inlet and exhaust port sizes

[brucer]

hi guys. how much bigger can the ports be made on a e16se head?

i assume to match the exhaust to the manifold sizes but just wandered how much of an increase is made to both the inlet and exhaust

thanks.

[pul16v]

bigger isnt allways better shape is the decideing factor not size match them up yes but dont try resize them or reshape simply match them between head and manifolds :thumb:

phil

[maccas]

by all means match the inlet manifold and gasket to the head but i have heard that having the exhaust header stepped slightly it can help prevent exhaust backflow into the head and hence power is slightly better off, apparently the best bet is to match the top of the header to the port and then make the bottom of the header slightly lower than the exhaust port in the head so that there is a 1-2mm lip above the floor of the header pipe

maccas

[therealnovaboy]

the inlet ports dont need to be increased as the valves are considerably small compared to the port size. possibly it would be best to grind the edges from the steal valve seat to the aluminium to get a smoother finish. the last time i did a head there was a lip in there about a mm or so but be careful not to mark the valve seat. you can also remove some of the alloy on the bottom edge of the port where the tighter radius curves round to the valve. on the exhaust ports there is not much point in port matching but you can match the bottom edge but leave the top edge with a step, stepping down to the exhaust manifold with the manifold being the larger diameter.

[Ash]

I'll double check when it's back from the 'shop, but im sure my Blydenstien B+ head has standard size ports, just better shaped.

[pul16v]

possibly it would be best to grind the edges from the steal valve seat to the aluminium to get a smoother finish.

good advice about a 80 grit finish is perfect for the inlet ports polish the exhausts


you can also remove some of the alloy on the bottom edge of the port where the tighter radius curves round to the valve.

really wouldnt do that you will ruin the flow of the head ive got several cylinder head modification books and from reading these its not a good idea can post up the names if you want the part you talk of is called the (short radius) and its job is to align the air on top of the valve head so it flows in rather than the air going in and hitting the valve head sideways them haveing to turn a 90degree corner

phil