for you guys with too much money!
Discussion
Edlebrock are doing some canted valve heads and GMPP now have their LSX-DR heads which apparently flow over 400cfm from monster ports.
So some absoultely spastic stuff available for the LS platform now. Over 1000bhp easy with the right bits. Just read an article about a 900bhp NA setup a few days back. I think 18:1 compression though.. not streetable..
So some absoultely spastic stuff available for the LS platform now. Over 1000bhp easy with the right bits. Just read an article about a 900bhp NA setup a few days back. I think 18:1 compression though.. not streetable..
I think there's some pro's and con's to all these massive flowing heads......massive ports alone aren't condusive to big hp (big compression, big valve-train please). These 32 valvers are good in theory as they flow huge numbers without going to crazy with port volumes. I just have a feeling that the valve-train gear will be a weak point as 2 valves are opened by a single push-rod, I've never had any dealings with anything similar before, i just think the push-rod and cam lobe load will be immense. Not heads for a massive lift cams and prolonged high rpm ranges by any means. However, easy big horsies for milder combos as big cams aren't necessary with heads that have dynamic low-end flow like these babies.
TTLS1 said:
I think there's some pro's and con's to all these massive flowing heads......massive ports alone aren't condusive to big hp (big compression, big valve-train please). These 32 valvers are good in theory as they flow huge numbers without going to crazy with port volumes. I just have a feeling that the valve-train gear will be a weak point as 2 valves are opened by a single push-rod, I've never had any dealings with anything similar before, i just think the push-rod and cam lobe load will be immense. Not heads for a massive lift cams and prolonged high rpm ranges by any means. However, easy big horsies for milder combos as big cams aren't necessary with heads that have dynamic low-end flow like these babies.
Yes a much more sensible approach to street use.Here is a light afternoon read for anyone interested in an all out NA setup http://www.maxchevy.com/tech/2009/iv_1-lsx-1.html
Not a bad idea...
Due to the way valves work it's the circumference length that is more important than the overall size. A big advantage of 4 valves over 2 is that this value is larger for a given area taken up with valves.
I don't see a massive problem with the single pushrod. If it's done properly (and thats a big if) then the two smaller valves should be lighter than a single large one, thus requiring less spring rate and therfore a smaller force (per valve) to operate. It obviously remains to be seen if operating the two smaller lower sprung valves is significantly more than a single large valve but the potential is there (esp if the valves could be made out of more exotic material such as titanitum but then you get other issues like thermal expansion diffrences but the priciniple is sound.
The big gains would be in forced induction - you could run substantually lower boost and get the same power as the air would be moved by the supercharger more efficiently.
If the £/$ rate was better then maybe but not at the moment.
Due to the way valves work it's the circumference length that is more important than the overall size. A big advantage of 4 valves over 2 is that this value is larger for a given area taken up with valves.
I don't see a massive problem with the single pushrod. If it's done properly (and thats a big if) then the two smaller valves should be lighter than a single large one, thus requiring less spring rate and therfore a smaller force (per valve) to operate. It obviously remains to be seen if operating the two smaller lower sprung valves is significantly more than a single large valve but the potential is there (esp if the valves could be made out of more exotic material such as titanitum but then you get other issues like thermal expansion diffrences but the priciniple is sound.
The big gains would be in forced induction - you could run substantually lower boost and get the same power as the air would be moved by the supercharger more efficiently.
If the £/$ rate was better then maybe but not at the moment.
Spring rate & size is usually more indicative of the need to close the valve faster, stopping it floating under high rpms ..or to assist them closing under high boost applications. If you're intending on still making good hp you'd still need healthy springs whether or not on 2 valves or one. I can see you're point though, as the cam profile does not need to be as aggressive to make the same power and new valve technology, ie: hollow or lightweight valves will help to close them with less seat pressure.
I've often wondered about this boosttheory holding valves open. I'd have thought that pressure in the cylinder would be pretty equal to pressure in the port in which case the spring would be more then man enough to close the valve. Once closed, pressure in the port wouldn't be able to overcome cylinder pressure acting on the valve face. I suspect float is more about valve bounce and they all do some of that especially if you use those extra rpm's boost gives you 
yeah, it really depends on what type of boost and how much....any engine with 15psi and above will experience diificulties. A blown small block with 15psi running at around 5500 rpm will require 50% more force to keep the intake valve seated.
When talking turbos it's slightly different as any backpressure crated in the exhaust manifold will attempt to open the exhaust valve on the intake stroke much the same as boost on the intake side will.
When talking turbos it's slightly different as any backpressure crated in the exhaust manifold will attempt to open the exhaust valve on the intake stroke much the same as boost on the intake side will.
I was thinking that any pressure in the cylinder will be matched to any pressure behind the valves while they are open. Whilst a valve is open there isn't any real pressure acting upon the rear of it, it's open. Pressure, be that exhaust or inlet will move past the valve into the cylinder. Once closed cylinder pressure is massive compared to any pressure in any port.
Boosted LS1 said:
I was thinking that any pressure in the cylinder will be matched to any pressure behind the valves while they are open. Whilst a valve is open there isn't any real pressure acting upon the rear of it, it's open. Pressure, be that exhaust or inlet will move past the valve into the cylinder. Once closed cylinder pressure is massive compared to any pressure in any port.
that's all well and good but we're talking about valves that are seated not open. stocko springs aren't going to keep the valve seated when you've got high psi (15+) in the intake port and the cylinder is at exhaust stroke and vice-versa when you have back pressure built-up in the exhaust manifold?But on the exhaust stroke you have high exhaust pressure in the port/manifold (it's probably there most of the time). Pressure in the exhaust port and cylinder would be equal or maybe greater then the inlet pressure acting on the back of the closed inlet valve. This is also the energy that drives the turbine so we know it exists. This pressure acts against the inlet valve face and helps keep it seated once already closed. If the intake valve is open exhaust gas would/could contaminate the intake during scavenging. Equal pressures across the cylinder would mean no change to the valve actions. Even when the exhaust pressure has blown down a bit and I'm not sure it does the inlet pressure isn't enough to unseat the valve but by then it's already opening.
On the exhaust side of things, during the intake cycle the cylinder is filling with air under boost pressure which I believe would help to counter any pressure behind the exhaust valve. Don't forget the exhaust valve has a smaller head and force is proportional to area.
Tiz still a bit of a mystery to me
I suspect it could be that FI allows an engine to rev up so much quicker that the valves bounce more uncontrollably and springs become weak so going for stiffer springs is usually a good thing to do anyway.
On the exhaust side of things, during the intake cycle the cylinder is filling with air under boost pressure which I believe would help to counter any pressure behind the exhaust valve. Don't forget the exhaust valve has a smaller head and force is proportional to area.
Tiz still a bit of a mystery to me
I suspect it could be that FI allows an engine to rev up so much quicker that the valves bounce more uncontrollably and springs become weak so going for stiffer springs is usually a good thing to do anyway.
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