I just bought my car, being the firse Firebird I have owned and my third car, unlike the other two, this one runs well AND won't fall apart on me... however, when I got it "inspected" I was told that it would need some missing smog equipment i.e. a Cat that hasn't been gutted and a belt to go along with the smog pump. My question here... is there an easy way to add parts so that my car passes inspection every year that and I can remove after inspection, or is the performance gain so little that I should get it fixed and retune it to a cleaner exhaust? I would also like to know what the difference is between the L69 and LG4 305's? How much does a catalytic converter cost anyhow?

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1984 Firebird T/A
305 LG4
T5 - Hurst Short Shifter
Edelbrock 600 CFM Performer Carb
Open Element Filter
Gutted Cat - 3" Exhaust to dual 2"
IROC 16x8 Wheels

[This message has been edited by ChillPhatCat (edited July 18, 2001).]

 

The AIR pump has been shown to draw maybe 4hp and a modern high-flow cat won't provide any power restriction on your 305. Be a green hotrodder and use your emissions equipment... the AIR pump will help light your cat off faster, and modern cats are significantly more efficient and flow better than the original that came on your car.

--andrew

 

I'd be surprised if it pulls 4 hp. I kept track of every run I made last summer (racing almost weekly), pulled the belt off the pump mid-July, absolutely no difference in times.

However, I went to put the belt back on after a couple of weeks, and the pump had frozen up! If yours still works after having the belt off, count yourself very lucky.

Otherwise, I agree with everything gun says. You can get a free-flowing cat for around $60.

Just curious, how'd they know your cat was gutted?

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82 Berlinetta, orig V-6 car, now w/86 LG4/TH700R4. 2.93 limited slip. Cat-back from '91 GTA, ZZ3 intake, Accel HEI SuperCoil. AMSOIL syn lubes bumper-to-bumper. Daily driver, work-in-progress (LG4 w/'87 LB9 block, ZZ3 cam, ported World 305 heads, Hooker headers & y-pipe, 3" Catco cat & 3" cat-back).
57 Bel Air, my 1st car. '66 396, 9.7 CR forged TRWs, Weiand Action+, Edelbrock 1901 Q-Jet, GK 270 cam, Magnum rockers, Jacobs Omnipack, 1-3/4" Hedders & 3" Warlocks, TH400 w/TCI Sat Night Special conv & Trans-Scat shift kit, MegaShifter, 3.08 8.2" 10-bolt w/Powertrax, AMSOIL syn lubes bumper-to-bumper. Idles smooth @ 600 RPM in D. Best 15.02/95.06 @ 5800' Bandimere (corrected 13.93/102.4 @ sea level).

 

Is there a piece of equipment readilly available that would measure the gasses coming out of the tailpipe? or would the cat have to be taken off? Also, would you notice a deaper exhaust note without the cat? If it is impossible to tell it's gutted from the outside, then I would guess that the belt was on for inspection then removed afterward... in that case, would they notice that the pump didn't work or do they actually fire it up?

 

The smog checkers probably whack the cat converter shell with a rubber hammer. A good cat will have a dull thud, a damaged cat will rattle, and a hollowed-out cat will have a noticable hollowed-out sound. Plus, I'm sure the smog-sniffer will read high CO and HC levels anyway.

 

Thats what I figured... I still want to know what the difference is between the 150 Hp LG4 and 190 Hp L69 is... which part makes the greatest Hp gain and how much Hp gain I might get from the open element Vs. stock snorkel in the LG4?? They must be nearly identical engines...

Might have to move topic to a new category...

 

I thought that NY does emissions tests every 2 years.

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92 Camaro RS, LO3, 5-spd, T-tops

Performance:
K&N Open Air Filter, Edelbrock performer TBI intake, Fastchip Prom, Timing +4 degrees, Centerforce clutch, Xact 8mm wires, SLP 1 3/4" Headers (coated), Flowmaster Catback Exhaust, Z28 Grille w/aftmkt fog lamps, MacEwen white-face guages
Electronics:
Alpine 8030 Alarm System, Valentine One Radar Detector (How did I ever drive without one?), Pioneer DEH 7450 Head Unit w/6-pack CD changer, Pioneer DEQ 7600 Sound Processor, 2 Kenwood KAC-846 Amps powering 2 12" Pro Red subs, 2 Pioneer 6x9 and 2 MTX 4x6 speakers.
NEXT UP: TBI mods, 3.42 gears w/Torsen posi

 

I'll let someone else go into more knowlegeable detail, but the differences between the LG4 and L69 aren't that subtle. The biggest is the Compression ratio (more compression in the L69). I "think" they might have had different cams, jets, and pulleys as well.

Clem

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Clem
SCCA TransAm Series Race Mechanic/CrewChief
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1983 Z28 with LG4, 5 speed, and (unfortunately) T-tops
1983 Z28, NO T-tops, (unfortunately) Auto Transmission (hopefully not for long)

 

What doesn't make sense to me... the specs for both engine say 240 lbs/ft (correct abbreviation? can't remember...) wouldn't higher compression lead to better torque or does the final gear ratio have a lot to do with it...

 

LG4 vs L69:
Lame cam vs. somewhat better cam
Single snorkel air cleaner vs. dual snorkel
8.6:1 vs. 9.5:1 compression (until 1985, when LG4 got 9.5:1)
Constipated exhaust vs. slightly bigger & better flowing exhaust
5000 rpm redline vs 5500 rpm redline

That last one is why they have the same max torque but the L69 has 40 more equines (a combo of cam, air intake, exhaust that let it spin higher). Compression helps as well, but only about 5 of those 40. Note that the L69 makes its max torque at a higher rpm than the LG4.

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82 Berlinetta, orig V-6 car, now w/86 LG4/TH700R4. 2.93 limited slip. Cat-back from '91 GTA, ZZ3 intake, Accel HEI SuperCoil. AMSOIL syn lubes bumper-to-bumper. Daily driver, work-in-progress (LG4 w/'87 LB9 block, ZZ3 cam, ported World 305 heads, Hooker headers & y-pipe, 3" Catco cat & 3" cat-back).
57 Bel Air, my 1st car. '66 396, 9.7 CR forged TRWs, Weiand Action+, Edelbrock 1901 Q-Jet, GK 270 cam, Magnum rockers, Jacobs Omnipack, 1-3/4" Hedders & 3" Warlocks, TH400 w/TCI Sat Night Special conv & Trans-Scat shift kit, MegaShifter, 3.08 8.2" 10-bolt w/Powertrax, AMSOIL syn lubes bumper-to-bumper. Idles smooth @ 600 RPM in D. Best 15.02/95.06 @ 5800' Bandimere (corrected 13.93/102.4 @ sea level).

 

It's pounds times foot (lbs x ft), also referred to as foot pounds (communitive property of multiplication), not pounds per foot as you wrote it.

The final gear ratio has absolutely nothing to do with the torque the engine puts out, but will have an affect on the thrust the engine puts on your seat.

 

hes right, gears will make no difference in the engine torque produced. gears multiply the already output torque .

 

I knew that it was foot pounds I just didn't remember whether there was a / or a - symbol... I was just at the auto parts store today and I tried to find a spacer for my open element and they had no Idea what I was talking about... am I calling it by the right name? I need a 1/2" thick round pice to go between the air cleaner and the carb... it's a drop filter on an edelbrock performer carburetor and it is hitting the fuel pump so it sits a little crooked... enough to let bad unfiltered air in so I need to find this piece quick... one last thing before I go to bed... how should I go about cleaning my air filter and how long does it take to dry out (is it a weekend or weekday project?) Is there a specific air filter oil? Or is it just a general purpose type of oil?


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1984 Firebird T/A - Daily driver
305 LG4, T5 - Hurst Short Shifter
Edelbrock 600 CFM Performer Carb
Open Element Air Filter
Gutted Cat... missing stuff I'll need next year
IROC 16x8 Wheels
Goodyear P215/60/R16 87S - S stands for suck
(but I'm a cheap *** and I don't go 112... don't think I do...)
Quote from my sister: "It sounds like a boat"

 

try a search on l69 vs lg4, its been talked about a lot. Just to clarify a few things, five7 nailed almost everything down except the l69 has an electric fan vs a clutch fan, l69 has slightly bigger jets and i've been told a few times the t.c. on auto trans l69's has a slightly higher stall.

h and the redline of the l69 is 6000, 5500 is the tach warning on l69, 5000 and 4500 respectively on the lg4

 

'86 & '87 LG4's got electric radiator fan as well.

Jetting, stall, etc., varied so much and is something you taylor when you modify, anyway.

 

All I can say is wow... this post is three years old... I don't even have that firebird any more... I just got this email saying someone replied to my post... LOL. I will return to this site the next time I aquire a third gen.