burnout88

I found this information on a Monte Carlo SS website. Wondering if all of this is correct. Differences between the LG4 and L69

LG4 vs. L69

Starting with a standard issue Chevy 305 small block, here are some interesting notes:
•both use aluminum intake ◦early LG4 models had a cast iron intake however

•both use the same heads ◦casting: 601
◦58cc chambers (60cc ?), 178cc runners (158cc ?)

•valve size in L69 heads were larger ◦L69 : 1.84/1.50
◦LG4 : 1.76/1.46

•L69 has 9.5:1 CR (flat tops) [these numbers changed]
•LG4 has 8.6:1 CR (dished pistons) [these numbers changed]
•L69 has a special cam, from the L-81 Corvette (hydraulic) ◦This is NOT a roller cam

•L69 uses a performance calibrated PROM
•L69 takes advantage of special exhaust/catalytic converter
•L69 takes advantage of a higher stall torque converter ◦L69 : approximately 1900 RPM stall
◦LG4 : approximately 1200-1500 RPM stall

•L69 uses a better fuel pump (from the Z/28)
•the changes in the L69 setup yielded *roughly* 30 more horse power
•the same changes actually yielded slightly less peak torque for the L69, but had the advantage of a flatter torque curve overall


http://www.chevyasylum.com/tech/L69vsLG4.html

navy02ws6

Weird, I've never seen a factory aluminum intake on an LG4. Then again I've never looked at one in a Monte Carlo either.

MY87LT

iTrader: (2)

Mine is aluminum painted black. 1987 LG4. Aren't the mechanial fuel pumps the same for all carb'd cars?

MrPackstin

iTrader: (9)

Interesting. I had an '84 L69 and an '86 LG4 and always wondered the difference aside from the CR.

Jeffs82TA

iTrader: (1)

My h.o had 416 heads not 601 & I thought the L69 used a L83 cam

sofakingdom

iTrader: (1)

Not correct, as applied to the F-body.

LG4 and L69 both had 1.84"/1.50" valves.

Both had aluminum intakes. Same casting #.

Both most often had 416 heads; 601s are scattered randomly among them. Both of those castings are nominally 58cc chambers although the 601s tended to run a bit smaller than that usually. The ports are closer to 158cc than 178 although they're so crude and random and full of casting irregularities that you'd need to specify a mean and a standard deviation to actually characterize them.

AFAIK the TC is the same but I don't mess with autos too much so I could be wrong.

AFAIK the fuel pump is the same. No need for anything special there; a 305 can only eat just so much gas, and it doesn't take much pump to pump that. You can get about 6 times as much effect just from changing out the 10-lb fuel pump push rod as what you can from doing anything to the pump anyway, and I'm sure the factory knew that same as the rest of us, but they didn't do it; so I doubt the pump could possibly be any different anyway. Service replacement for both is the same.

In a lot of years the LG4 had 145 HP, the L69 had 190 HP on regular and 205 - 210 on premium. Not sure how this equals a 30 HP difference? Must be the "new math".

Don't know anything about either L81 or L83; totally unfamiliar with those RPOs, but of course, I'm still a n00b so there's plenty of room for me to learn. However L82 was a very well-known one back then. OTOH the L69 cam isn't the same as the L82 cam AT ALL. Not even close. About all they have in common is the # of lobes.

LG4 came with a clutch fan; L69 had electric. That all by itself is probably 12 HP of the difference between them.

LG4 had the 2Ľ" coffee-stirrer exhaust; L69 had the huge oval with 2ľ" connections in front of the muffler.

LG4 had typical crappy grocery-cart gears like 2.73 and MAYBE 3.23 in a few lucky applications; L69 had 3.42 MINIMUM in the lower-rank auto cars, and 3.73 in the (good) stick cars.

LG4 had dished pistons up through (I think) 85, then flat-tops after that. Raised its HP to about 155 or 160 in those later years. Woohoo.

L69 T-5s got the better gear ratios (.73 5th) where the LG4 got the grocery-cart version of that too (.63) to where it always seemed like it needed a 4˝th gear. Just too much of a step between the 2. Like 1st to 2nd in a 700, except ... trying to cruise down the highway for hours at a time like that.

Never heard of "chevyasylum.com". Although, sorry, my knowledge, limited though it may be, comes from OWNING them, so I don't feel like I need any such thing.

Jeffs82TA

iTrader: (1)

the auto l69's could be ordered with 373's

yaj15

iTrader: (3)

For the L69/700r4 cars the 3.42 gear ratio was standard. 3.73 gears were the G92 performance option for L69/700r4 cars.

chazman

iTrader: (4)

I don't know about this L81 cam stuff. But the L83 cam came in the 350 cid L83 CFI and the 305 LU5 Crossfire. I believe it was the same specs as the old carbed LM1 350. The L69 definitely had a larger cam than that, perhaps it was similar to the L81, don't know. The L81 basically split the difference between the L48 and L82, so could be.

Jeffs82TA

iTrader: (1)

L69 also had knock sensor and baro sensor LG4 didnt at least in the early years

sofakingdom

iTrader: (1)

That would be, the 929; 194°/204° give or take, .390"/.410".

Significantly weenier than the L69 cam which was similar to the 049 at the bottom of this page although I don't recall the exact specs off the top of my head. https://www.thirdgen.org/mods3

L69 didn't have the baro sensor at least in 83; not sure when it appeared. I found it on a 84 California one once.

burnout88

My 85 sport coupe LG4 had an aluminum intake from the factory on it that was painted black from the factory.

jmd

iTrader: (4)

A comment: The LG4 goes back to 1979 or so; the relevant 1983-on years wer aluminum.

These were changed for 87.

I can't speak for the electric assist pump equipped third gens. LG4s did not all have a return line. All L69s did.

I've seen them back to 1983.

I can't vouch for current parts listings. Back in the 1990s, the L69 and LG4 carried a different FP PN for years when both engines had a return line.

Definitely different in stall.

I've pulled an 84 L69 T/A T5 (and used it for a while) with .63. Fifth of 0.73 makes no sense with 3.73.

Influence of the write-up comes from a long-running email list. Yes, there is G-body influence in it, but I've pulled apart my share of F-bodies.

Right. LG4 got the knock sensor in 87.

naf

iTrader: (7)

F Body LG4 got the KS in 85. Can't say about the difference in stall but there was a different part number for the converter for an 85 LG4 vs an 85 L69 when I purchased one a few months back. I got the L69 converter.

The 87 LG4 is supposedly the first with the in-tank assist pump standard, although I don't have personal knowledge that the 86 did not have one.

TransamGTA350

iTrader: (2)

Also, 86' LG4's got the electric cooling fan.

zee28

my 86 lg4 does not have electric pump in tank and does have return line

Brother Al

A bunch of the Monte SS stuff is old/incorrect but all they had to go on when it was posted years ago.

Some more info:
- 305 was released in 1976 with 130*hp.
- LG4 Released in 1982 with CCC and 4 bbl E4ME Qjet.
- L69 became available in late-1983 production as GM phased out the LU5 Crossfire and ended, (in F-Body's), in early '86... very few made in '86, mostly for "Player's Challenge Racing".
- LG4 had a cast iron intake until very early 1983, then switched to aluminum, Chevy revised it several times before 1987 when they changed the bolt pattern.
- All L69's had an aluminum intake.
- All L69's had a mechanical fuel pump w/a light pressure rated electric fuel pump to help prevent vapor lock and fuel starvation under high RPMs.
- All L69's have a knock sensor.
- LG4 got the knock sensor in '85.
- In 1986, the LG4 got the electric pump.
- All L69's had an electric fan with a high output motor.
- In 1986, the LG4 received a low output electric fan.
- L69 E4ME Q Jets carbs received a richer DR" metering rod with the "M" hanger combo, & no throttle limiter on the AV... could flow the 750 cfm ALL E4MEs are capable of (tough to make happen with any stock 305 tho LOL).
- All L69's had a better, performance calibrated ECM/PROM combo.

PISTONS:
- 1982 -'83 F-Body LU5: GM PN: 364702 8.6:1 CR (dished)
- 1982 -'84 F-Body LG4: GM PN: 364702 8.6:1 CR (dished)
- 1985 -'86 F-Body LG4: GM PN: 14081291 9.5:1 CR (flat) 4 valve reliefs
- 1983 -'86 F-Body L69: GM PN: 14081291 9.5:1 CR (flat) 4 valve reliefs
- 1985 -'86 F-Body LB9: GM PN: 14081291 9.5:1 CR (flat) 4 valve reliefs
- 1987 F-Body LG4: GM PN: 14094013 CR (flat) 4 valve reliefs

CAMSHAFT:
- '82-'86 LG4: GM PN: 14088841 Hyd. Flat Tappet - Duration @ .050": 178/194 - Max Lift .350/.385 - 108 Idle: 650 rpm "Peanut Cam"
- '83-'86 L69: GM PN: 14088843* Hyd. Flat Tappet - Duration @ .050": 202/206 - Max Lift: .403/.415 - 115 - Idle: 650 rpm
*Note: L69 cam is*not*the same as the L81 "929" cam.
** GM Replacement PN: 12523897
The 1985 LB9 305 TPI used the basic L69 shortblock, same camshaft and pistons.

TRANS/AXLE Combo:
1983: The L69 was ONLY available with the T5/3:73's
1984: The L69 was avail w/ T5/3:73 or 700R4 (1900 rpm Tq conv.)/ only 3:73 or 3:42 optional
1985/86: The L69 was avail w/ T5/3:73 only
1982 -'86 F-Body LG4/L69 AT Flexplate: GM PN: 471529
1982 -'86 F-Body LG4 T-5 Flywheel: GM PN: 366860
1983 -'86 F-Body L69 T-5 Flywheel: GM PN: 14085720*
(*L69/T-5-Only, lightweight flywheel.)

jmd

iTrader: (4)

Nice post Al. You may want to correct the flywheel info; 86 was the first year for the new flywheel, taking a smaller bolt circle, weighted for internal balance, version.

sofakingdom

iTrader: (1)

You may also want to correct the year that the LG4 was first offered in... 1976 is a bit off the mark.

And, "All L69's had a mechanical fuel pump w/a light pressure rated electric fuel pump" is wrong.

And, "All L69's had a better advance weight/spring combo" is wrong; the reality us, ALL L69s were computer-controlled, and therefore NOT ONE SINGLE ONE had any weights or springs at all.

Brother Al

Thank You.

Sofakingdom, you are absolutely right:
- "All L69's had a better advance weight/spring combo" is wrong; the reality us, ALL L69s were computer-controlled, and therefore NOT ONE SINGLE ONE had any weights or springs at all.
Yes, my bad... Id forgotten that CCC HEI did not have them, only had the provision for them. Been a bit since I had to replace the cap n rotor on an LG4/L69.

All due respect but, I do have to disagree on several other points:

- 86 was the first year for the new flywheel:
The F-Body L69 does have the lightweight flywheel/pn 14085720... I have personally verified on an '84 L69/T5 car I chopped up as a parts car for my Recaro TA... this part number is also listed under the L69 T5 combo in the GM parts manual. This flywheel was used for many Chevy Hi-Perf engines until the 2pc RMS was introduced in '87 models,
('85 production = "1986" Model Year, 2 piece rear main seal.

- All L69's had a mechanical fuel pump w/a light pressure rated electric fuel pump...
What part of this is not true? They have a mechanical pump and a light pressure rated electric fuel pump in the gas tank... this is not new info.

- You may also want to correct the year that the LG4 was first offered in... 1976 is a bit off the mark.
Yes, the Chevy 305 LG3 2bbl was introduced in the 1976 Chevelle Malibu, ('75 production), LG4 was '78 or '79... dont remember, but the engine didnt change outside of the carb & RPO until CCC was introduced in '82.

sofakingdom

iTrader: (1)

Well, the 83 L69 sitting in my driveway doesn't have an electric pump. So I'd say, the part about the electric pump.

Yes I'm well aware of that; I was working in the new-car aftermarket accessory business in 1975. However those 305s had 2-bbl carbs, such as the 78 El Camino also sitting in my driveway, and were NOT the LG4. If memory serves, the first LG4 motors (305 w computer-controlled 4-bbl) appeared in about 1980 or 81. Couldn't say for sure because I avoided them like the plague whenever possible. Although, my wife did buy a 84 Caprice, that had one.

Brother Al

I was trying to edit my statement on the 305... you are correct...

You have an '83 L69... the fact it doesnt have one is news to me and likely plenty of other folks. As you know, few VIN 7 cars were built and GM did not openly document many things about the late changes for LU5 to L69 production.
As for '83, every piece of GM info I have states all '83-'86 L69's have both. I have yet to find a wiring diagram for '83 listing the L69. However, the harness and pump are fully present on the '84 diagram and is also present on my '84 Recaro T/A...

sofakingdom

iTrader: (1)

Possibly so; has little influence on reality though.

I guess that's one of the benefits of having been there at the time. You sound like you weren't, and therefore all you have to go on, is "documentation". Take advantage of the opportunity to learn what REALLY existed from people who WERE there at the time, rather than trying to argue about it.

I traded in a 79 Z28 350 4-speed for the 83 car, FYI.

Brother Al

Another Thread goes to pot....

Yes Sofa, OK, you win... I was 8 in 1983.

Guess thats one of the benefits of*"Having Been There at the Time" doesnt include any of the time after that point either. Yes, I posted some incorrect info amongst all of that correct/detailed info... and I readily admitted being wrong, I also saw what I had written about the 305 vs LG4 my bad man... I typed a damn 4 instead of a 3. Easy to do when you are talking and typing LG4 a dozen times on a smartphone.

No, I dont happen to have an '83 L69 car handy, nor do many people... Most have never seen one, so Yeah, I go on what authentic GM info is available... What I do have is a 54K Recaro TA in very original shape and I have done quite a bit of research verifying part numbers and aquiring spare parts. I have also torn apart quite a few 3rd Gens, including (2) '84 L69 cars, wrenched on a bunch of 3rd Gens, have about 2 cars worth of parts For Sale, plus a host of rare used and NOS pieces. I have also procured a number of GM Service Manuals and GM Parts Books Through 1988... so maybe its stupid of me to try and learn as much as I can, instead of taking things for granted.... or assuming that "Everyone That Was There" is a damn expert because God only knows how many "People Who Were There" claim:
"My '85 Iroc-Z had a Corvette TPI 350 and a 5 Speed."

This said, I have seen many of your posts. Rather than posting as you did, perhaps join the conversation with a constructive attitude and post up some solid correcting info with an explaination...

sofakingdom

iTrader: (1)

That's pretty much what happens when you post something and claim it's "definitive" or the like, but the facts aren't right.

Being young, and therefore having no experience with the things that were going on before we were there, is a character flaw all of us have been guilty of at one time or another. Lord knows I sure have. But, go ahead and keep trying to learn; just don't come in here and start trying to tell us all about "all" whatever that simply isn't so, and part numbers that weren't on the car I bought back then, and all such as that. While I certainly don't claim to "know" "everything" about those cars, I'd be happy to share my personal experiences and observations at the time, should such be requested.

And no, I won't talk about a 350 TPI 5-spd car. EVER. At least, not from the factory. Although, I did use my 83 car as a work truck for a long time, and wore out the 305 in it by around 88 or so; at which time I put a 400 in it because the 305 was so ..... underwhelming. No testicular fortitude. But I won't claim that it was factory, original, or anything of the kind.