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1989 pontiac swap from 2.8mfi to 3400 sfi


1989 Pontiac Se
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The 4T60 and 4T60E have the same bellhousing but obviously the later years had electronic controls whereas the original 4T60 was mechanical. The real issue will be getting the computer to run the 3400. The engine should swap over, but you may have to custom make a mount or 2 (that's the case on the Cavalier and Sunbird) and you have to splice wiring. The computer for sure needs to be tuned or converted to OBD2. 

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Will a 3400sfi bolt to a 4t60 tranny

 

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The engine will bolt to the trans without issue, the bell housings are the same.

 

The 3400 is an OBDII engine, to get it to work properly in an OBDI environment you will need to replace the existing ECM for the larger displacement engine, the 2.8 ECM will not be able to handle the electronics. If you pick up a 1993 ECM for the OBDI 3.1 *T* code LHO engine *1227727* or the 1993 3100 L82 engine *16184164* those ECM's should do what you need in reference to the chip for the fuel mapping/timing curve for the 3100 engine series II. The 3400 will properly run on the L82 3100 chip mapping as the two engines use the same injector sizes.

 

The earlier engines were designed to *roll* forward, the 3400 will not, the oil pan is cast, the block casting is a different casting that the earlier blocks. The front engine mount support on the block is not the same that was used under the earlier stamped oil pan engines. The 3400 throttle body is larger as well, your present snorkel will not fit. The 3400 throttle body has no trans TV cable to downshift the trans.The exhaust manifold flange used on the 3400 is designed for a 2 1/2" exhaust pipe, what you have is not.  You can use the existing trans torque converter that is behind the 2.8 engine but when driven by the larger 3400 the stall speed will go up, the 3400 engine has more inherent torque than the 2.8 and will naturally drive up the stall rpm. There are some other smaller hurdles that one has to overcome as well in the installation.

 

This is a common engine *update* that I get into in Fiero engine transplants.

 

   

http://www.exatorq.com/ludis_obd1/p4xref.html

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For the most part, it's a relatively direct swap.  You will need to play GM Legos to make certain parts work.  I was going to do this into my '89 Cutlass before I scrapped it due to moving.  Expect to spend a couple of days in the junkyard pulling parts off 94-96 3100 W cars. 

 

ECM control is as simple as a chip swap. https://wot-tech.com/3400-swap-chip.html

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