Today, we continue on with the budget build stuff we spoke about earlier this week. We discussed how you should have a plan (or at least an idea) about what you want to do with your car, and a rough estimate about how much you want to spend.

Remember that we are looking at this from the point of view of a budget restomod build.

Photo Credit: Mecum

We talked a bit about exhaust systems in my last post, and we’re going to pick up right where we left off. More often than not, the exhaust is usually one of the first upgrades to any car.

The main reason for this is because you get the most bangs for your buck since you’re not only changing the way your ride is perceived, but also increasing your power a bit by helping the engine breathe better.

The car breathes better because aftermarket exhaust systems are less restrictive than the one that originally came with your car. Here’s the catch: the more of your exhaust you replace the better off your car will be.

For example, if you just replace the muffler, you’ll get a deeper and more aggressive sound. However, you’re not really helping it breathe all that much better. So, you’ll only gain a small amount of power – if any at all.

But if you start with the manifolds, and replace them with tubular headers, the sound changes even more. And, as a bonus, the power is dramatically increased because the exhaust gases can exit the engine that much faster.

Photo Credit: Mecum

Depending on the system you go with, the material it’s made of and the type of car you’re driving, you could buy a bolt in replacement exhaust for just hundreds of dollars.

Even better, the types of cars we’re working on allow us to do this type of upgrade by ourselves, in our own garage or driveway in a weekend’s time.

On the other side of the breathing equation, is the intake system. If you’re running fuel injection, the following paragraphs won’t apply to your application. But to get it out of the way right now, you could upgrade your intake tubing and filter to a less restrictive unit for pretty cheap.

For carbureted engines, increasing your power is so incredibly simple, it should be illegal (I’m kidding!). I know you’ve heard me say that bigger is better. And while this is usually the case within the powerful engine world; too much fuel could be bad for your engine.

So, while the carb that came on your car from the factory is likely insufficient, you don’t want to go overboard. I’d like to say that there isn’t an exact science to picking out the right carb for your restomod, but I can’t say that.

The big carb companies have a formula that they use to determine how big of a carburetor (in CFM) is needed for your engine. I pulled this information off the Edlebrock website:

Take the cubic inches of your engine, and multiply that by your maximum RPM. Take that number, and divide it by 3,456 which represents volumetric efficiency.

So, a 396 big block looks like this: 396 (CI) X 7,000 (RPM) = 2772000.

2772000/3,456 = 802 CFM. So in this case, you wouldn’t need to go any higher than an 800 CFM carb, because that is the maximum amount of flow that engine needs. And in all reality, you’d be better off at around 750 CFM.

Photo Credit: Mecum

Now, there is some other technical jargon, and another step that I’m not including on purpose – because there is no way that I can figure it out for you from where I sit. Basically, the formula outlined above assumes that your volumetric efficiency is 100%.

However, this only happens with forced induction engines – like with a supercharger. Yours is likely somewhere between 60-80% but there is no way I could figure that out here. Check out this resource for a much more detailed look.