Spark knock on Merc 4.3 LX

[Happy Days]

I have posted on this topic before but have not gotten anywhere yet...<br /><br />I have a new engine (4.3 Vortec) attached to my old Alpha One. I get a spark knock at about 2500 RPM when I get stuck in a trough and the engine is working REALLY hard. It runs great at idle up to 2400 RPM and above 2800 RPM. <br /><br />I've checked the timing and retarded it from 8 to 6 BTDC. I've tried premium fuel. Following Bondo's advice, I tried replacing the step-up spring in the carb with stronger springs (the new engine HAD a "rebuilt" Carter AFB carb). I replaced the carb with a NEW Edelbrock 1409 and changed the metering rods a jets to the richest settings. <br /><br />Still getting the ping. If I had a vacuum leak I would suspect other problems like rough idle. <br /><br />Any takers?

 

[Bondo]

Re: Spark knock on Merc 4.3 LX

If you are in fact experiencing Detonation,.....<br />It's Usually caused by Advanced Timing,... Or a Lean condition........<br /><br />What Color are your Spark Plugs after a run,.???<br /><br />What are you running for an Ignition System on this New motor,.???<br /><br />It Could be a vacuum leak,... But that'll Usually offer More Issues than you've got..........<br /><br />Quick Cure,................<br /><br />Back down to 2400rpms,.......<br />Or,.... Bump it up to 2800rpms............

 

[Happy Days]

Re: Spark knock on Merc 4.3 LX

According to the plug chart.. they're perfect. I have Thunderbolt IV ignition with the 4.3 LX module. I was thinking of trying a cooler plug.<br /><br />If that doesn't work I'll stick with your quick cure. <br /><br />Thanks.

 

[Happy Days]

Re: Spark knock on Merc 4.3 LX

Test..