Manifold Vacuum port on GM TBI unit - Off-Road Forums & Discussion Groups
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post #1 of (permalink) Old 05-18-2001, 12:17 PM
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Manifold Vacuum port on GM TBI unit


i was wondering where the manifold vacuum port is on the GM TBI (i have the Howell-CA EFI kit)? is it port J; port J is left of the PCV port while looking towards the back of thr truck which Howell suggests to plug up since it's not used. or can i get manifold vacuum from the port comming out of the intake manifold which is right under the TBI throttle linkage?

i took the vac reading from both ports and the pressure dips to about 5in right when i increase the throttle but returns steadily back to about 20in when i hold the throttle at any position. isn't manifold pressure suppose to drop as throttle position is increased?

basically i'm trying to look for a manifold vac source for my HEI distrib. have it on ported vac right now and want to just play around a bit...



83 CJ7 258/T5
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