I’ve got a ’66 Chevelle with an inline six cylinder and a Powerglide and I want to swap in an LS engine. I’ve been reading about LS swaps but there is so much confusing information that now I’m not so sure. Do I have to hack up the floor pan to install a 5.3L truck LS and a 4L60E in my Chevelle? Is there an easy answer to this?  Thanks!

B.P.

The problem with the internet is that everybody has an opinion—and often times they are just flat wrong. We’ve done the exact swap that you’re talking about in a ’67 Chevelle and also in a ’66 Chevelle with a variety of transmissions.

The good news is your swap is pretty easy.

We don’t have the space here to look at all the variables but we’ll hit the high points to cover your question. You mentioned the 5.3L truck engine and 4L60E so we’ll go with that.

Tips & Advice for LS Swapping a 1966 Chevelle

We’ll offer some insight with Holley LS conversion parts since we’re most familiar with their products. (I’ll put a parts list at the bottom of this article.) If you use the standard stock location motor mount adapter plates, the engine will fit but the oil pan won’t. First, the truck oil pan is too deep and will be about 1-1/2 inches deeper than your crossmember.

We’ve found that the Holley 302-2 oil pan fits pretty well in these cars. All Chevelles are front steer cars, which means the steering linkage is in front the crossmember. Even with a stock small or big block, the linkage comes very close to the oil pan at full lock. So watch for this.

This oil pan swap also will require a new LS3 dipstick and tube for the proper oil level indications. Because the pan in shallower in the front to clear the crossmember, you also will have to trim the windage tray but that’s also a simple job when the original oil pan is replaced.

With the engine in the car with the proper oil pan, the next hurdle will be squeezing the 4L60E under the stock floor pan. On the 1967 Chevelle we converted, several people told us that we would have to butcher the floor in order to get the trans into the car. In our case, that was not necessary. There were two places where the 4L60E was close to the floor. The first was the front servo cover actually hit the floor in the upper portion of the cover.

We marked this location and then used a large hammer and an equally large radius body dolly to move roughly a two inch by one inch section of the passenger side floor upward. This allowed for sufficient room to clear the servo cover. The second area was the cooler line connectors which were very close to the floor as well. We were able to use some forged AN fitting adapters to clear the floor with the cooler lines but you may have to hammer the floor in this area as well.

Sometimes the body will fit closer to the frame because the original rubber body bushings have collapsed, this tightens the clearance between the body and the frame and this directly affects transmission tunnel clearance. Of course, the 4L60E will also need to have the transmission crossmember relocated as well and you will need a different length driveshaft as the old driveshaft will likely be too long. But neither of these are difficult to resolve.

The OE truck intake manifold should also clear the hood if you plan to re-use that stock manifold. If the engine is equipped with drive-by-wire (DBW) throttle, you will have to eliminate the stock throttle pedal assembly and convert to a DBW throttle pedal that is available from multiple sources including GM and Holley.

man working on an LS engine in a Chevelle
We’ve swapped several LS engines into early Chevelles. This particular swap put a 5.3L truck engine bored to 5.7L and fitted with an LS2 intake along with a 4L60E much like your conversion. In this swap we used a Painless engine harness and a stock ECU. (Image/Jeff Smith)

Of course, there are about a hundred more little details you will need to address like using the truck accessory drive and the power steering pulley is very close to the Chevelle upper control arm area and you may need to address that, but overall the swap is fairly simple. The only large hole you will have to make in the firewall will be for engine harness.

Otherwise, the hacking of sheetmetal should be minimal—have fun!

1966 Chevy Chevelle LS & Transmission Swap Parts List

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You might also enjoy the Summit Racing LS Engine Swap Guide.

Keywords
4L60E, Ask Away!, chevelle, Jeff Smith, LS Swap
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Author: Jeff Smith

Jeff Smith has had a passion for cars since he began working at his grandfather's gas station at the age 10. After graduating from Iowa State University with a journalism degree in 1978, he combined his two passions: cars and writing. Smith began writing for Car Craft magazine in 1979 and became editor in 1984. In 1987, he assumed the role of editor for Hot Rod magazine before returning to his first love of writing technical stories. Since 2003, Jeff has held various positions at Car Craft (including editor), has written books on small block Chevy performance, and even cultivated an impressive collection of 1965 and 1966 Chevelles. Now he serves as a regular contributor to OnAllCylinders.