When it hits it breaks off enough of the buildup so that it stops knocking for awhile until it redeposits. Then it knocks again. This is very hard on rod bearings, rods , heads, pistons and your wallet. The carbon pieces can also ruin valve seats and clog up the exhaust.
The key thing here is to eliminate to cause of the carbon not the carbon itself. If you are carboning up the pistons there is a mixture/timing/fuel quality issue.
These engines required premium (ethyl) gas in there day. Also keep in mind that octane calculations changed in 1976? What used to be 88 is now more like 93.
I pumped Ethyl at a Phillips 66 when I was in high school that was rated 96/100. It would be called White gas today.
I have run 10 % ethonal in all my engines since 1979 and when used in a high displacement big block it does several things that are pluses. Almost eliminates pinging or precombustion, engine run-on after the ignition is turned off, lowers operating tempurature at cruising speeds, costs less per gallon, ect.
It does however not deliver the same HP as it is lower in octane. But the loss is not that bad in my book. The Minnesota Highway Patrol clocked me at 146 mph back in 1982... and the tach said I had 300 more revs to go.
I recall in my 72 455 the temp gauge ran 15-20 degrees cooler with the ethonal blended gas at 75 mph sustained driving. Plus no knocking when you hit detent and ran up to triple digits in second gear.
Longivity of the is very subjective. My personal best has been 300K. But I have seen ones with 500k on them. I am sure that was a mill that was never abused.
Joe did well with this Centurion. By the way, that is one sexy ride!
Cams, I just poked around on ebay and found several 455 cams with mild recurves priced at slightly over $100. If you are building up the rest of the motor you can concider a 3/4 rise but and if money is not an object you can get 750 HP out of the engine without NOS, blower or turbos.
But there is not anything more mean looking that a big boat with a 6-71 sticking out through the hood! Go-Baby-Go......
And again with Joe's suggestion, big pipes. The engine has to breath out both ends. Go with 2.5 inch exhaust pipes and low restiction mufflers. Not Cherry bombs as you do not want that much attention . Additionaly you will find a deeper more throaty note when the mufflers are moved further back. A 26-30" glass pack on either side of the gas tank sounds much better than the same can installed in the factory location under the seats.
If you are going over 425 HP also have a crossover or equilized pipe fitted under the front seat to balance out the sound and back pressure.
And yes, the Q-jet's a good product and very tunable to whereever you want to set it up. The very same carb produced 21 mpg one year and some really scary HP the next but limited it to 11 mpg.
I put an HEI system on my 70 that I bought a salvage yard for $40. Came from a Caddy and bolted right on. The difference in spark output is enlightening... pun intended.
