Swap

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StingRay1502

Not-quite-so-new-guy
Feb 15, 2007
15
0
0
AZ
How Much Skill And Time Does It Take To Swap A 350 Into An 85 Cutlass Supreme That Has A 3.8? Im 17 and want a little more power than the 3.8 could ever give me.
 
Sep 1, 2006
6,687
34
0
Tampa Bay Area
It all depends on what you want from your swap. Do you just want the car to move under it's own power, or do you want the A/C, Cruise control, gauges, etc to all work? You can do it with just a simple engine/trans combo out of an old truck and get the car to run just fine. However, you should really change the front springs, radiator, exhaust, fuel line routing, some of the wiring, etc when doing this swap. It isn't a weekend job by any means unless you really butcher it. On my 1985 Cutlass, I did the same swap, and used a 1977 350 and a 1986 TH200 4R automatic. I changed: springs, radiator, mounts, trans x member, exhaust, alternator, starter, hoses, brackets, wiring harness, PS hose, distributor, fan shroud, fuel pump, fuel lines from tank to pump, trans dipstick, sway bars,plug wires, distributor, carburetor,belts, pulleys, steering box, body to frame mounts, rebuilt the front suspension with new joints and poly bushings etc. and did not have full functionality of all major systems right away. I botched the HVAC vacuum controls ( easy fix) , ran out of money and did not get the A/C hooked up, the used trans gave way 15k miles later, the 2.41 rear axle gears and .67 overdrive didn't like each other- a $50 3.23 geared rear solved that. It is an involved job and while it is do able by yourself, be sure you have a parts runner and enough space to do it before you start. My car was down for almost a month due to a comedy of errors that kept me from finishing it quickly-and the engine/trans were assembled to each other with all accessories, exhaust downpipe and a complete 85 305 G body wiring harness already attached to the engine before I started removing the old drivetrain.As far as satisfaction goes, I am very happy with my setup. It gives better fuel economy and driveability that the V6 did, and it has plenty enough power for my needs. My engine was built to maximize low to midrange torque and as such idles at 650-750 RPM. I estimate that the car would run mid to high 13's with enough traction, and with the last few pieces of the puzzle in place, should be capable of 17-18 MPG around town ( it gets 15-16mpg now with the wrong carb and no torque converter lockup). I would run different heads than I did if I built the engine today, but it is an overall satisfying engine for what I use it for.It also does not overheat, and runs around 185-195 when it is 95 degrees out with just a simple rebuilt waterpump , used clutch-type fan and a 3 core radiator out of a junkyard car ( it was almost new). I spent $4,000-5000 on the initial swap, but used a new engine and other parts rather than used ones. You can do it cheaper than I did by using a well chosen parts car.
 

85t5mcss

Master Mechanic
Apr 24, 2006
343
2
0
Indy, IN
First of all, will the smog police allow it? Some states will not allow such a swap, others will allow it if the engine is newer than the car with working emissions for the engines year. Find this out b4 u begin. But, to answer your question....yes. It's doable and its not that hard. A couple of extra tools are needed, though. An engine lift being the key player. I know that there r a few of us here who have done this swap, some have done it multiple times. Let us know about the regulations in your state and we can help guide u in the right direction.

BTW, how soon do u need the car back up and running? How much have u figured it will cost for the swap and what do u have already?
 
Sep 1, 2006
6,687
34
0
Tampa Bay Area
I was not trying to discourage you from doing this, but just trying to give you the full truth about the whole thing before you begin. I would consider getting a beat up old 4 cyl pickup for a few hundred bucks to chase parts with before taking your car apart. Pickups make life MUCH easier when working on car projects. I have had my Nissan since it was new, 9 years and 263k miles ago and consider it indispensable when doing any kind of project. It has been used to haul engines, transmissions, body parts, etc. since it had less than 500 miles on it. I hauled away the old transmission, a 3.8, and a 305 when it was less than a week old. Just remember that if you buy parts, you need to get them home and if you don't have access to a truck it becomes a major hassle. An old Minivan ,SUV or station wagon could also do the trick, so long as it runs and can get you around while your Cutlass is in pieces.

Another thing is to determine what you want from the car and plan your purchases accordingly. If you plan on headers, get a good set of plug wires, like those from MSD, from the start. Cheaper ones will disintegrate in the presence of header heat( I ruined 2 cheap sets in a week before I ponied up to the good ones). Figure out the gearing and transmission you want. Is it going to be a daily driver, occasional driver, or something more radical? There is no need to buy parts twice when you can get the basics right the first time. If it is a street car, use a quadrajet carb, an HEI and 1 5/8 headers along with a cam with less than 230 degrees duration at .050 and a wide lobe separation angle-more than 110 degrees. Don't use more than a 3.73 gear-3.2-3.5 is ideal. Get an overdrive trans. Get the biggest radiator you can find that fits. Consider a closed element air cleaner with dual snorkels, open elements need more frequent replacement and are not easy to convert to cold air. Shop at U pull it yards with fixed prices per type of component rather than application. I paid $35 for my TH200 4R, $10 for the starter, $10 for the Alternator and $15 for the HEI. I got the radiator for $45 , the rear axle for $50 and most of the stuff I got was fresh parts store rebuilt or new parts in excellent condition. GM actually built some really great parts in the 70's and 80's that are quite reliable and capable of supporting decent power numbers, you just gotta know where to look. ( It's not the GM of today whose cars fall apart as soon as they are out of warranty!)
 

StingRay1502

Not-quite-so-new-guy
Feb 15, 2007
15
0
0
AZ
I dont need the car too fast and i dont know how much it will cost. I want to have it street legal, but also have the power to run some good numbers at the track. i know it takes time, and im going to school to be a mechanic, so i thought it would be some good experience. Thanks For all of the help.
 
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