Lets Talk d-series

**dougie_504** · 15-08-2011 12:10 PM

Originally Posted by Sexc86

I think people have got the slight incorrect impression of SOHC Vtec. Its not simply that intake has vtec and exhaust does not... It is a Vtec engine, variable valve timing or valve overlap etc. Its just simply with the SOHC only the intake valves profile changes (the timing in which the valve opens and its duration etc) when vtec is engaged.. The DOHC both intake & exhaust have separate profiles for both on and off vtec.

Read more here

http://en.wikipedia.org/wiki/VTEC#SOHC_VTEC

Pretty much exactly like what we were saying, only you said it differently. The SOHC VTEC doesn't effect the exhaust valves, so in what way does the SOHC VTEC effect the exhaust? It doesn't really. SOHC VTEC effects intake only.

You just have to assume that the standard exhaust flow of the SOHC D can cope with the increased flow during VTEC, which it surely can, but if you want to optimise your power output with a built head (cams, ported etc) then you'd have to worry about the standard exhaust flow and therefore oversized exhaust valves are probably an excellent idea, whereas many manufacturers believe this is not the case for the B-series.

**TheSaint** · 15-08-2011 03:03 PM

im still on the fence with changing the valves in my head build

would i have to oversize both intake and exhaust or can i just oversize the exhaust side?

**Sexc86** · 15-08-2011 05:56 PM

Originally Posted by dougie_504

Pretty much exactly like what we were saying, only you said it differently. The SOHC VTEC doesn't effect the exhaust valves, so in what way does the SOHC VTEC effect the exhaust? It doesn't really. SOHC VTEC effects intake only.

You just have to assume that the standard exhaust flow of the SOHC D can cope with the increased flow during VTEC, which it surely can, but if you want to optimise your power output with a built head (cams, ported etc) then you'd have to worry about the standard exhaust flow and therefore oversized exhaust valves are probably an excellent idea, whereas many manufacturers believe this is not the case for the B-series.

i know mate but "Sohc vtec only has vtec on intake valves" is poorly worded and does not really make much sense to me. haha

**trism** · 15-08-2011 06:24 PM

How is that poorly worded? It describes exactly how it works, nice and simply

**dougie_504** · 15-08-2011 09:09 PM

Originally Posted by TheSaint

im still on the fence with changing the valves in my head build

would i have to oversize both intake and exhaust or can i just oversize the exhaust side?

I've also been wondering this the last few weeks since we started talking about it in your build thread.

Why don't you email the guys at Endyn and ask?

I don't think it's worth it TBH unless you're running a decently aggressive cam profile, in which case I'd do both. But funding isn't an issue for me, so if you're trying to stick to a budget (and an OEM cam of some sort) then I'd just use regular valves.

**TheSaint** · 16-08-2011 03:04 PM

Originally Posted by trism

How is that poorly worded? It describes exactly how it works, nice and simply

i agree ... sexc86 ur saying pretty much the same thing as us just in a different way - stop being pedantic

**TheSaint** · 16-08-2011 03:05 PM

Originally Posted by dougie_504

I've also been wondering this the last few weeks since we started talking about it in your build thread.

Why don't you email the guys at Endyn and ask?

I don't think it's worth it TBH unless you're running a decently aggressive cam profile, in which case I'd do both. But funding isn't an issue for me, so if you're trying to stick to a budget (and an OEM cam of some sort) then I'd just use regular valves.

im probably just going to leave it stock for now and see how it all goes down the track ... dont wanna get carried away - especially on a budget and it being my first major head/build work