Hi guys,

I have 2 heads to choose from. A B16a2 thats lying around and the B18C5 which is on the car now. I plan to send the head for a full race PNP job. From my understanding, the valve area is the most important factor determining the flow. However, practicality is another issue and would like the experts to chime in on their thoughts. I also have a few camshafts in mind and they are quite radical and the law of diminishing returns applies so would like some input too.

for example, a stock sized valved B16A head fully PNP etc. What is the highest valve lift where maximum flow can be achieved? I am sure that the valve will not flow as much up to a certain lift point? Reason i ask is because there is the option of using a 13.5mm lift cam and i doubt there will be any extra gains using that high lift.

Duration of a camshaft, how much is too much? Is it largely dependant on the valve to valve clicking distances and the engine's ability to rev higher? ie if the valves have lots of clearance and engine is good to rev, we can go with longer duration?

I've spoken to a few head porters and they are always interested in the size of the valves as the limiting factor for power. I am very tempted to go 1mm over intake and standard exhaust. Problem is with this combination, valve to valve clearance is an issue, even though the seats are cut to suit.

Question: Is it better to run bigger valves + less duration n lift or standard sized valves with more lift and more duration?

Finally, what is the smallest combustion chamber size on B16a head thats ever done?

Thanks for reading and please chime in on your thoughts and experiences.

 

I am assuming you will have this head flowed . . . there is a point when lifting the valve any further (on an NA car) won't do anything for flow so it is pointless to open it further. You should be able to check that by looking at the flow data of your head. Making the valves bigger can help but it may also shroud the valves and actually impede flow. Flow testing is the only way to test for this. The higher your compression ratio, the more duration you will need generally. The compression ratio at the point the intake valve closes (the effective compression ratio) should be 8 to 8.5:1 for 92 octane fuel. The amount of overlap you run depends on how high you are going to rev it also.

 

Well, your C5 head and B16 head are of the same casting, and since the B16 is just layin around, I would send that one to Brad at RLZ. That way you won't have any downtime, and just let Brad know what cams you are gonna be running...he'll give you the best possible port job that anyone could give you. The dude knows his ****, and he'll be able to answer any questions you have. His screen name is MAX_CFM. Hondaraceengines.com