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Mighty Mouse Motor | Budget-Built Small-Block: Part 1

Posted in How To on January 1, 2013 Comment (0)
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Photographers: Agustin Jimenez

To make a long story short, we bought an ’82 GMC C20 3/4-ton diesel truck … with a shortbed and a 350ci small-block. Someone had swapped in a gas engine, cut the frame, added a shortbed, and done a clean job of the conversions to boot. For $900 we purchased a cool 2WD truck with no emissions testing requirements and an engine that “needed work.”

We were told by the third-party seller that the owner had run it low on coolant and blown the head gaskets. Upon getting it home, transferring the title from two owners prior, adding a battery and little fuel, we were able to get the truck running and confirmed blown head gaskets without any leakdown test.

With only $900 into this unique 3/4-ton shortbed, bad engine heads were no big deal. Right from the get-go, we planned on building a 350ci V-8 in some boxy Chevy truck. Purchasing the exact truck we did was just a lucky find, as we really were looking for the right motor and price more than a unique truck to start with.

Dreams of small-block building came after rifling through a Summit Racing catalog and finding that we could make more than 350 horsepower out of a 350ci V-8 for less than we’ll eventually spend on tires for this truck. Summit has a number of top-end kits for both small-block Chevys and small-block Fords that come with loaded aluminum heads, a cam, an aluminum intake manifold, a timing chain set, and the necessary gaskets.

01. After scouring Craigslist for a cheap boxy truck with a 350ci engine, we came across this rare ’82 GMC diesel C20 that someone had converted to a gas 350ci V-8. A previous owner had also cut the frame and added a shortbed. It will be a neat little hot-rod single-cab shortbed truck when we’re done. You can see we were already trying to see what size of tires we could fit in the back.

We called the hotline and went about ordering the kit when our Summit phone sales rep intervened and suggested a different kit that was actually a little less expensive and had a better powerband for what we wanted. For about $1,300, we got the SME-K-355-400 Top End Kit coming to the office that makes power from 1,500 to 5,000 rpms. If we could build a 350-plus-horsepower truck for less than $2,500 (including the truck), we would be winning.

We waited to tear down the original engine in the truck because it could still move itself around the yard, even with a blown head gasket. When the parts arrived from Summit a few days later, we pulled the truck into the garage and started in.

02. The Summit Racing Street & Strip Top End Kits come with a pair of assembled aluminum heads, a hydraulic flat tappet camshaft and lifters, an aluminum intake manifold and bolts, a timing chain set, and all the necessary gaskets. We ordered the SME-K-355-400 kit that makes 355 horsepower and 400 lb-ft of torque on a 350ci block.

A couple hours later, we had the engine torn down enough to find evidence of more than just head warpage and blown gaskets. Unfortunately, there was some scarring and even a little pitting on the cylinder walls. Our rare find had just gotten more expensive than we wanted, but not so much so that we’d scrap the project and use the Top End kit for something else. Instead, it was time to scour Craigslist to see if we could find a nice replacement short-block for our budget Mighty Mouse motor. Rebuilding this block would take more time than we wanted, and we’re going to see if we can find a loaded short-block that’s already been rebuilt and someone doesn’t want anymore.

We’ll find a block, have this Summit Top End kit installed, and get this unique truck running soon enough!


03. The Summit aluminum heads (SUM-162109) included in the kit come assembled with valves and springs in place. All you’ll need to add are your original or new rocker arms and pushrods once the heads are bolted in place. They have a 170cc intake runner volume, 69cc exhaust runner volume, 62cc combustion chambers, standard-location rectangular intake ports, and D-shaped exhaust ports. It’s worth noting that these aluminum heads have a CARB E.O. number and are street-legal on ’95-and-older vehicles. If you were to buy these heads alone, you could put them on a pre-’95 Chevy V-8 and still be smog legal.

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Total Buy-In So Far

1982 GMC C20 $900.00
Summit Top End Kit $1288.00
Battery $75.00
Five Gallons of Gas $21.00
TOTAL $2,284.00

07. Trick Flow’s full gasket set (TFS-3140E915) ensures that you won’t be making late-night runs to the parts store for the correct gaskets to complete the entire top-end build.

Contents of the Summit Top End Kit

There are a number of kits that Summit offers for the small-block V-8, and after some advice from a Summit phone rep, we got the SME-K-355-400 kit with Trick Flow 62cc chamber aluminum heads and a Summit hydraulic flat tappet camshaft that is good for the 1,600- to 5,200-rpm range. The kit includes:

  • Summit Racing hydraulic flat tappet camshaft, 272/282 duration, 0.442/0.465 lift
  • Summit camshaft lock plate
  • Summit hydraulic lifters, flat tappet
  • Summit/Trick Flow loaded smog-legal aluminum heads, 62cc chamber, 170cc intake runner
  • Summit True Roller timing set, double roller, steel sprockets
  • Summit Stage 1 aluminum dual-plane intake manifold
  • Summit intake manifold bolts
  • Trick Flow full gasket set
  • Trick Flow cylinder head bolts
  • Trick Flow adjustable pushrod length checker

08. Unfortunately, things did not turn out exactly like we planned with the bottom end. When we bought the truck, we were told the engine didn’t have many miles since a rebuild and that the head gaskets had been blown. For $900, the truck was a great deal and it wasn’t a big problem since we planned on doing the Summit Top End kit right from the get go. When we cracked into the engine, we found a slightly different tale. It looks like the engine either had a lot more miles than stated or had been really pounded on when the head gaskets blew. We’re also not sure how long it had been sitting since the head gaskets had been blown—the license plate tags were last updated in 2010, so we assume at least two years. The surface rust and marks on the cylinder walls ensured this bottom end was not usable in its current state.

09. Before we got the heads off, we saw a good indicator that great care was not taken the last time this engine was rebuilt. The red paint overspray on the valves and valve springs say “rush job” to us. Instead of messing with our existing short-block, we decided to scrap it completely and look for a rebuilt four-bolt main short-block to start with. While the Top End kit we’re using may be inexpensive, that doesn’t mean we want to start with a junk bottom end.

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