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williamM
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Joined: August 07, 2008
Posts: 4333
Location: southwest Arizona
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 Posted: Thu May 25, 2017 10:53 am Post subject: FI plenum chamber differences and years |
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I was cleaning plenum chambers for T-4 FI when one came up without a EGR mount/hole- no tubes inside- the next one had a EGR mount and hole but no tubes inside- then came one with the tubes inside going to the mouth of each runner.
Any one enlighten us as to those changes?
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raygreenwood
Samba Member
Joined: November 24, 2008
Posts: 21520
Location: Oklahoma City
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| Posted: Thu May 25, 2017 4:21 pm Post subject: Re: FI plenum chamber differences and years |
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| williamM wrote: |
I was cleaning plenum chambers for T-4 FI when one came up without a EGR mount/hole- no tubes inside- the next one had a EGR mount and hole but no tubes inside- then came one with the tubes inside going to the mouth of each runner.
Any one enlighten us as to those changes? |
Are you sure they are all bus plenums?
Ray |
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airschooled
Air-Schooled
Joined: April 04, 2012
Posts: 12728
Location: on a bike ride somewhere
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| Posted: Thu May 25, 2017 5:32 pm Post subject: Re: FI plenum chamber differences and years |
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EGR pipe went straight into the throttle body when the EGR valve was mounted on the engine tin until mid '76. That year, when the EGR valve mounted itself to the plenum, you get the holes in the plenum. 
I can't speak for the pipes inside… But I think the vacuum ports also differed from year to year; I've seen ~4mm manifold vacuum ports on the left and right side, but the vacuum signature is the same, so the switch was probably a manufacturing or hose-reduction (read: cost cutting) measure anyway.
What are you cleaning the plenums for? Clean engine components are over-rated.
Robbie
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Randy in Maine
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Joined: August 03, 2003
Posts: 34890
Location: The Beach
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| Posted: Thu May 25, 2017 5:34 pm Post subject: Re: FI plenum chamber differences and years |
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| And of course the 79CA version has no EGR on the plenum. |
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williamM
Samba Member
Joined: August 07, 2008
Posts: 4333
Location: southwest Arizona
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| Posted: Fri May 26, 2017 1:45 pm Post subject: Re: FI plenum chamber differences and years |
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Great info. thanks- I'm putting the 79 one on and then the other one gets the egr with no pipes- (think they would do that so the EGR plugged up ---- so- beware- if one plugged up you might get all your egr directed at 1 or 2 cylinders.
All these came in a pick up load with the Adventure wagon- so hav no clue where they originally came from- then there was 3 sets of FI that had components. from different classified here.
mistakenly left the one with no pipes in the acid over night and some one stole it  - well maybe it just went awaaaay.
As far as cleaning goes- all of these had carbon and rust built up inside- throttle bodies too. what a mess. pic later- still no wifi 
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some days I get up and just sit and think. Some days I just sit.
opinion untempered by fact is ignorance.
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williamM
Samba Member
Joined: August 07, 2008
Posts: 4333
Location: southwest Arizona
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| Posted: Fri May 26, 2017 1:51 pm Post subject: Re: FI plenum chamber differences and years |
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| asiab3 wrote: |
But I think the vacuum ports also differed from year to year; I've seen ~4mm manifold vacuum ports on the left and right side, but the vacuum signature is the same, so the switch was probably a manufacturing or hose-reduction (read: cost cutting) measure anyway.
What are you cleaning the plenums for? Clean engine components are over-rated.
Robbie |
There were 2 varieties of ports on this pile- most had the small ported tap- (whose drilling on the throttle body was plugged by carbon on most throttle bodies) Then one had a bigger tap with the ported one- that tap was behind the butterfly, so maybe the vac retard at some point.
 
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some days I get up and just sit and think. Some days I just sit.
opinion untempered by fact is ignorance.
Don't step in any! |
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williamM
Samba Member
Joined: August 07, 2008
Posts: 4333
Location: southwest Arizona
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| Posted: Fri May 26, 2017 1:54 pm Post subject: Re: FI plenum chamber differences and years |
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| raygreenwood wrote: |
| williamM wrote: |
I was cleaning plenum chambers for T-4 FI when one came up without a EGR mount/hole- no tubes inside- the next one had a EGR mount and hole but no tubes inside- then came one with the tubes inside going to the mouth of each runner.
Any one enlighten us as to those changes? |
Are you sure they are all bus plenums?
Ray |
| Quote: |
These were completely unidentified- came with different boxes of FI from the classifieds. Most had the full rich micro switch-
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some days I get up and just sit and think. Some days I just sit.
opinion untempered by fact is ignorance.
Don't step in any! |
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