Tim Burgess

Were there any differences between the LG4 & L69 carbs? GM has the same replacement part number listed for both - but that may be due to them wanting one replacement part for both applications - seems the secondary jetting should be a bit larger for an L69.......Also, what is a good source for a new performance computer controlled carb - if anyone makes one - or any recommendations on good place to have a performance Q-jet rebuild done?

Tim

Ed Maher

The only sure difference between LG4 and L69 cars is the secondary rods (CH vs. DR respectively)
Their has been contention that the AV on L69 cars open wider than LG4s, but i think this is due to the presence of the severly restricted 307 Olds style carbs on some LG4s. As far as my eyes could tell, L69 AVs only open as wide as a regular LG4 AV.
AFAIK nobody makes any kind of replacement for the E-quad, holley used to make one, but i have never even actually seen one of them. As for where to get a rebuild, hopefully somebody else will chime in with their experience here. Why not just do it yourself, it's not that hard.
...ed

Tim Burgess

Are CH & DR rod size specifications? What does AV mean?

Tim

five7kid

iTrader: (14)

"CH" & "DR" are secondary rod designations or part "numbers". The letters are stamped on the rods themselves. There's no rhyme or reason behind the letters they used relative to size or taper.

"AV" stands for the secondary air valves, which open with increasing air flow and pull the secondary rods out of the jets to increase fuel flow to maintain the mixture ratio. Check the tech article on getting them to open more.

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82 Berlinetta, orig V-6 car. Rescued w/86 LG4/TH700R with all harnesses, sensors, ECM, etc. 2.73 open. Cat-back from '91 GTA, Accel HEI SuperCoil. AMSOIL syn lubes bumper-to-bumper. Daily driver, work-in-progress (LB9 w/ZZ3 cam, exhaust, paint, etc.).
57 Bel Air, my 1st car. Currently 396 .030 over, Weiand Action+, Edelbrock 1901 Q-Jet, Jacobs Omnipack, 1-3/4" headers, TH400 w/TCI Sat Night Special conv & shift kit, 3.08 10-bolt, AMSOIL syn lubes bumper-to-bumper. Best 15.1 @ 5800' Bandimere. Daily driver while Camaro was being put together.

Tim Burgess

Thanks, guys......

Tim

Tim Burgess

I went to GM & ordered an L69 jet & rod kit. The part number is 17111698 & it runs $49. The kit comes with (DR) secondary rods, secondary jets, secondary rod hanger, primary rods & springs & a screw & a cotter pin. The corresponding LG4 kit part number is 17111697. Thanks, again, for the info....

Tim

five7kid

iTrader: (14)

That's good info. I hadn't heard of such a kit. What hanger comes with it? There should be a letter stamped on the top.

Not to be contrary, but there's no such thing as secondary jets. Must be something different, or you got carried away in your excitement .

johns84bird

I have a carbed 350 with the same carb as the old 305, and I need to upgrade it. Would the 305 HO kit be enough for this setup?

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84 Firebird with Trans am ground effects- 350 4bbl GM crate motor (LM1), T-Tops, automatic, K&N filter, 180* thermostat, ram-air hood scoop, flowmaster muffler, Accel cap & rotor, MSD Super Conductor Wires. Coming soon: new interior (grey), rear end work, subframe connectors, polyurethane bushings

Tim Burgess

The hanger has a "K" stamped on it. What are the two threaded brass things that have a hole drilled through the side & have a tapered steel tube pressed in to them called? The kit is called "JET ROD" - are they the primary jets??

Tim

Tim Burgess

Looks like they are the primary jets from the exploded view in the shop manual - no secondary jets. Thanks for the correction.

Tim

84FTA

L69's ECMs also utilized a knock sensor which then could let the ECM increase the curve for better performance/fuel economy. Just a thought for a full L69 upgrade....


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1984 WS6 Trans Am Hartop
Former L69 Car under restoration
1984 WS6 Trans Am T-top car
4-bolt main 350, headers, Holley 650, T-5 and 3.23's.
Daily driver and restoration

MRZ28HO

No, the knock sensor hinders the "curve". The L69 uses a knock sensor because the increased compression ratio (9.5:1 = L69 vs. 8.5:1 = LG4) and agressive timing (8' initial for L69 vs. I don't know, 4'-6' initial for LG4), and therefore the ECM uses it to reduce advance timing.

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

BLACK Z

The lg4 usees a knock sensor to.


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86Z28, GM 350, Jet perf Q-jet & chip Dual snorkel air cleaner, Edelbrock performer intake, Edelbrock headers, Edelbrock cat-back, Off road pipe, MSD 6AL, Accel Super Coil, Taylor Spiro-pro wires, Rapid fire plugs, Jet fan switch, World class t-5, Hurst Short Throw Shifter, Ram Flywheel, Center force dual friction clutch,Aluminum drive shaft, BW disc rear 3.45's & a posi, PBR calipers, Earls braided brake lines, Polygrapite bushings all the way around, poly tranny mount & torque arm mount, Hotchkis lower control arms & panhard rod, Rancho limiter straps, KYB struts & shocks, Gm Wonderbar, Edelbrock strut tower brace, SSM sub frame connectors, Jamex lowering springs, Carbon metallic brake pads, Crossed drilled rotors, Mobil 1 Tranny fluid & motor oil, GM syntheic rear end oil, K&N, Grant stering wheel, 1,200 watt system, Jet Black Paint, 91 Z28 rims, 92 wing, Tinted windows.

MRZ28HO

You're right, but only the later ones ('87 IIRC).

84FTA

Yes, I meant indirectly advances the timing by letting it have an initially more agressive timing curve. The early LG4's had a very strict and rather lacking curve.

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1984 WS6 Trans Am Hartop
Former L69 Car under restoration
1984 WS6 Trans Am T-top car
4-bolt main 350, headers, Holley 650, T-5 and 3.23's.
Daily driver and restoration

Phil87IROC

iTrader: (1)

Tim,

There are two good books out that discuss many Rochester Carb mods and HP tuning. One covers the older non-ECM carbs and the other covers the newer ECM controlled carbs. Both give good tips.

As you know Tim, I had an '84 L69 Z28 for many years and modded the carb extensively. I used these books to bring the Quad to life!! I believe 'Doug Roe' is the author. Anyone else have any thoughts or use these books to tune/modify their QJets?

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Phil87IROC
Blue '87 IROC, 383 Crate Motor, KB pistons, AFR 190s, TPIS ZZ-9, Edelbrock RPM intake, TES and Edelbrock 750 cfm Carb (#1411), stock T-5, 3.42 rear GM gears w/Auburn posi.
Ohio Valley Dragstrip Trophy Bracket WINNER - 8.39 ET on a 1.82 sec. - 60'. Best MPH = 84.44. Still Tuning Carb!
Red '89 IROC L98, 700R4, T-Tops, K&Ns w/open air boxes, 160 T-stat, Hyper Chip, gutted MAF, 53kv coil, MSD wires.

Tim Burgess

You still have the book?

Tim

BLACK Z

My 86 lg4 has a knock sensor.

MRZ28HO

Tim, you can get the book from Jeg's, Summit (IIRC), or Classic Industries. It is called Rochester Carburetors by Doug Roe for ~$15.

Could be right, I know that when the L69 was discontinued, the LG4 received the L69 computer stuff.

[This message has been edited by MRZ28HO (edited November 02, 2000).]

Phil87IROC

iTrader: (1)

I still have the older book. I'll bring it to Tucson in Dec/Jan when I return for work.



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Phil87IROC
Blue '87 IROC, 383 Crate Motor, KB pistons, AFR 190s, TPIS ZZ-9, Edelbrock RPM intake, TES and Edelbrock 750 cfm Carb (#1411), stock T-5, 3.42 rear GM gears w/Auburn posi.
Ohio Valley Dragstrip Trophy Bracket WINNER - 8.39 ET on a 1.82 sec. - 60'. Best MPH = 84.44. Still Tuning Carb!
Red '89 IROC L98, 700R4, T-Tops, K&Ns w/open air boxes, 160 T-stat, Hyper Chip, gutted MAF, 53kv coil, MSD wires.

Tim Burgess

Cool!........It's about time you got back to work!!! It will be good to have you back in town! I'll try to stop by your new house for the ground clearance test tomorrow nite. Does it matter that I now have an 8 inch 4WD lift kit on my Z?? Better et's end over end......

Tim

Camaro_Drvr

Are you saying that the LG4 ecms with the knock sensors are the same ecms as the old L69's?

Randy

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360ci '84 Berlinetta
000ci '68 El Camino

MRZ28HO

Could be Randy, I'd have to look at the ECM number to figure this out, though.