foreign [Music] here and you guys are watching Powertech 10. give me a few minutes of your time and I will give you the benefit of over 60 years of building race winning engines in this episode going by up there we are going to delve into part four of rule number one and basically this involves valve seats valve shapes and Port design foreign the valve seat just a basic valve seat and then we're gonna plow them from there it's a good a place to start as any is at the basic performance voxy so follow along with this upcoming diagram what we have here is a 30 degree Top Cut a 45 degree seat then a 60 degree cut or a radius the radius being preferable below that that's the green section we have a 75 to 80 degree cut now that will serve as a good starting place for the valve seat design so how important is the valve seat number one important factor in sauna had design especially at low lift and especially in an undervolved engine which almost all V8s are so let's focus on this next diagram and I'll go through how the efficiency of the bouncy changes with design at position number one we have a sharp edge and the diameter of the valve's throat is the diameter of the valve in other words we've got the largest hole possible that a valve could theoretically seal up in you'll notice the efficiency is not very good 45 percent Now we move on to number two that's just a plain ordinary valve seat typically of about sixty thousands wide on what we would typically find for a V8 engine right efficiency goes up to about 57 still not very good number three we do a lead-in a 60 degree cut below the 45 and the efficiency jumps to 65 percent at number four we do a top cut a 30 degree Top Cut and the efficiency jumps up to 70 percent then we do one of these really fancy ones as in five and that is a lead out of the sea a 30 degree Top Cut 45 degree seat 60 degree bottom cut and it's Blended in that gives us about 72 to 73 and that's about it now it can improve on that with super trick seats but out of the box for just putting a seat on that's what you can expect now before we go much further I should Define some terms that I commonly use one of the most important of these is what I mean by the 0.25 D lift or the quarter D lift so let's take a look at the diagram here so looking at the diagram we see that the valve diameter is represented by the letter d and it should be easy to see that the quarter d ipped is a lift that corresponds to a quarter of the valve diameter that means if we've got a two inch valve the quarter D lift would be five hundred thousands now you may well ask well so what certain things happen at a quarter day left in terms of flow if we do not know about them they can we could be sacrificing a whole load of top-end flow figures this phenomena is what makes Pro Stock Motors so effective in terms of making a horsepower from what looks to be limited valve area so let's move on and keep that quarter D factor in mind oh that was one thing I wanted to mention here about that quarter D lift at the quarter D lift the curtain area around the valve equals the area of the valve now it does say on the diagram but the thing we need to note here is that at a quarter D lift the area that the valve could present to the cylinder cannot get any more because the curtain area will now exceed the valve area right and technically or to be more accurate we reach that limit of area sooner because if we took the throat diameter we would find that it would reach the quarter D point after the area had ceased to increase from valve opening let's talk about seats a little more here so what I want to do now in this next section is talk about valve seat angles so let's how about it take a look at the diagram in the right here you will see two valve seats one the top one a 45 degree seat and the lower one the 30 degree seat now it's not commonly realized that if you lift the valve say fifty thousands as shown here the gap between the seat of the valve and the cylinder head does not end up at 50 000. 45 degrees C lifted 50 000 gives us thirty five thousandth gap between the seats whereas a 30 degree seat gives a 43 thousands Gap now you may well think why don't we use a 30 degree sheet because it will present area breathing area to the cylinder faster well we'll get to that in a moment but for now let's take a look at the diagram on the left what we see here in the area indicated is the Improvement of 30 degrees heat gives in the amount of area that it presents to the cylinder this gain in area decays as the lift gets higher and higher and by the time you get to about 250 thousands left there's not a lot of difference between the two but it initially gives a huge increase in low lift flow and that happens in practice now the theoretical line based on the OD of the valve is shown in red that's simplistic form what I'm showing here with the 30 degree over 45 degree area is what happens in real life because the areas presented go through three different phases that's where it's a funny shape like that and it doesn't become a fixed formula until the lift on a typical V8 engine is passed about 250 300 thousands here's an example of a well-developed 30 degree seat as for flow efficiency as a seat like this will at low lift deliver over 80 percent flow efficiency so it's well worth considering but it comes with its own set of drawbacks so what are these drawbacks that we have to uh uh address and they're relevant to valve seat angles well this all cropped up while I was doing research for anti-reversion valves for my a series Mini Engine that's the original Mini Cooper I was racing on at the time and I certainly couldn't afford any of these fancy cosmith engines to put into it which were costing more than my house cost but that meant I had to research the iron based rice engine using the original type head modified extensively and one of the things that became apparent was that valves tended to leak at high RPM without necessarily showing any signs of such and here's how it happened the a series engine can suffer quite a bit of reversion due to the Siamese ports on it no one port feeds two cylinders and um so what I did was I designed a valve which on the flow bench had a very bad reverse flow and it involved cutting a Groove in the valve face as per this shot that I'm showing over here it causes a it gives a ridge on the side of the land that any flow trying to go round the valve and out has a very poor shape a very unstreamlined shape which inhibits the flow Cuts reverse flow by quite a bit but another thing it also does is it makes the seat flexible hadn't occurred to me at that moment in time anyway when I Dyno tested these valves they really worked at low RPM they added something like a thousand RPM of usable RPM down at the bottom end of what was normally the power curve so you know this motor came on the cam at about 3 500 before now it came on the cam at 2500. so at 2500 rpm up to 35 or 40. 100 RPM the torque was up considerably mid-range it didn't change now much to my surprise when I got to Peak power the engine didn't drop off in the normal way it kept on going and I achieved well no the engine achieved about five horsepower more and about a 500 RPM increase in usable RPM range this puzzled me why because there was no indication of any reversion at those RPMs but it must have been curing something so I had to look into it and that's what I did over an extended period of time I investigated what the situation was with valve seats and seat flexibility as time went by more and more evidence for this leakage Theory turned up it didn't prove it but it did indicate in a stronger fashion each time a little bit of suggested leakage was cured but anyway before I get to that let me backtrack and show you what a 30 degree seat will do and how the fix that I had for anti-reversion also applied to leakage first a look at our 30 degree seat flow gains well it doesn't take much to see that the gain at low left was as much as 21 percent off the seat and at fifty thousand twenty one percent up that is a big gain what it does is it makes a two inch valve look like it's actually 2.4 inches try stuffing a 2.4 inch valve into a typical small block Chevy but the gains only hold good to about 300 thousands and I'm talking about typical V8 there after that it's not a lot to do with the seat it's almost all to do with the port so the flow let's get back to our leakage situation and how it pertains to various valsy angles to understand why we may get valve linkage even for apparently perfect vouchy job we need to investigate what happens to the cylinder head as it expands from the heat generated by combustion well here's the diagram this was developed from work I did during my tenure at UNC Charlotte now what we did was we measured the temperatures on a running engine I think I did that in my shop and then I used a computer program that the university had to generate the form that develops as temperature variations across the width of the chamber distorted now I want you to study this diagram carefully note that between the exhaust valve and the intake valve there's High expansion low expansion on the other side of the intake valve also the center line of the uh valve guide changes right so it actually wants to move the valve over slightly at an angle also the sheet the and I'm just talking about the intake seat here also the seat is ovalized it becomes more egg-shaped than anything and of course this is greatly exaggerated on this drawing I think the ratio was a hundred to one or something or even 500 to 1 on the on the drawing also the seat gets higher on the intake valve adjacent to exhaust whereas the exhaust seat gets lower there because it's cooler right so there's a lot of distortion goes on there now we need to cut our seats not to be super accurate when they're sitting on the bouncy machine but super accurate when they're actually being run under full power well we might be asking too much of them well if our valve seat form isn't enough to contend with consider this just worsens the situation if you take a look at a valve or a valve train being run on a spintron with high-speed photography you will see that the valve both the retainer end and the head end wobble around like they're made of rubber now I kid you not I have seen as much as a 16 inch deflection at the valve tip end on the other hand is usually less at the valve head usually not always I mean I don't have enough experience to say how common one is compared with the other but it is easy to have the valve head 10 or 15 thousands off center the moment before it hits the valve seat what happens is it has to when it hits that valve seat it has to slide down it right now then if that valve seat is not a steep enough angle the friction level will not be overcome by the wedging action of the valve hence the use of 50 and 55 degree seats they work parking because they give more high lift flow than a 45 degree seat and partly because they seal better I don't think many people have taken this ceiling uh aspect into account but anyway the trick is can we get a flatter angle to seal as well well the answer is yes it takes a bit of work but we can do it so hence that 30 degree seat which has very poor self-centering action compared with a 55 degree seat can be made to work so earlier on I showed you a diagram face on the valve with the confirmation Groove around it well we find that almost any valve benefits from having this groove because not only does it sort out and reduce reversion but also it will make the valve seat more flexible so that it can conform to an outer round seat a 30 degree seat the use of a 30 degree seat virtually demands This Groove diagram over there and it's not a bad idea to to apply it to either a regular 45 degree sheet and it will help power and I've done it once on a 50 degree seat and it looked like it was slightly better so it has almost Universal application but to be honest for a really effective seal we need to go slightly further and I'll look at that in a while for now let's move on to valve forms as that can be a very significant factor in our airflow I think it's pretty common knowledge that the simplest thing you can do to any valve especially a 45 degree seat valve is to cut a small 30 degree back cut on it this helps streamline the back of the valve into the seat when I'm doing a cylinder heads for my self or clientele I get most of the valves I use either from foraya or manly between the two of them they have almost always got an off-the-shelf valve that works and if I don't have The Good Fortune to have the shape I want off the shelf Freya will make them up for me now what we find is if we look through the high performance valves we find that they tend to go from the valve shown here on the right to the valve shown on the left that's the span of their range you may see a small difference in the back of the valve and another factor is you will find that exhaust valves have a larger diameter from the back of the valve into the stem that's so that they can conduct heat away faster now let's look at some valve shapes that cover the extent and some that you may not have seen before the valve to the left is what is most commonly used in a high Performance Engine which has a shallow downdraft angle typical Chevrolet Ford Chrysler engines of the 60s 70s 80s and into the early 90s maybe LS engines as well the center valve is what we will use mostly on engines with a steeper dandruff Port than average probably something like a late model Chrysler Hemi the back angle on that is about 18 to 20 degrees whereas the one on the far left is typically 12 degrees now let's move to the valve on the right this was a purpose design valve which I did for my British Touring Car Championship Avenger we had a lift limited to 390 because that was the spec the advantage of this valve is that I could blend the back of the valve into the sheet at 30 degrees so there was no back cut on it the valve shape itself was an entire back cut the other factor is the port on the Avenger was a relatively steep downdraft angle that valve worked very well especially at low lift so what happened was it made the engine think that the valve was opening far faster than it really was and believe you me the cam I designed for it was opening it fast already although we're only looking at a valve of about 1.65 and a lifter 390 I had a valve spring preload on the seat of about 180 pounds and over the nose of 440. why because I was turning that SOB to 11 400 RPM pretty high RPM for a road racer in fact I was turning more RPM on this thing because we're doing with their their bdas and bdds and so on one thing about that spherical shaped back on that valve is that outside of testing on my Avenger cylinder head which I did considerable amount of airflow work I did not or have not used it on anything since so there really needs some more exploration done there Charlie call to duty okay a changing subject here I'm going to start talking about bowls and ports and although this is part four of rule number one which is find the greatest restrictions and eliminate those first it's going to merge into rule number two which is as you see over there essentially this rule says let the air go where it wants to go and you'll see that start to blend in with what I'm going to tell you next so here we go down to Basics here is an absolute basic portrait well here's our basic board shape it's essentially a round Port from one end to the other in reality every port is based on this with certain variations and that's what we're going to look at now first and second drawing in the column here is our basic Port looking at it from above and from the side now there it has been said many times that around whole flows more than any other shape however whoever said that or whoever tells you that has not allowed for the fact that an engines Port has to have a curve in it and a valve at the end of it and that rewrites the rule books right there so what we are going to do is to see how we can manipulate the port shape over that basic Port shape to make it work better so let's drop down to the third drawing on that list in the next diagram down you'll see that the port floor has been raised and it's made to short side turn much bigger now you can be forgiven for thinking that's got to help the flow but no just doing that look actually cause that port to flow less why because we reduced the cross-sectional area at a point where it actually needs more area making raising that pork floor has caused the speed to go up and so it still detaches itself from the floor of the port so the Big Radius did nothing however this is where the domino effect comes in what we do now is to widen the port which is the next drawing down which is what we've done there we've widen both sides of the port now as an isolated Port that will flow well but nearly all of the ports we're going to do now I should say all of them I've got a cylinder to feed and there's going to be a cylinder wall on one side of the valve so what we do is we bring the enlargement of the port across to the cylinder wall side because the air is going to go out of that at an angle and you'll see how I mean in the upcoming drawings what we're going to have is a diagram showing why the 0.25 D point is important so let's just move on to that now just to refresh your memory here here's the 2.25 D diagram again and this is how it affects flow you will see that the majority of the flow at a lift figure above 0.25 D starts to window out towards the center of the cylinder this causes the flow efficiency to go up and just so that you know exactly what I mean by flow efficiency that's the simplistic name for the discharge coefficient and let's have a look and see just how we can make that flow go up by biasing the port actually on the diagram it's biased this way how we can buy a support to take advantage of that windowing effect and you'll see that the flow efficiency can climb to way higher than it was at when it was at the 0.25 D mark so here's a diagram what you're seeing here are the discharge coefficients of a dart Chevy head that I ported some time back now I want you to notice that it has high flow efficiency figures compared to those flow figures I showed earlier on and I'm talking now about the low lift as the lift goes up you can see the efficiency drops off until it reaches the bottom of a hook that Hook's indicated now at that point you'll notice there's two vertical lines on the graph a red one and a blue one these represent the 0.25 D lift of the valves in other words at that red line and blue line the valves are a quarter of their diameter in lift now at that point you'll see that the efficiency swings up that is because I've taken advantage of that windowing effect that happens at high lift and that is all there to getting the uh the bias on the port right in other words we're trying to lean that port we're trying to lean that Port either this way or that way depending it towards the center of the cylinder when we get that right things really work out well for us when I'm flowing Pro Stock heads these are the kind of efficiency figures that I see and for what it's worth I've seen a Pro Stock had up to 90 plus percent efficient in flow let me make a point here that's higher than virtually every F1 head that I've ever flowed now a comment here you'll notice that the exhaust climbs at a steeper angle than the intake does well that is because the exhaust favors bias far more than the intake in fact the bias on the exhausts of most cylinder heads is barely enough uh there comes a time when the bias needs to be about let me see let's put this in terms of as much as 25 of what the valve is right that's that's a lot now I'll give you an idea of just how effective that can be my friend David Anton at apt specializes in modifying mini heads and they're five port and the exhauster right angle things like this the worst Port you could ever have or the most basic you could ever have and he puts just a ton of bias into those ports it's a pretty delicate job and I've tried doing it have not got there but he has achieved 88 discharge coefficient from where the world's worst exhaust ports so Lely because of attention to bias [Music] although we haven't come to the end of the line on Bowl work at this point I feel it's necessary to turn our attention to the actual main body of the port again I'm going to use the cfd drawing which shows the path of the air I must admit I'm getting some really good mileage from this joint so here it is at first sight this generous short side radius looks like it's a good deal but there's a little more to it than meets the eye here if you look carefully you'll see that the flow just starts separating from the port about an inch in from the manifold face by the time bulk of the air has got round to the seat the boat flow Direction is over a quarter of an inch away from the seat so the flow has basically broken away from that turn now just how imagine how it is with a typical port with a short side term which is probably only one third of that radius well is it any wonder that the valve does not flow very well on that side now let's look and see how we can make this such that we apply rule two and that is let the air go where it wants to go not where we think it should go so how can we modify this port to more abide by that rule well first off look at the arrow which shows where the bulb flow goes what we should do is try and apply a port which follows that line so let's move on to the next frame here watch carefully the support transforms from its original curve shape to a much straighter shot to the back of the seat now there were some constraints I applied here in as much as the port had to start at the same place and end up in the same position at the valve as the original on the face of it it looks like all we've done here is make a straighter shot to the bulk of the port but the final inch or so still has the same radius that Port originally had now if that Port the parallel bit is more effective what's going to happen there is that the air could come scooting across and where it starts to curve sharply it will separate quicker and therefore that straight Port may not be the answer to the job what we've got to do here is get it around the corner that's what a porter does a good portrait is good at getting air to go around the corner and I'm talking about going around convex turns not concave of course you can get it to go around the long side it can't do anything else the short side is always the problem what can we do here well I'm going to start a little story right I'm sure you've heard of speed bumps well I'm going to introduce you to a speed bump that is nothing like the ones that you know about right so let's take a look at that now I should mention before going into details on this speed bump that this will be a technique you will apply after you have widened the port at the region around the bend as shown by that previous uh diagram where we went down a list of the progressive modifications until we came to the very last one which had all the bias on one side now after the port's been widened to what you think is going to be the limit of any benefit you'll still find that in 99 of the cases that the air is still going too fast on the floor on the typical V8 engine port only those that are very sophisticated will have little trouble at this point but for 99 of the heads out there they will still be too fast over that short side turn so this is where our bump comes in now what you're going to see next is a mid War years biplane and I've never been able to find out what the correct way of pronouncing the name is whether it's a wacko or a Waco right but a friend of mine had one of these and he spent a seven figure number on having it restored well there I went to see it the day after it came back to his home which had its own Airfield at the back by the way and the one thing I have to say is I can't believe that they ever built this well that plane when I got in it smelt of leather both cockpits there's a cockpit for two people up front and the pilot sits in the rear cold pit that is so that the weight balance always is the same right when you put the two people in the front cockpit their weight is over the center of the Wings so it doesn't affect the white balance whether there's three people in there or one now if you look carefully and I'll zoom in you'll see some black painted bulges on the cowling and you may well suspect and rightly so that those bumps are to cover The Rocker covers which may stick out further than the rest of the engine and it's what we call a round motor or radial motor right the cylinders are all going out like this and I think that's a seven cylinder uh engine about 300 and 50 horsepower on there I can't remember exactly but my point is this you look at those and you think well that's an easy way to save putting on an entirely bigger cowl so the frontal area is cut now if you thought that that would be very good but the bottom line is this those bumps help the air go around the corner so they make the cow look smaller than it really is right if you position those bumps just right on that cowl whether they have to cover a valve part of the valve gear or not they will actually help the air make that turn and have less tendency to break away as it makes that turn the result is that the cow looks smaller in diameter than it really is and on the Waco I believe it's worth about five miles an hour on top speed then don't quote me on that that's what I've heard anyway how can we apply those speed bumps to the port this next diagram will show just that well this diagram shows where we are at the last point of our Port reshape what I'm going to do now is treat the short side turn as if it was part of the perimeter of an aircraft cowling I am going to take one of those black streamlining shapes that are on the very edge of the cowling and apply it to that short side turn so what we get is this to better appreciate side and plan view of that speed bump here's a drawing which should make things totally clear well I'm going to wrap things up for now as I run way over the intended time in fact I thought I was going to get this video done in a day and this is actually the end of the third day on it if you want to continue to find out about ports then the next episode will go on to rule number two proper in that I'm going to look at lots of things that affect how we should think of and treat the air in the ports so let's get together on rule number two thank you for watching [Music] foreign [Music]