<VV> low vacuum

[Dan Kidder]

I am looking for input on the subject of low vacuum readings. All the corvairs I own as well as all the ones I have checked belonging to other people have readings about 12 to 14 Hg. in neutral gets worse in drive 8 to 10 Hg. Also the readings are very erratic the needle on my handheld gage vibrates and jumps. All the engines I have checked have aftermarket lifters, some with many miles, some fresh. This indicates valves not closing. I have tried replacing valve springs and it no effect. The only thing that seems to raise the vacuum any is to run rockers at zero lash then it gets much better. This problem is bad with powerglide as the modulator quits working when vacuum drops below 15 Hg. Any one else addressed this problem it seems to a common one as others in our club say they are having the same trouble. 
 		
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