Thread: Chevy 350 rebuilding tips

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Every engine has it's own timing requirements and there is no way to predict what an engine will require. Around 30 degrees total is a standard number. You will just need to put the car on a dyno to figure out what its timing requirements are. I do recommend disconnecting your vacuum advance as it has no effect on the timing at full throttle and will help simplify the process of adjusting. Also, if you do get a lot of dyno time, play with your cam timing. You'll likely loose a lot of power in the lower rpms, but you can get a sharp peak in the upper rpm range and you're only looking at peak power, right? Anything you do to move your peak power output up in the rpm range will increase peak power.
You will also need to adjust your carburetor based on the same trial and error basis.

Also, don't ignore the oiling system. There are very large losses in the oiling system and there are certain things you can do to minimize these losses. Don't use high volume, high pressure, or hv/hp pumps because they all require more hp to turn than a stock pump. Aim for 30 psi oil pressure at 3500 rpm. 5-10 at idle. Windage trays and crankshaft scrapers to keep the oil in the sump and off the crankshaft will give you large gains in the higher rpms. Light weight oils like 5w20 or 0w20 will also reduce power lost to friction and windage. Don't use oil coolers because cool oil has more viscosity and will create more friction.

Porting the heads will give you your biggest gains. I wouldn't polish the combustion chambers, cut the valve seats, or do anything that might increase the volume of the combustion chamber because the stock 350 chevy is compression ratio deficient enough as it is.

Wrapping the exhaust will increase the velocity of exhaust through the system and increase the scavenging effect (fast moving gasses have a lower pressure than slow moving gasses so it creates a kind of a vacuum in your exhaust system to help pull air into the cylinder during the period between the intake and exhaust stroke when both valves are open at the same time). Also, every engine has an overall ideal length of its exhaust system. This can be calculated using engine rpm and exhaust tubing, but the calculations are very complicated and I don't know any of the formulae. I do believe the length will be something between 36 and 60 inches from the exhaust port to the end of the pipe. The more rpm you turn, the shorter the length.

Carburetor spacers can help. An open spacer vs the one with 4 holes will turn your stock dual plane intake manifold into a single plane manifold which will build more power in the high rpms at a cost to your low rpm power. But, we are only looking at peak power, right?