Jfoster

carb I put on was a quick fuel 850. and old card was Holley 1050 4150 flange. I could tell it was rich because transom was black and it fouled out plugs after one day on the water. my old motor died because I got water in it.

motor run great at the low end to the 4000 rpm. if I broke a ring or did permanent damage would it keep making the sound because after a few min noise will go away and run strong to 5200.

Jfoster

I it cant be diagnosed over the net just looking for thing to check and Ideas of what to look for thanks for the infor.

MACDAD260

On my stock 502 with a Holley 800 mechanical DP I would get a spark knock at just above 3500 RPM, the exact RPM at which the secondaries would start to open. It was a very narrow RPM range at which it would occur. I learned from my research on the subject that it is not uncommon for this to happen. As the secondaries just start to open it can create a lean condition until enough airflow velocity is produced to pull fuel through the jets. I solved my problem by changing fuel from 89 octane midgrade to 92 or 93 octane premium. I have heard that a good carb tuner can fix it but my solution has worked for me. I am jetted very conservatively at 84 p, 98s. It starts good, doesn't foul plugs and doesn't soot up the transom. Been running it that way for 10 years without any problems. I don't know if your problem is the same but it is a possibility. Good luck.

Jfoster

I run 93 octane as often as I can. And I just put bigger jets in hoping to test it next week.

Jfoster

I put bigger jets 84p 98s and noise seems to have gone away. going to mess with it a bit more.