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Gufshoz · 09-17-2023, 04:42 PM

Hey people,
I have 1,500 miles on a rebuild: cylinders sleeved, new babbitts, new Scat crank, tour ground cam, and a 5.5 Snyder head.
I did a 500 mi break-in drive, 100 mi/day, starting at 25 mph and increasing, daily to 45 mph. I normally drive around in my area and try to stay under 45 mph. Yesterday, I was driving around a corner, revved and downshifted, then floored it to merge into traffic. I had the spark fully advanced (usually I keep it around 2/3) and she started knocking.
I experimented by advancing and retarding the spark to about 1/2 during hard acceleration but not going faster than 45 mph. Hard acceleration at full advance = knock and hard acceleration at 2/3 advance = no knock. Is this just normal pre-detonation due to timing or should I be looking more deeply.
Surely, it's too early to be checking bearing clearances on the crank.
Thanks
P.S.: I've been told that I'm my own worst enemy for imagining problems that aren't.

09-17-2023, 04:42 PM	#1
Gufshoz Member Join Date: Feb 2012 Location: Gulf Shores, AL Posts: 78	knock during hard acceleration Hey people, I have 1,500 miles on a rebuild: cylinders sleeved, new babbitts, new Scat crank, tour ground cam, and a 5.5 Snyder head. I did a 500 mi break-in drive, 100 mi/day, starting at 25 mph and increasing, daily to 45 mph. I normally drive around in my area and try to stay under 45 mph. Yesterday, I was driving around a corner, revved and downshifted, then floored it to merge into traffic. I had the spark fully advanced (usually I keep it around 2/3) and she started knocking. I experimented by advancing and retarding the spark to about 1/2 during hard acceleration but not going faster than 45 mph. Hard acceleration at full advance = knock and hard acceleration at 2/3 advance = no knock. Is this just normal pre-detonation due to timing or should I be looking more deeply. Surely, it's too early to be checking bearing clearances on the crank. Thanks P.S.: I've been told that I'm my own worst enemy for imagining problems that aren't.