My 82 GSL hasn't revved beyond 5500 or 6000 since purchased on ebay over a year ago. Tinkered with carb and timing, little change. I finally addressed the leaking coolant passages behind the Lake City Intake Manifold. The PO had blocked them off with two electrical "slugs" and copious amounts of sealant. It has left a puddle on top of the intake, and smelled like burning coolant. Although the old gasket looked as though it was sealing okay, it tored quite easily when removed. I plugged the passages with two 20mm freeze plugs and installed a new intake gasket. Now she revs to 7000 and the idle is a bit higher than before the repair. The cooling system develops more pressure than previously, evidenced by the release of pressure when I lift the "handle" on the radiator cap (didn't used to happen). Any ideas on the original problem? Could coolant have been sucked into the intake? Vacuum leak? Engine too hot? Either way it is a nice improvement.

 

I will also consider if I had knocked an obstruction out of the carb while moving around the engine compartment. I didn't remove the carb from manifold, or anything alse for that matter. Just intake from housing. Gas line, linkages, vacuum, etc. all remained in place.

 

when the intake gasket gets wet, it leaks vacuum