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In part one of this series we introduced you to the concept of the 302 based stroker. We also began work on our 331 cubic inch stroker engine. The engine will replace the 302 in our '67 Mustang project car (formerly known as "Project 11.99").

We left off last time having clearanced the cylinder skirts to prevent interference with the rod cap-screws due to the increased stroke of 331 crankshaft. As we detailed previously we have selected a complete 331 stroker kit from SCAT Crankshafts. The kit includes 5.400" forged H-beam rods, 3.250" stroke cast steel crank, and SRP forged flat-top pistons. We completed the kit with Total Seal rings and Clevite bearings.

In this article we'll take you step by step through the assembly of the motor, and discuss the cam, heads, and intake selection.

Machine Work and Engine Assembly

1. A Sunnen boring and honing machine completes the over boring and torque-plate honing of our '89 302 block.

2. Block is back from the machine shop with a 4.030" overbore, decks milled 0.005" and squared to the crank centerline.


3. Part of the machine shop work was to install new cam bearings and freeze plugs. Notice how the oil galley plugs are "staked" into place to prevent from coming loose. Alternatively you can tap and install screw in plugs.


4. One of the first things we after receiving the block back is check for proper main and rod bearing clearances using Plastigauge. The green Plastigauge is used for 0.001"-0.003" range.

5. The ARP main studs are screwed, hand tight, into place.

6. The Clevite main bearings are installed, dry, for the purposes of checking clearance. Note the grooved bearings go into the block saddles.

7.
The crank is carefully laid into place. Then a strip of the Plastiguage wax is carefully placed on several journals.

8. The non-grooved bearing halves are set into the main caps. Use a very light smear of oil on the crank side of the bearing to prevent the Plastiguage from sticking.

9.The studs are then torqued to specification (80 lb.ft. working from the center outward, and using moly lube on the threads)

10. Do NOT rotate the crank while checking clearances with Plastiguage! After torquing to spec, remove the nuts and main caps. Usually a whack on the side of the cap with a mallet or piece of wood will dislodge a stubborn cap.

11. Carefully remove the main caps, and you are left with a squished piece of Plastiguage Using the template gradations on the packaging, you can determine how much clearance exists. The wider the wax, the less the clearance. We're at 0.0015"


12. The same procedure can be used to measure rod-bearing clearances. For main bearings 0.001" - 0.002" is ideal for clearance on a street - strip motor. For rod bearings aim for 0.001" - 0.0015". If clearances are out of specification, talk to your machine shop about cutting the crank down to use oversize bearings.

 


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