s have produced around an extra 7-8 BHP on the rollers with a gas flowed head from QEP. Obviously the valve sizes were the same in these examples.

30th January 2008, 09:18

waste of time unless your going for something like a super charger or TB's

30th January 2008, 09:33

In my experience, and I've said it elsewhere on these boards, the centre of your engine is the cylinder head. Any modification you make *after* the cylinder head will yield a bigger % gain. If you fit the head first, then later you can enjoy bigger jumps with each mod be it air filter, ECU, TB's, Cams, exhaust, de-cat or anything else.

Big valves, port shaping, combustion chamber shaping and volume balancing and correctly chosen compression ratio will form an excellent basis for future mods and complement all of them.

30th January 2008, 19:03

Quote:

Originally Posted by dannygti

then wih those mods there would be a gain, but i dont know if i could justify spending over £500 and gaining few bhp, id spend money on brakes, supension unless you have future mods planned?

brakes and suspension are sorted by billies on the front with 266mm brake set up. the reason for the change is a possible crack in the head. if the head was fine it would not be getting changed as you said it would be a quite expensive.

31st January 2008, 18:00

you would also need another remap to see the real benefits

31st January 2008, 22:11

a big valve head will give u a benefit in one way. why do you think the newer tu5jp4 engines found in c2's and 206's have larger valves than vts. they dnt do it for nothing.
some jp4 variations produce more power than a vts yet they use milder cams than the vts. the milder cams give a less 'peaky' engine with a broad torque curve but the larger valves help bring the power back up.

i would defo go out and find a jp4 head and fit that, leave it std if only planning on fairly mild cams like 708's ect but if u go for t/b's, high comp pistons and big cams then u can get the head ported and polished ect then u will be looking at big power figures. QEP are currently developing an engine for gorge on SSC, with all the above and catcam 734's which u can use the std hydro lifters, it produced 190bhp but that is with a highly modifed jp4 head and a bloody raceland manifold!!!

2nd February 2008, 20:06

yet the headwork for georges engine by qep/pumaspeed will not come cheap now!