Vacuum Spec for 67 427/435

[Gary C.]

What would be a typical vacuum gauge reading as measured at the choke pull off tube on a healthy 67 427/435?

[Joe L.]

Re: Vacuum Spec for 67 427/435

What would be a typical vacuum gauge reading as measured at the choke pull off tube on a healthy 67 427/435?

Gary-----


My VAGUE RECOLLECTION is in the range of 10-12". However, I hope we hear from some others with recent, empirical information.

[Duke W.]

Re: Vacuum Spec for 67 427/435

Reports I have from owners with verified OE cams are about 14"@900, and converting to full time vacuum advance and a proper 12" VAC for full time vacuum advance will usually increase vacuum at the same idle speed.

Remember that vacuum varies with idle speed, so vacuum should only be quoted in full context, which includes the idle speed at which it was measured.

The problem is usually verifying that the cam is actually OE or an exact OE equivalent. Many SHP big blocks have been rebuilt with aftermarket cams that have more overlap, which lowers idle vacuum - kills low end torque and fuel economy, but doesn't improve top end power.

Duke

[Gary C.]

Re: Vacuum Spec for 67 427/435

Thanks Guys

I believe that my engine has a original equipment equivalent camshaft. I get about 14" at about 800 rpm and wanted to know if that was normal.

[Larry S.]

Re: Vacuum Spec for 67 427/435

MY 66 427-425HP gives 14"-15" vac at 800 RPM.