Quote:
Originally Posted by dlloyd
Is 12” at idle low for a performance cam?
I was told that it was going to be in that range because of the cam.
I was not going WOT on run stand. That would have hit the rev limit in distributor. I had rev limit set at 5,500.
Maybe 4,000 to 5,000 RPM is where I thought I saw 20”.
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MAKING A LOT MORE SENSE NOW.
1( You are on a engine run stand
2) Very easy to have 12" of vacuum at idle with a decent camshaft.
3) You do not have any load on the engine when you rev it up on the engine stand. No Torque Converter drag/Trans drag.
4) With no load on the engine you basically can be at 4000 rpm and have 20" of vacuum because you are now above the Cams reversion point (due to overlap) so the engine shows 20" vacuum on the gage.
The info is valid but only for a reference point if you put the engine back on the same test stand with a different camshaft profile for example.
The run-In stand basically puts a light firing load on the pistons/rings and helps get the initial timing close and the carb idle close, before engine installation.
Tom V.