PowerTec 10 EP 9 Porting the WORLDS BEST? BBC Iron Heads

hi my name is david bizard and you are watching power tech 10. give me a few minutes of your time and i will give you the benefit of my over 50 years of race winning engine building today's subject big block chevy heads in iron my question is are we looking at the world's best iron big block chevy head i'll let you decide when i've given you all the numbers on it and shown you how it was all done let's do a little analysis on the big block head when it first came out it was known as or the engine equipped was known as the mystery engine and then the cylinder head became a entity named under the porcupine-headed engine now porcupine that made the nickname for this the rat motor right and consequently the smaller small block chevy became the mouse motor so if you wondered about all that terminology that's how it came out but back to the technical side what we had here was a cylinder head with canted valves and a equally comparatively speaking complicated valve train and it looked like well who would do that for no reason at all but the truth of the matter is if general motors had scaled up their best small block chevy heads i like the uh like the current or the the last of the small block chevy heads the vortec heads they would have had a cylinder head virtually equally as good but at a lot less many so when we look at a big block head it's not that technical wonder that has so often been uh portrayed by uh general motors but anyway let's get back to that how does this cylinder head fare in real life if you can hear some background noise it's pouring down outside it's like the heavens have opened up but that's not going to divert us any here uh this project was a little less than usual in as much as the porting or the prototype porting was not done by me it was done by one of my students and on this particular group of students i had who were pretty much all heavily into porting and all but one they ran engine companies so they were professional now ironically the one that didn't run an engine building company was the one that got the best results but he was very dedicated to this now could there be any more flow in it than than my student got or was what he did just okay well at this stage we don't know but the point is this all of them got good very good flow figures from this eq head and one of them got exceptional flow figures maybe exception wasn't the right word you've got very good flow figures and i'm sure there's more flow in these heads i'm looking at them and i'm thinking they could go 450 maybe even 460 but it would be a lot of work to get it so with all that just remember it's possible to be taught how to do this flow testing and flow development and porting etc etc etc i don't like to look at this as porting so much as cylinder head development engineering right so with that let's go on as i said let's get the ball rolling what we're going to do is we're going to look at the combustion chamber first and the valve seats i'm going to emphasize the valve seats because on a big block they're important on any engine but a big block they're especially important because you need to get flow right off the seat because as i've said the big block is one of the most undervalved engines on the face of the planet so we have to make the valves look as far as the engine is concerned as big as possible with that let's go and look at the chambers what you're looking at here is the combustion chamber virtually finished and the basic pre-finishing job on the seats is done what i did here was do a rough cut on the seats and then using a fan-like disc wheel i went in and blended all these curves here you can see how they're blended in and there's a neat entry now a few points on this these are blended in at the top exhaust is going out these the blend is most concentrated on the bottom this angle here is about a 35 degree angle this valve is slightly higher than this one so that the high efficiency off the seat of this valve does not lend itself to a reverse flow the flow comes out of here and it goes over the top of the exhaust valve during the critical overlap phase where both valves are off the seat so this mod sinking this valve about 50 000 deeper into the head that's about as much as you can go then this one makes the cam look about 10 degrees shorter and it's something like 3000 rpm it can be worth as much as 20 foot pounds note how the chamber is cut away here i'll do a little drawing of the surface form going down here and into the seat this cutting this away here is very good to increase output from about 4 500 up there is no downside to it it actually will add the odd couple of foot pounds up to about 4 500 then it starts to add foot pounds big time by the time the engine an engine like this gets to about 7000 rpm that laid back there is worth about 30 to 35 horsepower just so that you can better understand what's going on from that last scene i've done this drawing here this is the plateau on the quench side of the chamber you see how it comes down to the seat but it doesn't join the seat straight off there's a radius into the seat like this so that as the gases the gas flow or the general flow of the exhaust products when the piston is close to tdc is in a near horizontal format so it's got to go around this corner and out hence this radius into the seat on the other side of the chamber we have this form this is the spark plug about where the arrow head is and this is the form here we don't want this to be too efficient because it'll separate here and it will cause that reverse flow right after that underneath the seats we have a form which gives the initial opening area or it maximizes it and that's what i call an area ruled exhaust port this is also something that is not generally talked about and i don't think it's much known except in any field other than maybe formula one so why does laying back the chamber like this work on big blocks two reasons one if the chamber is too close here the and shrouds this slightly this is can be the most efficient side for flow just here what happens is it gets around the corner here but it's going too fast to make it around the short side turn and what happens is on when we test on the flow bench and on the same happens on the engine obviously there is a big reversion of flow on the floor of the port it has been a problem with big block ports for years if you've ever seen some of these fancy shaped ports that's an effort to cure it the problem lies not in the port it's the chamber here right the second reason is when the piston comes up and we have this mighty quench punch here we don't want the gases going over the top of the exhaust valve we want them to come round here this this will be rounded off here after the head skimmed round here and go underneath the valve and reinforce the flow out of this side that also that is the major contributor towards stopping reversion so that cuts out there not only makes the engine run better at low rpm but it really helps at the top end it's going to add 500 rpm to the useful range on a 700 horsepower engine plus about 30 to 35 horsepower as i said just now there's many ways to form a seat the radii before and after the actual seat itself the most expensive way of doing it is like the car guys or some of them do is to cut their seats on a new and uh computer-controlled machine now they don't necessarily use a radius before and after or whatever they use their own designs however i also have got the goodson 3d system and i have form cutters that i can cut a radius on the seat but to be honest the fastest way to do it and you can do this at home if you're careful with your grinder is to do it with a flap wheel but you have to modify the flap wheel like this here's a close-up of the flat wheel i use for big block size valves it's a three inch disc and i cut sections out of it like this now what can happen is is you can now crunch it up like that put it in the hole here is what happens when you power it up this is when centrifugal force on these here works in your favor here's what happens when we apply this tool into the throat of the valve right ready you'll see that it catches it at the top and at the bottom the area where it's got the sharpest corners it removes metal first the actual seat itself that was cut here is where the least amount of metal is removed by this process so although it looks pretty vicious on the seat it's not as bad as it looks however it's not something that's a slam dunk you do need to experiment with this on a used scrap cylinder head what we see here is the seat it is the right od and slightly undersize on the id i cut them like this because when i go in there to polish them i take the edges off the inside of the seat but not so much on the outside so they'll come out the right size which is about 50 000 wide for the intake looking at the chamber here we see some very relevant things firstly you'll notice that this is all cut away here compared with the stock one or a typical big block chevy head there's a good reason for that during the piston reaching tdc on the exhaust stroke normally the gases the quench area would come right to here the gases go over the top of the exhaust valve and they do so with great deal of velocity so what happens is it excites this side of the valve but it starves this side the gases go out here and they're traveling at high velocity and they don't make it ram the turn and they tend to block off the port on this side here and we get a reversion on the bottom of the port so cutting the chamber like this alleviates that now after this head has been milled off this area here will be rounded off this edge here so that it provides a nice smooth transition into this slope here so that those exhaust gases go out of the exhaust port and they energize this side of the port and it fixes the reversion that's something you won't find on any other video let's look at a couple of other things firstly now well not firstly but a point here this side of the exhaust valve is slightly shrouded and that's intended because otherwise it will exaggerate the flow here and develop the reverse flow now if you look at this very carefully you'll find that the exhaust is actually in a slight pocket and that there's a nice radius leading up to the the seat all around again that's so that during the overlap period the gases can travel out the exhaust port easier now this causes a spike in vacuum generated to suck the charge in intake charge so what happens is we get rid of the exhaust more efficiently and we get the intake charge started more effectively now have a look at the valves here you'll notice there's a sharp edge here that's intentional we don't want the gases coming in here and out there right there's a 35 degree uh top cut on all of this here 45 degrees seat and a nice radius coming out of it so nothing conventional there just good workmanship here this is very carefully described now if you look carefully you'll see a light showing here there is a slight valley going up here because the gases don't come out like that they come out and the gases here have to turn those so they the ones coming out here have to turn right so there's a general trend of the mixture to be going out and around like that we need to exaggerate that trend right so that's that there very little has had to come out because this original cylinder head was very well designed in terms of porting to start with a few things about big blocks and big block heads in general that you should know and probably don't appreciate first off looking at that the biggest valve you can get into a 454 or bigger cylinder head then it looks pretty big for the job so you're probably going to be surprised when i tell you the big block chevy is one of the most undervalved engines on the face of the planet uh if we had a valve in let's compare a 350 chevy small block chevy with a big a 454 big block chevy if we had proportionately sized valves the 202 valve in the small block chevy to get the equivalent of that we'd have to have a 2.7 inch valve in the big block chevy well no one uses a 7-inch 2.7 inch valve you just can't get it in so this makes it very important to have a very efficient valve because we need the biggest we can get in is about 2.3 we can fudge in bigger ones but not as a direct replacement 2.3 we have to make that valve as efficient as possible so that the engine thinks it's got a bigger valve so valve seats become very important secondly although the valves are canted you'll notice that the ports are still very flat compared with the axis of the valve so it's important that we shape the ports so that they in themselves are efficient not just big we can always get flow by making big ports that loses velocity we lose energy in the port and consequently we lose the potential of making horsepower and torque now then let's consider this in a nutshell what we've got is an engine capable of a lot of cubic inches but not very capable in terms of cylinder heads for those cubes anything over about 360 cubes doesn't have enough intake valve surprising so modifying big block cylinder heads to get good results can be a very beneficial thing unfortunately big block chevy heads are not the easiest to modify in terms of where the air is going i'm going to give you a lot of tips here when we look at these cylinder heads here these eq heads and we'll go from there okay here we have a shot down the intake port this is the bad port that's the one that runs into the cylinder wall now look in the back there and you'll see a shadow that goes across like this from that you can see that the air is not trying to go in straight in like this it's trying to sweep across the cylinder wall and chamber face which is where it wants to go so this is something that you have to build in note that the trailing edge of the guide boss or the tail is off at an angle also this corner here and on in around there is critical what you need to do is to widen this area here as much as possible as it goes in it needs to sink a bit so that the air slows up progressively so it can make it around this corner also it exposes this side of the port and consequently it gets this side working much better that does two things one it flows more air and two and this is important it generates a lot of swirl what we have here is the good port i'm showing you this angle because i want you to see this hole in the wall here that goes into the bolt hole here when the bolts in it seals it up that should be a good reference point for you to figure out whether you've got the port wide enough why widen it down there because that's where the majority of the flow wants to go also now i'm going to move the camera here and take a look down the throat of the port to the guide boss you'll see that the the trailing edge of the guide boss is almost in line with the front of the guide boss and that's because this port is already aimed towards the center of the cylinder again like the other port i'm just going to move the camera here so hang on just a moment this area here is very important that side of the valve is shrouded by the fact that the ports aim this bias this way instead of sufficiently that way so like the other port this here this area here is very important it's very touchy get that right and you'll get those flow numbers here's a look down the exhaust port on a big block all the exhaust ports are symmetrical that means they're all the same for every cylinder if you look carefully you'll see that the lead-in part of the guide and it's the lead-in because the exhaust is coming out going the opposite way to the intake is offered a slight angle and we have a bulge in the port here that's because the gases want to go out at an angle like this from the center of the cylinder so we let the gases go as far as we can where they want to go not where we try and dictate they should go mother nature is not our slave so we have to go with whatever works here and that is to take care of the rudimentary principles of porting let the air go as far as possible where it wants to go you'll get the most flow out of the port that way port's not big the chamber mod we've done has prevented the reversion that takes place in this area here and i'll give you some figures here some of the heads i flowed when the exhaust is coming over the air on the flow bench is coming out of here at 320 feet the second it's going in here at 300. goes in tumbles like this and it comes back out here is it any wonder it kills the flow so we've done all of our flow testing now let's take a look at the results what i did here was i compared this eq iron head with one of my ported sets of afr 338 heads now these afr heads are real powerhouses right on a 556 i've seen just over a thousand horsepower so they will go there and that was not a super trick double throw down deal it was something that well you need a kind of a budget for it but nothing outstanding anyway don't have figures for the iron head but the reason i checked out this head was because i had several engine builder friends of mine who are very reputable engine builders call me up and say had i tried it no david hasn't tried it yet well have now at least the flow testing not the dyno bit so i'm going on there say so that these heads will make big horsepower they've talked about 800 plus horsepower for a street motor on a that's on a 555 or maybe a 540. i can't remember but anyway really good results but first why would we use an iron head right difficult to repair if you drop a valve in fact they're scrap but they're pretty tough the reason that you would go with an iron head is for marine use where corrosion might be a factor that needs to be taken into account so if you want a cylinder pair of cylinder heads for a big block that's for a boat that's got to have torque right off low speed then this could be the head for you or heads for you also if you've got a big truck having 50 pounds of extra weight up front is neither here nor there but having another 30 or 40 foot pounds of torque down low is so there's your reasons for using it also cost as it happens the heads we're doing here are going to go into an s10 street strip car right they're going to be moving everything to the back of the car to make up for that 50 or 60 pounds of extra weight anyway let's look at the results the thin line here is the afr heads intake exhaust and this is the port velocity what i need to do first is to go and look at the no let's talk about port velocity right as quantified by this program this is my aop program for cylinder heads we know for a fact that to make sure we get the best of the torque and output over as wide a range as possible we want to have a port which is up in the 300 feet per second range well that means we'd have to lift the valve 800 a little too much for a daily driver 700 though is not out of the question and up here we're still doing okay at around about 270 cfm it's okay it's not the best but this is big block territory for you big blocks to get the flow you have to have the port a little larger than would necessarily be the case problem port velocity is low if it's too low torque suffers right now look at this at 700 lift we are very close to 300 for our uh eq head that's very good as far as exhaust goes it's better than the afr head at least the way i ported them right don't forget this afr head here did make big power let's now take a look at the flow that's uh cfm flow we go there calculate right here is the flow curves you can see from 300 on up the eq heads the way my student ported them to my instructions as per dished out when he was in class in in our cylinder head porting school right they are better from here on up oh by the way all of my students got good results with these heads this guy got the best results right so this this is nothing the skill of doing that is nothing to do with me my skill was in teaching the guy how to do it there's the afr one you can see top end they made almost the same looking at the exhaust flow for all practical purposes they were identical now let's have a look at one more factor here that is not generally shown and that's port energy for a big block chevy or for any engine but especially for a big block chevy this is very important if you do not have enough port energy there is enough mass flowing at high enough speed you do not make the most of the ramming effect that is possible to have and a big block chevy because it's under valved is very susceptible to losing out if it doesn't have enough port energy well here's the port energy for our eq head compared with the port energy for the afr head and remember the afr head was a killer so what conclusions can we come to here based on this and the tests done by some of my friends who are among them nascar engine builders they've had very good results with this cylinder head right this all shows why if you want to port cylinder heads like this i do run a school to teach you how to do it in closing i'd like to make a few points about using these heads successfully or any big block head firstly no successful engine is the result of one trick part it doesn't matter how good these cylinder heads flow if they're not used with the appropriate spec on the rest of the engine they will fail well they won't fail you will fail let's look at our big block uh deal here we've already said it's undervalved this means that it's very important that we not only open the valve as quickly as possible not easy on a big block it has a heavy valve train but also we need to open it to the area where the flow regime is the best possible we can get this means that with these eq heads you should not use anything less than 650 lift preferably about 700 if it's not a high mileage motor you're dealing with then maybe 750 or even the lofty goal of 800 for a street strip deal and that's about it now if it's just a race only thing a one inch lift would be perfect uh not practical for the road though now uh the other thing is is it's no good having all the flow in the world if the valves are opened and closed at the wrong time right and let me make a point here since we are just about to hit the subject of camshafts the wrong cam will cost you just as much as the right one in fact more because if you realize you've got the wrong cam you've got to buy another one right now for any of the vehicles that we're likely to be dealing with that is between compressions between about nine and maybe a max of about 11 to one right we are going to need a camshaft that is a pretty tight lobe centerline angle these hundred and twelve hundred and fourteen lobe center line angle cams will not cut it now they're not just a little bit off you are going to lose 60 or 70 horsepower and probably as much as 80 foot pounds of torque don't believe me go ahead and try it right what you need to do is to call walter's engines terry walters up in roanoke and get a cam spec to your big block specification this cam will take it into account everything that is needed to on that motor and i personally will spec that cam out for you using my torque master program it's deadly accurate and it gets results what else oh well still on the valve train bit you'll need to take care of the valve train by having the best springs possible that is springs with a high resonant frequency that means buying a good spring that means buying one that's expensive and probably low mass well almost certainly low mass so that it doesn't run into surge is easy doing that you'll need less load on the valve and consequently the valve train will be more reliable and you'll be able to lift the cam the the lift the valves higher as far as intake is concerned a single plane a good single plane manifold is best here i would recommend a sniper junior preferably with a dominator on it but it can work very well with a good 4150 carburetor in the 1000 cfm range if you're going to use a two plane be a be aware that there is a problem the two plane manifolds especially for metal block the runners on them flow very well but the carburetors they're built for don't so a lot of the flow capability of this or any big block cylinder head is compromised by that very issue with that i think i've got to about the end of what i want to talk about here oh there is one other thing if you want to know more about big blocks i do have a best-selling big block book from car tech it's got stuff in it that you can't get from any pro engine builders right not unless they've read the book and they're just quoting me right now i know that sounds kind of arrogant but the fact of the matter is that is the real world case thank you for watching you

Channel: David Vizard Performance

Views: 19,914

Rating: 4.9628649 out of 5

Keywords: Cylinder head, Edelbrock, IOP, Induction optimization program, SBC, Vizard, chevy, Big Block Chevrolet, Big Block, BBC, Performer RPM, David Vizard, Pro Porting, EngineQuest, Engine Quest, AFR, AIR Flow research, cylinder Head, Cylinder Head Porting, porting BBC, how to port, porting for dummys, flow test, flow testing, holley, 4150, Dominator, EQ, Port velocity, Darin Morgan, port energy, 128 formula, highperformance, rat motor, porting school, best heads, best cylinder heads

Id: NTqXHfs5GIA

Length: 38min 29sec (2309 seconds)

Published: Fri Apr 09 2021