[Prowbar]

Did a couple of things last weeks:

1. Made some better battery cables. The old ones were junk and made out of old welding wire and battery terminals we had laying around. One of the reasons for poor starter performance. Bought some 50 mm2 wire (equal to 1 AWG) cable with fine strands, very flexible stuff. Proper fitting battery terminals were soldered in and heavy-duty connectors were crimped and soldered. Heat shrink with glue protects from moisture and corrosion. I've added an accessory wire to the positive cable to supply the new relay-operated headlights with direct battery voltage. A connector will be added to easily connect/disconnect them in case of repairs.
The engine turns over much better now.

2. There is a picture of the added bronze bushings to the clutch pedal. I've mentioned this before but did not show a picture. As you can see a washer welded on the lower clutch rod. This prevents the clutch linkage from wearing in to the corner of the rod. The clutch linkage was made from hardened material, and couldn't use a regular drill, endmill, or reamer to cut the material. However, a carbide burr and some patience made a nice 1/2" hole, and the made up bronze bushings were pressed in with LocTite.

3. Made a new adapter for the Impco mixer to go on top of the carburetor. Hood clearance is minimal but present due to the higher raised manifold on the earlier 478s.

4. Welded up one of the downpipes, in this case, the right side. Still need to weld in the O2 sensor bung.

5. Started tearing apart the engine to remove the camshaft. Been studying the original grind and seeing how one could extract a little better performance from one. I've considered Pete Chronis' grind, but it is more of a higher RPM camshaft. Another issue is the lack of CNC camshaft grinders - all of the companies use a copy camshaft machine with existing cam profiles to regrind camshafts.

Some thoughts:
All durations are based on advertised numbers since this is what the GMC book gives.

- Stock cam LSA (Lobe Separation Angle) is 110 degrees. I would have liked to go lower, for example, 108 or 106, to improve low-end torque. However, not possible without welding up the cam I would think. Still open for discussion. Pete's specs keep a 110 LSA as well.

- Keep the stock 63-degree overlap between intake and exhaust. Pete's cam has a 32.6 crank degree overlap, which is much less. I believe the book also gives all cam duration in crank degrees since advertised duration numbers comparable.
- Stock intake closes 61 degrees after BDC. I would like to close the intake earlier, for example, 50 degrees ABDC for an increased dynamic compression ratio. Since the static compression ratio is low as is, one could extract a little more compression out of one. However, cylinder filling might become a problem. Pete's cam closes intake 46 ABDC, which is even earlier.

-A bit more cam lift would be nice to compensate for later intake closure. Still need to measure the stock camshaft lift.

-Keep the same intake duration of 268 degrees, if possible. However, reduce exhaust duration from 298 degrees to about 275-280 degrees.
Pete's cam has an intake duration of 236 degrees and an exhaust duration of 268 degrees.

Seems like Pete's cam really 'sacrifices' on intake filling by closing the valve early, having less intake duration, and less valve overlap.

Your thoughts on the camshaft?