chazman

iTrader: (4)

If you had to choose between the final 1987 version of the LG4, with the centerbolt heads, 9.3 to 1 compression and roller cam and the '88 and up L03, which would you choose.


I know that many are tempted to post neither one and stick to a TPI, but I'd like to hear the pros and cons of both of these base V8 engines, which were sold in the tens of thousands every year the 3rd gens were produced.

I don't think I've ever driven the 1987, 165-170 hp version of the LG4, but the last L03 I drove reminded me a lot of a good truck motor. Lots of torque down low and very little grunt after 3500 RPM.

Eric-86sc

iTrader: (18)

Id rather have the 86 9.5:1 compression non center bolt lg4 over either for cheaper parts to build it up, but id choose the later lg4 over the l03. Mainly because of the fuel lines being on the passenger side making a carbureted motor easier to build when you want to swap a real motor in. Id prefer carb over a tbi which is another reason why i made my choice, but I've driven cars with both motors and they felt pretty much the same.

burnout88

My first Camaro was an 85 sport coupe with an lg4 and my friend had an 87 lg4 with the roller cam and center bolt heads. My 85 was a full three car lengths faster in quarter mile. I have no idea why my early lg4 was so much faster. Maybe it was gearing?

I have driven a couple of TBI LO3 cars and did not like the feel of them. I would take the carb'd LG4 over the LO3 any day. I also found after doing some basic bolt on's to my LG4 I could run faster then any LO3 and equal to a stock LB9 TPI auto car.

LG4 are not as bad as everyone makes them out to be.

chazman

iTrader: (4)

Agreed!

Eric-86sc

iTrader: (18)

LG4 are not as bad as everyone makes them out to be.[/QUOTE]

I think that depends on the year. 82-84 were the bad ones with only like 140 hp and low compression. The 85-87 were the better years with flat top pistons allowing 9.3:1 and 9.5:1 compression which makes for a better engine to cheaply modify effectively. 86 and 87 also had the electric fan over the mechanical freeing up a few horses. With a full exhaust and a higher stall converter in front of decent gears they're pretty fun to drive.

dmccain

iTrader: (2)

I had an 87 LG4 and now have an 89 L03. I prefer the Lg4. Stock it was about 3 tenths faster in the 1/4 than my L03 and simpler to work on.In defense of the L03 I do like the reliability and great gas mileage. Ive gotten as good as 26mpg on the hwy and the best I can remember was around 20-21 with the LG4. The L03 has a lot of low end torque and would be great in a pickup. It does not in my opinion belong in a sports car. The Lb9s should have been the only alternative to the L98 in Firebirds and Camaros alike after the L69 was taken off the table.

Fast355

iTrader: (2)

I have driven both stock for stock, IMO the TBI has a slight edge in driveability and ease of simplicity. The last of those LG4s had about 50 vacuum hoses nestled all over the electronic Q-Jet. The Q-Jet was also neutered in those cars, setup to run very lean.

okfoz

I have had both... the last year LG4 actually had the same heads as the LB9, but the L03 had its own unique neutered heads. I made reasonable power with my LG4 with a mild cam, but the rats nest of vacuum hoses was possibly the worst part about it. Ever have a vacuum leak? what nightmare trying to figure out where to start without replacing everything, only to realize that the parts store does not have the correct size hoses..

In so many ways I actually find the TBI more simple to work on... I understand it better...

As for power... I did not do a side by side comparison, my LG4 started up perfectly every time, and it ran like a dream...

I think I actually have the original fuel lines around here somewhere...

chazman

iTrader: (4)

As has been stated already, it seems the later LG4s can be awakened a lot more easily with simple mods than the L03 can.

Fast355

iTrader: (2)

Actually IMO a L03 can awaken just as well if not better than the last LG4s. The heads are not really a restriction until you are start making more than 250 HP. Its more the exhaust system and camshaft.

chazman

iTrader: (4)

I wonder what a bone stock L03 would feel like, if it a factory N10 exhaust from the manifolds back?

1MeanZ

iTrader: (9)

If I were planning to stay totally stock, I'd go TBI. Much less underhood clutter, better reliability, better mileage, same gutless performance.

If I wanted to build something that would actually run, I'd start with a late LG4. They are just a cam and L98 vette head swap away from 300+hp capability.

If I wanted a cruiser that did good burnouts. I'd go with the L03. Fast355 is right. The swirl port heads have their place. I built a swirl port headed LB9 with an LT1 cam for my 91 TA a few years ago and that was a fantastic combination. Great part throttle and low rpm torque and response, even with stock manifolds and Y pipe. It got 27mpg on the highway but was still was musclecar fast. I could slide sideways coming off a corner in 2nd, pop the clutch and roast the tires from a dead stop, all with a 2.73 posi. It was a surprisingly lively combo.

1MeanZ

iTrader: (9)

The L03 manifolds AND the tiny 2.25" Y-pipe suck. If you did L98/Lb9/L69 manifolds and a larger single cat Y-pipe, or a dual cat Y-pipe I think it would feel the same. The cam is so lame on an L03 that by the time it's turning enough rpm to need a dual cat Y-pipe, the cam is out of breath already. As is the stock throttle body....

An L03 with the ultimate TBI mods, a cam swap and stock swirl port heads with L98 manifolds and N10 Y-pipe would run as good or probably better than a stock LB9. Somewhere on this site is some good documentation comparing swirl ports to regular heads on 305s. As I recall, comparing swirl ports to regular LB9 heads, the swirl ports made more power and torque on a 305 everywhere below something like 4000rpm. There were actual chassis dyno numbers posted. It's the reason I ran swirl ports on the LB9 in my TA, and I didnt regret it one bit.

chazman

iTrader: (4)

So, sounds like the swirl port heads are actually NOT the devil.

Fast355

iTrader: (2)

Nope...Its mainly the exhaust and lack of lift at the cam. You could retard the factory cam 4* and add 1.6:1 rockers and wake it up a good bit but might as well swap the cam.

I put 1.5" primary long tube headers with 3" collectors, 2.5 to single 3" exhaust, high flow cat, flowmaster 40 series single in/dual 2.5" out muffler, a 1" open center TBI spacer, and an ultimate TBI moded TBI with 350 injectors on a 305 in a G-van. Turning the factory 700r4, 2 piece driveshaft with carrier bearing, factory clutch fan, and all accessories it put down 178 RWHP and 268 RWTQ.

Fast355

iTrader: (2)

I don't necessarily agree...The LG4/L03 manifolds and Y-pipe suck. They are already building substantial back pressure by 2,500 rpm. The factory cam peaks HP around 4,000-4,400 rpm. The larger L98 manifolds and N10 or larger single Y-pipe make a good bit more HP. The only difference in the 1990+ LB9 engines was the crappy LG4 exhaust on the lower HP model and the L98s N10 dual cats on the higher HP.

okfoz

The Cam in the LG4/L03 IIRC is actually the same cam used in the LB9/A4 from 1986-1992

Fast355

iTrader: (2)

Actually that is not a completely accurate statement. The 90-92 speed density TPI 305s ALL had the L98 cam. No peanut cams in 305 TPIs after 1989. I have had 3 1990-1992 TPI 305 engines apart, all 3 were automatic cars, all 3 had L98 cams.

dmccain

iTrader: (2)

The difference in a stock L03 and stock Lb9 auto car with same gearing is about 1.4 sec in the 1/4 mile. I know because I tested them myself. So the exhaust, heads, and fuel injection setup in the L03 must be very sorry performance wise. I know they had the same peanut cam. 14.76 vs 16.16 in the 1/4 mi.

dmccain

iTrader: (2)

Interesting i never heard that. I always thought my automatic 5.0 TPI 91z28 ran great for what it was I had always been told it had the weaker "peanut cam".

1MeanZ

iTrader: (9)

We are in agreement, I worded my statement poorly. Here is an expression of what I meant to say:
L03 manifolds 2.25" Y-pipe = sucks

L98 manifolds and large single cat Y-pipe = better

L98 manifolds N10 dual cat Y-pipe = best

Can you tell difference between better and best on an stock L03, probably not. Either setup is a vast improvement over stock L03 stuff.

okfoz

Yes you are correct... I forgot about the change in 1990...

The biggest difference from 90-92 was the gear ratio... If you were to take an (90-92) LB9 & put a taller gear in it I bet it would wake it right up... I know my 87 looooves the 3.73... I digress.

chazman

iTrader: (4)

Was the cam change in '90? I always thought it was in '91-'92?

chazman

iTrader: (4)

BTW, this often copied and pasted, definitive post, tells you all you need to know about factory exhaust systems for our cars:

Fast355

iTrader: (2)

I think something was wrong with the TBI car you had. With the only modifications being suspension and tires I have personally watched a L03/700r4 2.73 gear Camaro run low 15s @ 90 mph.

Fast355

iTrader: (2)

Gear ratio and N10 exhaust. The difference in LG4/L03 vs N10 exhaust on an otherwise stock LB9 from 1990-92 was worth a rating change of 25 HP and 15 TQ.

Honestly that would not be the only strangled 305 due to the factory GM exhaust. The L30 vortec trucks had a single catalytic converter with 1 7/8" pipes leading into it and a 2.75" exhaust. At 230 HP it had a design/test restriction of 10.5 in/hg at 4,600 rpm, which is over 5 psi of backpressure!!! The L31 trucks with dual 1 7/8" pipes into dual cats faired a bit better, but not much. They tested at nearly 8 in/hg of back pressure @ 4,200 rpm.

MY87LT

iTrader: (2)

I'm biased as I have a 1987 LG4. I love the sound of a carb'd car when accelerating. But, I have driven the LO3 and it is smoother but not by much.

Yea, the LG4 has many vacuum lines and looks cluttered compared to the LO3 but it's really not that bad as you should replace vacuum lines since they do rot over time.

DynoDave43

iTrader: (11)

I don't know Fast...those numbers dmccain posted are pretty close with my experience. My new '90 L03/T5/3.08 Camaro ran a 16 flat, which matched the time Car & Driver had gotten from the same combo. My T/A with L03/700 and 2.73 is about a .5 second slower than that.

If I can get mine running low 15s, I'll be one very happy camper.

chazman

iTrader: (4)

Dave, you got a new car? What are you waiting for, post some pics!

DynoDave43

iTrader: (11)

No, and there's a typo in my post too.

My first new car was a '91 RS (not '90). I sold it long ago. Should have run the VIN when I had my CarFax membership back when I bought my T/A, but it slipped my mind. I'd like to know what happened to it.

chazman

iTrader: (4)

Okay, off the hook.

dmccain

iTrader: (2)

NO. That car was running PERFECT. PERFECT. Just stock. Almost everything in the suspension from end links to sway bar bushings to shocks, coil springs.. etc had been replaced also. I am certain the L03 would turn 15s but it would take headers and full exhaust replacement at the least, and taller gears would help. My bone stock Lg4 turned 15.80 before any mods then turned 14.88 with cam, headers,and aftermarket intake and holley 650 DP.

Fast355

iTrader: (2)

Its been my experience that a bone stock L03 has more power than a bone stock LG4. Same gearing and same transmission makes the L03 quicker than the LG4. I have seen a LG4 car not break out of the 17s.

Apparantly it wasn't running that perfect. I have seen the fuel pressure regulators on those cars alone set at anything from 9 to 13 psi in STOCK form.

dmccain

iTrader: (2)

Ok Fast I know you are a smart guy and I respect that and wont argue with you or be disrespectful. But I know my car, DynoDaves car, and others I have seen over the years had nothing wrong with them and I have saw what they turn and will leave it at that. The 16 sec pass surprised me because it felt really good out of the hole with 2.2 sec 60ft but it just didn't pull over 60mph with the anemic 2.73 gears. Now I have 3.73s it seems much faster and I will test it again after I do a few more mods, headers + y-pipe,etc.. if I don't swap engines first. Saying that im sure its probably already a solid 15sec performer with the gears and 3in exhaust now. I don't consider that exactly STOCK though.

dmccain

iTrader: (2)

Headers, full 3 in exhaust, 3.42 gears, L30 vortec heads and maybe anLT1 cam with a good tune and from what ive read you should be well into the 14s.

okfoz

I have read so many good things on the Vortec Heads... Throw a good cam and Cat-back in the mix and I bet it would be a really good runner.

I have considered doing the Vortec Heads on my 87, but I just have not been that ambitious AND I would need to have them machined for my cam...

Fast355

iTrader: (2)

Agreed not trying to argue with you, rather help you get your car running to its potential. That being said you can have a car that seems to be running perfectly fine that is still out of spec and slower than it should be.

I see many of these cars with 048 ignition modules in them. The 048 modules retard the timing 6* at 4,200 rpm while the 369 advances 2* above 3,200 rpm. That alone could make an 8* difference in timing advance between the cars, then throw in the fact that a TBI car not running at 13 PSI is running too lean, it is easy for the car to have poor WOT performance despite driving around on the street perfectly fine. Also many 700r4s no longer have the correct governors in them and shift in the 4,000 rpm range rather than the 4,500 rpm range that these cars will run through. TV cable adjustment and weak TV springs also compound this issue.

I can tell you in decent air, with decent track prep, a slightly wider tire and lower control arm relocation brackets an otherwise stock L03/Auto/2.73 Camaro ran into the lower 15s. Just a few weeks before the car had run mid 16s in warmer weather. It would spin the right rear tire off the line and then fall on its face. It had an 048 module and 9.5 psi of fuel pressure to start. Simply swapping in the correct IC module and replacing the old regulator spring made a dramatic difference in the way the car ran.

With good traction and a good launch your 60' should have been closer to a 2.0x even with a stock engine. That alone is close to 4 tenths ET reduction.

Fast355

iTrader: (2)

Alex spring/retainer set and you are good to .550" lift with ZERO machine work.

Fast355

iTrader: (2)

Maybe even quicker than that! That setup is good for the 270-280 HP range which is LT1 power in a lighter car.

The little 196/206 marine cammed 305 when GM was still making it made a net rated 250 HP and 300 TQ.

I would use a performer RPM and a TBI-Carb adapter if it will clear your hood.

chazman

iTrader: (4)

That's interesting. Why would they have the wrong ignition modules? From the factory or replaced by someone later in the car's life?

dmccain

iTrader: (2)

And this is why I will replace the L03 TBI with an old school carb setup 350. I know how to get full potential out of it I am not very saavy on the TBI.

Fast355

iTrader: (2)

The factory did it in most cases...Its more of a performance killing/rev limiting module from the factory.

chazman

iTrader: (4)

That makes so much sense now. I drove an L03 Camaro a few weeks ago. Lots of torque off the line and somewhere between 3500 and 4000 RPM it dropped dead, like it hit a rev limiter or something.

Fast355

iTrader: (2)

When they are running right the L03/L05 engines will pull well up to about 5,000-5,200 rpm. The L05 350 TBI in my van with little more than headers and tuning would pull to 5,500 rpm without dropping off much.

It probably ran out of fuel about that RPM too. I have datalogged 100% stock TBI engines running lower than 12 psi of fuel pressure run out of fuel above 3,500 rpm and watched the narrow band o2 sensors drop into the double digit values which is leaner than 14.7:1!

Fast355

iTrader: (2)

There were more than a few times I reved my stock longblock L05 to 5,500 rpm manually shifting while tuning. It pulled strong up to 5,000 rpm then fell off. My G20 had a 700r4 and 3.08s. At 5,500 lbs it would pull a 2.2-2.3s 60' time and ran 10.80 a few times in the 1/8 in cool weather. In hot summer weather, heat soaked it ran 11.40s on a 2.4-2.5s 60', pass after pass after pass. It put down about 176 HP and 260 TQ at the rear wheels with a 190 hp/300 tq factory rating, headers, Y-pipe, high flow cat, and custom chip.

86firebird350

I had a 91 auto L03 Firebird and ran it many times at the track. Bone stock it would do ~16.3. With only an open element and 160 stat, I was knocking on the door of 15's!! I was running 16.0x's consistently. After a gear swap to 3.42's and a set of underdrive pulley's along with some timing, I was able to run a best of 15.38 at 88-89mph with a 2.2 60ft in VERY favorable weather. A few months before that run, I was only able to pull high 15.70's to low 15.80's in hot humid weather.

I would be very impressed (and maybe even a little angry if I still had that car) to see a car with the same motor, trans, gears running the same or lower times than mine with engine/drivetrain mods.

Fast355

iTrader: (2)

Thats respectable for that car. The 2.73 gears are a bit flat when you hit 3rd about 80-85 mph. With a 25" tall tire, you really want more like a 3.73 gear in a ~5,000 rpm 305 car honestly speaking. With the auto that puts you trapping 4,500-5,000 rpm in 3rd gear at 90-100 mph.

DynoDave43

iTrader: (11)

Lots of good little tuning tips there. Thanks Fast! And to be clear, mine in 100% stock form is probably less than optimal (O.E. wires, plugs, cap, rotor, fuel pump and filter, etc.).

chazman

iTrader: (4)

From this thread, seems like an L03 with the right ignition control module, right fuel pressure and a TPI exhaust would make for a fun driver.

dmccain

iTrader: (2)

I wish ole Fast355 lived closer to me I would love to send him my car to tune it! He is very knowledgeable on these cars! Thanks Fast. I will be definitely bumping my timing up to 6* atleast being it is set from the factory at zero checking my fuel pressure,and may get a chip burned for it after a few mods if I don't just pull the lil powerplant out. It runs so good and smooth I really haven't done much to it yet, its just slow.