vaccum readings


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By 63 Red Stake Bed - 18 Years Ago
I was curious what others are able to get with their specific combo's the last time they checked.

I'm @ around 5200' in Elevation

292 .060

C1TE's ported w/1.72 /1.51

Isky E-4 installed Straight up(.015 lash) with stupid silent chain; 1.6 rockers (rocker arm specialists)

current carb:  1.14 2100: 12-13 inches of vaccum @ 700rpm in Neutral.

bouncy idly(not lopey, sounds like poor valve sealing)

Think I need to have the valve seats re-ground as when I checked them last they were not concentrick when I lapped them.(crappy seat install by machinist 10 years ago??)

By Doug T - 18 Years Ago
What would you expect a stock motor to make at such an altitude.   If the valves aren`t sealing it isn`t too surprising that the vacuum is a little low.  

In my car with a cam selected to work with headers (it has a lot of overlap) I have about 9 in at 900RPM after warmup.  It wont keep idling much below that no matter what I try.  But that comes with the overlap and can`t be tuned away.

By charliemccraney - 18 Years Ago
The last time I checked it was 15" at 750rpm.

My engine is at 318ci. The cam is 226@.050, 274adv, 112 sep, .295 lift. Its somewhere around 2 degrees retarded. It's in my notes somewhere.

Not sure about elevation. I'm near Atlanta.
By DANIEL TINDER - 18 Years Ago
My worn-out, stock '55 292 makes 22"s of vacuum, and will idle so low I can zero the P&G gapper with the motor running.
By Unibodyguy - 18 Years Ago
Mine is a 292 .40 over,  stock "G" heads, and a 254 duration cam. 1:43 rockers, 2 bll. Motorcraft/Holley 2100 , and dual exhaust, and Petronix in a stock 57 or later distributor. It pulls about 17.5- 18 lbs. at idle that I guessing is 600-650 RPM. I don't have a tach so i can't tell. The timeing is also at 8 degress advanced and runs much better and with a higher vacume at that setting.

                                       Michael

By Ted - 18 Years Ago
272 with the Isky E4 camshaft is 15” at ~700 rpms (no tach also) and at 900’ above sea level.  Engine has the ’55 heads with hardened seats, camshaft originally advanced 2°, 7½:1 compression ratio, and now with over 100K miles.  The Isky E4 camshaft is ground on 108° lobe centers which will automatically cost some idling manifold vacuum by lieu of increased valve overlap.  Also running a four hole carburetor spacer which keeps the vacuum readings marginally higher than with an open style spacer.