Chevrolet 8.1L swap into 88 one ton

The Chevrolet 8.1 liter engine was produced from 2001-2006 and installed in HD 2500 and larger trucks and vans, as well as motor homes, Suburbans and Avalanches. It is similar to previous big blocks, but has the advantages of better cylinder head and intake manifold flow than the earlier 7.4 liter engine did. It has larger displacement from an increase in stroke. It is factory rated at 340 HP @ 4200 rpm and 455 lb/ft of torque @ 3200 rpm The following chronicles the fabrication and modifications required to install a 2002 8.1 liter Chevrolet engine into a 1988 one ton crew cab.

The 8.1l engine has bosses for old and new style engine mounts. You may use your existing engine mounts with this configuration. The bell housing bolt pattern is the same as previous small and big block Chevy’s. Note that all fasteners in this engine are metric. The flex plate is unique to the 8.1l. Note the crankshaft sensor, oil pressure sensor, and the EGR valve tubing in the picture, below right.

The frame rails on the Silverado pickup (in which these engines came in) are wider than earlier trucks. This creates some clearance issues with the frame, firewall and engine cross member. Since the complete frame on this truck was going to be boxed, I decided to use the manifolds that came with the 8.1l as they are cast out of stainless steel and have the port for the EGR tubing. One could use headers for an earlier big-block, but be sure to check clearances as the 8.1L uses a tall-deck block. Other wise, the flange bolt pattern is the same as other big-blocks. The frame rails need to be notched, back by the exhaust manifold to flange area, and the top edges of both sides of the frame need to be trimmed back to make room for the heat shields. You are removing a fair amount of material, so be sure to box all of this in with 3/16” plate to strengthen the frame.

Another clearance issue is the LH front corner of the oil pan. This was corrected by first cutting a hole in the cross-member, fabricating a piece out of 3/16” flat stock to fill the hole and welding in.

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