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Is it possible to use a 2.08" Intake valve on 243's?
Hey guys,
Like the post title says, I wanted to ask around to see if/how I can make use of a set of 2.08" Ferrea F1047P Hollow Stem Intake valves on a set of bare CNC 243 heads. These are going on my GTO's 6.0 LS2
The heads were described as being made for a NASCAR feeder class 6.0 LS2 spec engine, so the head specs are as follows:
Cylinder head casting number 12564243 or 799
Intake port volume 229cc
Exhaust port volume 84cc
Chamber volume 64cc
Valve guide material powdered iron
Valve seat material powdered iron
Intake valve head diameter 2.00
Intake valve length 4.960
Intake stem diameter .313
Exhaust valve head diameter 1.550
Exhaust valve length 4.965
Exhaust stem diameter .313
Valve spring installed height 1.800
My questions are:
The heads are currently cut for the stock 2.0" intake valves. What machine work would I need to have done to the heads to adapt them to the larger sized valves? Would I even benefit much from this?
The valve stems are +.100 on the overall length (5.0 overall length)according to the Ferrea website. What effect would that have on installation and use on these heads?
I'd like to use the valves if I could, if not advisable I'd probably just sell them and get a stock size valve.
Thanks for any help you can offer.
Last edited by detunedstring; 02-06-2016 at 09:40 AM.
If you change the intake seats then yes, you can use 2.08" intake valves. However, a 2.04"-2.05" is a more EFFICIENT valve in that head on a 4" bore and is what I would recommend as the largest intake valve to use. The stock intake valve diameter will make the best low end torque and still make really good top end power.
If you change the intake seats then yes, you can use 2.08" intake valves. However, a 2.04"-2.05" is a more EFFICIENT valve in that head on a 4" bore and is what I would recommend as the largest intake valve to use. The stock intake valve diameter will make the best low end torque and still make really good top end power.
I agree with this 100%
I have a set of 2.055" valves which I'm going to turn into 2.02 for this exact reason, plus they're the biggest you can go without installing new seats - typically a $175 plus a few bucks for each seat upgrade.
I guess I would have one last question now that I'm going to go with the 2.0"-2.02" intake valve.
I'm seeing a bunch of different valve overall length's advertised from the various valve manufacturers.
Not sure if the information I posted on the original post is accurate, but how can I verify the overall valve length won't be an issue?
I'm seeing that the Manley intake valves come in lengths of 4.874" and Ferrea shows 4.9". Does this factor in with my cylinder heads showing intake valve lengths of 4.96"?
Why is that? Wouldn't a slightly bigger valve which say flows 5% more from .100 to .600 make more torque everywhere?
First you have to understand what makes a engine make torque below the torque peak point.
At peak torque the intake valve is closing at exactly the correct point and trapping the maximum amount of air. Below this point it's closing the intake valve too late, which allows air to go back up into the intake port rather than trapping it, or intake reversion as it's called. And past peak torque the intake valve is closing too early or not giving the engine enough time to fill the cylinder with air.
As you make the intake valve bigger, it does flow more in the forward direction, however it also flows more in the reverse direction, which contributes to reversion back up into the intake port which causes loss of low end torque.
If bigger valves made more torque everywhere, LS3 and LS7 heads would be torque monsters, which they don't tend to be. A bigger intake valve can contribute to making good peak torque, but are not as good below peak torque due to the air being pushed back up into the intake port. This is where a smaller intake valve helps act like a check valve. This is also why we always tried to get less airflow at .100"-.200" but then tried to get maximum airflow from .300"-.500" lift.
The key to making best power everywhere is to achieve the most airflow possible per given valve diameter and bore, which we calculate using the coefficient of discharge formula. We use a very simple formula which is airflow divided by valve curtain area, valve curtain area is calculated by taking the valve diameter times Pi times lift.
For example, when we were developing the TFS 225 heads while I was at TEA/TFS back in 2005, we tested a 2.05" and a 2.08" intake valve both on a 4" bore. The sweet spot for making power with a hydraulic roller cam street head is getting maximum flow at .400" lift. With a 2.08" valve we achieved 270 cfm, which would be 103 cfm/sq in. The 2.05" intake valve yielded 280 cfm which is 108 cfm/sq in, so we went with the smaller valve.
We developed the 225 head for LS2 engines, however TFS ended up testing them on a 402. They put them up against the AFR 225 heads that have 2.08" intake valves and flow about the same at higher lifts as the TFS 225 heads. In back to back testing the TFS 225 heads made 20 hp more than the AFR 225 heads, which is a ton of difference in back to back testing.
We saw the same thing when we finished the TFS 235 heads and tested them on a 440 cu in engine back to back against GM LS7 heads. The LS7 heads flowed more air everywhere, the TFS heads made 20 hp and 30 tq more power.
I've been preaching coefficient of discharge for almost 20 years, but no one seems to be listening...
Thanks for the explanation Brian, very helpful. Going one step further in trying to limit said "reversion" which lowers power before peak torque...wouldn't changing and perfecting the valve events help offset that issue somewhat?
So with the right cam, you can have just as much torque up to peak with a 2.08 as with a 2.00 (by limiting reversion) but then have more peak and more past peak due to the increased size and flow?
Thanks for the explanation Brian, very helpful. Going one step further in trying to limit said "reversion" which lowers power before peak torque...wouldn't changing and perfecting the valve events help offset that issue somewhat?
We can crutch overly big ports and valves using the intake valve close event, we close it a few degrees sooner than we otherwise would. However the lower you go in RPM, the greater the loss in torque when using larger intake valves. There's just no way around it in the real world.
Originally Posted by redtan
So with the right cam, you can have just as much torque up to peak with a 2.08 as with a 2.00 (by limiting reversion) but then have more peak and more past peak due to the increased size and flow?
This would be assuming that bigger valves make more power, which in a hydraulic roller cam street car they generally don't. If they did, cathedral port heads wouldn't have a chance against the square port heads.
If you look at the fastest hydraulic roller cam'd cars in America, most have cathedral port heads. Look at the examples of back to back head testing that I mentioned earlier, where the heads with smaller valve made more power everywhere. Once you start to understand how and why this happens, you're well on your way to better understanding of what makes cylinder heads make power.
Falling back into this bigger is better mentality means you completely ignored my dissertation on coefficient of discharge, which everyone seems to ignore... lol
We can crutch overly big ports and valves using the intake valve close event, we close it a few degrees sooner than we otherwise would. However the lower you go in RPM, the greater the loss in torque when using larger intake valves. There's just no way around it in the real world.
This would be assuming that bigger valves make more power, which in a hydraulic roller cam street car they generally don't. If they did, cathedral port heads wouldn't have a chance against the square port heads.
If you look at the fastest hydraulic roller cam'd cars in America, most have cathedral port heads. Look at the examples of back to back head testing that I mentioned earlier, where the heads with smaller valve made more power everywhere. Once you start to understand how and why this happens, you're well on your way to better understanding of what makes cylinder heads make power.
Falling back into this bigger is better mentality means you completely ignored my dissertation on coefficient of discharge, which everyone seems to ignore... lol
What about the EMC stuff that seem to do well with a big valve and a small port? I know it's not exactly apples to oranges, but the Hemi's that blew away everyone else had horrible discharge coefficients.
What about the EMC stuff that seem to do well with a big valve and a small port? I know it's not exactly apples to oranges, but the Hemi's that blew away everyone else had horrible discharge coefficients.
The EMC stuff is unique, and it's interesting that they test smaller valve stuff, get better average numbers, and then take the big valve stuff to the shootout.
I don't know how a Hemi would have bad CD, the Hemi stuff that I had on a flow bench was better than the best wedge heads that I've ever seen. I saw a 5.7 head with a stock 2.00" intake valve flow almost 300 cfm at .400" lift! Lack of shrouding like a wedge head helps the Hemi stuff a lot.
The EMC stuff is unique, and it's interesting that they test smaller valve stuff, get better average numbers, and then take the big valve stuff to the shootout.
I don't know how a Hemi would have bad CD, the Hemi stuff that I had on a flow bench was better than the best wedge heads that I've ever seen. I saw a 5.7 head with a stock 2.00" intake valve flow almost 300 cfm at .400" lift! Lack of shrouding like a wedge head helps the Hemi stuff a lot.
Well, for a hemi they were bad. IIRC, the first time they competed with the Hemi, Bischoff took the smallest Hemi port and shrunk it, but put in a 2.20" valve and stock it in a 3.9" bore.
Then the Ford Mod motors came in and just prison raped every two valve engine ever. A lot of people were saying it's all about getting the most valve area possible that gets the best score.
Any advice on the overall length of the valves? Like I said, I'm seeing varying lengths advertised from Manley and Ferrea. Not sure what to go with here in terms of what I should order and what machine work should be done.
Any advice on the overall length of the valves? Like I said, I'm seeing varying lengths advertised from Manley and Ferrea. Not sure what to go with here in terms of what I should order and what machine work should be done.
Thanks for the help guys.
I don't think an extra .010" or so will make a big difference. I think the tolerance for stem protrusion was like +/- .010". If you're not replacing seats, I'd err towards the shorter OAL since the machining will sink the valves. If you are replacing seats, then get a longer OAL since the new seat could decrease free drop.
Thank you Brian, for dropping some science on us, once again. People seem to get all dick-high over the bigger is better attitude, and conveniently forget that it has to all work together as a system.
To the OP, sorry you can't (or at least shouldn't) use the valves you already have. It sucks when you have to sell something you were hoping would work. But you have some solid heads, so replacing valves isn't too bad. As stated earlier, I think what KCS said in relation to the valve length and whether or not new seats are being installed is the answer to your question. Longer valves are probably meant for new valve seats, and shorter valves are probably for older (possibly worn) valve seats. I'm not sure is valve seats wear down, or settle deeper into the head over time, but what KCS said makes perfect sense.
If you change the intake seats then yes, you can use 2.08" intake valves. However, a 2.04"-2.05" is a more EFFICIENT valve in that head on a 4" bore and is what I would recommend as the largest intake valve to use. The stock intake valve diameter will make the best low end torque and still make really good top end power.
Brian,
How would a 2.08" valve behave on a 4.070" bore? Would the extra bore diameter be better with the larger valve?
02-06-2016, 09:21 AM
Is it possible to use a 2.08" Intake valve on 243's? 
