claytonsmith

does anyone know:

do the non Vtec d series motors ( d15b7, d16a6, d16y7 lets say) all use the same head casthing? ive "heard" that the a6 is the best suited head for making power.. but i havent heard that confirmed.... as far as i can tell they all have the same CC combustion chamber...but i cant find info regarding wheather the runners are the same size or dirrerent etc.....used the search function with no results...

anyone know?

r_Senik

tryed asking on d-series.org??

d16vtecx

the d15b2 and d16a6 have the same head the only difference is a more aggressive cam in the a6
not sure about the others though

lohatch

b7 and A6 are very simular, if not the same. y7's are different and also have 1mm larger valves on both sides i beleive

KingOfQB

i think d-series.org is down

d16dcoe45

I am not so sure that the y7 has one mm. larger valves...I know the z6 and y8 have one mm bigger on both intake and exhaust. A6 and b7 are 29 intake, 25 exhaust. Y8 and z6 are 30 intake, 26 exhaust. Also a6 and b7 are the same casting but the b7 has much softer valve springs. Because of the light valves a6 springs are good to around 8500 and z6/y8 springs to around 9000!!!

claytonsmith

wait so which engine has lighter valves??

can i run z6/y8 valve springs on a non Vtec head??


if so it would seem like the best combination would be a6 valves with z6 retainers and springs in a a6/b7 head.. am i way off here?

d16dcoe45

The a6 valves are probably lighter for two reasons: 1) the diameter is smaller and 2) the valve has a shorter stem. I don't think you can run z6/y8 valves in a non-vtec head because the valves are a lot taller--and you would probably get into coil bind running them on the short(er) non-vtec valves.

For those who run a big reground cam on a d15/d16 non-vtec, it leaves only a few threads engaged on the valve adjusting nuts, which could possibly lead to them loosening when you don't want them to!!--using z6/y8 nuts alleviates this because they are threaded all the way to the bottom unlike a6 nuts, giving more thread engagement and less of a chance for loosening. The a6 nuts have a wide space at the bottom that isn't threaded so thread engagement is reduced.

claytonsmith

awesome man!! thanks for the heads up on the adjustment nuts.. i didnt know that.. not a problem though since have a z6 head laying around.. thats why i was wondering if i could use the springs off it


anyone else have more info?

d16dcoe45

My recommendation really only applies to people using VERY big regrinds on non-vtec d heads. When you regrind the cam, the only way to get more lift is to make the base circle smaller--with a smaller base circle the rocker is now farther away from the tip of the valve--to make up the difference you have to crank down the rocker adjusters until there is only 3 or 4 threads remaining for rocker nut to grab. The a6 has very large nuts, but the threads don't go all the way to the bottom--there is an "open space" at the bottom which reduces even more the threads that will grab. The sohc vtec nuts are not only much smaller and lighter (which is better for high rpm) but the threads go all the way to the bottom--so you are able to grab every thread. If you have a stock cam or small regrind or a cam ground on a new billet--this doesn't apply to you, since you will the same thread engagement as stock.

d16dcoe45

If you started with an a6 head--those springs are good to at least 8000. They will hold 8500--but its a gamble at that point. I would fully trust 7800-8000 with stock a6 springs. The d15 non vtec springs are a different story though--like a DX, those are soft and will float above 7000 rpm.

claytonsmith

thanks a lot man for the info.. goooood **** there