Ramblings on P/B resricters

[rauscher at icst.com]

Map sensors and power brake restricter's. In the prog 101 and
tunetips documents, Bruce waxed eloquently about the need to
restrict the vacuum line to the power brake booster. This is to
prevent a sudden change in vacuum due to applying the brakes from
affecting the MAP output.

In my quest of a DYI OEM system, I've come across some OEM
components that serve this purpose.

The first is a canister that connects inline with the P/B vacuum
line. They are typically black plastic, ~1.5" in dia, ~ 3.5" in
overall length. They have 3/8" barbed hose ends, one straight, the
other at 90 deg.

I've seen them on a lot of GM cars and trucks, GM must have bought
a tanker boat-load of these. You can find them inline of the P/B
hose on Astro's & full size vans, along with Buick and other GM
cars. I've even seen them at Pep-Boys for $8US as a 'P/B booster
filter', on the 'Help' rack.


For a cleaner installation, GM has updated the P/B booster check
valve. This is the unit that plugs directly into the P/B booster,
that prevents the loss of vacuum whenever the engine is off.

On a '92 Camaro, 3.1L V6, the check valve is also the restricter.
It also appears to be more restrictive than the canister. This unit
fits directly into the P/B booster of older GM's, say a first gen
Firebird booster.

The vacuum line fitting is larger thou, being 15/32" as opposed to
the 3/8" that is used on the older cars (minor).

HTH

BobR.

Who now has all sensors mounted, distributor and coil in place,
4bbl to TBI adapter built, and is getting ready to attack the
firewall with a hole saw.

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