87FormulaGuy

Hi Everyone,

I just recently got an 87 Firebird Formula with the LG4 Engine and 5spd trans. I've heard the L69 is significantly more powerful than the LG4, and was wondering what the main differences are, and if they'd be worth doing to my engine to make the car a little faster Also, any ideas what kind of times I'd get with a pretty much stock LG4, save for an open element and removed cat? Thanks,

Steve

Vader

87,

The LB9 (VIN "F") engine is equipped with the TPI system. The LG4 (VIN "G") engine is equipped with a Rochester E4ME carburetor. There was another earlier 305 carbureted engine in that series (VIN "H") that you really don't want to assocoate with. It had larger chambers for lower compression, and smaller valves (1.72"/1.50"). They all have the same "LA" (LameAss) camshaft with an automatic transmission (.350"/.385"), but '87 and later 5-speeds had an improved camshaft (.404"/.414") and the LG4 may have been factory rated at 40 HP and 30lb/ft less output than the LB9 engine.

In all honesty, neither one is a real powerhouse out of the box. But that's why we're all here, isn't it?

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Later,
Vader
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"Make Me Bad"
Adobe Acrobat Reader 4.0

87FormulaGuy

Thanks for the information Vader. I'm glad to hear I have the improved camshaft Now that I think about it, maybe the "LG4" name isn't the proper name for my engine? It is the 4bbl 305 V8 original to the car, for 1987, and as far as I know it was the last year these carb. engines were made. In any case, according to various manuals I've read, it has a whopping 165 hp vs. the 190 hp in an L69. So what's holding this engine back from making more power??

MRZ28HO

Actually, on the carb'ed 305s, Vader is totally wrong!

Here is the real scoop (again):
'82-'87 ('76-'81 sucked massive a$$)
LG4 VIN code "H"
dish pistons for 8.6:1 comp ratio
cam spec, I don't know (too small)
cylinder heads:
'82-'87 58cc 1.84/1.50 int/exh
4bbl carb E4ME
Single snorkel air cleaner
2-1/4" exhaust pipe
conventional catalytic converter
HP 165 @ 5000(?) rpm
TQ 240 @ 4500(?) rpm

L69 VIN code "G"
Flat top pistons for 9.5:1 comp ratio
Cam specs: 202'/206' duration @ .050" lift, .406"/.415" gross valve lift, on a 115 LSA (same cam as on the CFI (LU5) and the 'vette CFI (L83), predeccesor to the roller LB9/G92 and L98)
cylinder heads:
same as LG4 (or LG4 had the same as L69 )
4bbl E4ME tweaked (better rod hanger and secondary rods) for increased performace due to increased CR and cam.
Dual snorkel air cleaner
More aggressive spark timing
Incorporated a knock sensor and EST (due to increase in CR and advance timing)
2-1/2" exhaust pipes
3" oval monolithic catalytic converter from the 'vette.
HP 195 @ 5000(?) rpm
TQ 240 @ 4500(?) rpm

They both shared the same intake manifold though. For a stock engine, it is a very good one (just ask 84305HO, he's running 14.4 with a very near stock L69. ), but for a mod'ed engine you can do better.

*Edit: forgot somethings. BTW: this needs to be in the FAQ!*

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George P. Lara
1994 Z28 LT1 T56
1984 Z28 High Output
Member: SCCA, SCFB, SC3GFB

[This message has been edited by MRZ28HO (edited September 17, 2000).]

fb305svs

i thought the lg4 for 86 and 87 got the higher ratio. and the heads for the 305 between the ho and the lg4 were the same.. maybe i am just disalusional, but with just an cat back exhaust my car was rated at about 200 hp at 3200 rpm. these motors were never camed for such high rpms... max torque for these motors was around 32-3500 rpm, not 4500!
EDIT i am right with the compression ratio change... take a look at this:
http://www.f-body.org/tech/3rd_gen.htm

Steve

[This message has been edited by fb305svs (edited September 17, 2000).]

Vader

George,

Oops! I got my "G"s and "H"s all messed around bass-ackwards. I know that the lesser of the two ("G", I guess) has the weenie cam grind at .350/.385 (GM P/N 10088155), and a lower CR of 8.6:1. The better of the two has a CR the same as the LB9/VIN "F" (9.5:1) and a better cam grind in SOME YEARS and SOME MODELS. All auto trans 305s in 1986/1987 got the weenie little cam. The only 1987 that got the .404/.415 (GM P/N 14093643) were 305s delivered with T-5 manuals and 350s.

Just to further confuse the issue, the 1987 B4C cars (SEO police package) had a cam grind somewhere in the middle, (GM P/N 14093640) with .383/.404, 191 °/202°, 112° LSA.

The situation got a little clearer in 1988, when you could only get a weenie little .350/.385 "LA" cam in the 305 autos or a .415/.430 cam in the 305 manuals and 350s.

I also know that some earlier 305s w/8.6:1 CR had 1.72/1.50 valves, but I don't know what VIN code they were (probably pre-1984).

Sorry if I confused the numbers with the right components. I'll still stick by my last statement - no matter which one you have, none of them are really rockets as delivered from the factory.

I think you're absolutely right. If there isn't already a tech article on this topic, we should pool all the hard data we can find on the topic, exceptions and everything, and put together an article on the similarities and differences of the available engines. This is presumed to be the best source for ThirdGen info on the web, so we should make sure the data is complete and correct. Email me if you're interested in putting together a complete tech article, or contibuting whatever information you have on the various specifications.

Thanks for clarifying my error.

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Later,
Vader
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"Make Me Bad"
Adobe Acrobat Reader 4.0

MRZ28HO

No prob Vader. I fully understand, we're only human. That is one reason I try not to answer FI questions, I don't know anything about it. As for helping with the engine/year tech stuff, I'll compile a list of what I know to be the differences between the LG4 (and early ones) and L69. Hey, what ever happened to the FAQ submission's Forum we had previous to the downtime? I think it was working quite well.

[This message has been edited by MRZ28HO (edited September 17, 2000).]

MikeDwhoROCZImports

iTrader: (1)

"H" is the LG4, and the lesser of the two. I've got an 87 IROC, 5-spd, LG4, and I remember reading it had 9.0:1 compression, but it did have the "peanut" cam and was rated at 165hp or 170hp (I've read both).

The first things I would do to mod your engine is to swap out the CHOKING single snorkel intake for a dual snorkel unit with a K&N and swap out the exhaust and cat for a free flowing cat and a 3" mandrel bent exhaust.

I read that an 87 IROC (your car would be the same) with the LG-4 and 5-spd run's about 16.8 in the quarter. With no other engine mods besides the ones listed above and plugs and wires (not really mods) I ran a 15.6 ...nothing spectacular....but considering how little I did, I was fairly happy. I've also calculated that I have about 208hp at the flywheel...which really surprised me. But the best part about these mods is how long the car pulls. I may have the peanut cam, but after the exhaust and intake the car pulls much stronger through the upper RPM's. Before it would die off at about 4,000 RPM and then pull SLOWLY to redline, but now I can pull past 5,500 RPM NO problem. The car just feels much quicker and is definatly much more enjoyable to drive. You'll notice a big difference on the highway as well when you open it up.

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"Doin 120 Mowin' over mail boxes, radar detector, to show me where the cops is."

"Ain't no such thing as a front wheel drive sports car...I can smoke the tires in my 1985 Accord with 87hp (factory rated)."

1987 IROC-Z28 Camaro
-ADS Super Chip-Replaced all fluids with Red Line Racing Synthetic fluids-Griffen "Nascar" Aluminum Racing Radiator-Good Year Super Hi-Miler Cooling Hoses-160 Degree Thermostat-Jet Fan Switch- Center Force Dual Friction Clutch-Hays Flywheel-New Alternator-Polyurethane transmission mount-Doors sound insulated with Dynomat Super-Replaced Ratted Hoodliner with new one from GM-Accel 300+ Spark Plug Race Wire with Pro-Sleeve -Bosc Platinum +4 Spark Plugs-305 H.O. Dual snorkel intake-Four Dunlop SP Sport 9000 tires (245/50ZR16)-New 3.70 gears in a Posi Rear End off 89' Trans-Am (Sandblasted and Painted Black with Yellow rear end cover)-Rear Disc Brakes (11.65 inch rotors with PBR Aluminum Calipers off 89' Trans Am)-Polyurethane bushings on rear sway bar-Catco free flowing high performance catalytic converter-Hooker Super Competition 3" Mandrel Bent Cat back exhaust-Replaced cardboard headliner with a waterproofed fiber glass headliner....much more comin' soon. =)

Vader

George,

I'm not sure if the FAQ is still working the way we are accustomed to seeing it. I'll bet that if we get a good database on the years.engines/transmissions/specs, Dirk would gladly post it as a tech article.

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Later,
Vader
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"Make Me Bad"
Adobe Acrobat Reader 4.0

[This message has been edited by Vader (edited October 01, 2000).]

ws6transam

Ahh, It's Good to be back. 84305HO is running 14.4 witha nearly stock L69? Really?? Geez, just when I thought I was doing something special.... See my SIG.


------------------
Daniel Burk
http://www.isthq.com/~dan/fcar.html
'84 Trans Am WS6/L69
KB SFC, Moser axles, Torsen Diff. PST suspension, Braided stainless brake lines,
5-point racing harness, Koni struts, 11-inch rear disks,Spohn Adj. torque arm,
Ported 305 heads w/1.94"intake valves, Comp Cams XE262H, Griffen alum. radiator,
Speed-sensitive steering conversion, underdrive pulleys, Crane Hi-6 & more. 1.05g skidpad verified.
New best E/T! 14.400 at 98.6 MPH in 88 degree air at Stanton, Michigan.

84305HO

Actually Dan I went 14.52 @ 96.24 but my 60ft
was 2.27, (lots of room for improvement).
The thread is last dated on the 15th its not too far back. I would say your L69 is doing
great considering you ran in 88 degree weather. Just think of what it might go in
some nice cool Autumn air .......

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Tom K.
84 z-28 M5 305 HO
pulleys,coil,3:73(stock)
Jet StageII, fan switch
14.55 @ 95.02 2.15 60ft

fudgelunch

Hey! I just bought an 84 WS6 with a L69 about 30 months ago. It's a nice car as long as I stop hitting deers with it! I'm debating a 350 swap, but the more that I read I'm not sure it's worth it. Sounds like I'm gonna have to make a lot of changes to make it worth while. Is there anything that's a direct swap. Let me know what you think.

MIKES 88GTA

My first thirdgen was a 86 IROC 305 5spd, 3.27 posi, it had the 3inch cat and HO exhaust manifolds but the single inlet air cleaner(I just flipped the lid over).
With the exhaust cut off after the cat I was almost even with a 14.5 sec mustang convertable .Does this sound about right?
Do you think the car was a strong LG4 or an L69 or what? I don't remember the VIN but it sure did run strong for a 305.

Ray87Z

To answer the original question directly, the LG4 had the infamous peanut cam, whereas the L69 had a decent cam, the LG4 had crappier exhaust manifolds, and had less compression.

Its not worth it to actually swap to L69 parts since they still aren't that great, but the cam, intake, and exhaust are excellent things to upgrade w/ aftermarket parts on the LG4.

CarCraft did a Lg4 buildup awhile back, w/ headers, a Performer RPM intake, new carb, etc it made 230hp. That is w/ the stock peanut cam. W/ a 218/224 cam it made 269 hp I believe it was. That is w/ the stock heads still (that is also w/ a Victor Jr intake, but it made no power over the Performer RPM prior to the cam swap, might have accounted for a few w/ the better cam though...) Anyway, upgrade the intake/cam combo, and throw on a good exhaust from the headers on back and you'll see a good upgrade in performance. Those mods should keep you from getting walked on by everyone on the road, which with a stock LG4 you are in danger of having happen to you.

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Ray87Z
-Vortec headed 350.
86 IROC w/ a cammed 305 TPI.
Formerly Ray86IROC.
www.inter-scape.com/Ray

[This message has been edited by Ray87Z (edited October 02, 2000).]

rusty Z

I too have the LG4 in my '85 Z28. I would be very suprised if mine was pulling 200hp. I have the dual snorkel, headers and a free flow exhaust. I also have an Accel H.O. coil and cap. What gives? Am I missing something?

Ray87Z

Stock intake/carb, just headers and I assume open element and the CarCraft LG4 was only making like 190hp I believe it was. Factory intake on them (same as L69 I think) sucks pretty badly too... A standard performer upped HP to around 215 I want to say, the RPM being worth another 15. May have also been a later model LG4, which started up 20 hp over the older ones...

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Ray87Z
-Vortec headed 350.
86 IROC w/ a cammed 305 TPI.
Formerly Ray86IROC.
www.inter-scape.com/Ray

jasons86iroc

i had an 84 z28 with the high output, and i had no problem beating mustangs, new camaros, and that was completly stock, 0-60 times were 5.9. i never checked quarter mile.

i ran against an 96 cobra(we both had 4 guys in the cars), and were were exactly the same up untill 135-140 mph, then i pulled away with ease. also the top end was 158 mph.

the best car i have ever owned.

Zepher

iTrader: (1)

Not sure what my HP is now, but last saturday at the track I ran a 14.94 @ 91.67mph with my LG4 engine.
My Timeslip

This was my first time drag racing and my 4th run was my best.

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Zepher
'86 Pontiac Trans Am WS6, 5 Speed:
Edelbrock 1406 Carb, Edelbrock Performer RPM 7101 Intake Manifold.
Edelbrock Open Element Air Cleaner: Flowmaster Exhaust, 160* Thermostat,
Grant GT Steering Wheel, MSD HEI Coil, Taylor 8mm Wires, Recaro Seats,
Alpine CD+Changer,Rockford & Soundstream Amps, Premier TS-1040C Subs, Polk Audio highs/mids.

WS6 Trans Am

mjoekingz28

According to the tech article,

The LG4 made more torque- but at a lower rpm. So it seems to be a better street engine.

The L69, made 240lb-ft vs 250 in the LG4 but at 3200 rpms instead of at 2000.

So, one is more of a runner and the other seems to have a strong bottom end for around town use.

3rdgenmaro

iTrader: (9)

15 years. Most impressive revival Ive seen.

mjoekingz28

Just scouring around the boards. I cant find anyone to conversate with, so I learned touse the search function as was mentioned to me.


My screename is about thatold as well. Google it if you dont believe me!

86LG4Bird

iTrader: (1)

The LG4 MIGHT win a race from 0 to 5 mph, hardly making it a better street engine! In stock form, it's a great tractor engine
The L69 is not a high rpm screamer by ANY means. It has a much better overall powerband for street performance.

Maze

What can I do for my "lame ***?" Also I thought a brake upgrade is in order. The master cylinder has that ah burned look. The fluid is beyond dirt but hay it has been idle for 20 years.

86LG4Bird

iTrader: (1)

Which engine do you have? LG4? Vin G? Vin H? LB9? L69?

Maze

H 305-160 (LG4)87 Firebird, the engine even looks lame.

86LG4Bird

iTrader: (1)

What are your intentions/goals for the car? A certain 1/4 mile number? You can get some decent performance from that mill..... See my sig: high 14's on motor; low 13's on the juice

dmccain

iTrader: (2)

I put a cam, headers, and upgraded intake and carb on an LG4 and only turned a 14.88 in the 1/4. Then bought a bone stock LB9 car and turned a best of 14.76

86LG4Bird

iTrader: (1)

That makes sense. 1/4 mi performance is hugely influenced by gearing, torque converter, and traction . With stock gearing / TC, you don't get much payback on those engine mods.

dmccain

iTrader: (2)

True. Both of those cars were 2.73s and stock TC. Even with the whopping 170hp surprisingly 3.73s and 2200 stall really perked up my L03 car.

Maze

My last Fire bird was a slug with a S 173-135 (LB8. My friend so of wrecked it and it was never the same. I would like car to match the performance of my XSE Camry. I do not travel fast but getting to speed is half the fun. Second I do not think the Firebird can really handle a lot of hp. So far the engine and trany are scrap as well as the basic systems like brakes. Why does the brake resivor have that burnt look? I hate drum brakes as they lock up. The cooling and ac are scrap as well. Have not looked at the oil but the brake fluid has broken down. Thus I want quality performance not insane though it scares my hubby when I give my Camry moderate acceleration in the Camry.

84 1LE

iTrader: (9)

Not much you can do w/a H code LG4. Total timing is limited to 24deg. Burnt look? Maybe there was an engine fire at some point. Or do you mean brake booster. Ive seen some that never had paint and are rust colored.

Maze

No it was the brake fluid reservoir and it had that burnt look. The fluid was so bad as to be separating. I want 4 wheel disk brakes

Scott's 83' Z

Some info I found on another site..It has camshaft and head informations as well.

https://cofb.forumotion.com/t1979-ch...on-performance

Saxondale

iTrader: (2)

These cars are too much fun to have to pamper and protect. Drive them hard but not abusive and do it at least two evenings per week.