What would be a good starting point on base timing? Engine is a 351w, 69 block, the heads are the newer square water jacket. In a straight drive truck with a 600 Holley. Things giving me a fit. Think I've got it right and the next time I drive it it goes to spark knocking again. Any help is appreciated. Clint

 

I would start with around 6-8 degrees BTDC with vacuum line disconnected from carb. I'm assuming you're using a relatively stock distributor? Check it with a timing light and then go for a drive to see if it pings and then make adjustments from there.

1979 F150 Custom: 84 351W: 91 heads, Crane PowerMax cam, double roller timing chain, Edelbrock Performer intake & Edelbrock carb
1987 F150 XLT Lariat: 88 351W EFI
86 & 87 Bronco II: next winter's beater

 

6-8 degrees advance with vacuum advance disconnected sounds good.
Some other problems may be present. Is your motor old? More specifically, how old is your timing chain? Are you experiencing a loss in horse power? The 69 351W was designed to run on 98 leaded octane. Are you running premium gas and lead substitute. If not, and it's pinging, you'll burn the valves and valve seats out quickly. The 69 351W was one of the highest horsepowered years built that means highest compression ratio. Run the good gas with lead substitute and see what you get.
Good Luck, Have Fun, KingFisher

 

I agree with previous posters, about 6 deg btdc initial timing. I have found that how fast the timing advances is more important than the initial, though. You may have to adjust the vacuum advance, along with the distributor springs, to get the right curve to prevent pinging. The vacuum advance is adjustable with a 1/8" allen wrench inserted in the vacuum can hose port.