We're not going to lie and tell you that it's easy to build your own motor. Even though you've read other articles in the past and have seen the photos, the amount of work required to put together the engine of your dreams is quite intensive. Instead, we want to show you how to not only build your own 302 short-block, but how to turn it into a stroked behemoth with a whopping 347 cubic-inch displacement (this is relative; remember, considering the short 8.2-inch deck height.)
At first, this wasn't going to be a stroker engine buildup, but rather a 306 buildup (a 302 with a .030-inch oversize bore.) But once we saw how affordable Summit Racing Equipment's 347 kit was, we decided to go the stroker route.
Considering that the cost to machine a stock crank, prep a set of rods and to purchase new pistons, bearings and gaskets was fast approaching $900, we figured that for $600 more, we could reap the benefits of 41 more cubic inches. With Summit Racing's 347 Stroker kit (part # SUM-CSUM347KIT, $1,479.95) and a prepped production block, we ventured off into the world of backyard engine building.
Your first order of business is to locate a good block to start with. The idea here is to keep costs down (since this is a budget stroker motor) but to use the best possible production block out there. The most desirable casting years for roller cam motors are 1986-1995.
From what we understand, these blocks were virtually unchanged in alloy content and casting strength, so any of these stock HO blocks will do.
The good thing about Summit's stroker kit is that its crankshaft is machined for both two-piece and one-piece rear main seals. This allows you to use an older, non-HO block as your foundation. Some of the older high-performance 289 and 302 blocks were much beefier in the number one main area, where the later "weaker" blocks are known to crack. Again, if you have access to an older block, try to get it. But if the availability is low or the cost is prohibitive, just use any late model casting. If it hasn't been done already, tear down the whole motor to the bare block, and inspect it for cracks or damaged threads in important areas such as engine mounting pads and bellhousing bolt bosses.
With your block bare, send it to a reputable machine shop for a good bore and hone, set at 4.030 inches. A good machine shop will ask you what kind of pistons you will use so that they can match each bore for proper piston skirt-to-bore clearance. Don't forget to leave your machinist at least one of the pistons that you will be using. As a general rule of thumb, lightweight cast and hypereutectic pistons should have about .002-inch clearance and heavier forged pistons as much as .005 inches. Lightweight forged pistons (such as Wiseco, JE or Arias) will live happily with .003-005 inches. But always check with the manufacturer of your pistons to make sure what it recommends.
While you are at it, have the block fully boiled, cleaned and Magnafluxed, with new freeze-out plugs and camshaft bearings installed. If extra funds permit, a line-hone of the main saddles would be great, and a good cleanup mill of the deck surface isn't a bad idea, neither.
What You Need
Summit's 347 stroker kit is all inclusive for a complete short-block. That means that you don't have to purchase anything else to put that oil pan on. As a matter of fact, the stroker kit includes a new oil pump, a complete Fel-Pro engine gasket set, a new nodular iron Scat 3.4-stroke crankshaft, a set of H-beam 5.4-inch connecting rods (which appear to be the excellent Eagle "ESP" rods, and a set of Keith Black hypereutectic pistons in 4.030-bore sizing.