305-350 Engine Swap...ECM Change/Reprogram needed?
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Joined: Dec 2005
Posts: 4,795
Likes: 15
From: St. Cloud, MN
Car: 1984 Trans Am
Engine: LS1383 in work
Transmission: Magnum F - to be installed
Axle/Gears: Zexel Torsen 3.73, 28-spline mosers
305-350 Engine Swap...ECM Change/Reprogram needed?
Hey everyone,
I just finished swapping a built 350 into my 84 TransAm that replaced the stock 305. I do still have the CC Q-jet and CC Distributor in it. I've been having stumbling/stalling issues at idle as well as running a little hot. It's been suggested that it might be trying to run to lean (hence hotter) due to incorrect or mis-read readings from the o2 sensor and the idle might be a timing issue caused by the ECM not being able to run the new larger motor correctly. And so here I am. I was wondering how much, if at all the new engine would be affected by the stock ECM? Also, would I even benefit from a reprogram/new chip due to the fact that I've got about the simplest ecm out there since I'm not running EFI?
Engine Specs Original
L69 305 H.O.
Engine Specs new:
350 bored .040
9.3:1 compression (estimated)
Sportsman II heads 2.02 intake, 1.6 exhaust
Edelbrock Performer Intake
Stock Torque Converter
3.73 Gears
700R4
Headers
3" catback
CC Q-Jet from Jet performance Products
CC Distributor (original) with MSD Coil, Cap, Rotor and plug wires
I've got a Jet Fan switch in it (for what that's worth) and I did get a 350 Knock Sensor.
Cam Specs:
Cam Style: Hydraulic roller tappet
Basic Operating RPM Range: 1,800-5,800
Intake Duration at 050 inch Lift: 219
Exhaust Duration at 050 inch Lift: 227
Duration at 050 inch Lift: 219 int./227 exh.
Advertised Intake Duration: 270
Advertised Exhaust Duration: 278
Advertised Duration: 270 int./278 exh.
Intake Valve Lift with Factory Rocker Arm Ratio: 0.515 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio: 0.530 in.
Valve Lift with Factory Rocker Arm Ratio: 0.515 int./0.530 exh. lift
Lobe Separation (degrees): 112
Intake Valve Lash: 0.000 in.
Exhaust Valve Lash: 0.000 in.
Computer Controlled Compatible: Yes
Grind Number: VDSC-270
Any help would be greatly appreciated. Thanks!
I just finished swapping a built 350 into my 84 TransAm that replaced the stock 305. I do still have the CC Q-jet and CC Distributor in it. I've been having stumbling/stalling issues at idle as well as running a little hot. It's been suggested that it might be trying to run to lean (hence hotter) due to incorrect or mis-read readings from the o2 sensor and the idle might be a timing issue caused by the ECM not being able to run the new larger motor correctly. And so here I am. I was wondering how much, if at all the new engine would be affected by the stock ECM? Also, would I even benefit from a reprogram/new chip due to the fact that I've got about the simplest ecm out there since I'm not running EFI?
Engine Specs Original
L69 305 H.O.
Engine Specs new:
350 bored .040
9.3:1 compression (estimated)
Sportsman II heads 2.02 intake, 1.6 exhaust
Edelbrock Performer Intake
Stock Torque Converter
3.73 Gears
700R4
Headers
3" catback
CC Q-Jet from Jet performance Products
CC Distributor (original) with MSD Coil, Cap, Rotor and plug wires
I've got a Jet Fan switch in it (for what that's worth) and I did get a 350 Knock Sensor.
Cam Specs:
Cam Style: Hydraulic roller tappet
Basic Operating RPM Range: 1,800-5,800
Intake Duration at 050 inch Lift: 219
Exhaust Duration at 050 inch Lift: 227
Duration at 050 inch Lift: 219 int./227 exh.
Advertised Intake Duration: 270
Advertised Exhaust Duration: 278
Advertised Duration: 270 int./278 exh.
Intake Valve Lift with Factory Rocker Arm Ratio: 0.515 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio: 0.530 in.
Valve Lift with Factory Rocker Arm Ratio: 0.515 int./0.530 exh. lift
Lobe Separation (degrees): 112
Intake Valve Lash: 0.000 in.
Exhaust Valve Lash: 0.000 in.
Computer Controlled Compatible: Yes
Grind Number: VDSC-270
Any help would be greatly appreciated. Thanks!
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