L89 427 Big-Block Engine Build - L89, Version 2.0

We Recreate The Iconic L89 427 With Aftermarket Parts And Make A Lot More Power.

The idea was to recreate the L89 427 with all aftermarket parts just to see if we could best the GM power numbers. What we didn't know until we chucked the motor on a dyno is we built a little 427 that is knocking on the door of the race-only L88. Not only did we build a pretty healthy engine, we did it without pushing everything to the limits. If we want to expand our pump-gas 427-or we should say our 0.030-over 427 (433ci)-it can be built up into the 600ci range because we used an aftermarket block. Funny how we are calling a 427 small-man, how things have changed.

Sucp_1101_19 L89_427_big_block_engine_build Dyno_testing 1/20

Last month, we covered how to blueprint an engine using this engine as the guinea pig. This story will cover the parts recipe and dyno tuning of the rev-happy Rat. Instead of trying to find a clean block out of the junkyard or swap meet, we decided to start with something better. Dart's Big M iron block will be the foundation for the build. Inside the block, we used an Eagle forged 4340 chromoly-steel crankshaft, Eagle I-beam rods, and forged JE 30cc domed pistons.

To make sure this 427 sounded as nasty as possible, we ordered up a Big Mutha' Thumpr cam from Comp. Let us tell you, this cam does thump. Again, instead of trying to find a factory set of painfully expensive, rare aluminum heads, we grabbed a set of Darts new 275cc Pro 1 oval port castings. These heads have many cool features that make them better than factory, but we will get into that later. To cap off the top end, we picked up a Weiand Stealth dual-plane intake manifold and a Holley 750 CFM Street HP carburetor. Providing spark is a digital E-Curve distributor from MSD. It's a billet aluminum small body distributor that has a digital module inside so you can set the timing curve with two rotary dials.

Now that you have an idea of the components we used to build our version of the L89, let's get into the good stuff. Jeff Strech from Speed-O-Motive took time out of his busy schedule to finish assembling our long block and tune it on the dyno.