transcorpmerc
New member
Hi, I'm new to this forum and have a question about the Rochester Quadrajet 4BBL carb on my 1982 Mercruiser 260 I/O
I recently replaced the OEM carb with a rebuilt one from National Carburetor. My mechanic has tuned it to the point where it is performing very well, except for WOT. When attempting WOT from idle or mid-range, I get hesitation and an intermittent loud "knocking" sound that seems to be coming back through the carb. I've posted this video so this knocking (popping) can be heard (towards the end of the video):
https://youtu.be/9qSTvK6KxnM
I suspect the rebuilt carb isn't quite right. I know there could be 100 things causing this (i.e. lean condition, improper jetting, secondaries out of adjustment, anti-siphon fuel line blocked, etc.) but my main concern is that just running it to the place where it begins to knock 3-4 times might have caused further damage to the engine. I've always backed off of it whenever I've heard it. The engine runs almost perfectly otherwise.
Any thoughts?
I recently replaced the OEM carb with a rebuilt one from National Carburetor. My mechanic has tuned it to the point where it is performing very well, except for WOT. When attempting WOT from idle or mid-range, I get hesitation and an intermittent loud "knocking" sound that seems to be coming back through the carb. I've posted this video so this knocking (popping) can be heard (towards the end of the video):
https://youtu.be/9qSTvK6KxnM
I suspect the rebuilt carb isn't quite right. I know there could be 100 things causing this (i.e. lean condition, improper jetting, secondaries out of adjustment, anti-siphon fuel line blocked, etc.) but my main concern is that just running it to the place where it begins to knock 3-4 times might have caused further damage to the engine. I've always backed off of it whenever I've heard it. The engine runs almost perfectly otherwise.
Any thoughts?