305 to 350 engine swap
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From: Glen Burnie, MD, USA
305 to 350 engine swap
I'm thinking about purchasing a 300hp, 350 target motor from a local speed shop and I need to know a few things first. Can I reuse the stock 305-exhaust manifolds and emissions equipment? What about my electronics? Is there a chip to change? If so, change it to what? I would like to change the manifold and carb over to an Edelbrock setup but will that match up with any electronics or should I stick with the stock 305 equipment and just swap it over to the new motor. Also, If I do use the 305 stuff, how will it affect the performance of the 350? SOMEBODY HELP ME!!! Thanks!
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Fudge,
The exhaust manifolds from the 305 should fit the engine, but will most certainly be restrictive. You will eventually need to change to larger iron manifolds of tube headers to get the best flow.
The only change you should have to do to the electronics would be to install a knock sensor element for a 350 instead of the 305 unit. The ECM PROM only controls the fuel mixture solenoid on the E4ME Rochester carb, and timing advance curves. The carb may require some tuning to work well with the 350, and the secondary metering rods and cam will likely have to be changed to feed the 350 with enough fuel. It's possible that the main jets would have to be increased in size, but an older carb probably already has its jets worn open enough so that the mixture would be fairly close. (Yes, the bronze jets do get larger over time.) Idle mixture may be a bit lean, but overall the Rochester can be tuned to run the 350 well. An Edelbrock replacement would have to include the TPS and solenoid to be completrely compatible. As a routine maintenance step, you might consider installing a new oxygen sensor with the new engine, just to be sure the system is operating at peak with the new changes.
All of this is under the presumption that you have an '83-'86 350 carbed engine anD the stock ECM for that setup. I hope that is correct.
------------------
Later,
Vader
------------------
"Make Me Bad"
Adobe Acrobat Reader 4.0
The exhaust manifolds from the 305 should fit the engine, but will most certainly be restrictive. You will eventually need to change to larger iron manifolds of tube headers to get the best flow.
The only change you should have to do to the electronics would be to install a knock sensor element for a 350 instead of the 305 unit. The ECM PROM only controls the fuel mixture solenoid on the E4ME Rochester carb, and timing advance curves. The carb may require some tuning to work well with the 350, and the secondary metering rods and cam will likely have to be changed to feed the 350 with enough fuel. It's possible that the main jets would have to be increased in size, but an older carb probably already has its jets worn open enough so that the mixture would be fairly close. (Yes, the bronze jets do get larger over time.) Idle mixture may be a bit lean, but overall the Rochester can be tuned to run the 350 well. An Edelbrock replacement would have to include the TPS and solenoid to be completrely compatible. As a routine maintenance step, you might consider installing a new oxygen sensor with the new engine, just to be sure the system is operating at peak with the new changes.
All of this is under the presumption that you have an '83-'86 350 carbed engine anD the stock ECM for that setup. I hope that is correct.
------------------
Later,
Vader
------------------
"Make Me Bad"
Adobe Acrobat Reader 4.0
Thread Starter
Junior Member
Joined: Sep 2000
Posts: 4
Likes: 0
From: Glen Burnie, MD, USA
Originally posted by Vader:
Fudge,
The exhaust manifolds from the 305 should fit the engine, but will most certainly be restrictive. You will eventually need to change to larger iron manifolds of tube headers to get the best flow.
The only change you should have to do to the electronics would be to install a knock sensor element for a 350 instead of the 305 unit. The ECM PROM only controls the fuel mixture solenoid on the E4ME Rochester carb, and timing advance curves. The carb may require some tuning to work well with the 350, and the secondary metering rods and cam will likely have to be changed to feed the 350 with enough fuel. It's possible that the main jets would have to be increased in size, but an older carb probably already has its jets worn open enough so that the mixture would be fairly close. (Yes, the bronze jets do get larger over time.) Idle mixture may be a bit lean, but overall the Rochester can be tuned to run the 350 well. An Edelbrock replacement would have to include the TPS and solenoid to be completrely compatible. As a routine maintenance step, you might consider installing a new oxygen sensor with the new engine, just to be sure the system is operating at peak with the new changes.
All of this is under the presumption that you have an '83-'86 350 carbed engine anD the stock ECM for that setup. I hope that is correct.
Fudge,
The exhaust manifolds from the 305 should fit the engine, but will most certainly be restrictive. You will eventually need to change to larger iron manifolds of tube headers to get the best flow.
The only change you should have to do to the electronics would be to install a knock sensor element for a 350 instead of the 305 unit. The ECM PROM only controls the fuel mixture solenoid on the E4ME Rochester carb, and timing advance curves. The carb may require some tuning to work well with the 350, and the secondary metering rods and cam will likely have to be changed to feed the 350 with enough fuel. It's possible that the main jets would have to be increased in size, but an older carb probably already has its jets worn open enough so that the mixture would be fairly close. (Yes, the bronze jets do get larger over time.) Idle mixture may be a bit lean, but overall the Rochester can be tuned to run the 350 well. An Edelbrock replacement would have to include the TPS and solenoid to be completrely compatible. As a routine maintenance step, you might consider installing a new oxygen sensor with the new engine, just to be sure the system is operating at peak with the new changes.
All of this is under the presumption that you have an '83-'86 350 carbed engine anD the stock ECM for that setup. I hope that is correct.
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