Just wanna know since I'm probobly gonna be getting a 84 Z with the L69 option.... but I dunno what the real differences are, and what advantages the L69 has over the LG4. Tech specs are welcome

Adam

 

The L69 got a better cam which is where most of the power increase comes from.

 

It also recived a dual snorkle air intake and usually came with the performance rear axle. I have been told they come with differn't heads but I haven't seen anything to prove that. If I recall it was rated around 160-180

 

The L69 was the performance package of its day. The LG4 is a slug. From the factory the L69 was rated at only around 190 hp, however stock would do the 1/4 mile in low 15's.

I'm still looking for those articles, but there were a couple of magazines that have done write-ups on the L69. Running stock one magazine dynoed it at somewhere around 230 hp and actually hit high 14's in the 1/4.

The biggest difference though is compression ratio. 9.5:1 is what the L69 runs due to flat top pistons. The LG4 is.....now I can't remember, but closer to 8.5:1 to 9.

In my opinion, the LG4 is one of the biggest reason why a 305 gets a bad name. It is a pure dog!

Even when I was running stock with my 84 L69, people didn't believe I only had a 305 in there. Not by the sound, feel or performance.

It's a good power package.

Oh, supposedly, in 84, the Z28 was the fastest production car made, faster than the Corvette! Could be true because they were trying some stupid crossfire injection system that was a huge failure.

Get the L69 and you'll love it!

Do you have emissions?

 

Basically to sum it up, they got a "tweaked" carb, corvette camshaft, flat top pistons and bigger exhaust. They dont have different heads. I have verified this.

Plus they got 3.73 rear ends which is kinda cool.

And I'm pretty sure they didnt beat the CFI vette.

 

The tech data on this board has most of the info.

FWIW, '85-87 LG4's got the 9.5:1 compression. And knock sensor to go with it.

Otherwise, to summarize, differences are: Compression (for 2 years only), cam, exhaust, air cleaner, carb tuning (rods, hanger, sometimes how far AV opens), knock sensor (again, 2 years only), ignition timing.

Basically, anything that was different couldn't be distinguished on my car now...

 

I read somewhere that they got a lightweight flywheel but dont know if it is true or not.

 

We can get away without having any emissions on down here in FL.... and if I do indeed get that engine, I'd be putting headers on it and backing them up with 3" pipe into a Flowmaster 80 Series exhaust, as well as doing an overhaul on the engine itself. So you think its be worth it huh? Hmmmm, any more info on it that would be interesting?

Adam

 

I got an 84 WS6 T/A with the L69 and I'm sure once I''m running her again I'll blow the doors off my G/F's 87 Formula. I would have to say that I wished I could just run headers right to sidepipes and be ddone with it but here in PA we have to pay off our friends in the inspection stations to slip and "accedentaly" put the emmissions exempt sticker on the "wrong" car. So in short I would go with the L getting more for your money. I haven'd ever seen anything to say that it came with a lightweight flywheel.

Tell you another thing though... Hopefully you get a stronger trans then the 700 cause with my bird, I just tear them to shreds.. After the tranny swap is compleat and I blow this one I'm just gonna say f it and lose the OD and go to the th350

 

L69 DID have diffrent heads we had a L69 and an LG4 apart 'cause one of the heads on the L69 was cracked and the LG4 had no valves so we tried to take the valvetrain out of the L69 and transplant it to the LG4 but the L69's valves were bigger, they were 1.94i and 1.50e compared with 1.8x i and 1.50e and I am not sure if it makes a diffrence but the heads had diffrent casting #'s, by the way the L69 had flattop pistons and the LG4 had dished pistons and the L69 had a lumpier cam, and the flywheel were all the same - GM called them all lightweight (yeah right).

 

The L69 and LG4 both have the 416 heads, I have verified this by tearing tons of engines apart. They both have 1.84/1.5 valves.

They had to be changed somewhere along the line.

 

I don't think they put 1.94/1.5 heads on any stock 305. The L69 had better exhaust as well.

 

damn I got rid of those heads too oh, well guess they were aftermarket ar someone changed them

 

How many times do I have to say this - ONLY in '83 and '84!

Don't bother rebuilding a 305. Get a 350 core, rebuild it (with good aftermarket 350-style heads, nice cam), put it in with the L69 supporting hardware, headers, 3" exhaust, etc., etc., etc. The computer needs an O2 sensor, by the way.

Don't bother rebuilding a 305. Doesn't matter if it's an LG4 or L69.

Don't bother rebuilding a 305.

 

yeah 305's are junk I just needed a head for my dad's regal that I cracked the head on, we put a 350 we found in a wreacked vett at the junkyard in it anyways, man we did allot of fixing cars in '98

 

Also,

The heads aren't different L69s, the valves are 1.84's in the L69, not 1.94's

the flat tappet cam was different, fuel pump was different (I've been to 140mph on a stock fuel pump when I had a q-jet), the L69 got a higher stall converter in automatic applications, the L69 got the 4 bolt monolith cat converter that was in the 84/85 vettes too, L69 also got a diff. PROM.

And the L69 had a flatter torque curve, but less peak torque than the LG4.

No, on the compression. Yes, on the knock sensor.

stick L69s got the 15lb nodular flywheel; same as the 15lb one in TPI's but 2pc seal vs. 1pc. obviously.

Being that their chambers were the same size and the LG4 was NOT a 9.5:1 motor, please stop saying it because it's wrong.

Matthew

 

Matthew,

The 85 and up LG4s had flat top pistons which provide a 9.5-1 compression ratio. At least that's what GM says.

Also, I think the L69s had better connecting rods.

 

Sorry bro but the 85-87 LG4s were 9.5:1 compression and they did get the L69 pistons. I have verified this too

How many times do I have to say that the L69 and LG4 engines both had the 416 heads??

 

I have one, it has flat top pistons and (had) 416 heads.

The data says they have flat top pistons and 9.5:1 compression.

Conclusion: F-body '85-'87 LG4's had flat top pistons.

Why is there even a discussion?

 

I've got my LG4 sitting here on the floor, pistons looked flat with 2 half moon looking indentations on top of them.
A buddy of mine has an 85 305HO T/A 5 speed, I'll see what his head casting numbers are.
His car is pretty quick with the stock 3.73 gears.

 

Weird, my 84 LG4 which is sitting in pieces in the garage right now, has completely flat pistons.

 

Well, so far the 1986 factory service manual says 5.0L motor w/ VIN code H is *not* 9.5:1, hence my skepticism. I would assume even if 1985 had a rolling changeover, the 86 Svc. manual would reflect it, but it does not.

The LG4 for other GM apps (Caprice, Monte, Grand Prix) is also not listed w/ 9.5:1.

The only LG4 I own is a 1988 Monte one. Should have the same slugs as 85-87, but it's kinda in a car right now


Matthew