It all started one afternoon when I returned home from the office. I was getting ready to back the Valiant into my parking spot when the engine mysteriously stopped running. "That's funny," I thought, until I tried to restart the engine. Then I heard the sound of a freewheeling engine that has no compression. After I pulled the No. 1 spark plug and brought the No. 1 cylinder up to the top of the compression stroke, removal of the distributor cap confirmed my suspicions-timing jumped.
The part that bothered me the most is I was unable to get to the dyno before this happened, and baseline numbers of our seasoned engine are unavailable. Oh well, I guess we'll wing it. The 360 in the Valiant is a '71 model that came with a two-barrel carb, 1.88 and 1.60 intake/exhaust valves, and 8.8:1 compression ratio. Peak horsepower was rated at 255 at 4,400 rpm, and 360 lb-ft of torque at 2,400 rpm-definitely not setting the world on fire with performance.
With the engine out of the...
With the engine out of the car, we pulled the heads. It was painfully obvious where our compression was going. All eight exhaust-valves were bent.
Assessing The Carnage
After we loaded the car on the trailer and got it to the shop, a decision needed to be made: "Do we fix the engine in the car, or take it out?" When I finally reasoned with myself and came to the realization that the engine is an "interference engine" (meaning if the timing chain "jumps", valves will hit pistons), I decided I'd better just pull it. With the engine finally out and on the engine stand, I removed the intake and heads. As soon as the heads were placed upside down on the workbench, I knew it was bad. Every exhaust valve was bent. Worried, I checked the pistons. The carbon buildup on the pistons had quite possibly saved me from piston damage. Only small marks were visible on the pistons and were easily removed. The next question was, how much compression ratio did I lose by knocking the carbon off of the pistons (yep, it was that thick)? Further parts removal, like the balancer, water pump, and timing chain cover, revealed the stock plastic timing gear was now a smooth wheel.
With the top half of the engine on the workbench, it was time for a game plan. Where do I go from here? Do I just replace the bad pieces and put it back together? Not hardly. I decided it was time to put at least a decent top end on the short-block. After all, the engine didn't use oil, had good compression, and the oil pressure was 45 pounds at idle. Nah, let's rebuild the top, add a few aftermarket pieces, and see what happens.
We decided to disassemble...
We decided to disassemble the heads at home before giving them to Jerry at Wilt Engine Services for the refurbishing they needed.
Since our engine retains the...
Since our engine retains the stock bottom end, a full-blown port and polish would definitely be overkill. We simply gasket-matched the ports and removed some of the "pinch" in the pushrod location.
We found eight exhaust valves...
We found eight exhaust valves on the shelf, and since the intake valves were fine, we reused them. We cleaned them all up with a wire brush, and then sent them to the shop with the heads.
We checked our valve-to-piston...
We checked our valve-to-piston clearance before making the plunge into shaving the heads. With plenty of clearance, we had the go-ahead to cut .020 inch off. Cutting more than this means the possibility of intake port and attaching bolt alignment issues.
We checked our valve-to-piston...
We checked our valve-to-piston clearance before making the plunge into shaving the heads. With plenty of clearance, we had the go-ahead to cut .020 inch off. Cutting more than this means the possibility of intake port and attaching bolt alignment issues.
We degreed-in the cam per...
We degreed-in the cam per the cam card.