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post-headpic.jpgThere’s no such thing as a bolt-in engine “swap.”  If anyone tells you different, they’re lying.  Even though GM Performance found us a really close match for the Yukon, none of the brackets that direct wiring looms and hold electronic packs over the intake manifold fit.  So, in this project garage update we show you how we fabricated replacements.

If you’re considering a late model engine swap — or just want to see how to make brackets from scratch — this is a must read.  (20+ pics)

Our Yukon’s original engine sported four “brackets” that attached under the intake manifold bolts:  A front engine hook, rear engine hook, a wiring loom bracket, and a throttle body injection (TBI) electronics pack bracket.  None of them fit the new engine.  Luckily, the fifth bracket — holding more electronics and bolting to the valve cover instead — worked fine.

The Front Engine Hook

This piece almost fits.  It’s the right shape, but the bolt holes don’t align right. 

We started by tracing the shape of the new intake manifold’s bolt pattern on a small piece of paper.  We then laid old hook on the paper and rolled it over to trace the shape of the curved upper hook and the hole where you hook your engine hanger.  Now we have flat  pattern.

Note: Click on most any of the pictures below for larger versions.

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Next, we transferred the pattern to some 1/8″ x 5″ bar steel by tracing around it with a silver pencil.  (We’ve seen all kinds of expensive pencils for marking steel, but we find that silver-colored pencils — like you can get cheaply at any craft store or department store — work great.)

In any fabrication project — even simple ones — the hardest part is figuring out the order of operations.  In this case, we decided to cut and shape the bracket, drill the hole, then bend the curve into it as it’s a lot easier to cut and drill a flat plate than a curved one.

We were able to align most of the square parts of the template with the square edges of the pre-cut steel, so we saved a band saw cut.  We cut the curved part with Hobart’s AirForce 250A plasma cutter — one of our long-term test tools.  (Look for our first full hands-on post regarding the AirForce 250A early next week.)

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The 1/8″ steel required for the hanger was right at the edge of what the AirForce 250A can cut cleanly, and our inexperienced hands left us with a few rough edges that we cleaned up easily with a flap-disc-equipped angle grinder.  If you don’t have a plasma cutter, you could accomplish this task by cutting numerous angles around the curve, then grinding it down with the angle grinder.  However, the plasma cutter turns this (and many other jobs) into a 10-minute job instead of an hour job.

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We drilled the large hole using one of Irwin’s Unibit step drills.  It’s self-starting, so we just punched a nice divot in the center of the hole to align the bit and went at it until the hole was the right size.  The other two holes we drilled with normal bits, also center punching to keep the drill from walking.

Finally, we needed to put a curve on the new piece.  We considered using the anvil or a vice, but after a little looking around the shop we discovered that our (very solid) metal workbench has an almost identical curve on its front.  So, we clamped our piece to the bench and wailed on it a bit with a small sledge hammer.

Read on to page 2 where we start the rear engine hook.

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