slate blue

The thread the other day about the valve sizes in the 2 valve heads gave me an idea. When we did our porting development, I told them not to increase the size of the port that the manifold bolts to. The reason was to avoid the custom aspect as this at the time was a budget build up. Unfortunately the budget bit has changed.

The engine will now have its billet stroker crank and a semi to full custom intake, I mean why not when everything else is custom

So what was interesting was that Porsche increased the port size with the increase in valve size. It makes sense that if you proportionatly increase the port size with the valve size your flow should also increase at the same rate.

What we found when developing the head was that while the flow increased it hadn't increased in the same percentage as the valve area. Now I do still have the development head, I think if I increase the port to 49 mm from the 40 to 41 it is now then we may well see some increase.

For those who don't know what we had this was the baseline for the intake side. At 0.500" we had 211 cfm and 216 cfm at 0.600" with the big valve we had 275 cfm at 0.500" and 300 cfm at 0.600". Now given that we only have 0.550" of lift, the 0.600" is irrelevent and as such the figure at 0.550" is approx 288 cfm.

Now if we actaully managed to get a directly proportioned increase in flow by increase the inlet port size we would have 305 cfm or max flow of 625 hp. That is significant as the 4 valve strokers have about 330 to 345 cfm in well ported heads so I'm not that far behind, especially since the Porsche 2 valve head is still a high velocity port.

So whereas the 4 valve strokers can achieve 575 rwhp I think that 500+ will be possible for my 6.0 liter 2 valve engine. That from an old 2 valver will be great and plenty of power for me. There is one problem I haven't solved as yet and if anybody can help me out please speak up.

The valve seat material for this engine is proving very difficult to procure. What I require is a copper infiltrated powdered metal seat. I will use the same material for both the intake and exhaust seats as they are siamiased.
The one company I have a lead with is this one, Valve seats JP 25 If you look at the material make up it has lots of iron and copper, I think this is good for the Ti intakes. Del West say that standard Ti valves should run on a seat material harder than Rockwell C 32.

The thing about that is, my valves have a Cr Nitrided finish and also they run light spring pressures, both of whic a Del West engineer said are going in my favour. They couldn't tell me who supplied the valve seats to Chevy for the LS7 engine, nor could Federal Mogul. So what do the engineers on the board think of the hardness of JP 25? Any help here anyone?

Now 305 cfm from a 2 valve Porsche head, I want to see that. Along with my Honda stroker crank in about another 2 months!!!!

Cheers Greg

Rick Carter

Is there a reason you don't want to use Berylium?

Chuck Schreiber

I thought Lindsey Racing was getting a lot out of their heads
http://www.lindseyracing.com/Merchan...de=944CYLHEADS

Sounds like you are rocking and rolling there Greg!

slate blue

Berylium wont last as it is too soft, rated Rockwell B, when Chevy certified the LS7 engine for emissions that meant that that engine should last at least 150K miles, well the Berylium ones wont. i want those Chevy ones.

I think our numbers are roughly the same for the stock head so I suppose we are beating them. The thing is that they have concentrated on using the stock valve and turbo work. I was thinking about using a bigger Porsche valve for my current engine but in the end thought why bother, everything will be done with the next engine. My heads for this current engine (5.0L) flow about 237 cfm at 0.500", you have to remember it was only a $200 port job so on a bang for buck basis that is pretty good.

I'm hoping for 300 rwhp on a Dyno Dynamics machine.

IcemanG17

Greg
I want to say the new Z06 LS7 heads flow 360-370 cfm? Granted this is a pretty race oriented engine...but it is only a 2 valve...

I want to say the stock 928 4 valve head flows about 270cfm.....which is quite good considering the viper V10 is only 205!! But 8+ liters of displacement make up for alot!

drnick

greg, are you saying that simply increasing the port size gives proportionaly more flow without changing the valve size? what would you do to a set of S2 heads if you didnt want to spend a fortune on them and were going to put the spider intake on, say with cis injection??

BC

The valve size always needs, obvously, to be a certain ratio/percentage of the port size, even though the port size can many times vary from one end to the other end.

There is also the ratio of Valve size to bore size. A. Graham Bell talks about this.

slate blue

IcemanG17Well for a start you are correct about the Chevy flow figures, I have 360 cfm and what you need to remember here is that that figure occurrs at 0.591" lift wheras I only have 0.550" they are also able to use a larger valve 2.20" V 2.10", they also have a larger bore which gives them an advantage.

The S4 flow figure if I'm not mistaken is at 13 mm of lift or about 0.525" so that is not a normal lift figure for an S4. Infact I have never seen one so big. The GT3 cup cars only use 12 mm.


Cheers Greg

docmirror

Greg, valve lift looses a lot of value once you get much beyond (Valve lift = port dia X 0.25). further increasing lift doesn't do much for CFM, and it's starts to get pretty costly on valve train actuation and wear. The chevy lift is already over that value, and so is the 928 with the 2.1" valve face.

Curves play a part in the flow characteristics, which I'm sure you know very well.

Doc

slate blue

Hi Doc, thanks for your reply, I did post the actual early flow charts, unfortunately I couldn't get them to be hi res. Anyway what was happening with the 928 head was that the flow was increasing dramatically with lift and valve size. I know this is not always the case as with valve shrouding in the bore and peak flow reached with valve lift. This couldn't have been better demostrated than with the stock head.

Which was 0.500" 211 cfm and then only a small increase of 5 cfm when the valve was opened to 0.600". Now this was not the case when we modified the head. At the same figures it was 275 cfm and 300 cfm demostrating real gains when the lift was increased. In fact when the valve was removed the port was flowing in the high 300s.

Remember Nascar lift is 19mm or 0.750" Formula one cars also have very high lift figures. So what you say is correct in many circumstances but in this case gains were being made. I take your point on the wear aspects, let me address that.

Piper ground the cams with wear in mind and wouldn't go any farther, the lifters will be DLC coated and the valve train weight has been decreased dramatically. As follows.

Old valves 108 grams
New valves 70 grams

Old Retainers 32 grams
New retainers 12 grams

Old Springs twin coil 32 grams
New springs Comp cams beehive 10 grams.

The new springs have a rating within the lift figures and provide approx 60 pounds of seat pressure on the intake and 75 pounds on the exhaust with approx 260 pounds of open pressure for both. I'm hoping that will be enough given the lighter weights in the valve train and that I don't want to pound away my Ti valves.

Lifter is the same at 100 grams, the DLC lifters will save both wear and power robbing friction said to amount to upto 2% of power.

I could if I have to go to solid lifters and save another 50 grams, this would be a PITA. I will avoid this if I can. I'm after 7500 rpm limit, the bottom end will do that safely. The top end is in question, the valves at peak rpm will go from 53 cycles per second to 60, that in itself is not the problem, it is more the lift. It has gone from 12 to 14 mm on the intake and 11 to 13 mm on the exhaust.

Cheers Greg

slate blue

Dr Nick My spider is modified If I happen to beat Mr Kibort on the dyno, that will be one of the reasons. I will post pics of this at my victory post No I am not saying to increase the port size without increasing the valves, infact I am saying the apposite. We achieved our big flow with a standard sized port and large valve. I just think that increasing the port now will result in even bigger flow.

Cheers Greg

918-S

this site says Federal Mogal has um...

http://www.federal-mogul.com/en/OETe...ValveSeats.htm

Are you saying Federal Mogal doesn't supply the seats for the chevy heads or they don't sell the seats your looking for?

slate blue

Federal mogul wont sell these copper infiltrated seats to the public, only the OEM market. I have tried there unfortunately.

Cheers Greg

918-S

That sux! Who is doing your head work? You mean they won't sell these to a machine shop on a whole sale purchase for repairs to a damage head? I find that hard to believe.

slate blue

I mean they wont sell to you unless you are Ford GM or Chrysler, Toyota etc, I dealt with Fed's local aftermarket rep, he contacted the states and they said no deal.

Cheers Greg