[AdamHoud]

So my father now holds the firebird, and I recently picked up a very good original condition '70 buick electra 225 with the high compression 455 (factory 10.25:1), literally was an old lady purchase.

I spent the weekend tuning it up to original specs, compression checked the engine and was happy to see all cylinders were 190-200 PSI.

My problem is that after updating/tuning the ignition and timing components, I am getting serious knocking when putting any load on the engine. (the previous owner had it retarded so it wouldn't knock).

What did high compression owners do when premium leaded gas became unavailable?

[67 Lamnas]

Originally Posted by AdamHoud

So my father now holds the firebird, and I recently picked up a very good original condition '70 buick electra 225 with the high compression 455 (factory 10.25:1), literally was an old lady purchase.

I spent the weekend tuning it up to original specs, compression checked the engine and was happy to see all cylinders were 190-200 PSI.

My problem is that after updating/tuning the ignition and timing components, I am getting serious knocking when putting any load on the engine. (the previous owner had it retarded so it wouldn't knock).

What did high compression owners do when premium leaded gas became unavailable?

Go for a 20 minute drive on the highway to get the engine up to normal operating temp. Get a 20 or 24 oz bottle of water and remove the air cleaner. With the engine running about 2800-3000 RPM, SLOWLY empty the contents of the water bottle in to the primaries of the carb. The water will turn to steam and help to clean off any old-lady carbon build-up in the combustion chambers and from the tops of the pistons which may be leading to your detonation issues. She probably lugged it around town to church and back and to the pharmacy.

You might have to do it more than once.

It would also probably be helpful to change out the thermostat to a 160 degree unit.

In addition, it would be helpful to find a vacuum advance canister that will limit the vacuum advance to about 12-14 degrees. I'm assuming the advance source is ported, not manifold vacuum.

You can also try heavier advance springs, but the factory ones already on there are probably pretty stiff...make sure the advance limit bushing hasn't fallen off or is missing.
Obviously you're running 92 or 93 octane fuel already....right?