1990 gmc pickup

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  #1  
Old 12-09-03, 07:59 AM
tygar663
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1990 gmc pickup

Hello, My Question is i have a 1990 gmc pickup with a 4.3 vortec i want to swap out this motor and put in a 305 or 350 v8 . how much work is involved with this swap and is it worth the effort. it has a tbi and computers i need to know everything that has to get changed in the swap ... thanks
 
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  #2  
Old 12-09-03, 08:43 AM
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that's a huge project...

even on a chevrolet where so many parts interchange well. the list of things to look for and change would be extensive and i'm sure i'd leave many out. also...there's the issue of changing the emissions certification of the vehicle by changing to a different engine than it was originally built with...could be a major problem down the road. 4.3's are good engines, why do you want to change it?
 
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Old 12-09-03, 09:14 AM
tygar663
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the 4.3 has 125k on it and was not taken care of by prevous owner. the 305 has 26k on it and is clean. the rebuild for the 4.3 is about 700 bucks... so i just figured i would ask. where i live there are no inspections or anything for cars. so i was thinking that why not go with the bigger enginei know the basic stuff that has to be changelike the motor mount brackets and stuff but my concern was the comuter and all the other sensors speedo junk like that..
 
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Old 12-09-03, 11:07 AM
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Sensors, ECM and Prom are different, which means harness is also different. For $700.00 I'd go back with the 4.3. Also, you might look around for a Delco crate engine. A few more $$$ but a great replacement engine.
 
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Old 12-09-03, 11:36 AM
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$700 is a VERY cheap rebuild. Sounds more like a refresh. I dont blame you for wanting to change the tired old 4.3 out for a 5.0, but if you are going to do it you might as well put in a 5.7. I have been trying to talk my Dad into doing the same thing for years on his 1987 Chevy P.U. As Dan said the computer, harness and all of the sensors will have to come from the engines donor vehicle. If it is not available, scour your local salvage yards for the needed harness and computer. I would personally replaces the needed sensors with new Delco parts rather than used parts.
Hope this is helpful to ya,
Billy
 
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Old 12-09-03, 12:02 PM
tygar663
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well no parts from the other car all i got was the motor (the 305).

i know this is going to change the post a little but the 4.3 runs good not the best but good it has power but leaks out the rear main seal plus a few other spots. the main problem is that it smokes like a chimney plus leaks oil i get great gas mileage but the oil kills me its like 20 miles to a quart of oil dosent leave big puddles in the driveway just a few spots.i pulled the plugs and only one had oil on it the rest were burning fine. i put some high dollar gm valve fogger in it to see if maybe it was a stuck valve but it did clean up some carbon cause it was black smoke that came out.

so the question is what else could i check to see what needs to be done to get it to quit smoking ...
 
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Old 12-09-03, 12:09 PM
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If its not leaving puddles and its smoking then its really burning most of the oil and the leaks are minimal. Sounds like you need to at the very least have the heads rebuilt. And since you have the other noted leaks, you can either pull the engine or the tranny and replace the rear seal. If you pull the engine you might as well rebuild it. Providing you have the available funds.
Billy
 
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Old 12-09-03, 12:22 PM
tygar663
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thanks i am going to do that . rebuild the 4.3 and heads. put it in and drive it ... while im driving it i will look for a donor for the next step... it is going to have a v8 in it 5.0 or the 5.7. but i need to have the truck running . my other truck is a 2003 silverado 2500hd with the 6.0 gas mileage sucks but love it .... once again thanks and happy holidays

you guys do a great job here helping people out
 
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Old 12-09-03, 04:16 PM
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If you dislike the gas mileage on your newer 2003 with a 6.0 why do you want to put a v-8 in this truck if mileage appears to be a concern?
 
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Old 12-21-03, 04:54 PM
tygar663
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the 6.0 is in that heavy truck and gets about 10 mpg that lil gmc short bed would get much better mpg than that but im thinking of and leaning to just rebuild what i have and look into a super charger if i need more power
 
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Old 12-21-03, 05:16 PM
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OK... youre going about things all backwards. A super charger isnt exactly going to be fuel efficeint. What exactly are you trying to accomplish here?
Billy
 
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Old 12-21-03, 06:31 PM
tygar663
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ok i had a 4.3 in a 2000 silverado was nice for gas mileage but just wasnt powerful enough to tow trailers and jet skis around ... the work trailer is heavy although it did a good job .... so i bought the 6.0 2500hd tows like crazy but the mpg is low even when not towing ... so i picked up this 1990 gmc cheap dirt cheap has that 4.3 in that smokes and a few leaks..... heard that they are a difficult engine to rebuild right...if this is true or not im not sure .... my uncle said hey i got a 5.0 you can have to put in that truck so im like cool would be a great lil run around truck like i said its a short bed... nice straight body very few dings or dents .... so i was trying to figure out what i should do 5.0 or 4.3...but as i hear it is not as easy as 123 to put the 5.0 in ... im not driving the truck right now so i have time to do what i think is best or to play around with it there is just so much i dont know about these new damn computers and stuff.... i had a 72 chevelle and put a motor in it easy as pie.....so im open to suggestions .......i got it to work on so its a project car so i just want some input can it be done how to go about it or even forget it
 
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Old 12-21-03, 06:50 PM
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Computers in vehicles do play a huge role in what you can and can not do without making a whole lot of changes. From what you are saying you want a truck that is powerful enough to pull a heavy trailer plus get good gas mileage. Unfortunately those 2 so not always go hand in hand. The 4.3 is not a powerhouse, but can do the job if it is properly tuned. The best thing the 4.3 has going for it is that it is a 5.7 with 2 cylinders chopped off. So most all theory related to a sbc can be applied to the 4.3. If you have the time and the funds to do the job right then what you want can certainly be accomplished.
Billy
 
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Old 12-21-03, 06:56 PM
tygar663
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the question now is do you have the time to explain what has to be done and the best way to go about it ...
 
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Old 12-21-03, 07:11 PM
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As much time as it takes to get you where you need to be. The first thing is to make a plan.
Take the engine out and strip it down.
Take it to a reputable machine shop
- have them check EVERYTHING. Once they do this you will know what you need to do to the block.
- Have them do all needed machine work. Heads included.
Purchase a good quality engine kit that promotes good torque. This is what you need to gain the performance you are seeking.

This will get you back running without changing your computer or any of the other components.
This is it in a nutshell. Feel free to ask further questions.
Billy
 
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Old 12-21-03, 07:24 PM
tygar663
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thats good advice and that is the plan for the 4.3..... now if i was to go with the 5.7 is the best way to get a truck that is wrecked and get the motor computer and everything else .....im going to get the 4.3 rebuilt cleaned up under the hood and get it driving again but in the meantime im going to keep my eyes out for a 5.7 truck .... with the two trucks side by side how hard would the swap be
 
  #17  
Old 12-22-03, 04:15 AM
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Not hard at all, just time consuming.
Billy
 
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Old 12-22-03, 02:48 PM
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Be prepared to change every bit of wiring both under the hood and under the dash. I think it's a lot more than your expecting and problems can come up. The engine year and vin code has to match exactly. If there is any mismatch in emission controls or fuel controls, you'll never put out the check engine light. Your getting into a pretty technical area there.
 
  #19  
Old 12-22-03, 11:13 PM
tygar663
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sounds like ill just stick with the 4.3 and if it is not good enough....ill sell it and get one with a 5.7
 
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