How do you go about building an engine?
08-14-2006, 07:07 PM
#1
How do you go about building an engine?
"Well before I start, I better introduce myself. My name is Erik Koenig and I go by Racer7088 on some of these bulletin boards. I’ve been racing in some capacity for over 25 years from tractor pull and mud trucks to motocross to endurance racing to drag racing and everything in between. I raced with the SCCA, for over 15 consecutive years and basically stopped only when I started my engine building business and started working for the School of Automotive Machinists. I still have both jobs right now and am around racing engines of one type or another almost 16 hours a day. I’ve been lucky also to know many professionals in the racing industry. I attended Texas A and M University, in addition to the many I know through SAM who have people employed in every area of the engine building world.
So now for the meat and potatoes of why you're here. Building racing engines or even a weekend warrior street/strip engine! The FIRST thing I ask people is what kind of realistic budget do you have? I would say that if you don’t have this figured out you are just wasting your time and the people who are talking to you as well. The worst thing you can do is to try and do something if you are way out of line with your budget. Try and race in a class you can afford or you will always be mad about people outspending you. I know since I’ve been there so just keep that in mind before getting in way over your head in something you can’t afford to be competitive in.
Secondly, you need to be very clear about what you want to do with this engine. By that I mean many things like how long does it have to last? Can it last maybe 5 passes between freshens or maybe more like 200 passes between tear downs, or do you want a whole season or maybe way out there like 100,000 miles? What kind of maintenance are you expecting or not expecting to do on it. What fuel can you run or will you run in it? Are you constrained by any rules such as exists in almost all race sanctioning bodies? Is it in fact a street car or a race car? Do you drive it in heavy stop and go traffic or is it solely a weekend warrior? Does it have to pass emissions or does it have to have a really nice idle? Only you really know what you are looking for so you need to communicate that very clearly or you may not be happy with what you build.
Third, you need to look at how much power you want to make and how fast you are expecting to go in order to be satisfied with what you have spent and with all the time and effort you will put into this. You need to sit down with the Moroso Power Speed Calculator and see how much power it is going to take to make you happy. You also need to try and also think about the money you have and the intended usage of your car. Durability and streetability requirements also play a factor, and you need to make sure you don’t have unrealistic goals. It just simply takes a certain amount of power to go fast and there is no way around that. You also have to put the power to the ground so if you are seriously into your quarter mile times you better look at the chassis options too and their prices.
To start out with I’ll just say that I want to go high nines (9.90s @ 135) in a 3200 pound mustang and the Moroso Power Speed Calculator says I need right around 600 HP to do that. Let’s also say that I am building a weekend warrior street and strip engine. The requirement is that it must last for a couple of years minimum and run on pump gas. I am willing to adjust valves and check plugs etc. and I am also not concerned about mileage or emissions but I do expect to drive this car at the track and on the street and maybe even on some longer trips etc. However, I don't expect to drive it everyday or in rush hour traffic etc. I also want to use either a 302 based OEM block or a 351W OEM block.
Ok so now I know I want 600 HP (or more) so what do I do, as the engine builder? Again, I look at the budget and then look at my cylinder head choices and see what I can get that will work with my budget and intended usage. I know many of the common aftermarket 20 degree wedge heads are pretty economical and can use commonly available headers and intakes etc. I also know after seeing tons of real live engines run on the dyno and the track that a head can usually make around 2 HP per CFM. This is flowed at 28 inches of water column on a Superflow SF600 flowbench, which is the standard of the industry. Keep in mind that when I say this I also mean paired up with a good intake, cam and headers too. So if I need 600 hp I probably need around 300 CFM at 2 HP per CFM. I look at my options and there are many heads that can do this. For example, I pick out the AFR 205 cylinder head from Airflow Research and see it goes 310+ on intake and also has a very good exhaust port too at 230+CFM. I decide to use this one since I can get a good deal on it and it uses regular parts. I could use other larger heads that flow more but I know this will work and stay in my budget.
I will also say that to make the 2 HP per CFM I am talking about on pump gas you still need a manifold, cam and headers that will NOT become the limit on power. So I will choose the newer Ford 351W Super Victor manifold from Edelbrock and also some of the larger headers on the market. Something probably in the 1 7/8 to 2 inch range so I can grow in the power department a little if I need to. Both of these choices are to keep me in the 600-700 HP ball park and not limit the engine because of the peripherals used. A 310 CFM head does no good if you kill it with a long runner manifold that is too small and too restrictive. The carb or throttle body I would choose would also be probably very large compared to what some would pick but with only 14.7 PSI natural “boost” (the atmospheric pressure) I don’t want any restriction at all.
Even though we haven’t even talked about the short block yet, we now have the airflow and peripherals in place to make the power we want, so we can now make some decisions about what we will really do on the short block. Everyone on this board knows I like BIG. Why do I? Well to start off with I will say that with a single plane manifold, pump gas, and 10.5 to one compression ratio, you will usually make around 1.25 foot pounds of torque per cubic inch. You'll also be pretty safe from detonation with a good pump gas. This is very consistent and common among most engine builders on normal good pump gas engines. We will also lose around 10-12% of that torque at peak power almost every time if you look at many dyno sheets like I do everyday. Now how long you can hold onto that torque level is totally dependent on your top end and your camshaft. We have already chosen those pieces based on the combination to carry us into the 600 HP range.
What this means is that if I say, try to make 600 hp with a 306, I will probably have around 383 ft. lbs. at peak torque, and this will drop off to around 344 ft. lbs. of torque at peak power. So basically I would have to turn the 306 to 9160 rpm at this torque level to make 600 hp on pump gas! I hope I don’t have to tell anyone but budget pushrod engines aren’t really that reliable at 9160 rpm! Now try a 347 with 434 ft. lbs. peak torque, and with 390 ft. lbs. of torque at peak power. It would have to turn 8070 rpm to make 600 horsepower, which is much better and maybe more realistic, but still way up there. It's more in line with an all race engine that is torn down very regularly! Now take a 418 Windsor that can make 522 ft. lbs. of peak torque on pump gas and 470 ft. lbs. of torque at peak power and you can now make 600 hp at that same very achievable pump gas torque level at a realistic 6700 rpm. I think now you can also see why there aren’t any nine second pump gas 306s on any of the boards that any of you frequent. At least not any that are NA and run on pump gas. However, there are many 400+ inch Windsor's there on the exact same lists. I’ve helped build quite a few of those and also helped many with these combos even though some were staunch small engine guys before they saw the light so to speak!
Last would come the camshaft and to really achieve this 2 HP per CFM that we need, I would use a pretty large cam. It would probably see around 255-265 degrees @ .050 on the intake and maybe 260-270 degrees @ .050 on the exhaust. To keep it extremely reliable I would also use a fairly mild street roller cam profile that was designed to use more moderate spring pressure and not kill parts. I would not go for extreme lift maybe .600-.650 max lift. Also necessary would be a good set of lifters and good valve springs that are known to be reliable. I can’t go much more into this or I would have a phone book on my hands. Again, you get the picture and it’s always a package or combination rather than just a list of individual parts. I use parts I know will last longer rather than those parts I know will make more power but will also fail fairly early, or require much more maintenance than a street car should have. We've got our goals, and need to stick by them. With the larger cubes the engine speed to make our power will be much lower and the valvetrain life will increase exponentially so it’s all good!
Hey it’s been a long ride but here we are and we’re through and we have a nice 418 inch 600 HP pump gas engine that is shifted at 7000 rpm and will last a long time and is still fairly cheap to build and maintain. We could have gone with a hydraulic roller and probably still made this power on an under 7000 rpm engine and in fact with a solid roller we can make even more than 600 hp. On pump gas but I always try to stay on the conservative side. Then the customer is happy instead of just satisfied or disappointed since he (or she!) didn’t make the numbers and performance that they were “expecting.” If you use rational and sensible thought to achieve your goals you are not often disappointed."
So now for the meat and potatoes of why you're here. Building racing engines or even a weekend warrior street/strip engine! The FIRST thing I ask people is what kind of realistic budget do you have? I would say that if you don’t have this figured out you are just wasting your time and the people who are talking to you as well. The worst thing you can do is to try and do something if you are way out of line with your budget. Try and race in a class you can afford or you will always be mad about people outspending you. I know since I’ve been there so just keep that in mind before getting in way over your head in something you can’t afford to be competitive in.
Secondly, you need to be very clear about what you want to do with this engine. By that I mean many things like how long does it have to last? Can it last maybe 5 passes between freshens or maybe more like 200 passes between tear downs, or do you want a whole season or maybe way out there like 100,000 miles? What kind of maintenance are you expecting or not expecting to do on it. What fuel can you run or will you run in it? Are you constrained by any rules such as exists in almost all race sanctioning bodies? Is it in fact a street car or a race car? Do you drive it in heavy stop and go traffic or is it solely a weekend warrior? Does it have to pass emissions or does it have to have a really nice idle? Only you really know what you are looking for so you need to communicate that very clearly or you may not be happy with what you build.
Third, you need to look at how much power you want to make and how fast you are expecting to go in order to be satisfied with what you have spent and with all the time and effort you will put into this. You need to sit down with the Moroso Power Speed Calculator and see how much power it is going to take to make you happy. You also need to try and also think about the money you have and the intended usage of your car. Durability and streetability requirements also play a factor, and you need to make sure you don’t have unrealistic goals. It just simply takes a certain amount of power to go fast and there is no way around that. You also have to put the power to the ground so if you are seriously into your quarter mile times you better look at the chassis options too and their prices.
To start out with I’ll just say that I want to go high nines (9.90s @ 135) in a 3200 pound mustang and the Moroso Power Speed Calculator says I need right around 600 HP to do that. Let’s also say that I am building a weekend warrior street and strip engine. The requirement is that it must last for a couple of years minimum and run on pump gas. I am willing to adjust valves and check plugs etc. and I am also not concerned about mileage or emissions but I do expect to drive this car at the track and on the street and maybe even on some longer trips etc. However, I don't expect to drive it everyday or in rush hour traffic etc. I also want to use either a 302 based OEM block or a 351W OEM block.
Ok so now I know I want 600 HP (or more) so what do I do, as the engine builder? Again, I look at the budget and then look at my cylinder head choices and see what I can get that will work with my budget and intended usage. I know many of the common aftermarket 20 degree wedge heads are pretty economical and can use commonly available headers and intakes etc. I also know after seeing tons of real live engines run on the dyno and the track that a head can usually make around 2 HP per CFM. This is flowed at 28 inches of water column on a Superflow SF600 flowbench, which is the standard of the industry. Keep in mind that when I say this I also mean paired up with a good intake, cam and headers too. So if I need 600 hp I probably need around 300 CFM at 2 HP per CFM. I look at my options and there are many heads that can do this. For example, I pick out the AFR 205 cylinder head from Airflow Research and see it goes 310+ on intake and also has a very good exhaust port too at 230+CFM. I decide to use this one since I can get a good deal on it and it uses regular parts. I could use other larger heads that flow more but I know this will work and stay in my budget.
I will also say that to make the 2 HP per CFM I am talking about on pump gas you still need a manifold, cam and headers that will NOT become the limit on power. So I will choose the newer Ford 351W Super Victor manifold from Edelbrock and also some of the larger headers on the market. Something probably in the 1 7/8 to 2 inch range so I can grow in the power department a little if I need to. Both of these choices are to keep me in the 600-700 HP ball park and not limit the engine because of the peripherals used. A 310 CFM head does no good if you kill it with a long runner manifold that is too small and too restrictive. The carb or throttle body I would choose would also be probably very large compared to what some would pick but with only 14.7 PSI natural “boost” (the atmospheric pressure) I don’t want any restriction at all.
Even though we haven’t even talked about the short block yet, we now have the airflow and peripherals in place to make the power we want, so we can now make some decisions about what we will really do on the short block. Everyone on this board knows I like BIG. Why do I? Well to start off with I will say that with a single plane manifold, pump gas, and 10.5 to one compression ratio, you will usually make around 1.25 foot pounds of torque per cubic inch. You'll also be pretty safe from detonation with a good pump gas. This is very consistent and common among most engine builders on normal good pump gas engines. We will also lose around 10-12% of that torque at peak power almost every time if you look at many dyno sheets like I do everyday. Now how long you can hold onto that torque level is totally dependent on your top end and your camshaft. We have already chosen those pieces based on the combination to carry us into the 600 HP range.
What this means is that if I say, try to make 600 hp with a 306, I will probably have around 383 ft. lbs. at peak torque, and this will drop off to around 344 ft. lbs. of torque at peak power. So basically I would have to turn the 306 to 9160 rpm at this torque level to make 600 hp on pump gas! I hope I don’t have to tell anyone but budget pushrod engines aren’t really that reliable at 9160 rpm! Now try a 347 with 434 ft. lbs. peak torque, and with 390 ft. lbs. of torque at peak power. It would have to turn 8070 rpm to make 600 horsepower, which is much better and maybe more realistic, but still way up there. It's more in line with an all race engine that is torn down very regularly! Now take a 418 Windsor that can make 522 ft. lbs. of peak torque on pump gas and 470 ft. lbs. of torque at peak power and you can now make 600 hp at that same very achievable pump gas torque level at a realistic 6700 rpm. I think now you can also see why there aren’t any nine second pump gas 306s on any of the boards that any of you frequent. At least not any that are NA and run on pump gas. However, there are many 400+ inch Windsor's there on the exact same lists. I’ve helped build quite a few of those and also helped many with these combos even though some were staunch small engine guys before they saw the light so to speak!
Last would come the camshaft and to really achieve this 2 HP per CFM that we need, I would use a pretty large cam. It would probably see around 255-265 degrees @ .050 on the intake and maybe 260-270 degrees @ .050 on the exhaust. To keep it extremely reliable I would also use a fairly mild street roller cam profile that was designed to use more moderate spring pressure and not kill parts. I would not go for extreme lift maybe .600-.650 max lift. Also necessary would be a good set of lifters and good valve springs that are known to be reliable. I can’t go much more into this or I would have a phone book on my hands. Again, you get the picture and it’s always a package or combination rather than just a list of individual parts. I use parts I know will last longer rather than those parts I know will make more power but will also fail fairly early, or require much more maintenance than a street car should have. We've got our goals, and need to stick by them. With the larger cubes the engine speed to make our power will be much lower and the valvetrain life will increase exponentially so it’s all good!
Hey it’s been a long ride but here we are and we’re through and we have a nice 418 inch 600 HP pump gas engine that is shifted at 7000 rpm and will last a long time and is still fairly cheap to build and maintain. We could have gone with a hydraulic roller and probably still made this power on an under 7000 rpm engine and in fact with a solid roller we can make even more than 600 hp. On pump gas but I always try to stay on the conservative side. Then the customer is happy instead of just satisfied or disappointed since he (or she!) didn’t make the numbers and performance that they were “expecting.” If you use rational and sensible thought to achieve your goals you are not often disappointed."
Nice.
Trending Topics
08-19-2006, 10:57 PM
#8
TECH Enthusiast
iTrader: (3)
Join Date: Nov 2005
Location: Cabool, Missouri
Posts: 591
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by jblack6527
Good read, i also have the "bigger is better" philosophy when it come to cubic inches. You obviously know what you're talking about here, very good info.
