"problem" performance continues in a rebuilt 2.8L GM ..... Engine now has 4000 miles on it and still has relatively low manifold vacuum. Vacuum is running 14-15 in hg. at idle and should be a few inches MORE vac. to adequately run all the vacuum controls: Brake booster, heater controls, dist. vacuum advance, *power piston* (2SE carb), etc.
I checked and checked for manifold leaks, reset the damn manifold gaskets three times.... etc. Im pretty damn sure the problem is the engine 'mechanicals' . Compression is 130 psig all cylinders Mechanical valve timing has been degreed, and verified OK. Ignition timing perfect - both by vacuum gauge (max rpm less 1/2" hg.) and by accurate degreeing + timing light. --- both methods equate to the same EXACT timing advance. NO leaking vacuum hoses or controls. If I remove a vac. hose from the manifold port the engine
**increases*** rpm --- which tells me I dont have a leak. Poor vacuum causes power piston in carb to lift 'early' (for over-rich mixture) - if I manually hold power piston / metering rod and remove a manifold vac hose = same rpm increase.Engine was broken in with 20 weight straight weight non-detergent oil.
Im about ready to dump a half can of cleanser down the carb to scuff the cylinder walls in desparation and run the valve lifters with ZERO lash ......
Your sage advice would be appreciated. I need another 2-3 inches of vacuum to make all the vac. controls, brake booster and power piston-ed carb. to operate properly. Any advice of why this damn engine is running 'short' by about 2-3 inches hg. of vacuum and what to do about it would be VEEEEEEEERRRRRRRRRRYYYYYYYYY much appreciated.
;-)