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Im not sure how far people have gone with the cylinder heads and what data is around however :
Over the years ive had quite a number of heads done for me (40 or so) on a variety of cars , there has always been gains ,some better than others , and ive always used the same guy , he is an old friend ,and his work is superb .
He has been doing heads and nothing but heads for decades now,for every possible level of motorsport ,and years of feedback from rally teams and race teams .
This is what I have experienced ;
Oversize valves , these always provide more performance ,but only on the exhaust side ,and sometimes on the inlet as well ,this all depends on the ratio of inlet to exhaust size
Valve supplier - ive used G & S , uk based ,high quality ,can custom make them to spec and prices are very good ,never had a problem
valve angles and seats , always requires a fresh cut , not only flow improves but longevity when the width of the seat is controlled (this dictates the heat that is passed through the seat )
CC ing , this ensures each cylinder has exactly the same capacity , so power/heat is exactly the same in each cylinder
Porting - this is a black art , and does not do what any text book tells you , the head porter learns this over hundreds and hundreds of heads , what works and what does not - flow benches give a guide but they are a static test , and do not replicate the real world , where valves are opening closing and air is pulsing .
1 test head is required that can be ported to destruction , so material thickness is known , how far can you go til the water jacket is hit .
The head must be in good condition to start with - old aluminium can be full of cracks to start with , and the surfaces must be perfectly true .
Boost level ;makes large differences in results as airspeeds change and turbulence alters .
The head should look like new when finished , and be properly packed ,there is a lot of labour and time goes into a good head , measuring,cleaning ,skimming , porting and assembly .
Done well the heads last many many years , hand work beats CNC , the experienced eye sees what the computer does not .
Is it worth doing ?, yes your engine will love it !!!!
Over the years ive had quite a number of heads done for me (40 or so) on a variety of cars , there has always been gains ,some better than others , and ive always used the same guy , he is an old friend ,and his work is superb .
He has been doing heads and nothing but heads for decades now,for every possible level of motorsport ,and years of feedback from rally teams and race teams .
This is what I have experienced ;
Oversize valves , these always provide more performance ,but only on the exhaust side ,and sometimes on the inlet as well ,this all depends on the ratio of inlet to exhaust size
Valve supplier - ive used G & S , uk based ,high quality ,can custom make them to spec and prices are very good ,never had a problem
valve angles and seats , always requires a fresh cut , not only flow improves but longevity when the width of the seat is controlled (this dictates the heat that is passed through the seat )
CC ing , this ensures each cylinder has exactly the same capacity , so power/heat is exactly the same in each cylinder
Porting - this is a black art , and does not do what any text book tells you , the head porter learns this over hundreds and hundreds of heads , what works and what does not - flow benches give a guide but they are a static test , and do not replicate the real world , where valves are opening closing and air is pulsing .
1 test head is required that can be ported to destruction , so material thickness is known , how far can you go til the water jacket is hit .
The head must be in good condition to start with - old aluminium can be full of cracks to start with , and the surfaces must be perfectly true .
Boost level ;makes large differences in results as airspeeds change and turbulence alters .
The head should look like new when finished , and be properly packed ,there is a lot of labour and time goes into a good head , measuring,cleaning ,skimming , porting and assembly .
Done well the heads last many many years , hand work beats CNC , the experienced eye sees what the computer does not .
Is it worth doing ?, yes your engine will love it !!!!
