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Discussion Starter · #1 ·
On my SPID label I have GU5, and I cross referenced it with a website that matched with rear axel 3.23 ratio, but I have only heard of 3.08, 3.42, and 3.73... Was 3.23 available or was it a typo on the website?
 
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Discussion Starter · #2 ·
If you have an L99 (4.3L V8, aka the "Baby LT1") 94-96 9C1, then it came stock with the 3.23 gears (and ONLY 3.23s). LT1 94-96 9C1s came with 3.08s (and ONLY 3.08s).

Easiest way to tell if you have an LT1 or not is to look on the SPID label for the code "LT1". Also, the LT1 cars came with dual exhaust, while the L99 cars came with single exhaust from the factory.

Ed
 
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Discussion Starter · #3 ·
It originally had the L99. The previous owner transplanted the LT1 into it from a 95 Impala SS. Why were the 3.23's not put on the same car as the LT1? Is the match better or worse that with 3.08's?
 
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Discussion Starter · #4 ·
The 3.23s basically were used to give a little more off-the-line "oomph" to the pretty anemic L99 motor. Whereas the 3.08s were probably (just a GUESS) used to MAYBE tweak an extra MPG or so on the EPA ratings for the LT1.

If the car already has 3.23s I'd leave them (as opposed to swapping back to 3.08s). If it now has 3.08s, I would goto something a bit more of a change than 3.23s (i.e. 3.42 or 3.73) if you are gonna go to the expense of a gear swap.

Ed
 
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Discussion Starter · #5 ·
<BLOCKQUOTE>quote:</font><HR>Originally posted by AutocroSSer:
If the car already has 3.23s I'd leave them (as opposed to swapping back to 3.08s). If it now has 3.08s, I would goto something a bit more of a change than 3.23s (i.e. 3.42 or 3.73) if you are gonna go to the expense of a gear swap.

Ed
<HR></BLOCKQUOTE>


I agree with Ed. I just put some 3.73's in my 96 Impala and can't believe they all didn't come this way from the factory. If you're going to change the gears, don't go backwards.

Mike


[This message has been edited by Brewdawg (edited March 27, 2001).]
 
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Discussion Starter · #6 ·
Its not like the 3.23's wont hold up behind your LT1 or anything, both 9C1 cars (L99 and LT1) came with 8.5 inch 10 bolt rearends, the ratios were different, but the strength is the same, keep em until you want to go to 3.73's.

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95 9C1 LT1
 
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Discussion Starter · #8 ·
Sleeper : show me a SINGLE documented case of a car that actually left the factory with L99 AND Dual Exhaust.

Just because GM claimed it could come that way doesn't mean that any were actually BUILT that way


Ed
 
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Discussion Starter · #9 ·
Gordon Chevrolet in Garden City, MI delivered 4 (yes, FOUR) L99 civilian sedans with Dual Exhaust. I was shopping for a new car and badly wanted a SS, but couldn't afford one. I was looking at Caprices knowing that they came with LT1's. I was looking for a stripped model (couldn't find one). I saw 8 Caprices on their lot, 6 had dual exhaust. I assumed all were LT1's, but because I was looking at content I was looking at each window sticker. When I saw that they were stickered as 4.3 V8's, I looked at the VIN. Sure enough, it was "W". I even made the salesman get the keys so I could look under the hood.

I assure you that Chevrolet indeed made L99's with dual exhaust. Saw it with my own eyes.
 
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Discussion Starter · #10 ·
BTW, the other 2 dual exh cars were LT1's, and 2 L99's with single. These cars were all on the lot in March of 1994.
 
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Discussion Starter · #11 ·
My '95 9C1 has the 3.08. I would take the 3.23 over the 3.08. There is only 5% difference between them. I would take the 3.42 over the 3.08. My recommendation is don't go to the 3.08. FWIW, the '91-'93 9C1's came with 3.42's.

3.42 would be better still, in my opinion. I would spend more of my commute in OD than I do now and life would be easier on my engine. At the same speed and gear, 10% more RPM than 3.08 but lower cylinder pressure and temps per revolution to get the same power.

I am more interested in miles per engine than miles per gallon. Besides I might get better miles per gallon with the 3.42's since I would do more of my driving in overdrive fourth gear. I avoid operating my engine below 1500 RPM in third or OD (fourth) gear.

With the additional 10% of RPM of 3.73's over the 3.42's I don't know how it would work out, gas milage and engine life wise. The consensus seems to be that you take a gas mileage hit going to 3.73's. Even with 3.73's, with the overdrive .7 fourth gear, you have an overall ratio of .7 * 3.73 = 2.61 which is not unreasonable.

One nice thing about this forum is that there is generally no shortage of opinions.


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Rowland Hill,
'95 9C1 (mine),
'95 Roadmaster (hers), front 9C1 springs, Bilstein 1516's
 
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Discussion Starter · #12 ·
<BLOCKQUOTE>quote:</font><HR>Originally posted by Sleeper:
Gordon Chevrolet in Garden City, MI delivered 4 (yes, FOUR) L99 civilian sedans with Dual Exhaust. .... I saw 8 Caprices on their lot, 6 had dual exhaust. I assumed all were LT1's, but because I was looking at content I was looking at each window sticker. When I saw that they were stickered as 4.3 V8's, I looked at the VIN. Sure enough, it was "W". I even made the salesman get the keys so I could look under the hood.

I assure you that Chevrolet indeed made L99's with dual exhaust. Saw it with my own eyes.
<HR></BLOCKQUOTE>

I can't dispute what you saw, but your assertion about Chevy isn't the only explanation.

What you PROBABLY saw was a DEALER that was selling several L99 4.3 v8 engine Caprices with dual exhaust, and that's not the same thing as L99 cars made by Chevy with duals. i.e. you CAN'T be sure that the manufacturer (Chevy) made them that way at the Arlington TX factory.

Did they come that way from the factory?

Or did the dealer put a factory-issued dual exh on the L99 car, using parts taken off an Impala SS ? The dealer might have had several employees that wanted aftermarket exhausts on their SS cars.

Now let's instead suppose you are right. IF the cars came from the factory, then they would have also had to go through emissions testing with the feds because the dual exhaust factory set up uses dual cats -- not the single cat the L99 cars were certified with. This means GM would have had to get the L99 w/duals certified.

Furthermore, since it would be a very unusual option, then it would likely have a code on the SPID. Like:

N10 Exhaust System, Dual

which is the exact code for the duals in my '94 9C1, and for the duals in _every_ other LT1-ed dual exhausted 94-96 B platform car to come out of Arlington.

So it isn't enough to see an L99 car on a dealer lot with duals. To prove your assertion, you'd need to see an L99 car with duals, AND in addition you'd need to see:

a. code N10 on the SPID of the car;

b. you'd need to see "dual exhaust, stainless, with dual cats" listed on the Monroney (window) Sticker of the car;

c. and that GM had either done the emissions test certification for the L99 with duals, OR, they had the Feds (EPA) bless the LT1 dual test for use on the L99. The EPA and/or GM would have that info.

My guess is that GM never tested, nor certified the L99 with duals, and that you won't find a Monroney or SPID with N10 duals.
I don't dispute what you saw. The cars you saw were probably done by the dealer. IMO.

I'll eat some crow when someone comes up with proof positive on items a-b-c. - Ken '94 N10 LT1 9C1
 
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Discussion Starter · #13 ·
For you disbelievers out there.


On the window sticker it listed the dual exhaust on the option list (and NO it was not one of the dealer add on type stickers, it was on the manufacturers window sticker). Also note that the 1994 window sticker gave a horsepower rating at the top of the sticker, under the vehicle type and powertrain. The standard 4.3 sticker said 200hp.

The sticker on the 4.3 dual exhaust cars stated 220hp.

And no I didn't check the SPIL because I didn't know what N10 was at the time (March of 1994), but it was as plain as day on the option list.


Whether you guys want to believe it or not 4.3 cars were available with dual exhaust from GM, at least in 1994. I can't prove 1995 or 1996, but 1994 definitely.

If the dealer still has the paperwork for those cars, I will get the VIN #'s so that you can have some crow pie, since you have a hard time taking my word.
Just make note of the window sticker hp rating, I didn't just pull that out of my ***.

[This message has been edited by Sleeper (edited March 29, 2001).]
 
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Discussion Starter · #14 ·
Just another note, Ken. The 4.3 cars came with dual cats. The Y pipe was after the trans crossmember, and while the EPA is finicky, the chassis roll cert standard probably didn't change for the dual exhaust cars.
 
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Discussion Starter · #15 ·
<BLOCKQUOTE>quote:</font><HR>Originally posted by Sleeper:
Just another note, Ken. The 4.3 cars came with dual cats. The Y pipe was after the trans crossmember, and while the EPA is finicky, the chassis roll cert standard probably didn't change for the dual exhaust cars.<HR></BLOCKQUOTE>

Good point abou the dual cats; I can check my parts bible easily enough to verify this... and that would make it MUCH easier to get the certification.

But I am still amazed by this however. I have NEVER seen any ref to a dual exh (N10) L99, nor of the 220 hp rating, in any Chevy literature anywhere.

In fact, for the L99 to gain hp from purely an exhaust mod is very hard to believe, because it suggests that the stock single exh was very restrictive to begin with.

Consider the stock engine parameters:

LT1 350 cid 260 hp 330 ftlbs
power/displacement: 260/350 = .742 hp/cid
torq/displacement: 330/350 = .942 ftlb/cid

L99 265 cid 200 hp 240 ftlbs
power/displacement: 200/265 = .754 hp/cid
torq/displacement: 240/265 = .906 ftlb/cid

Note that the ratios of power and torque to engine displacement are nearly the same. Looking more closely, the above comparison shows that the L99 was slightly less torquey for it's displacement than the LT1 (i.e. 0.906 is less than 0.942 ftlbs/cid) but that it's power-to-displacement ratio was trivially better (0.754 to 0.742 hp/cid).

So at high rpms (5000+) the L99's breathing with a single exh was arguably as good as the LT1 with duals, and at moderate rpms (at the torque peak), the L99 was slightly hindered as compared to the LT1.

And one could make the claim that the ratios are so close to each other, in a comparo sense, that it's a wash.

Now you just claimed seeing 220 hp on an L99 window sticker, presumably from an exhaust change (single to duals) only. And yet the L99 wasn't really troubled by the single exhaust based on the factory power/displacement comparo to the LT1 (shown above).

So it's hard to believe, especially with 1 April right around the corner, that the L99 will gain +20 hp from duals alone.

I'll argue that an exhaust mod isn't enough; there would have to be AT THE VERY LEAST some slight PCM tweaks to the fuel table (to fatten up the fuel delivery given the better - if any - exhaust scavenging from duals, and hence to make more power) and perhaps a minor cam change. The PCM cal for the L99 with duals should be documented somewhere.... and it might be a fun one to get a hold of for the PCM DIY group. A different cam is *not* likely though because the engines were not built at the ARL plant.

IF the L99 car came from the factory with N10 duals... at the very least as listed by "dual exhaust" on the window sticker ---- assuming the dealer wasn't printing their own (this DOES happen btw), then THERE SHOULD BE A RECORD or mention of it somewhere in the FSM, or in the illustration and parts manuals, and/or in other Chevy documentation.... like the documentation change notices that GM issues to dealers.

The LAST thing I'll add to this (which could provide a very good reason for your claim of factory L99 cars with duals) is that the factory may have been short some parts used on the L99 single exhaust. So they built a number of cars with N10 duals until the missing parts showed up (remember that the Impala SS production in 1994 was held up by missing wheels, so they might have had extra dual exhaust plumbing laying around). If so, then we should be able to find out... there are Bcar owners that work for GM, and I know someone at Milford PG.

IF you can find any info on those 4.3 L99 dual-exh cars (from the dealer), it would be neat to see if they were very early 1994 model year builds. If so, it would support the "missing parts" theory. Get the VINs because we can get their full SPID codes. - Ken, still dubious but willing to eat some crow, because it tastes just like chicken

[This message has been edited by kdrolt (edited March 29, 2001).]
 
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Discussion Starter · #16 ·
Ken, I agree that duals alone should not add 20hp to a 4.3, however that is the what the sticker said.

On the subject of stickers, there are a number of dealers that reprint stickers around here. These were the original stickers, not a reprint. Dealers usually don't go through the trouble of putting a GM part number on the bottom of the sticker. And these cars were on the lot less than a full day when I saw them, early March of 1994 (later in the model year, although that doesn't mean they couldn't have run short of parts).

The 4.3 cars use the dual cat and double hump crossmember. I have looked at single exhaust cars and the parts listings confirm it. And some of the forum's 4.3 members were discussing this (in the context of a LT1 conversion) a while ago. The parts listings also do NOT specifically call out the 5.7 V8 when listing the dual exhaust part numbers, indicating (although not specifically stating) that engine size does not matter with the availibilty of this option.

At the moment, the dealer doesn't know if it has paperwork on those unit sales. They are not exactly overjoyed by my asking (imagine a dealership not being cooperative
) them to dig through their archives. I am working on it, maybe I can even track down one of the actual cars.


What group and building does your Milford contact work in? I know several people out there, and used to work there as a contractor.
 
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Discussion Starter · #17 ·
<BLOCKQUOTE>quote:</font><HR>Originally posted by Sleeper:
Ken, I agree that duals alone should not add 20hp to a 4.3, however that is the what the sticker said.<HR></BLOCKQUOTE>

I understand, but it never hurts to question things. And you are the *only* person that has stated that some L99 cars came with factory duals. A statement like that seems to fall into the "175 mph stock 9C1 of the FHP", and "1993 factory silver Impala SS" that digest readers have had to endure.

Aside to moderator: this topic might be moved into the Exhaust Forum since we've gone way afield of 3.23 rear end gears.


<BLOCKQUOTE>quote:</font><HR> On the subject of stickers, there are a number of dealers that reprint stickers around here. These were the original stickers, not a reprint. Dealers usually don't go through the trouble of putting a GM part number on the bottom of the sticker.<HR></BLOCKQUOTE>

I'm not trying to be argumentative, but if the sticker is part of a precanned software package made by GM, then the dealer can add anything they want... including their own guess at a price. The GM p/n at the bottom of the page for the page itself is just part of the sticker landscape.

And it would be just like a dealer to add 20 hp onto the car....

Btw do you recall the rpm at which the 220 hp was generated? And was the torque rating of the motor listed? I'm not questioning that you saw these things, but rather I'm questioning if it's legit. If the dealer did the work, they would have been sloppy on the window sticker, and the SPID won't have N10 unless the dealer was savvy enough to make a new one (not likely).

<BLOCKQUOTE>quote:</font><HR> And these cars were on the lot less than a full day when I saw them, early March of 1994 (later in the model year, although that doesn't mean they couldn't have run short of parts).

The 4.3 cars use the dual cat and double hump crossmember. I have looked at single exhaust cars and the parts listings confirm it. And some of the forum's 4.3 members were discussing this (in the context of a LT1 conversion) a while ago.
<HR></BLOCKQUOTE>

I was briefly involved in some of the L99 discussion, and I know of one L99 Caprice owner that put a full LT1 N10 dual set up in his car two summers ago I think. Of course, last year he yanked the L99 and replaced it with a warmed over LT1...

<BLOCKQUOTE>quote:</font><HR> The parts listings also do NOT specifically call out the 5.7 V8 when listing the dual exhaust part numbers, indicating (although not specifically stating) that engine size does not matter with the availibilty of this option.<HR></BLOCKQUOTE>

I'll add to this. You are right about the dual cats for 94-96, and the way the pipes exit, you are probably also right about the crossmember (I haven't looked far enough yet to verify this, but it seems sensible from the exit path from the cats).

Furthermore, Book 1 Group 3 of the Parts & Illustration manual from GM, deals with Fuel, Exhaust and Carbs. pp. 3-F10 to 3-F22 are the pages specific to exhaust for 1994-1996 sedans (model code B19) and wagons (B35).

Sleeper is correct: the pages only make reference to "V8" models, and not to any engine designation; but the dual exh is specifically denoted in the book as RPO N10 (as I had said previously). There is no RPO code specific to the single exhaust system that I could see.

But here's where it gets more weird: there are four exhaust configurations shown. Two dual exhaust set ups (one for B19 sedans, and one for B35 wagons), and two single exhaust set ups (again, one for sedans (B19) and another for wagons (B35)).

How is that weird? Because ALL LT1 cars only had dual exhaust, and wagons ONLY got the LT1. So WHY is there a single exhaust set up pictured (p. 3-F20 to F22) for the LT1-only wagon? Put another way, were there any L99 wagons made? The P & I books suggests that there might have been.

<BLOCKQUOTE>quote:</font><HR> At the moment, the dealer doesn't know if it has paperwork on those unit sales. They are not exactly overjoyed by my asking (imagine a dealership not being cooperative
) them to dig through their archives. I am working on it, maybe I can even track down one of the actual cars.
<HR></BLOCKQUOTE>

Yes, I can well imagine a dealership balking at such an oddball question. Really, this whole discussion is rather bizarre even on THIS forum.... but it's a fun mental exercise just the same. And we're doing Mueller's homework for his book (if he ever writes it --- hey Scott, you reading this??)

It also occurs to me that IF the dealer did the dual install then they DID violate certain federal (and possibly state) laws regarding tampering with exhaust on brand new cars. IF they did that, you are not likely to get anywhere. And if you ask too many questions you might get to inspect a SPID more closely: from inside the trunk of a fullsize Caddy. Maybe we should just fughettaboutit.

<BLOCKQUOTE>quote:</font><HR> What group and building does your Milford contact work in? I know several people out there, and used to work there as a contractor.<HR></BLOCKQUOTE>

Dunno to both. He started there last year I think and I never asked him specifically. He's got a Ph.D. so he's probably doing noise & vib stuff (his area) for them at that level. He's not a gearhead.... or at least he wasn't. I'll write to him and ask. - Ken, one of us will be eating crow soon.... <g>
 
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Discussion Starter · #18 ·
Of course I'm reading this


(This topic has taken an unexpected turn, now hasn't it?)

Anyway, my SPID does not have N10, and an aftermarket Hooker dual exhaust system was added along with an LT1. Oh, and unless I'm wrong the LT1 was standard in wagons.
 
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Discussion Starter · #19 ·
To do this wouldent you have to alter the transmission crossmember?

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Shane Cobb
96 Impala SS "Big Green and mean!"
 
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Discussion Starter · #20 ·
Shane, no. The crossmember is the same for all 94-96.

Ken, the power peak for all 4.3 V8's is rated at 5200rpm.

I used to work at a Chevy dealer while going to college. Worked there right out of high school, did new car prep, and then worked in parts. I am pretty adept at spotting dealer made stickers. I swear it was the real deal. Hopefully the dealer will allow me to look at the files (provided they have them for spring of 94). It would be cool to document the VIN of a N10 L99. I am kind of like a bulldog on crap like this. It might take a while, but if the info is there I will get it. If they don't have the original deal paperwork (who bought it, etc.) then mavbe they have service records of one of those cars.


Autocrosser (Ed) and I have debated this next topic before (just to throw another wrench into things). I have literature that states that the 1994 Caprice wagon came standard with a 4.3 V8 (1995 was standard with the LT1). I have NOT actually seen a 4.3 wagon, but.... The fact that the parts detail lists a single exhaust system for the wagon seems to back up my literature. Interesting, huh?
 
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