If you show all the flow numbers on a graph overlapping each other then it's easier to see the difference in performance compared to one another. The raw data is too difficult to compare against one another when it's numbers on different pages. You might interpret the information differently when you can compare it visually on a graph. Also I would add up all the positives and negatives for each valve to see what the overall gain is and compare those against each other you might see a different picture.
I’ve heard Eric make a somewhat controversial statement concerning throat diameter percentages. A statement I fully agree with. I know the man can’t give it all away to us. I just happen to think he can pull some big tricks out of his hat in this territory. Something tells me he knows the answers to the questions he is asking. I think it’s smart to use this platform to gather some thoughts outside of the proverbial box. In my experiences boring throat diameters to a certain percentage is a dicey subject. I’ve been into troubled waters several times during my career in this very subject. Valve guide concentricity or lack there of sure can hurt a fellow that is trying to maintain port quality and it’s my belief that the industry utilizes this to their advantage.
Very informative- thank you for taking the time to detail all the “details”. My question is how to interpret any gain or loss of CFM to the performance of an engine. How important (or not) is 1 cfm? How much gain or loss is required to make the engine show a change- up or down? Thanks again…
Great Content, Great Work, Super Detailed explaination of the Synergy, Gains & Losses. Any benefit to Porting 832 Heads (any Exhaust Gains on 76% Ratio) on a 553 to 590 Max lift on a 416 (LS7 TI Rotating Assembly) Stroker for Low End to Mid Range "Torque" to move a Heavy 6850 lb Lifted 80's Land Cruiser
I am looking for quality air/fuel Efficiency and Endurance---not every drop of horsepower---efficient, durable endurance running engines. I am having somebody I know build my hi-perf engines, but I want somebody who does most of his work in the head and intake manifold AIR-FLOW department---someone who has the correct brain and frame of mind and energy to do it all. I want and I like being able to actually speak with the person who is actually performing the real work---Eric sounds like he's that guy.
Rule of thumb is that the larger the seat angle the more flow gains at higher lifts. This also relates to RPM in that higher lift cams accommodate higher RPM's. For instance industrial equipment such as fork lifts often have 35° and 40° seat angle with valve lifts less than .400, yet flow exceptionally well at those lifts.
@@WeingartnerRacing I'm thinking in terms of modern equipment, wear is reduced by material selection, harder valves, harder seats. Reliability is increased in the same manner to the point that valve angle becomes a function in the calculations of efficiency, complete cylinder burn, exhaust evacuation, ect. Angle may have played a large role in these two factors in the past, not so much anymore
With the 45* let’s just do what most common porters do and do 90%. Then as we get to the extreme valve jobs let’s get more aggressive with the throat size. JMO
I doubt you’ll be able to show us, because you’re running out of ports. But if you’re going to do any testing with filling in ports, can you suggest a maximum velocity when testing and when running on an engine? I’ve heard Mach 0.5 - 0.6.
Who cares about angle just round it and make a smooth radius. I only kept the valve angle for the seat and open the bowl 10% more and smoothed into the bowl. My TSP LS3 heads made 35hp more over stock, i did this on my aftermarket head before i installed them. Did the same on exhaust. Seems to work great, do guys not do this because of risk of damaging the seat. I used a burr.
You leave one angle under seat to break up fuel. You would have made more power if you had done that. Also when you do a full radius on intake you make reversion worse. The angle of the valve job lets you determine the throat profile.
Hello Sir,very interesting subject. Could you tell me please,do you work and change the valve angle only or and the the seat angle for the sealing?I do the question only for the main angle and not for the others
Hey Eric, Tim here (Dr. Bracket race)...... i was wondering if you got the head flow program, endorsed by David Vizard.....we all know him as a guru.......while ur doin these tests, the program he likes (IOP, intake optimization program) lend itself to some of the data ur after...just a thought....LOVE ur stuff!!
I have question about what type of valve job works best for gaining low end torque or is it even possible. I have a jeep tj and will be building another 4.0 straight 6. I do a lot of wheeling so any low and mid torque is ideal. If that comes into play based of cam then what would your recommendation be as a start.
I'm sending my Gen 5 Viper motor for heads and cam. The builder is opting for a 5 angle single cut as opposed to a port and polish. Is there any reason why?
I think it has something to do with the ex flow velocity is supersonic, whereas the intake flow is orders of magnitude slower. IIRC The intakes flow less on a bench with a radius from what I understand. I do recall cutting a radius 45% intake seat at the customers request back in the day, one time on a SBC 1.94 to 2.02 valve conversion. We didn't have a flow bench though.
Have you ever tried a 30 or 35 degree seat angle on a set of heads destined for street/ strip type of engine? From what ive read they flow much better from 400 lift down but the drawback is from needing a stronger spring and having to cut a groove on the combustion chamber side of the valve for it to seal better. Diesel engines are around 25 to 30 degree seats is my reason for asking and one of the most infamous names in engine building/ porting.thanks
Large diesels have 20 to 30 degrees to decrease the micro movement of the sealing surfaces against each other. It needs ti be decreased as the intake of a diesel is either not lubricate with particles in the fuel or gets a hard chrome-oxide layer as the exhaust valves get because of temperature . This oxide layer lowers the wear of these micro movements so much that a 45 degrees can be used. The 45 degrees seat angle flows much better , depending on intake port design , from 0.25" and up .
The old factory Pontiac V8 heads had 30% intake seats, with tiny ports and bowls. I think it may have been to get the most out of the tiny cross sectional ports by improving very low lift flow numbers, say from .050 to .200 lift range. Most of the cams they used rarely had over .480 lift IIRC. Then the exhaust had a 45% seat with a 90% cut directly below the seat. Really odd design decisions and I've always wondered why.
Just when you think you got a handle on things after years of trial and error, then comes along the next leap in technology. You think it's complicated now. Imagine what it's going to be like when valves aren't forced to be round anymore and they can be any shape you want them to be. The angle of your valve job will be infinite. Each valve will be machined with zero tolerance to match each specific port in each cylinder. Every valve different to match the specific performance of every cylinder because every cylinder will be optimized individually not all together in a group. In some ways we're still cavemen and have it easy.
As usual. This one was a great watch. But until the throats are enlarged and the short sides adjusted. I dont think the different valvejobs can be analyzed with any real concern.
I think a large problem is that each valve job requires different chamber profiles as well, hence the comment about not always being best suited. It’s far to much billable time and cost of a head to show the results from those kinds mods. Hey Eric…. Do you think you have a few customer heads out there that might show these mods.
I thought that "improving" the valve seat was supposed to improve the low lift flow more than anything, seems like your testing here shows this to be the other way round?
Legitimate question especially with shaft rocker arms and a set of $1200 pushrods. It can be calculated and can be done. Rocker arm ratio has to be known. Which side of the rocker arm the correction needed to be made are on. Details like head gasket thickness, machining done to the deck surface of the block and milling to correct compression ratio, all effect the length the pushrod has at the rocker arm and the rocker arm ratio must be applied to those length changes by multiplying them by the rocker arm ratio. The changes made that effect valve stem length on the “fast side” of the rocker arm must be divided by the rocker arm ratio to calculate.
@@issuesmotorsports2457 Yep. Valve stem height has to be reset (grind the stem tips) after a VG on non adj valve train for a stock engine. Of course there's a bunch of other ways to do it, not to mention the large lifter plunger travel in most stock hydraulic lifters.
I'll stick with what I recommended earlier on one of your other videos. 91 1/2% throat and 100-102% bowl. Thin and contour the guide and the short turns need slightly laid back and widened especially favoring the bore center. I like the more aggressive 45* seat because it's more along the line of what most people would be using. 50* and up would typically not be suggested on anything street driven. Chamber work will net some real results and will be interesting to see!!! Especially around the spark plug and bore-center side of the valve. Again.....thanks for laying a lot of the internet B.S. to rest!!!! And thanks again for taking the time out of your busy work to do these videos!!!!
Incredible seeing flow numbers after reading for years, the effects a valve job can make on flow. This really adds up to why the now defunct NHRA 'modified production' class cars with stock factory cast cylinder heads, allowed up to 1 inch down from including the seat, any modifications. Those things ran way better than they should have, based on what I knew back then, but now it's all adding up! Eric, in your experience and opinion, would a head flowing in excess of whats needed in the case of these heads, on say a around 600hp LS, would the increases in flow translate to increases in HP? Now lets say these heads were on a 725hp LS, it seems to me valve job flow increases would more likely translate directly in increased HP? In other words, a conventional SBC with factory head castings is VERY flow limited regarding HP above around 425. I can see huge HP gains in ANY mods that increase flow bench numbers. Would an over flowing cy heads capable engine, even respond to increasing the flow numbers? Example, a pretty much stock rec port LS making around 450hp? I'd like to see your max effort port job flow numbers within the stock (huge) valve sizes on this head. How tech has advanced since I was in the game! A stock LS rec port is better than most any 23% aftermarket SBC head available. Now port a stock LS rec port casting, and not even in the same ballpark.
I like to watch these videos to learn from. Not that I going to port a set of head . I prefer to buy that . I seen a few videos and if you get time and want to I like to hear your thoughts on the comparison between the rec port and the cathedral port heads as far as performance . Seems like I heard GM cast there heads in the rec port in a way to help the engine respond better at low rpms . Thanks for your time
Lots of folks. Small block and LS as well. Hell, I know street cars around here with well over .700 lift. Flowing at higher lifts also shows how stable the port is and if it's capable of flowing more air period.....because a running engine will draw a hellofa lot more vacuum on the port than any flowbench can simulate. Go back a few videos and you'll see where Eric explained SOME of his reasoning as well.
Go back and watch his other videos, it's well worth it....he explains why he likes the .400 lift range ( curious how AFR wins a lot of HP test with less peak flow)....and why you can see in this very test the port is dirty getting unstable then recovering just after most traditional LS hydraulic rollers ( .625 lift) and how that would affect real world power numbers....even though your not running a .700-.900 cam....he spells it all out.... Imho go back and watch every video he has put out and when your caught up, you WILL be more knowledgeable this shit is fantastic he is doing for us.... He is damn sure getting my LS7, LT or 317cc BBC heads or multiples....
