Post by BowtieGuy on Jun 25, 2004 17:06:30 GMT -5
The details I am going to cover here are most directed towards the newer models with ecm controls since swaps in older model trucks are pretty much straight forward. I am also going to deal mainly with swapping from a 305 to a 350 so some things will still apply to the older trucks.
I swapped out the tired and smoking 305 in my 86 Silverado for a remanufactored 350 long block. The basics of the swap are still staight forward, what I plan to cover are the things that need to be changed to prevent you from making several trips back and forth to the parts house. The engine I installed was an 85 and older style which is a 2 piece rear main seal. The 305 in the truck is a 1 piece. So a new flywheel is needed. A new oil pan will be needed also but make sure you get one with the dipstick located on the same side as the engine. The starter in the 305 is a low torque starter and will work on a 350 but when you get the timing set right the 350 will buck the starter making it harder to crank, and aggrevating also, I chose to get a new one to get everything right the first time. If you plan on disconnecting the ecm from the engine altogether like I did you will need to get another HEI distributor with a vaccum advance. When looking for another distributor make sure to get one for a 350, if you do get one for a 305 make sure you get a new mechanical timing curve kit for a 350. Hooking it up is still the same for the power wire only minus the plug in from the ecm. Also if disconnecting the ecm you will need another carberator. If you chose to use another besides a q-jet make sure you get a throttle linkage adaptor for the 700r4 t.v. cable, unless using another tranny then not required. I replaced my carb with another q-jet from a 74 model 1/2 ton truck,350, auto tranny. The throttle linkage was almost identical to the original. I removed all emission controls from the engine and engine bay so I can't give details on hooking them up, but the whole system was still fairly simple so it shouldn't be to hard to hook everything back up like it was without modifications. If you plan to keep the stock exhaust manifolds on the new engine, either check the heads on the passenger side for the 7th bolt hole for the exhaust manifold. See arrow in picture.
If the new engine doesn't have the extra bolt hole you will need another exhaust manifold for the passenger side that doesn't use this hole. And when bolting everything up the stock exhaust pipe probably wont line up right so a trip to the exhaust shop will be needed. Best fix is to make sure to get an engine that has the heads with this extra bolt hole or use headers and get a new exhaust. This will help the engine perform better anyways. The last thing that will need to be changed is the wiring to the transmission for the lock up, if the 700r4 is still going to be used. The lock up was controlled by the ecm so it will need to be rewired for manual control. For details on rewiring the transmission look in the 700r4 board, I will post details on how I rewired mine without an aftermarket kit.
I swapped out the tired and smoking 305 in my 86 Silverado for a remanufactored 350 long block. The basics of the swap are still staight forward, what I plan to cover are the things that need to be changed to prevent you from making several trips back and forth to the parts house. The engine I installed was an 85 and older style which is a 2 piece rear main seal. The 305 in the truck is a 1 piece. So a new flywheel is needed. A new oil pan will be needed also but make sure you get one with the dipstick located on the same side as the engine. The starter in the 305 is a low torque starter and will work on a 350 but when you get the timing set right the 350 will buck the starter making it harder to crank, and aggrevating also, I chose to get a new one to get everything right the first time. If you plan on disconnecting the ecm from the engine altogether like I did you will need to get another HEI distributor with a vaccum advance. When looking for another distributor make sure to get one for a 350, if you do get one for a 305 make sure you get a new mechanical timing curve kit for a 350. Hooking it up is still the same for the power wire only minus the plug in from the ecm. Also if disconnecting the ecm you will need another carberator. If you chose to use another besides a q-jet make sure you get a throttle linkage adaptor for the 700r4 t.v. cable, unless using another tranny then not required. I replaced my carb with another q-jet from a 74 model 1/2 ton truck,350, auto tranny. The throttle linkage was almost identical to the original. I removed all emission controls from the engine and engine bay so I can't give details on hooking them up, but the whole system was still fairly simple so it shouldn't be to hard to hook everything back up like it was without modifications. If you plan to keep the stock exhaust manifolds on the new engine, either check the heads on the passenger side for the 7th bolt hole for the exhaust manifold. See arrow in picture.
If the new engine doesn't have the extra bolt hole you will need another exhaust manifold for the passenger side that doesn't use this hole. And when bolting everything up the stock exhaust pipe probably wont line up right so a trip to the exhaust shop will be needed. Best fix is to make sure to get an engine that has the heads with this extra bolt hole or use headers and get a new exhaust. This will help the engine perform better anyways. The last thing that will need to be changed is the wiring to the transmission for the lock up, if the 700r4 is still going to be used. The lock up was controlled by the ecm so it will need to be rewired for manual control. For details on rewiring the transmission look in the 700r4 board, I will post details on how I rewired mine without an aftermarket kit.
