Beginner’s Engine Building Basics

I remember how daunting the task of rebuilding an engine was when I first began, now that I’m nearing the end of this project I realize how simple it is. Sure there are a lot of steps, but it isn’t rocket science. What I’ve been doing during Operation Stude is taking apart an engine and putting it back together – quite a bit different then actually choosing components to build a setup from scratch, which is what I’m referring to with the term “engine building“. I’ve got a lot more to learn before jumping into that endeavor, but as it turns out Operation Stude has given me the chance to get my feet wet.

If you’ve been following along, you know that I discovered that my Small Block Chevy (SBC) is just a 350 instead of the 383 that I believed it to be. Honestly, this didn’t come as a huge surprise to me based on my experience of driving this engine. It never had the power that a 383 should have, was impossible to tune (multiple experienced people tried), and just didn’t run at what I believed optimum should have been. Basically, finding out that my 383 was just a 350 was a relief because it gave me the knowledge I needed to make some informed decisions.

I talked with Eric Solomon at Westside Performance, a shop that builds a lot of performance Chevy engines, about the top things to consider when choosing an engine set-up. Here’s what he said are some beginner’s basics of building an engine –

1. Decide Your Purpose

What is your engine going to be used for? “Not all 500 hp is created equal,” says Eric. If you’re doing something like autocross, you’ll want a small high-revving motor to give you that low-end power. On the other hand, if you want burnouts for days you’re going to need a lot of torque. Where on the powerband you want to produce the power and how much you actually want/need should guide your engine building decisions.

For me, Stude is a daily driving hotrod. The way she’s driven in the past demonstrates that she’s put together to produce power at high rpms…yet that doesn’t fit how I’m using her. I end up throwing away a lot of gas through all those stops and gos and never get to utilize the top part of Stude’s powerband. First thing first, figure out what you want to do with an engine before building it.

2. Choose the Smallest Components You Can

For a performance street engine, “Smaller is always going to be better,” says Eric. Smaller components are a lot snappier, so “choose the smallest components you can get away with without hurting the number (horsepower) you’re trying to make.” And that horsepower you’re trying to make? Be practical about it – gearheads may “ooohh” and “ahhh” at a 600 hp engine, but in all practicality that horsepower will just go to waste in daily driving.

“Your engine is just a pump, how big is my pump and how much air can it really draw,” explains Eric. A big pump needs a lot of air, without it starvation will happen and the engine won’t be able to run properly. On the other hand, if you’ve got a smaller pump and you’re opening its air supply up too much – with big heads, intake, and carburetor – the motor ends up pulling in the air too slowly causing a weak signal. All of your parts need to be balanced.  A small pump can drive a lot of air but in order to do so you’re going to have to turn it much faster.

Since I spent college with my nose in biology books I like to think about an engine like a heart, because hearts are pumps too – just like engines need air and fuel the heart needs oxygen and blood. You wouldn’t want to put the veins, or lungs, of a cow on the heart of a hummingbird – or vice versa . If you’re starting with a cows heart…or a big block engine…you’re going to have to use components that can match that size and hold up to the power output. What’s delivering the air and fuel to the engine? It’s the top end of your engine – the carburetor, cam, heads, and intake manifold.

With these two engine building basics in mind, let’s take a look at how I’ve been able to put this information to use on my Small Block Chevy project…

Decision #1: Choosing a Carburetor

Other than the fact that my carburetor was a 4-barrel labeled “Holley Street Avenger”, I didn’t know much else. After Eric told me there were formulas to calculate optimal cfm (cubic feet per minute), I decided to figure out what cfm my carburetor was. Finding an identifying number I looked it up on Holley’s website to find that it was 770 cfm.

Next, using the target cfm formula: CFM = [engine displacement x max rpm x efficiency]/3,456…

I found out that my target cfm range was 493-523. Eric did warn me that the equation tends to give you numbers on the low side, and you do need some experience working with these numbers….but 770 is way above ~600! Why does this matter? CFM, or cubic feet per minute, is referring to how much air is being feed into my engine. Of course, a carburetor’s job is to mix air and fuel. So if I’ve got a carb pulling in lots of air, it’s going to be dumping lots of gas into it. Why were my spark plugs always turned black? My engine was running too rich on gas and it wasn’t getting completely “spent” during the combustion process! That large of a carburetor not only makes me waste money on gas, but it also makes my engine run crappy, and to top it all off it adds unecessary wear to my engine. So you see…choosing the right carburetor is important!

To start building a better engine for Stude, I’ll be replacing my 770 cfm carburetor with an Edelbrock 600 cfm Performer series carburetor. My electric choke version comes calibrated for maximum fuel economy. With this smaller carburetor not only will my gasoline bill decrease, but my engine will be able to run properly and safely! As a bonus, if I need to rebuild my new Edelbrock carburetor…I’ve already been taught how to do so when my car club visited Edlebrock. Not only did we get a factory tour (which is pretty cool to know exactly where your car products came from) but they also gave us a hands-on lesson on rebuilding and tuning their carburetors!

Decision #2: Choosing an Intake Manifold

Sitting just underneath the carburetor, an intake manifold has the job of getting that air and fuel to the valves in your heads where it then passes through to the cylinders. The design of an intake manifold has a huge affect on the airflow in your engine. Stude had a Team G single-plane high rise intake manifold whose design is meant to provide the least restriction for air passing through…again, no bueno on my engine.

In order to get a strong signal to my cylinders, I need a good steady flow of air that matches the amount my engine pumps. My old Team G intake is rated for up to 7800 rpm. My absolute max rpm is probably at 6,000 with highway driving being around 2,200. If you can’t tell by these numbers, that intake isn’t providing the right air flow for me. During Operation Stude I’ve swapped it out for Edelbrock’s Performer series intake manifold. With it’s dual-plane low-rise design it will actually restrict the air flow more then the Team G one…which in my application is good! I should see improved torque on lower rpm’s and a better throttle response from a stop.

The other important top-end component is cylinder heads. I found out from my machine shop that I have World Heads. After doing a little search for the casting number, I discovered they are Sportsman II heads. A performance head, but not too performance, it should serve Stude’s SBC well – so these were checked and surfaced by the machinist and are going back on my engine.

Speaking of which, I’m SOOOO close to the end – I can’t wait to see how this puppy runs and enjoy the fruit of my hard work!!! Sign up for the GreaseGirl newsletter to follow along on the journey!

What’s been the most important lesson in your engine building experience? Leave a comment!