Throwback Thursday: Replacing A Small-Block With Big-Block Power

Another week is almost over and Thursday is here once again. That means it’s time for us to celebrate another editorial throwback. Each week, we jump into the way back machine and open the vault that houses our vast collection of articles. In this Throwback Thursday, we’re taking a step back in time to bring you an article that you guys might have either forgotten about, or might not even know exists. Whichever the case, we are certain that you will enjoy this editorial flashback. So, without further ado, let’s take a look back at an article that gives you some much-needed insight when it comes to swapping a big-block into your once small-block-powered hot rod – No Replacement For Displacement: Swapping In A Big-Block

Engine Swap

To make room under the hood, big-block engines were offset 1/2-inch to the right by using asymmetrical brackets.

When it comes to Chevrolet engines, swapping accessories is usually a straight forward task, but swapping a big-block where a smaller version once resided, can be cause for some frustration. That’s why we reached out to Casey Mohr of Original Parts Group (OPGI), to get some professional input about accomplishing the task.

engine swap

The safety-lock feature keeps the engine from moving too much if the mount fails.

In the original article, Casey states that for the most part, this upgrade is a plug-and-play install. He does however, warn that there are a few key components that need to be changed in order to accommodate the new, larger engine. We even included a list in the original article that he put together to help make for a smooth swap for a couple different body styles.

engine swap

The big-block crossmember’s transmission mount opening is squared-off with a beveled corner whereas the opening of a small-block crossmember is oval shaped. The transmission mount slots for the big-block manual transmission crossmember are also in a different location than the small-block version. The slots are offset about 1/2-inch towards the passenger side and about 3/4-inch forward.

Mounting a big-block where a small-block once resided also means upgrading accessory brackets and pulleys. Pre-1969 vehicles used a short water pump, and most ’69 and later engines used a long water pump. We could probably develop a complete article about bracketry for this swap, but just keep in mind that brackets for the power-steering pump, alternator, and air conditioning will vary. Although some people will tell you the pump reservoir is interchangeable, the hoses actually use different connections.

engine swap

Using the wrong frame brackets could cause the engine to sit too low, causing a clearance issue like this pulley hitting the crossmember.

You’ll have to check out the original article to get all the information, but you’ll be glad you did. Since there are probably a lot of enthusiasts attempting this swap, I thought it a great piece for this week’s Throwback Thursday flashback. So, find out how Original Parts Group can help your hot rod after you check outNo Replacement For Displacement: Swapping In A Big-Block.

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About the author

Randy Bolig

Randy Bolig has been working on cars, and involved in the hobby ever since he bought his first car when he was only 14 years old. His passion got him noticed by many locals, and he began to help them with their own vehicles.
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