84 OMC 305 quadrajet carb too lean

I got a big problem... I had the carb rebuilt, ran it twice and burnt the #7 cylinder exhaust valve. Pulled plugs and all were white. I pulled head and replaced valve. I put it all back together bought new plugs gave a full turn out on both idle mixture screws, ran it a couple of minutes and plugs were white again. I can't seem to get it rich.<br /><br />My question is two fold, does anybody know the correct starting point for the screws, ( I seem to remember 1 and a half turns out after seated) and am I missing something here that would make the engine run lean. <br /><br />I am paranoid of burning another valve after all the work of tearing apart and re-assembling this engine.<br /><br />Thanks....

Re: 84 OMC 305 quadrajet carb too lean

Sorry, forgot to add that it's a 4 barrel....

Re: 84 OMC 305 quadrajet carb too lean

Idle only adjusts idle. To adjust mixture at speed you replace the metering rods. Most Auto parts store will help you with that. The carb should be already set up for sea level from the factory. So unless the rods have been changed, you should be ok. I suspect a jet is still partially plugged if indeed it is running lean. It can be difficult to really get a carb clean. <br />It's pretty difficult if not impossible to burn a valve at idle. White plugs can be something else such as water in the cylinder or antifreeze if it is a closed sytem. It's tough to make a judgment though without seeing the plugs. Can you post a picture of them?<br />Are there any other driveability problems? Check for vacuum leaks at the manifold.

Re: 84 OMC 305 quadrajet carb too lean

Thanks for the response.... I have to go to work so I can't get a picture up until tomorrow. The boat was running great with no driveability problems. I ran it all day at the lake the first day. The second day we were an hour into it when it happpened. I have a fresh water cooling system and it looked like there was no water in the cylinders when I pulled the head. I replaced the intake manifold as apart of fixing the valve and the problem continues. <br /><br />I have another question. The plugs I used to run in the boat had the firing tip even with the threads. The current ones have a much longer tip and I have been told that that makes them hotter. Could the hotter plugs be causing the problem, and if so, how would I find the correct heat range for the plug that should be in my boat.<br /><br />84 OMC 305 4 bbl. Thanks.....