How To Plan Your Engine Build: To Make Power, You Need to Have a Plan

(Pat)>> You're watching Powernation!

(Pat)>> When it comes to engine building there is no shortage of myths and misinformation.

(Frankie)>> Today on Engine Power we give you just the facts, showing you how to plan your engine build so it runs exactly like you want it. [ Music ] [ engine revving ]

(Pat)>> Right on target!

(Frankie)>> Heck yeah!

(Pat)>> Our favorite part of any build that we do here in the shop is the dyno session. When it all comes together and it makes the power that we want it's a great day. So we are gonna go into a deep dive on what it takes to plan an engine. Engines are application specific. No matter if it's a daily driver or a full tilt race engine, the process of planning and the parts selection are the most important part.

(Frankie)>> And if you know some very specific things about the parts and about the engine, like compression ratio, cam specs, head flow, and more you can not only predict where the engine will make peak power but how much power it will make within a given range. And that's important for planning your build but also for when it all comes together on the dyno to verify it. For instance, if the engine is making way more or way less power than it's supposed to you could have a calibration issue or something worse that you need to hunt down. So today we're gonna go over a lot of the cool tech that we use to plan our engine builds, and can help you plan yours at home. The first thing we're gonna do is explain a term that you've probably heard us use but we wanted to define, and that is specific output. Quite simply it's the output of the engine in horsepower or torque divided by its displacement in cubic inches. You can also use liters if that's your preference. This is a great bench mark for how an engine performs because it's universal as it takes into account the engine size. For a representation if a 400 cubic inch engine makes 600 horsepower that's a lot more impressive than a 600 cubic inch engine making 600 horsepower. Here in Engine Power we mostly run engines on pump gas. And although it has its limitations it's pretty easy to put together a bolt together combination that can make between 1.25 to 1.45 horsepower per cube and 1.15 to 1.35 pound feet per cubic inch. Once you get above that the engine build becomes a little bit more complex as the cost of parts, the time involved, and usually the r-p-m range go up.

(Pat)>> Now you have to be realistic on what your engine is actually going to be doing. Is it a cruiser, or is it a full tilt race bullet, or something in between? Now a lot of things have to be taken into consideration like that specific output number that we were talking about, the r-p-m range where that number wants to be, the durability of the parts for that application, and probably the most important one, the budget. Now everyone wants 1,000 horse for $1,000 bucks. We do too but that is not very realistic if you want something to last. So typically we operate any triangle of three different factors, cheap, reliable, and powerful. You can only have two of those. So you have to choose your parts wisely.

(Frankie)>> We generally like to pick reliable and powerful over cheap because we like having known good parts and a durable package, and we have a few of those here from previous projects that range in specific output.

(Pat)>> First up is our 445 cubic inch Ford FE. Now we built this engine to be a low r-p-m hot rod engine. So we picked the parts accordingly. It is 10.06 to 1 compression, has a hydraulic roller valvetrain, dual e-f-i throttle bodies, and on 93 octane pump gas it made 586 horsepower at 5,800 r-p-m and 566 pound feet of torque at 5,000 r-p-m. This was designed to make all its power under 6,000. Mission accomplished! That works out to 1.29 horsepower per cubic inch and 1.24 pound feet of torque per inch.

(Frankie)>> An engine that makes very similar power is our Compression Obsession small block Chevy that you just watched us build. This engine made 591 horsepower but it did it on 360 cubic inches. Which means the specific output is way higher at 1.64 horsepower per cubic inch. It also made great torque at 489 pound feet, which is 1.36 pound feet per cubic inch. It does require a little bit more of an involved build however. It has high static compression ratio at 13.36 to 1, has a solid roller valvetrain, very large induction, and it did that on 104 leaded oxygenated racing fuel. So it's not really a fair comparison. This isn't really a street engine, but it is on the upper end of the spectrum that requires a little bit more time in the build and a higher cost of parts.

(Pat)>> Right about in the middle of that range is our 410 cubic inch small block Mopar. Now this engine struck a great balance between horsepower and torque per cube. It is not exactly a budget build but it sure didn't break the bank. This engine made 537 horsepower and 550-pound feet of torque on 93 octane pump gas.

(Frankie)>> For that cost incurred we got a really great engine though. It has a forged rotating assembly, hydraulic roller valvetrain that's gonna last the life of the engine, and even though it is a single plane manifold the induction package was appropriately sized to make that big torque number. And it all did it in a relatively low streetable r-p-m range.

(Pat)>> Knowing all of that we are now gonna show you how we plan out a build for a target horsepower number and a targeted r-p-m range on 93 octane pump gas.

(Frankie)>> And the great part is that this tech can be scaled up or down for any engine depending on your r-p-m limit, the specific output number you want, and usually the most important limiting factor, your budget.

(Pat)>> To know how your engine will perform you need to know how much air and how much fuel are flowing through it.

(Pat)>> On today's Summit Tech Tip we're gonna be talking about valve spring install height, and what better person to have here than NHRA Top Fuel driver Clay Millican. Clay, tell me about the importance of checking your installed height on your spring.

(Clay)>> Well the springs have got a spot that they need to be in. It doesn't matter what kind of spring you've got. The height mic is how you get those things in their happy place.

(Pat)>> Nothing's quite universal. People think things just bolt on but that's not the case when you're building a custom engine.

(Clay)>> No, you've got to check each and every cylinder. You've got to have the correct height because if not you can coil bind the springs, or if they're installed too tall they don't have their proper close pressure.

(Pat)>> To do that Summit has a lot of great tools in their catalog, and one of them are these height mics that have different ranges, different diameters that you can measure that very accurately.

(Clay)>> Without a doubt! I am the one guy that is constantly calling Summit because they've got experts there that can help you. Literally walk you through the process of the spring that you bought from Summit, where they need to be installed at, the shims you need to go underneath, everything you need.

(Pat)>> Now I know some of this seems like overkill but in my opinion there's no such thing as overkill in engine building.

(Clay)>> Trust me, I've broken way more parts than the average. You better check it, and Summit Racing's got the parts to make it happen.

(Pat)>> Time to get down into the meat and potatoes of our engine build. We always have a plan. We don't arbitrarily throw parts together and hope they do something. Each engine is application specific. So, we have to determine what the application is before we even start. So, in ours we have to determine the engine, and that engine's gonna be a small block.

(Frankie)>> We picked a small block because they're generally a little bit cheaper, and easier to find, and easier to work on honestly. This is gonna be dictated by parts you already have, an engine you already have, or your limitations by the size that you can fit inside the chassis that you're working with.

(Pat)>> Next on the list is how much power do we want this rig to make. Well we choose 500 horse because a 500 horsepower small block's pretty spicy, but we have to determine what it takes to do that.

(Frankie)>> Today the parts are so good that it's pretty easy to put together a bolt together combination that can make 500 horsepower. So, it's a pretty tame goal but in a car that's still a decent amount.

(Pat)>> The next question is how many r-p-ms do we want to turn this safely? Generally, the higher the r-p-ms you turn the more expensive things become. So, we chose 6,500 r-p-m.

(Frankie)>> We didn't choose that arbitrarily. Because we want to keep this relatively cheap we're gonna try and use the stock crank, the stock rods, and probably even the stock pistons. So we wanted to keep the average piston speed under 4,000 feet per minute, and the way you calculate that is using the engine's stroke, multiplied by the max r-p-m, divided by six, and for this application that gives us 3,923 feet per minute. Right under where we want to be. Once your engine is built and running hopefully the most expensive thing you're gonna put in it is fuel. So, it's important to choose the right one. In most of our builds we use 93 octane pump gas because it's relatively easy to get and relatively cheap compared to a distilled racing fuel.

(Pat)>> Just because it is pump gas does not mean it won't make great power, but it does have its limitations as far as cylinder pressure is concerned. So that is always something you should be considering.

(Frankie)>> Now that we know what the goals of our engine our we can talk about the specs that the engine is going to have. For displacement we're gonna be using an LQ-9 LS style engine that's six liters, or 367 cubic inches, with a 20 thousandths overbore, which means we'll have to reach a specific output of 1.362 horsepower per cubic inch to reach our 500 horsepower goal. That should be relatively easy with that combination and the parts we're gonna be choosing.

(Pat)>> Armed with that information, now we can determine how much compression we need to make that kind of power. We need roughly between 10 and 10.5 to one based on data and previous dyno runs. Lucky for us the LQ-9 has a stock compression ratio of 10.1 to 1. So, we are right in the range already.

(Frankie)>> One of the most important things when planning an engine build is head flow. It's a crucial part of the induction package, and getting enough air into the engine, along with the fuel that goes with it, is how you really build horsepower. And in this application we can do a little bit of quick math to figure out the minimum head flow requirement that we're gonna need. Since we have a 500 horsepower goal an industry standard is that you can make about two horsepower per c-f-m of peak head flow. So, if we have a head that flows 250 c-f-m we should be right within that range. [ Music ]

(Pat)>> Mounted up to our Superflow SF-750 flow bench is a 317 LS casting. This is an o-e-m casting that comes on an LQ-9 six liter LS. This has a 210cc intake port, 75cc exhaust port. It has a two inch intake valve, and a 1-550 exhaust valve. We're gonna see what this unmodified head flows and see if it will be right for our application. We'll open the valve in 100 thousandths increments and take readings at each point. It takes a couple of seconds for the port to stabilize, and then we can get an accurate reading. These are great numbers for a factory casting. You couldn't get this back in the day with the old school small block stuff. We have already achieved our goal of 250 c-f-m by 500 thousandths lift, and I went ahead and flowed it all the way up to 750 to see if the head became turbulent. We had 258 c-f-m at 750 lift. Knowing this we definitely have the potential to hit our target with these numbers.

(Frankie)>> Up next, camshaft selection and setup make a big difference in how any engine performs.

(Frankie)>> Now that we know some very specific specifications about our engine we can talk about something that can be a little bit intimidating but is very important to the build, and that is camshaft sizing and specifications. Generally everybody knows the feeling when you open the camshaft book and there's a bunch of different options, and you don't know where to start. So, we're gonna go over some general trends that we have found through time, experience, and data.

(Pat)>> We are gonna be talking about durations on the intake side of the cam that deal with pump gas cylinder pressures. So first off 210 degrees to 235 degrees at 50 thousandths will produce 1 to 1.4 horse per cube. I know that is a big range but that number is very dependent on the rest of the engine being setup correctly all the way from the induction side to the oiling system.

(Frankie)>> On the next range we're talking about between 235 and 270 degrees at 50 thousandths lift, and generally what we see is that can yield between 1.35 and 1.65 horsepower per cubic inch. Again, this is a range and sometimes can overlap based on the engine's size and the combination that's put together.

(Pat)>> Last but certainly not least is durations over 270 thousandths at 50 thousandths lift, which can yield over 1.6 per inch. This is on the extreme side of what pump gas can handle for octane. So, these are few and far between but still possible.

(Frankie)>> In terms of exhaust duration we generally base that off the intake duration itself because they are related. We generally like to see an exhaust port that flows between 75 and 80 percent of what the intake will flow, and depending on this number we like to see between and 12 degrees extra duration on the exhaust. This can depend on the head flow and also the r-p-m range that the engine will be operating.

(Pat)>> The next thing that we're gonna add to this conversation is lobe separation angle. That for a given set of lobes determines when the intake and exhaust valves open and close, and that also determines the cam's overlap, which greatly influences how the engine runs.

(Frankie)>> In a tighter lobe separation angle it generally means that the engine will build a very specific torque in a very specific torque range. This is great for something like drag racing where the r-p-m range is relatively tight or something on the street where you want to build good torque lower in the r-p-m range.

(Pat)>> A wider lobe separation tends to have a broader and flatter torque curve, which works great on the street to make things run smoothly, but on the extreme side of that in drag race applications high r-p-m things tend to have a very wide lobe separation because it doesn't need all of that overlap.

(Frankie)>> That brings us to intake centerline placement, which will greatly determine where the engine makes peak cylinder pressure, and therefore peak torque. This is something that is determined by you or the engine builder. There's a lot of misnomers about the fact that cam cards come with an intake centerline number on them, but this is not a recommendation by the cam manufacturer. It's simply a reference point for checking the intake and exhaust valve's opening and closing points at that intake centerline.

(Pat)>> Advancing the intake centerline relative to its lobe separation will trap air sooner in the cycle and build more torque lower in the r-p-m range. On the other side of that retarding the cam relative to its lobe separation builds torque higher in the r-p-m range and makes better top end power.

(Frankie)>> Now that we know all this important information about our engine and about the cam specs we want we can go through and decide the ranges of these certain specs that we want in our cam. So, for intake duration we know we want something between 230 and 235 degrees at 50 thousandths lift. For the exhaust, because we've talked about having more exhaust duration and intake, we know we want something that's between 238 and 247 at 50 thousandths lift on the exhaust.

(Pat)>> Because we know the lift at what our cylinder head flows we want something in the 600 to 650 net lift for our valves. That will keep us in the sweet spot of our cylinder head and our flow range of our induction system. As far as the lobe separation is concerned we've decided that between 110 and 114 degrees will work for our application because of our r-p-m we've set at 6,500. Intake centerline, we will be advancing the cam at some point between 108 and 110 depending on what our lobe separation angle turns out to be.

(Frankie)>> And all that adds up to a cam that we found in the catalog. So it fits all of our specifications at 231 degrees of intake duration at 50 thousandths lift, 239 degrees of exhaust duration at 50 thousandths lift, 617 and 624 net lift on the intake and exhaust valves, 113 degree lobe separation angle, and we'll probably set the intake centerline at 109 or as close as we can given the parameters of the timing set that we're gonna be using.

(Pat)>> You could get a custom ground cam for this but it was easy enough to find one in a catalog that meets these specifications, and that makes it a little bit more economical to put together. We set out to build a 500 horsepower engine. Find out how close we got.

(Frankie)>> The next thing we're gonna talk about is choosing an intake manifold, and this can be a very important choice, but it really comes down to three P's, Personal preference, power, and price.

(Pat)>> That's four P's.

(Frankie)>> Anyways, this engine would have originally come with fuel injection, and there's a bunch of different manifolds that you can use in that application. Everything from a stock manifold that's easy to find and can still make good power, to an aftermarket plastic or composite one that could make even more power, a sheet metal manifold that's economical and light, all the way up to a cast aluminum manifold, which can be ported if the application requires it, and usually you can use several different tops like a forward facing, side facing, or up facing throttle body. Any of these fuel injection manifolds will run and make power, but in the end choosing the right manifold is about finding one that has the right power size and runner length for your power and r-p-m requirement.

(Pat)>> You could also do that in a carbureted style manifold for our application. The first thing you may ask is why go backwards and put a carbureted intake on something that was designed for fuel injection? Well, there are a few definite advantages. One, simplicity. If you have to convert your hot rod to a high pressure fuel system this will already work with your low pressure fuel system so you can just put your carburetor on that you probably already have and you can get it going. Another is the ease of setting up the timing. We are gonna be controlling our engine with a separate timing control box. This has several advantages including being able to put a timing curve in that is very precise. Better than you can get with just setting with a conventional distributor. And again, you also have choices on what you have for a manifold, a dual plane or a single plane. Now the argument is always single planes don't really run on the street. So, you should go with a dual plane. Well, I've got news for you. These are all single plane manifolds. So we have decided to run ours carbureted with an ignition controller on a single plane manifold. Our gold standard for our dyno carb is the QFT Black Diamond 950 c-f-m. We're putting it on top of an Edelbrock Victor Junior LS-1 manifold.

(Frankie)>> We put together the combination that we've been talking about, and we have it on the dyno. It's an LQ-9 with a stock bottom end, a stock set of 317 LQ-9 heads. It's 10.1 to 1, and it has the cam that we talked about earlier. A 231/239 at 50 on a 113-degree lobe separation angle. We also have a Victor Junior intake with a one and a half inch open spacer and our 950 c-f-m Black Diamond carburetor. So, we've got this thing tuned in. We think it's just pretty close at 26 degrees of timing, and we have the jets right in the carburetor. So we're gonna make a hit and hopefully it should make the power that we estimated it will.

(Pat)>> It's gonna be above or below it by a small amount, but this is a pretty solid combination, and this is one that with the parts that are involved almost predict what it's gonna make but you never can tell because that's why we dyno. We're not into guessing.

(Frankie)>> We have an idea that's gonna be pretty close to our goal. Somewhere between 495 and 505. We'll see if that's the truth. [ engine revving ]

(Pat)>> That's the warmup pull. If that's not it's gonna be close.

(Frankie)>> That is close. Right in our range.

(Pat)>> 497.7, I would say that's pretty close. 474.9-pound feet of torque.

(Frankie)>> And it's making peak power, 497.7, at 6,200, which is nice cause that's right in our range of 6,500. So, you don't have to leg it out past that.

(Pat)>> So you want to make a back up pull and check a plug?

(Frankie)>> I think we'll make a backup pull now that we've got oil temp in it. Then we'll check a plug and see what it looks like. [ engine revving ]

(Pat)>> I don't know if it was there or not.

(Frankie)>> I might have seen it.

(Pat)>> Yep!

(Frankie)>> 502!

(Pat)>> 502.0. The heat helped a little bit, 477-pound feet of torque.

(Frankie)>> Peak torque right at 4,800. So that's a nice spread between peaks. This would be a great street engine.

(Pat)>> We always preach that between peak power and peak torque you want the widest amount possible because that makes the thing drive a little bit better. All of our vitals look great. It's got 80 pounds of oil pressure.

(Frankie)>> I think we'll pull a plug and make sure it looks good, and then go from there.

(Pat)>> I like it! [ Music ]

(Frankie)>> Dang, I think the timing's dead on and the fuel is looking pretty good for pump gas. Now this is a great representation of putting together a little bit of math and a little bit of experience to have a combination that makes the power that you want it to make.

(Pat)>> Remember, this type of planning for an engine applies to any brand. It doesn't matter which one because what matters in the end is putting a plan together to make good horsepower. For even more information on planning your next engine build check out Powernation!