: Olds 403 swap from 307 olds



IPOITRA
09-20-11, 05:32 PM
Any opinions on olds 403?? anybody know much about them . was goint to swap out my 307 olds engine for a chevy 350 but olds 403 is easier but never driven one or had any experience building an olds engine . just looking for a cost effective 350 hp or so. 403 will bolt right in and accept all the 307 bolt ons.

dennis93coupe
09-20-11, 06:41 PM
It wasn't a very popular engine, but I don't remember much about them. Here's a link you might find interesting.
http://www.texastransams.com/articles/2002ron_l_403_article.htm

IPOITRA
09-20-11, 06:58 PM
Thanks . Dosent seem to be alot of usfull info out there on them .

Stingroo
09-20-11, 08:20 PM
They're basically Olds 350s just bored out. All small block Olds motors are the same dimensions, so it'll fit no problem.

sven914
09-20-11, 09:32 PM
The block is the same and everything is interchangeable. If you had a 307 that was made before '86, you could get swap the intake and heads to the 403 and not have to sacrifice power. After '85, the went to an Economy engine with restrictive intake ports. You would have to upgrade the transmission to a Turbo 400; the stock THM200 will bolt up to the 403, but isn't strong enough to handle the power.

csbuckn
09-21-11, 01:31 PM
I wouldn't put the 307s computer controlled Carb and dizzy back on. Let us know how it goes.

cadillac kevin
09-21-11, 02:12 PM
I wouldnt put 307 heads and intake on a 403.
the 403 had a better intake design (edelbrocks aftermarket olds intake is an aluminum copy of it).
as for heads- why replace apples for apples? get some 68-72 350 heads to raise the compression (and power output)
and I wouldnt want to use any of the 307 computer stuff on the 403 (unless your state has retarded laws about emissions or has to have original motor or something like that.)

IPOITRA
09-21-11, 08:46 PM
Well I havent decided yet was hoping someone here had done one . The origional plan is to just do a chevy 350 thats fuel injected from a later modle pickup to give it reasonable go power . I just happened to find out olds 403 is a small block too. Problem I worry about is emmisions with a carbed mild performance engine . Either way I want to keep the overdrive 200R4 because the gear ratios are better than the 4l60 . I found a guy that has built them for Turbo Grand nationals running alot more power than I plan on . I,m not sure if all 2004r bell housings are the same though?? to accept the chevy engine .

IPOITRA
09-21-11, 08:54 PM
Yes it has to pass emmisions but I was thinking of using the older non emmisions 403 with a small cam and a few minor power tweeks but I'm not sure how it would pass e-test . I dont think the guys at the e-test station would have a clue if the motor was changed . Maybe double up on low flow cats??

Stingroo
09-21-11, 08:58 PM
There's a massive thread here on a 350 Olds swap. Should be essentially the same for your 403.

sven914
09-21-11, 08:59 PM
The THM200-4R does have a universal bellhosuing, so it will mount to a Chevrolet engine but it would be unadvisable. The THM700 that will be bolted to the 350 will be a much more dependable and durable transmission and the gear ratios aren't that much different. If the 200 was able to withstand the 350, GM would never had discontinued it in favor of the 4L60.

Stingroo
09-21-11, 09:03 PM
The 200R4 can be made to handle it quite easily. Check out a Grand National forum for ideas. They're not as piddly as one might think.


Dad's Cutlass had a built one behind a 403 for the better part of a decade.

drewsdeville
09-21-11, 09:09 PM
I recommend using this site for an internet resource on Olds engines. Very accurate and quite detailed. http://442.com/oldsfaq/oldsfaq.htm

H (http://442.com/oldsfaq/oldsfaq.htm)ere's the specific section for the 403: http://442.com/oldsfaq/ofe403.htm#E403 403CIDEngineDetail

IPOITRA
09-21-11, 09:13 PM
Thanks I go look at the olds 350 thread . I have had a couple vehicles with 4L60 and the 2nd to 3rd big step has always bothered me so I want to try the 200 this time . My truck drove me nuts because it hit that big gap right about when you where trying to merge into highway and if pulling a load couldnt get out of anyones way to save my life .

cadillac_al
09-21-11, 10:37 PM
There is nothing wrong with a 403 Olds. They are good engines and have noticeably more power than a 350. I had a couple years ago and they both were sweet engines and could smoke some tires. If you can find one, that would be the ideal swap for a 307.

IPOITRA
09-21-11, 11:38 PM
Actually looking at some of the info on these links helped alot . I sure would likethis 403 thing to work for buget reasons . Never driven a 403 but had 79 eldorado im pretty sure had an olds 350 but I remember that car was pretty stinking quick compared to the brougham with 307 .the eldos tires would spin and squeel pretty easy .hard to say thougt was my second car and may not havebeen as fast as I thought

sven914
09-22-11, 01:06 AM
The 350 used in the Eldorado was a little more powerful than the 307. But you also have to consider that the Eldo was lighter, front wheel drive, and fuel injected, which gave it some advantages.

dennis93coupe
09-22-11, 02:13 AM
The 403 was a low compression engine, pretty much says why it was 180hp? Slip a set of 350 heads on it brings the compression up quite a bit and then you'll benefit the cubic inch from the 403. From what information i've read they only made them, the 403, a couple years could have been more. What are the smog laws in Denver now? That would be my only concern.

IPOITRA
09-22-11, 12:05 PM
It wasfuel injected I wasnt sure . Liked cars but that was before I knew much about them . Im not exactly sure what laws are for emmisions other than bring it in and they check for air pump and cats then see if it passes the computers records on the max for a particular vehicle . Im not sure but I dont think your allowed to swap motors but using the 403 there would be no way to tell quickly. I wonder if TBI from a chevy 454 with emmisions equipment would work with a mild cam and some decent compression ?

Stingroo
09-22-11, 12:11 PM
I'd do a quick read up on the laws. There's generally age cutoffs for stuff like this too....

EDIT: Wow just did some reading myself. Note to self, not moving to Colorado ever.

sven914
09-22-11, 02:58 PM
I wouldn't mess with anything that needs to be e-checked. You don't want to get into a situation where you make all of these expensive modifications and then can't drive the car.

IPOITRA
09-22-11, 04:48 PM
Your right . Thats probably the main reason to just do a chevy 350 . I compared emmisions sheets from my old 94 350to the carbed 307 and that would be well under the limits Im allowed on the brougham and for them to realize its the motors been changed is unlikley . plus even if they noticed they are probably use to seeing the chevys in these cads anyway. just makes alot of work getting all the bolt on changed but at least can use parts from one that had a 350 chevy . have to do something though car has a hard time up here at a mile up.

csbuckn
09-22-11, 05:25 PM
Take the CC Carb off and put a regular one on with a regular dizzy. Edel 1406 carb would fit nicely. You'll lose some MPGs but get the power you want. Worth a try and if you dont like it, use the carb on the next motor.

IPOITRA
09-22-11, 08:40 PM
True that is a easy swap and could hook everything back up and set it up for an e-test when that time comes around every 2 years. Dont need it too wild now just a good driver that will keep up with late model V-8 s.

cadillac kevin
09-22-11, 09:05 PM
a new carb is not gonna give you that much more power in a 307. if 750 cfm isnt enough to make the car go fast, something else would need to be changed
a swirl port 307 will never be able to keep up with late model economy cars, much less modern v8s.
to make a decent 307, you have to change the top half of the motor. you have a massive carb (750 cfm) that is wasted by it shoving fuel down a restrictive intake and heads
a cam slightly more aggressive than the HO 442 grind
pre 1973 olds 350 heads
olds 403 intake
non computer controlled quadrajet.
a new exhaust system. headers for a 350 olds and run dual 2.5 inch pipes with a cross over(no cats)

dennis93coupe
09-22-11, 10:49 PM
I'd do a quick read up on the laws. There's generally age cutoffs for stuff like this too....

EDIT: Wow just did some reading myself. Note to self, not moving to Colorado ever.
It's a nice place to be from 35 years ago. :)

csbuckn
09-22-11, 11:12 PM
a new carb is not gonna give you that much more power in a 307. if 750 cfm isnt enough to make the car go fast, something else would need to be changed
a swirl port 307 will never be able to keep up with late model economy cars, much less modern v8s.
to make a decent 307, you have to change the top half of the motor. you have a massive carb (750 cfm) that is wasted by it shoving fuel down a restrictive intake and heads
a cam slightly more aggressive than the HO 442 grind
pre 1973 olds 350 heads
olds 403 intake
non computer controlled quadrajet.
a new exhaust system. headers for a 350 olds and run dual 2.5 inch pipes with a cross over(no cats)

I think this is a better plan than mine but I will say that I built an Olds 350 with decent heads, torque cam, bigger exhaust manifolds and bigger intake only to put the 307s CC Carb back on it. It felt exactly how the 307 did except on the highway where it got a little better at WOT. I think the CC Q-jet is crappy unless the secondaries are open. Putting a better carb on will definitely make a difference, maybe the difference you are looking for.

IPOITRA
09-23-11, 10:55 AM
Did a lot more looking at olds small blocks last night . The more I read the less I'm excited about them . The origional blocks sound like they where pretty solid but then they lightened them ( put giant holes in the bottom of the blocks - windowed maines ) and lower compression . I forget what year they started doing all this but was still in the 70's . So if you want a pre lightened 350 with decent heads probably pulling one from a valuable muscle car . Looks like there are some aftermarket solutions to these problems ( alluminum heads and a brace for bottom end of the block) but why bother when a stock late 350 with a set of iron vortec heads has better compression and flow and a stronger block for 1/2 the price . ( and easy to find !!) So the more I think about it the olds is looking less and less apealing to me . I know these chevys and those blocks stock with minor tweeks like a cam , good exaust , intake and a good 750cfm carb will easily make 350-400 hp. I wonder how how much work is involved in getting all the engine accesorys working will be .

Stingroo
09-23-11, 11:03 AM
Really easy if you can get a 90-92 Brougham parts car....

cadillac kevin
09-23-11, 11:43 PM
Did a lot more looking at olds small blocks last night . The more I read the less I'm excited about them . The origional blocks sound like they where pretty solid but then they lightened them ( put giant holes in the bottom of the blocks - windowed maines ) and lower compression . I forget what year they started doing all this but was still in the 70's . So if you want a pre lightened 350 with decent heads probably pulling one from a valuable muscle car . Looks like there are some aftermarket solutions to these problems ( alluminum heads and a brace for bottom end of the block) but why bother when a stock late 350 with a set of iron vortec heads has better compression and flow and a stronger block for 1/2 the price . ( and easy to find !!) So the more I think about it the olds is looking less and less apealing to me . I know these chevys and those blocks stock with minor tweeks like a cam , good exaust , intake and a good 750cfm carb will easily make 350-400 hp. I wonder how how much work is involved in getting all the engine accesorys working will be .
most olds engine accessories wont be a direct bolt on
you will have to change the pulleys on the fronts of them
AC compressor will work (bracket will have to be changed)
alternator should work (you can make it work, but it is a PITA). pulley will have to be changed
I dont think anything else will bolt on (except air cleaner if going carbed)
then you will have to change the transmission to a 700r4 or get the 200r4 rebuilt and strengthened.
the olds 350 was pretty much the same no matter what car it came in from 68-72. there may be a slight hp/ torque difference, but they will all move the car with authority.
for an olds 350, you will need to beef up your 200r4 or change your trans to a turbo 350 (3 speed automatic).

caddytat
09-24-11, 02:14 PM
i just bought an olds 403 to put in my 86 fleetwood, when it is finished i will let you know how it feels.

DevilleDan
09-24-11, 08:35 PM
Back in mid 90's I did a related swap. I needed a running 307 to put in a 1986 Parisienne that was headed for auction to be exported to mid-east. Rather than waste money on one of these junks I took it out of my 1987 Brougham and dropped in a 1974 olds 350. At the time emissions mattered so I had to use the intake and carb off the 307 as well as have the heads drilled to accept the air tubes. When done anybody looking under the hood would never notice it had been a motor swap and all components operated original. I did notice way better take off and WOT on highway but by todays standards your average v6 lesabre would be faster. I heard someplace that the 1977 403 was better for building. Something about the crank or block on the bottom end that was more beefed up. Overall the 403 is an excellent engine and never have I seen an issue with one. I also learned that in 1988 the 307 Brougham received a better gear ratio to help overcome the sluggish response. Why GM never started using the Chevy motor sooner in these cars is beyond me. Even in the caprice cars you could only have a chevy motor in a sedan but the wagons through 1986-1990 had to have the 307 olds.

IPOITRA
09-26-11, 11:14 AM
I guess a few of the 403 blocks got away without having a lightning ( putting holes in the bottom of the block that would normally support the main bearings ) Your right about the gears I have to do the math still but Im thinking something around a 3:55-3:73 with the beefed up overdirve 200 . Im glad the ac compressor may work most of the rest is fairly easy . I hope the power steering plumbing will work as well . Id like to hear how your 403 does (caddytat) . I love this car but stopped driving it because it was sooooo slow . Grandmas in 4 cyl accords would pass me up with ease going into the hills because it cant even get itself to the speed limit .

csbuckn
09-27-11, 10:32 AM
I don't think you should worry about the windowed main webs, they really wont make a difference unless you plan on racing or hitting high rpms.

outsider
09-27-11, 11:06 AM
when doing a swap from a 307 to a bigger engine should you also replace the rear end?

Stingroo
09-27-11, 01:17 PM
I don't think you should worry about the windowed main webs, they really wont make a difference unless you plan on racing or hitting high rpms.

That. In a street motor, it shouldn't make a difference at all.

IPOITRA
09-27-11, 02:16 PM
I agree . The stock 10 bolt should be plenty strong for 350hp .

jayoldschool
09-27-11, 06:34 PM
Not quite. Remember, the 307 cars got the 7.5 rear, not the indestructible 8.5.

outsider
09-27-11, 07:33 PM
So you should swap out the rear? If so what would be a good swap?

csbuckn
09-27-11, 09:57 PM
Bubble caprice cop cars with disc or impala rears would be my target.