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On my parts car (which I can still drive, amazingly!), I was checking the vacum the other day, and it gave me a rock solid 17.5 vacum reading. My question is, when I gave it gas, the vacum dropped to about 7-9, but came back up immediately after I let off. I understand that revving the engine will 'subtract' vacum, but is this a bit excessive, and if so, what could it mean? I am planning on using this as a temp motor until I am done building the other one. Thanks in advance! The specs are as follows:

91 Z28
86 305 HO
4bbl q jet, no wiring (all wiring from computer has been stripped, as it was a TPI car originally)
416 heads, stock
stock intake and cam
all A.I.R. components removed/blocked

Also, while I have your guys ear, do you think that a Carter 625 carb, Holley Street Dominator Intake, port matched ported and polished 416 heads with 1.94int & 1.6ex, 1 3/4 headers, 1.6 aluminum roller rockers and a Comp Extreme 256 or 268 cam could make 375 hp? All but the cam is what I have left from a previous engine, and I saw a guy with a web page that had a similar setup and his 'pesimistic' graph boasted more than that, on a 305. Just wanting opinions on if it's a pot of poo or gold.
 

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As for vacuum your readings are normal. Imagine how the engine is sucking on the closed throttle blades at idle trying to consume air. When you pop the throttle, you let a rush of air into the intake which causes your vacuum to drop. It's not uncommon to hit 0"Hg for a moment. At WOT with the secondaries open, 0"Hg is very likely.
 
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