I have a 73 Riviera GS stage 1. It was "recently" rebuilt according to the previous owner (I have owned it 8 months). While sorting out the glitches that invariably occur (rebuilt the carb, replaced the distributor, installed an electronic ignition), one problem has persisted. Spark knock, especially at WOT. I use premium which helps, but what else can I do? I have the timing set at 4 degees advanced (factory setting) and I have standard advance springs...If anybody has any ideas I would love to hear them.. Thanks!
Check your total timing with vacuum advance disconnected and plugged. Sounds like you might be getting way too much total at WOT. You should recurve the distributor so you can use 12-14 initial for a total around 32-34*. There a ton of threads on the Street/Strip forum describing how to do this. When I bought my GS there was NO stop bushing in the HEI to prevent the mechanical advance from running wild; upwards of 45*. Check to be sure yours is there. I made one from vacuum line as a temporary fix until I found a kit that included stop bushings.
Gary's right on except I would cut total back to 28-30 all in at 2500 rpm. 430s and 455 have an appetite for octane and even the 8.5 comp motors will rattle esp in heavy cars without gear. I believe it's THE major cause for rod bearings going out....they just get pounded. Detonation is like wacking the piston with a sledgehammer! My 73 Riv (non GS) with 28 deg still rattled with 93....loved a 50-50 mix of Cam 2 and 93. Ran a 15.10 with it.
My 350 does the same thing, essentially... I haven't tried to recurve the distributor though, I was hoping to make enough money to send mine to Dave for an HEI conversion... but that doesn't look hopeful any time soon Good luck getting it sorted out.
