QuestionGood evening & Merry Christmas as the hour is now after midnight. May I ask who I am talking to? I had sent to both of the listed experts & have had almost a 180 degree difference of opinion. Also, I had ask you during my last Email for a list of remanufacture units &/or a good used unit? Enclosed is the answers I received from the other expert for your review & comment? We are anxious to start the project this week & sincerely appreciate all the expert advice.
Sincerely, Jeff, jlg@rocket7designinc.com
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Yes its very possible. You need to use the 4.5 computer on the 4.5 engine, these should have the same adapters but the software is different, most of the engine components are the same, though the map sensor, some vacuum lines, and small things such as the windshield washer fluid resovoir and battery are just some of the obstacles you must overcome, if you can rebuild a cadillac motor you have my confidence in swapping a 4.9 to a 4.5.
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Answer I cant predict whether every single wire is going to be identical, but to my knowledge most of the components if not all are the same for the motors, the main difference is the block design, the cylinder heads, intake manifold and transmission. Components should be the same. The wiring for the ECM should be the same as they are the same boards but different software. The wiring going to the engine will be different when things such as the MAP sensor or windshield washer resovoir are trying to be hooked up, also the battery is in a different location, you will probably have to extend the wiring for some components. This swap is very possible but in the same respect as doing any work on any car dont expect anything to be perfect.
p.s. caddis and most GMs are notorious for the ability to mix and match components and theyll still work 100% correct with one another.
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Good afternoon & Thank you for your first reply. I had received another response that indicated we would need to change the CPU & Map sensor. Can we move forwar with my 91 Sedan Seville with this change over from the 4.9l to a 4.5l out of a 88 Sedan Deville? I had asked the following in my first set of questions. Is the wiring different or just the computer? I was told third hand from a local general repair garage that even the bulk head was different? I have also been reading your articles & someone else with a totally different application was told that each & every wire needs to be traced? Is this the case with our two motors/cpu's & can we assume any of the wiring is the same, ie. all except the ones going to the engine? Please explain? A thought I had was what about trying to find a 90 seville computer & wiring harness that used a 4.5 or are they different from the 4.5 in my 88 Sedan Deville? Finally, I have intakes from two 4.9l, heads, etc, are they
the same? Could the motor be changed over or are you better off to leave the 4.5 as it is? Also, should we put the 4.5 transmission in the 91 Sedan Deville? Are all
the hook-ups the same?
Sincerely, JLG@Rocket7Designinc.com
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Good evening, I have a 88 Cadillac Sedan Deville with a replaced motor about 35k on it, runs good. However, this car had a tree fall on the trunk lid so it is a savage title. My 91 Seville 4.9l was taken out & tried to put in a savage yard engine only to find water coming out of one of the spark plug hole, we believe it may have taken water in the intake & may have frozen. So I am now really in need to move forward & unlike most wanting to put the 4.5l in place of the 4.9l. I realize that the wiring may be diferent & need to know if this can be done. One question is how about a 90 seville computer & wiring harness? Also, how about changing just the intake off the 4.9l & putting it on the 4.5l? What do we need to do to make it work? My final point is this, my Son & I at age 48 completely tore the original 4.9l down removing all to the heads, reworked all the values & the best of all but never did the rings on the pistons, was afraid of that stupid Cadillac design of O-rings. Put it back together with q-tips & scotch brite, looked like new but used a quart of oil every 25 miles after months & months of endless work so now I need to move forward with the 4.5 in place of the 4.9l, 88 Deville motor in the in the 91 Seville, help???
Sincere Thanks, JLG@Rocket7Designinc.com
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Not compatable intakes.
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The wiring harnesses are different and changing out the wiring harness you would have to remove the complete dash assembly to rewire the instrument cluster and all the gages, warning lights, etc, etc.
The transmissions have different electrical locations and internal valve body components.
Years ago you could swap engines and transmissions, But NOT with the computer systems that they put in the vehicles now days.
EVERTHING that has to do with the computer wiring and sensors, switches, transmission solenoids and wiring harnesses are ALL TOTALLY DIFFERENT .
Cut your loses and put A rebuilt engine of the same size and year back into your vehicle.
AnswerThis project is totally up to you. But you are going to have to get wiring schematics for every component to make sure that every wire location is EXACTLY the same and that the electrical connectors on the electrical harnesses will fit each and every device.
