I have an '87 Formula that had the 305 LG4 and T-5 tranny. A basic 350 was recently installed using the stock LG4 intake manifold and carb. Do I need to change out the ECM? Are there any other changes I need to make to ensure a smooth running car? Thanks in advance.

 

Well you should go to a knock sensor and the module to go with the sensor that are made for a 350, I am not sure of the correct part number though. You can go for a chip if you like it is not really needed though. I did and I did notice a slight diffrence. I am still runing the stock fuel pump but I am liiking into getting a diffrent one.

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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.

 

Your stock ECM will run it just fine, actually. It's a computer controlled carb, not FI and the carb self-adjusts to whatever engine it's on about 80% by itself. It only knows airflow, not what size engine it's on top of.

I would highly recommend upgraded the secondary rods in your carb to a set of "DR" rods (in place of stock CH or DP rods) and a "G" secondary hanger. Stock LG-4 calibration is too lean for a moderately strong 350.

I don't know what knock sensor you'd use to replace the stock one. 3rd ben carb motors and ECMs only ever dealt with 305 cube motors, never a carb'ed 350. So there's no obvious replacement to use that I am aware of. Someone else could have better info, though.

I reinstalled the stock 350 TPI knock sensor in my brother's 87 TA when we upgraded to a 400 engine recently and it works just fine despite the fact that the 400 block is quite different than the original 350. So I wonder if all this talk about "matching the knock sensor to the engine" isn't mostly unnecessary.

 

Talk to Ken Casey at Burt Chevrolet in Denver,Colorado.He's done tons of these swaps and was very helpful. I swapped out my 305 TBI motor for a 350 and he sent me the 350 Injectors,Knock Sensor and Module for a package-deal price.I'm sure he can tell you if anything else is required for your swap.
(303) 761-1286
Ask for him in the parts department.
I got his name from Chevy High Performance Magazine.

 

In the ZZ4 conversion kit, the parts lists includes: "Sensor, Knock" p/n 10456288; "Module, Elec. Spark Control" p/n 16128261.

It also has: "Controller, ECM" p/n 1228079; "Calibrator, Prom 1985-87 LG4, 83-86 L69" p/n 24502456. But, those are for automatic cars (have heard will work fine with manual).

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82 Berlinetta, orig V-6 car, now w/86 LG4/TH700R4. 2.93 limited slip. 2-1/2" cat-back, ZZ3 intake, Accel HEI SuperCoil. AMSOIL syn lubes bumper-to-bumper. Daily driver, work-in-progress (LG4 CC system w/'87 LB9 block, ZZ3 cam, ported World 305 heads, Hooker 2055 headers, 3" Catco cat & 3" catback, restalled TC, Spohn SFCs).
57 Bel Air, my 1st car. '66 396, 9.7 CR forged TRWs, Weiand Action+, Holley 750VS w/4150 conversion, GK 270 cam, Magnum rockers, Jacobs Omnipack, 1-3/4" Hedders & 3" Warlocks, TH400 w/TCI Sat Night Special conv & Trans-Scat shift kit, MegaShifter, 3.08 8.2" 10-bolt w/Powertrax, AMSOIL syn lubes bumper-to-bumper. Idles smooth @ 600 RPM in D. Best 15.02/95.06 @ 5800' Bandimere (corrected 13.93/102.4 @ sea level).