Typical vacuum for 308

50C8DAN
50C8DAN Senior Contributor
in HUDSON
Anyone know the typical vacuum at idle for a 308?

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  • dougson
    dougson Senior Contributor
    I am running a PCV valve which makes a bit of difference, but I routinely run at 18-20" at idle (one caveat, not all vac gauges are equal, I try to go with a higher quality).
  • 50C8DAN
    50C8DAN Senior Contributor
    I am swapping out my tredlevac for a modern vacuum booster that typically needs 18 in min.  So wondering if I need to add an aux. vac. pump.
  • dougson
    dougson Senior Contributor
    I would. I have a treadlevac and it works fine now but I know they can be troublesome.
  • RichardD
    RichardD Member
    edited April 2017
    Dan, just installed a PBR VH40 booster on my '53 {1450 psi @ 20"hg}. You will not believe how good the brakes are. EXTREMELY strong--in a heartbeat !! Check your messages.
  • RichardD
    RichardD Member
    attached VH40 & 44 data

  • Kdancy
    Kdancy Senior Contributor
    Richard, just wondering, have you checked your vacuum with a reliable boost guage?
    I checked a fairly new 308 with only a few miles on it and was getting 17 lbs, but the guage is many years old. I assume that as that 308 breaks in, the vacuum will increase.
  • RichardD
    RichardD Member
    edited April 2017
    No, Kerry, just stating what the attachment has on it at max. Think 16" would be good.  Thanks, now I am curious.
    Would need to be the vacuum when the brakes are applied. But I am glad stopping is not better than it is now. Not sure that the 18" above is a minimum; would be an unworkable system. That is why I attached the graph for 'typical' hydrovacs.

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