any difference between 1*2 cylinder heads?

[Daz Clio Cup]

i think i may have killed all my valves and as i've got to replace them was wondering if there's any difference between the various heads eg valve sizes, ports, flow rates etc.

Cheers daz

 

[Fred@BTM]

ph1 has larger exhaust ports, that's about it

rocker covers can differ

 

[ben_p]

As above,

what happend btw?

 

[Daz Clio Cup]

would it be an advantage to fit a ph1 head over a ph2 one then?
On the track day i missed 3rd and may have bounced the valves. Double valve springs ftw. Won't know the real extent of the damage till i get it apart. Fitting a secondhand head will be cheaper than buying 16 valves

 

[ben_p]

Are you using the PAC single springs or double? Im using Single PAC

 

[Daz Clio Cup]

single iirc but double may go in depending on funds or i'm gonna have to lower the rev limit

 

[ben_p]

whats the limit? 8?

 

[Daz Clio Cup]

yeah which i was told would be fine! Followers break at about 8.2k. I logged max revs at 7960. Obviously too much!

 

[Daz Clio Cup]

is it possible to get bigger valves in the head?

 

[Hutchie]

is it possible to get bigger valves in the head?

yes

i reccomend a 197 head as inlet is alot nicer

 

[BenR]

Bigger valves provide zero benefit at your level.

 

[fil_b]

gutted daz

hope u get it fixed soon

 

[Daz Clio Cup]

Bigger valves provide zero benefit at your level.

Could you explain please, i thought bigger valves give more flow

 

[Daz Clio Cup]

So i take it a PH1 head will fit ok then?

 

[BenR]

phs1 will fit yes, and it does flow significantly more on the exhaust port, but you have to quantifiy if its needed or not. Bulk flow rates mean very very little in the grand scheme of things.

AS for bigger valves, just because they are bigger again doesnt mean more flow. In the F4R you have issues primarily due to bore size and valve inclanation. If you go 1mm oversize, in the standard chamber and port you'll just end up loosing 'flow', but more importantly you'll affect quality. If you go 0.5mm oversize, then there is just no point for the cost outlay as its such an insignificant increase on a non optimised port.

 

[Daz Clio Cup]

phs1 will fit yes, and it does flow significantly more on the exhaust port, but you have to quantifiy if its needed or not. Bulk flow rates mean very very little in the grand scheme of things.

AS for bigger valves, just because they are bigger again doesnt mean more flow. In the F4R you have issues primarily due to bore size and valve inclanation. If you go 1mm oversize, in the standard chamber and port you'll just end up loosing 'flow', but more importantly you'll affect quality. If you go 0.5mm oversize, then there is just no point for the cost outlay as its such an insignificant increase on a non optimised port.

I've got to take the head off to sort the valves and seeing as a set of valves will cost £250 from the stealers, a secondhand head is a much more cost effective option.

Thank-you for explaining the bigger valves theory, makes sense now.

Cheers Daz

 

[Hutchie]

got a dremel??? port your own head

 

[Daz Clio Cup]

got a dremel??? port your own head

My head is ported, i've got better than a dremel, air tools ftw! if i get a new one, that will be too

 

[Hutchie]

My head is ported, i've got better than a dremel, air tools ftw! if i get a new one, that will be too

die grinder first yeah and then a fine sander and wd 40 im so pleased with my results

 

[Gez]

what other headwork can be done? i have a spare head and was thinking to port&polish it (match it to the manifold gaskets) and polish up the combustion chambers.
anything else be done?

 

[BenR]

plenty....depends how deep your pockets are.

 

[Gez]

care to explain?

 

[BenR]

Simply put, the 172 head has its own massive flaw in port design, but because it is CNC machined, this leaves you very very little in the way of rectifying the flaws. So 'typical' porting methods can only gain a finite amount because you simply do not have the material available to work in certain areas. Thus if you carry on porting you only make things worse.

If you have deep pockets you can correct things, but to tell you exactly what to do would be giving away what I work at hard.

Bigger valves and material removal does very little on its own, and frankly there are some areas which should not be touched period or you will loose performance.

 

[Gez]

ok, without giving away too much,
is polishing the combustion chambers worthwhile?
Matching the inlets and oulets of the head to the gaskets worthwhile?
Not planning to fully open up the ports, just match to gaskets and smooth in.

 

[Andyman]

Ben did my head a few years back under the GDi package from way back in the day. Not sure exactly what the difference is on its own but with basic other mods cars currently running 175 lb/ft as per RS Tunings rollers end of last year.

 

[BenR]

Things have moved on significantly since then.

There is zero point polishing anything or matching the head to the gaskets.

 

[Andyman]

Agree Ben. Theres far easier more cost effective ways to extract power now than there was a few years ago, even a few months going by some current threads

 

[Daz Clio Cup]

How important is it to have the matching cam cover? I've been offered a ph1 head minus the cam cover, will it be ok to put my cam cover on it or is it a risk i shouldn't take?

cheers Daz