307 to 403 Olds swap...info please?

81X11 · Jun 27, 2011

Hi all. The 307 in my 88 Cutlass has finally put in it's notice. I have almost no oil pressure, am getting a lower-end knock, and do not want to deal with oil pumps and bearings on a 307.

I know there are a lot threads about this swap, but can someone give me the complete "parts list" for this swap?

My car is an '88 Cutlass Supreme Classic, stock 307 and 200R4 transmission, floor shift car. I've got the opportunity to buy a '77 403 out of a full size Buick. It runs great and has low miles.

I'm on a super tight budget for this swap right now. This came at a bad time. I don't plan to hop up the 403, but I do plan to re-seal it, install a new oil pump, timing chain and gears, water pump, then clean it up and paint it, and will detail the engine compartment while it's out. I just want it to look good and be reliable.

My stock 200R4 is a weak link here, and I know it. I want to retain the overdrive, and the trans shifts fine now, so I'm going to cross my fingers. I don't plan to hot-rod around in this car, it's just a cruiser, so hopefully the little transmission will hold up for a while.

I want to retain my CCC so I can keep my Cruise Control and TCC in the transmission working, but I know the VIn 9 307 intake won't work on the 403. If I get an early 80's 307 intake, can I use my current carburetor and will everything else bolt up?

I've read all the pulley's and mounts off the front of the 307 will work fine on the 403. How about the 307 flywheel and starter? Also what do I do about the exhast manifolds? Anyone know if the Cutlass exhaust pipes will bolt up to the 403 manifolds? The 307 manifolds are tiny, the 403's look larger. I am planning to add cat-back dual exhaust after doing this swap, but for now it's going to have the single. Will it bolt up?

I really want to gather all the needed parts together so I can do the swap over a weekend with some help from my friends.

Any tips or a list of parts to grab are much appreciated!

Please help me bring my pretty little Cutlass back to life!

-Mike

81X11 · Jun 27, 2011

Ok I think Igot this 403 lined up. I'd LOVE to get rid of all the computer crap on the 307 but how do I engage the a/c, cruise control and torque converter lockup without keeping it original?

I was trying to keep this and "plug and play" as possible.

That being said you can not even see the valve covers on the 307 for the wire and vaccum hose speghetti under there. You open the hood on the 79 Buick and you can see almost all the entire engine thanks to no computer in 79. I'd LOVE it if my Cutlass looked like that.

Anyone?? :wink:

-Mike

FE3X CLONE · Jun 27, 2011

The computer doesn't control the A/C clutch engagement but rather disengagement at WOT. You could simply rig a micro switch to do the same thing.

Torque converter control is as easy as this (you need to weed through some bickering):

http://www.realoldspower.com/phpBB2/vie ... hp?t=76346

As far as the cruise control, I'm not entirely sure that the computer has anything to do with it. Should just need a vacuum source and working speed sensor. Someone else would have to chime in on that. Worst case is you could upgrade to a more modern all electronic setup from Rostra.

dogsht · Jun 27, 2011

A good shift kit. I bought one from WWW.ckperformance.com for $100. And a large cheap trans cooler and you should be ok.

anthonychacon80 · Jun 27, 2011

you might want to keep the computer, AIR and evap lines. The CCC will make the carb run right and keep your MPG reasonable. Taking it all off is a pain, makes the car run like crap. All those things were designed to make the car run well, start easy, and be very drivable. Plus when you go to service the car or sell it you can still refer to the service manual for help.

But in theory the 403 manifold should work. It should have all the correct ports that the 307 had including EGR. Did the 403 have Smog heads?

You will likely want to buy shorty headers if they are legal in your area. Just make sure you have a hold for the O2 sensor, and try to keep the EFE working if you can. I believe Edelbrock sells headers like that? i think the Olds heads have the AIR ports in the block itself so shorty headers should work and then you can take it to a muffler shop and have them bend a custom Y pipe back to your CAT. Then you can retain the rest of the system.

FE3X CLONE · Jun 27, 2011

anthonychacon80 said:
you might want to keep the computer, AIR and evap lines. The CCC will make the carb run right and keep your MPG reasonable. Taking it all off is a pain, makes the car run like crap. All those things were designed to make the car run well, start easy, and be very drivable. Plus when you go to service the car or sell it you can still refer to the service manual for help.

That might be true if your talking a stock 307 replacement here. But jumping to a 403, it WILL run better without all the computer stuff and your not going to get that much better gas mileage between not having the CCC and have one. Maybe 1-2mpg tops.

DoubleV · Jun 28, 2011

There's 2 black connectors that plug into a clear/white connector near the ECM. The clear/white connector is part of the ECM harness and this entire harness can be removed. When you remove this ECM harness, the 2 black connectors and all the wires that go through the dash will still be there.

Look at the 2 black connectors. They are lettered. Pin 'M' should be a black wire with a white stripe. This is the ground for the 'Vechical Speed Buffer' which is needed for cruise control. Just ground this wire and you'll retain cruise.

Pin 'P' should be purple. Get a Painless converter lockup kit and run it to this wire. You'll have converter lockup without even having to bother with the included brake switch from the kit because the G-body's already have it and it's allready wired up for you from the factory. This is why you just have to hook the Painless kit ( a purple wire ) to pin 'M' ( a purple wire too ).

Pop the circuit board out of the 'remote lamp driver' ( greenish colored plastic box wired into the ECM wires going through the dash and located behind the glove box ) and this will make the 'Check Engine' light go out.

I just recently did all this.

dougfather · Jun 28, 2011

I remember a few things when I considered a 403 for my Grand Prix. Anyway, be careful about swapping intakes. That 307 intake from a 85 and later will NOT work with your 403. Keeping the CCC system could require an earlier intake with possible wiring mods. Here's a site for some Olds power info:

http://www.robertpowersmotorsports.com/G-bodyV6-V8.html

88hurstolds · Jun 28, 2011

Its a direct swap, just use the 403 exhaust manifolds (should have an o2 bung) and intake or find an A4 or performer with EGR.
Those are about the only extra parts you should be conceerned about, you are just building a cruiser so keep the computer, dist and carb but ditch the AIR pump and tubes.
Retain your EGR, O2 sensor, vapor canister and such, it wont run any better without it. Get rid of the EFE or at least modify the flapper door on the spacer so it remains open.
Just keep in mind you are running a stock 403 with large combustion chambers and very low compression, its not a power house like early 350s, the only thing going for them is the torque which is what you want for a cruiser.
Dont waste your time fiddiling eith removing the computer, it will run fine... remember you dont want to wind up wasting your summer away getting carried away with the specialty mods trying to keep your cruise, AC, lockup (goes off of the TPS, VSS and temp sensor (not gauge sender)) and computer controlled EGR.

I just did this same mod except with a VIN 9 307.

81X11 · Jun 28, 2011

DoubleV said:
There's 2 black connectors that plug into a clear/white connector near the ECM. The clear/white connector is part of the ECM harness and this entire harness can be removed. When you remove this ECM harness, the 2 black connectors and all the wires that go through the dash will still be there.

Look at the 2 black connectors. They are lettered. Pin 'M' should be a black wire with a white stripe. This is the ground for the 'Vechical Speed Buffer' which is needed for cruise control. Just ground this wire and you'll retain cruise.

Pin 'P' should be purple. Get a Painless converter lockup kit and run it to this wire. You'll have converter lockup without even having to bother with the included brake switch from the kit because the G-body's already have it and it's allready wired up for you from the factory. This is why you just have to hook the Painless kit ( a purple wire ) to pin 'M' ( a purple wire too ).

Pop the circuit board out of the 'remote lamp driver' ( greenish colored plastic box wired into the ECM wires going through the dash and located behind the glove box ) and this will make the 'Check Engine' light go out.

I just recently did all this.

Thanks for all the comments and ideas. I'm liking the idea of getting away from the computer and cleaning up all the mess under the hood. The above post is exactly what I was looking for.

I have that brown 79 Electra with the 403 in it and there are no 02 sensors on the exhaust manifolds, so I'm thinking the 403 I'm going to buy will be the same, since they were made pre-computer, from 77-79 only.

If all the above will work, then I'll keep the stock 403 intake and carb and use the 79 Buick as my model to run the lines and wire everything up. All I needed was the above info on how to make the a/c, cruise, and TCC work. THANKS SO MUCH! Also good to know the stock 403 manifolds will line up with the 307 exhaust system. That will be a huge help....and it will only be like that until I can afford to do duals.

Last question, for now, is you mentioned I could remove the entire ECM harness. How hard is that to do?

Again I appreciate all the help folks!

-Mike

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307 to 403 Olds swap...info please?

81X11

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