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Discussion Starter #1
My '83 has the stock V6 in it still, but she's getting up there in miles and has an oil leak somewhere. Suffice to say, I think it's time to retire the old engine!
So I had some questions for all of you knowledgeable sorts, since I've never done this before.


  • The age old question, build or buy?
  • I've heard the motor mounts will have to be moved?
  • Will doing the swap require a new radiator and fan? I've seen that mentioned several times as well..
  • Any advice on a matching transmission?
I'm in college, so I'm on a bit of a budget! I'm not looking to put together a drag racing monster, but a bit of power would be nice. I've seen mentions of the right 350/tranny combos still pulling 20+ mpg?
Any advice would be greatly appreciated!
 

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What trans do you currently have?

I hope to knock down over 23mpg with my setup I have in the works.

350 mated to a 4L80e tuned to get into OD sooner than later.

If you do not want power find a pullout for a few bucks and a gasket kit. If the walls of the cylinders look like crap may want to try again or do a light hone and a rering kit.

My motor has around $300 in it with gaskets, new oil pump, fuel pump, and intake. I put a nicer carb on top to help with tuning but it was still had for $300 and change.
 

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TrannyMike
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You are gonna most likely have a 250 or 350 trans now. The easy way to go would be a 350 built for a V8, it will fit with no mods. Your trans may look the same as one out of a V8 but it's not. The clutch packs have fewer plates in the V6 version. If you want overdrive the best trans for you would be a 200-4R. It's not a cheap conversion but works well.

383tpimachine, how are you gonna run the 4L80E? Do you have an aftermarket computer and harness? Also you'll need sensors like a TPS & VSS at least. You'll also need to change how your speedo operates since a 4L80E has no way to install a speedo cable. There is more to it than what I mentioned to install it, but I'm mainly thinking about electronics, Just curious. :beer:
 

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You are gonna most likely have a 250 or 350 trans now. The easy way to go would be a 350 built for a V8, it will fit with no mods. Your trans may look the same as one out of a V8 but it's not. The clutch packs have fewer plates in the V6 version. If you want overdrive the best trans for you would be a 200-4R. It's not a cheap conversion but works well.

383tpimachine, how are you gonna run the 4L80E? Do you have an aftermarket computer and harness? Also you'll need sensors like a TPS & VSS at least. You'll also need to change how your speedo operates since a 4L80E has no way to install a speedo cable. There is more to it than what I mentioned to install it, but I'm mainly thinking about electronics, Just curious. :beer:
Never heard of a TH250. But OD will net the best MPG and if the engine is staying low HP and a 200-4r isn't easily found a 700r4 could be used with around the same modification level.

I have an Optishift from Jakesperformance and everything needed to play. Will have it attached to a B&M quicksilver rachetshifter.
 

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You will most likely need a larger capacity radiator. Its nice to match a new engine with a new or flushed radiator to prevent junk from carrying over. An electric fan (or set of dual fans) is nice to have also.

~JM~
 

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Discussion Starter #8
Hmmm. Thanks JM!
I was hoping the fan that's already there would work, but ah well.
I think the biggest pain is going to be moving the motor mounts. :dontknow:
 

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other than getting to the bolts moveing the mounts is easy.i use a long box wrench with tape to hold the bolts and feed them through the fuel line hole for the top two and a swivel socket and long extension to reach the bottom one through the a frame hole. you will need a bigger radiator and shroud, follow trany mikes advice on the trans choice. depending on which v6 you have chevy or buick will determine how much of your old stuff you can use. if you have the buick engine you will have to deal with the fuel line as it is on the opposite side as a chevy,some of the buick powered cars used a offset trans mount pad as well which will require a different crossmember
 

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Discussion Starter #10
Hmmm, that sounds workable.
One thing I've learned here, ALWAYS follow Tranny Mike's advice! :beer:
The different crossmember isn't bad either, makes it easier to run the dual exhaust eventually. :yell:
 

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At least one 1978 El Camino I've looked at had a TH250 behind a 3.3L V6. Some people call the 700r4 a 4L80E or 4L60E. Careful checking will reveal which is which. My motorhome has a 4L80E, behind a 454 and pulling 16,000 lbs. Overkill in a Camino!
 

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At least one 1978 El Camino I've looked at had a TH250 behind a 3.3L V6. Some people call the 700r4 a 4L80E or 4L60E. Careful checking will reveal which is which. My motorhome has a 4L80E, behind a 454 and pulling 16,000 lbs. Overkill in a Camino!
I have a 700r4 pos in my corvette. I had a th350 in the camino that I sold. I have a 4l60e, which is the same as a 700r4 besides the electric solinoids and lack of tv cable. After rebuilding my 700r4 behind 408rwhp in my vette 3 different times I do not want to deal with those POS any more. 4L80e=450rwhp stock and 750rwhp with a kit.

build for the future. Right the first time if you can afford it. :beer:
 

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My opinion is if you can afford it buy a crate motor or rebuilt motor with warranty from a reputable builder .With buying a used motor youmight get the deal of a lifetime or end up with someone elses issues ,at least with a new or rebuilt motor you have a warranty . I agree with using the 200r4 tranny .
 

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For cooling, a good radiator, a 5 or 7 blade fan, with a clutch. You may need a different shroud too, since the V6 is likely shorter, with a longer fan shroud. Keeping the engine driven fan will save the mounting & electrical wiring labor associated with electric fans.
And electric fans don't necessarily save power, since the alternator has to support them, and alternators do use some power, while the fan clutch slips when incoming air through the radiator is cooled enough for the thermostatic element in the clutch lets it slip.
 

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Discussion Starter #15
Any recommended crates, in that case?
And now just begins the long search for hopefully finding a wee bit of a deal on a 200-4R.. :secret:
 

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I like the 200-4R tranny over the 700. The gear ratios are closer together from 1st to 2nd. These tranny's require a bit of education along with some performance modifications to handle healthy amounts of torque.

"Build for the future. Right the first time if you can afford it."

That's a good philosophy. I like to try error on the side of caution & tend to over-build for my needs. That way there is more room for reliability.

Good luck
~JM~
 
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