Ask Away! with Jeff Smith: Should I Put a Small Block or Big Block Engine in My 1974 Chevy Truck?

I am trying to decide on an engine for my 1974 Chevy project truck. The truck has a 350ci small block and a TH350 but I am thinking of going to a big block like a 454. I’m not going to race this truck but it will be a nice, lowered street truck that will see lots of highway miles. I’m looking for plenty of power but I don’t have unlimited funds. Half my friends say put a big block in it and the others think a hot small block is more than enough. Can you point me in a direction?

A.K.

Wow, we could probably write a book length answer and still not cover all the issues here. Let’s start with the fact that you mentioned you don’t have a lot of money to spend and that you will be putting quite a few highway miles on this truck. Both of those goals push the answer toward retaining a small block Chevy in the truck.

But before we talk about that, let’s investigate the big block side of the question for a moment. Even a mild 454 performance engine would be a strong runner in your pickup. There’s plenty of room on the engine compartment and the big block will bolt right in. Buying a used 454 and bolting it in is an option but you run the risk of buying an abused engine that will need to be rebuilt.

We first thought in terms of a mild crate engine. We began researching 454 crate engines and discovered that our post-Covid situation makes for limited parts availability for crate engines. Given that, there are very few options for buying a 454 at a decent price. As this is written, Chevrolet Performance is currently out of stock on its 454 HO engine.

So this leaves you with the option of buying a used engine and rebuilding it. While machine work for a big block would not be that much more than for a small block, you will have to start first with a rebuildable core and invest in a pile of additional new parts including intake, exhaust, a complete accessory drive for alternator and power steering, a larger radiator and plenty of other parts to complete the conversion. One thing you can re-use from the small-block would be the carburetor and distributor – assuming you already have a decent sized four-barrel carburetor like a 750 cfm Holley for example.

What you’ll get from this investment is an engine with a ton of torque potential that will be really fun to drive. If you’ve never experienced big-block torque, find someone with a healthy big-block in their car and ask them for a ride. Large displacement engines pull really hard in high gear and are a ton of fun. We should warn you that doing this may seriously affect your decision!

The down side is that a big block will rarely be able to achieve the same fuel mileage that a smaller displacement engine can deliver. It’s an unavoidable fact of life that big inch motors use more fuel to push around all those big pistons. Given present fuel prices, this should be a real consideration if you plan to put miles on this hot rod. 

The advantage of building a small block is that you can reuse your existing 350 engine. This reduces your initial cash outlay. The easiest solution might be to decide if you‘d rather rebuild the existing engine or opt for a more affordable crate engine. Here, the options are also affected by this post-Covid situation.

In the past, it was a really good idea to invest in one of Chevrolet’s basic two-piece rear main seal small block new Goodwrench engines. The beauty of this engine was you could purchase one for under $2,500. But we have discovered these engines too are currently not available anywhere due to the same supply chain problems. This does not mean there are not rebuilt 350 engines for sale, but they will now be more expensive because of the increased demand.

For example, we found that many of the more affordable engine packages are not available right now. Instead emphasis is being placed on the higher output, more expensive engines. This leaves long block applications that are priced well into the $3,500 to $4,000 range. It’s entirely possible that these will become “normal” prices for even basic engines in the near future.

This really pushes the average enthusiast into rebuilding his own engine. This is not all that bad and it also allows you to choose the parts you want to run as opposed to the low compression and mild camshafts that come with the basic crate engines.

We’ve done some quick research into machine shop prices and to have the block cleaned, bored, honed, connecting rods rebuilt, the block decked, cam bearings installed, a crankshaft polished, and the entire rotating assembly balanced will add up to a little less than $1,000. At best, you’re looking at around $2,250 worth of new parts (this includes a new distributor, intake manifold, spark plugs, and wires which puts the cost to build your own engine at roughly $3,300).

I think I’m one of a slowly dying breed who prefers to build his own engines mainly because I will then know what parts went into the engine and all the clearances. One disadvantage to this is that you will also need to invest in some basic engine rebuilding tools. The other alternative is spend another $500 to $600 and pay the machine shop to assemble the short block for you and you can then bolt the rest of it together yourself.

This was a very long answer to your short question but with open-ended questions like this there are really no hard and fast solutions. I would stick with a purpose-built a small-block as the most logical approach but I have to admit—those Rat motors are sure fun!