why is there a tpi plenum difference [look at pic]
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From: Toronto,Ontario
Car: 1989 IROC-Z
Engine: 346 LS6
Transmission: T56
Axle/Gears: Hybrid 8.8 3.73
why is there a tpi plenum difference [look at pic]
Hello
I was just looking at some pics when i noticed the the grooves on one plenum extended much farther than the grooves on another.if you look closely on one the grooves end at the begining of the first two runners. and on the other the grooves go even farther than that.
I am not sure as to why this is. maybe it is a vette/camaro, bird difference or maybe they changed the look slightly one year. All that i know for sure is that both my 89 iroc and 90 gta have plenums with grooves like the blue one.
It isnt anything important but i was hoping just out of interest if someone could shed some light on the subject.
Speed
I was just looking at some pics when i noticed the the grooves on one plenum extended much farther than the grooves on another.if you look closely on one the grooves end at the begining of the first two runners. and on the other the grooves go even farther than that.
I am not sure as to why this is. maybe it is a vette/camaro, bird difference or maybe they changed the look slightly one year. All that i know for sure is that both my 89 iroc and 90 gta have plenums with grooves like the blue one.
It isnt anything important but i was hoping just out of interest if someone could shed some light on the subject.
Speed
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Car: 1992 Camaro RS
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I don't see any differences in those pictures. But in the later third gen years GM was phasing out the L98 parts and switching everything over to the LT1. So when the factories ran out of L98 parts, some third gens wound up with LT1 runners.
*Edit*
I just noticed you were talking about the plenum.
Maybe it's the same story?
*Edit*
I just noticed you were talking about the plenum.
Maybe it's the same story?
Last edited by ScottyRS; Jul 1, 2006 at 07:32 PM.
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Car: 1992 Camaro RS
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The MAF systems have a different plenum than speed density systems. The difference in grooves made it possibly to quickly tell what year car it came from. The longer grooves were used from 85 - 88, and the shorter were used on 89 - 92. The other thing that made them different is the earlier plenums had a passage for the cold start injector, they also had a cut out in the front for the IAC. The later plenums did not have this, in 90 - 92 the plenums got a MAP boss for the map sensor.
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Car: 1994 Trans Am
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Originally Posted by ScottyRS
I don't see any differences in those pictures. But in the later third gen years GM was phasing out the L98 parts and switching everything over to the LT1. So when the factories ran out of L98 parts, some third gens wound up with LT1 runners.
*Edit*
I just noticed you were talking about the plenum.
Maybe it's the same story?
*Edit*
I just noticed you were talking about the plenum.
Maybe it's the same story?
Yes, to tell the difference between the MAF and SD cars. Maf had longer ribs and were slower, and the SD cars were shorter ribbed but much MUCH faster.
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Car: '88 G T/A
Engine: L98
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Originally Posted by ScottyRS
I don't see any differences in those pictures. But in the later third gen years GM was phasing out the L98 parts and switching everything over to the LT1. So when the factories ran out of L98 parts, some third gens wound up with LT1 runners.
*Edit*
I just noticed you were talking about the plenum.
Maybe it's the same story?
*Edit*
I just noticed you were talking about the plenum.
Maybe it's the same story?
Senior Member
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From: Old Bridge, NJ
Car: 1992 Camaro RS
Engine: 383 SuperRam
Transmission: 4L60
Axle/Gears: 3:23 Posi
Originally Posted by ScottyRS
I don't see any differences in those pictures. But in the later third gen years GM was phasing out the L98 parts and switching everything over to the LT1. So when the factories ran out of L98 parts, some third gens wound up with LT1 runners.
*Edit*
I just noticed you were talking about the plenum.
Maybe it's the same story?
*Edit*
I just noticed you were talking about the plenum.
Maybe it's the same story?
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From: Cypress, California
Car: 1989 GTA
Engine: 369 TPI
Transmission: 4L60E
Axle/Gears: 3.70 Nine Bolt
Those LT1 runners for the L98 are pretty rare. I have been looking for some for quite awhile now but they are hard to locate as so few were made.
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From: SW Michigan
Car: '88 G T/A
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Originally Posted by GuitarJunki17
Since when do LT1's have removable runners?
Anything's removable with the right tools
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From: SW Michigan
Car: '88 G T/A
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Originally Posted by 87zjeff
since when do LT1's have runners??? with the exception of the fuel rails, the intake on an LT1 is all 1 peice isn't it?
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From: louisville, ky
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well, that's what i was thinking but someone posted before seemed to imply that they seperated from the intake like the tpi runners do. didn't sound right.
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Not quite. My 1989 MAF car is like the one on the right. So it well could be that the one on the right is for 1989 to 1992 cars.
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From: Toronto,Ontario
Car: 1989 IROC-Z
Engine: 346 LS6
Transmission: T56
Axle/Gears: Hybrid 8.8 3.73
I dont think the difference is a maf/map thing. MY 89 iroc tpi [maf] and my 90 gta tpi [map] both look the blue tpi pic. The plenums are slightly different because the is a hook up for the speed density on the rear passenger side of the plenum but the grooves are the same.
I side the 89 to 92 tpi plenum statement. I know for sure those look like the second pic .. but as for 85 to 88 i havent seen a tpi in one of those for a while so i couldnt be sure.
Speed
I side the 89 to 92 tpi plenum statement. I know for sure those look like the second pic .. but as for 85 to 88 i havent seen a tpi in one of those for a while so i couldnt be sure.
Speed
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From: Las Vegas
Car: 1987 Formula (original owner)
Engine: 305 TPI
Transmission: T5
Axle/Gears: 9-bolt/3.45
Originally Posted by speedmachine
so then really all we now need to know is what 88 has.
Speed
Speed
But assuming that number relates to the model year, then the 88 looks like the one on the right, whereas my '87's, like everyone else's '87, is like the one on the left(the better-looking of the two, IMO). But I've never had my '87's plenum off, so I can't confirm that its number is 87. Maybe someone else can though.
So if that's correct, then that also would make the SD/MAF plenum comparison inaccurate.
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There are several differences over the years of the plenums between the length of the grooves on top, which was more or less for astetics, to the different set ups such as ones equiped with the cold start injector or not, as well as MAF and MAP. I belive there are 3 or 4 variations, and the Corvette had another design if I recall.
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Car: Silver 1980 Corvette (L82 w/TPI)
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Originally Posted by bigals87z28
There are several differences over the years of the plenums between the length of the grooves on top, which was more or less for astetics, to the different set ups such as ones equiped with the cold start injector or not, as well as MAF and MAP. I belive there are 3 or 4 variations, and the Corvette had another design if I recall.
The plenums break down into three groups--'85-88 (left), '89 only (middle), and '90-up (right).
The fuel inlets and returns differ between the different years. The '89-91 Corvette fuel rail (left) has a female 16mm passenger-side inlet and a female 16mm return. The '85-88 Corvette (middle) has a female 16mm passenger-side inlet and a female 14mm return. The '85-92 F-body (right) has a female 16mm driver-side inlet and a female 14mm return
Three intake manifold styles were used on the TPI equipped engines. The '87-91 Corvette intake on the left used a heat-riser tube off of the passenger-side header and has a water crossover at the back to relieve hot spots on the back of the aluminum heads. The middle intake was used on '85-86 IROCs, T/As, and Corvettes with cast-iron heads with outside valve-cover bolt holes (early-style). (The two center bolts on these two intakes are at the same position as the end bolts and will fit the early head-bolt pattern.) The intake on the right was used on '87-92 IROCs and T/As with cast-iron heads with center-bolt valve covers. The '87-95 intakes with the later cast-iron head-bolt pattern can be machined to fit the early bolt pattern. If you want to run Vortec and Fast Burn-style heads, GM and S&P have new TPI intakes to adapt a TPI to both.
All the passenger-side TPI tubes (top) for all '85-92 models are the same. There are two different driver-side tubes. The '85-88 units (left) had the ninth injector port (arrow), while the '89-92 F-body and '89-91 Corvette tubes (right) didn't.
Identifying GM's Tuned-Port Injection Units
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From: Old Bridge, NJ
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The maf to sd is mostly true, except for 89. Check out Chevy TPI swapper's guide on page 20. It gives you the run down. There were actually three upper plenums made from 85 - 92. 85 - 88, 89 and 90 - 92. 89 - 92 had shorter fins than the earlier plenums.
Originally Posted by speedmachine
Hello
I was just looking at some pics when i noticed the the grooves on one plenum extended much farther than the grooves on another.if you look closely on one the grooves end at the begining of the first two runners. and on the other the grooves go even farther than that.
I am not sure as to why this is. maybe it is a vette/camaro, bird difference or maybe they changed the look slightly one year. All that i know for sure is that both my 89 iroc and 90 gta have plenums with grooves like the blue one.
It isnt anything important but i was hoping just out of interest if someone could shed some light on the subject.
Speed
I was just looking at some pics when i noticed the the grooves on one plenum extended much farther than the grooves on another.if you look closely on one the grooves end at the begining of the first two runners. and on the other the grooves go even farther than that.
I am not sure as to why this is. maybe it is a vette/camaro, bird difference or maybe they changed the look slightly one year. All that i know for sure is that both my 89 iroc and 90 gta have plenums with grooves like the blue one.
It isnt anything important but i was hoping just out of interest if someone could shed some light on the subject.
Speed
http://www.hotrodlane.cc/PDFFILES/TPIStory.pdf
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