i got a 87 cutlass salon with dat no power 307, looking to make a swap. which way should i go?

 

Looks like you have a choice, I remember reading you needed a manifold for the 307. Guess you decided to go with a replacement engine. Both of those engines are fine small blocks, I think it would come down to the vintage of either, the 350 may have really nice heads on it, do you know? This may help you in the decision process. Moving the thread to small block forum for you...

 

350 Olds motors are much easier to find (built 1968-1980) than the 403 (built 1977-79), but I would always go for the larger engine if I have a choice. Either motor is externally identical to the 307, so this is about the easiest swap there is.

 

You should find the non-windowed main web 403.

 

Has anyone ever seen one of those? If so, got any pix?

 

I've never seen one. I wonder if they even exist...

 

Chris Witt photoshopped some at one point...

 

i dont know how true it is , but i have heard that the 403 had a weak bottom compared to the 350

 

Resse, that is correct if you are comparing the 350 and 403 for a car that is going to be driven on the track often. However, if you are just building a street driven car that will only see really hard driving once in a blue moon then you will be happy with the 403.

As we stated earlier, the 403 has windowed main webs (there is less metal in the bottom end). There are rumors that 403s were cast with solid main webs; however, there is no conclusive proof that they exist.

 

You did not state intended goals.
An engine swap will NOT BE ENOUGH if you are saddled with a 2.29 gear ratio.
I can not emphasize this enough. Even a 455 can be a slouch with a 2.29 gear.

The first thing that should be done is installation of a 3.73 rear axle gear set (with a posi of some sort), and a quality dual exhaust to let the engine breathe better.

You will be amazed how much this will help even the 307.

If this is not enough, and all you want is a mild streeter, get the 403.
If you want more than an 11.50 car (my 455/425's never went that fast), you will be looking for a 350, or a diesel block.

WHAT GEARS DO YOU HAVE?????????????????????????????????
Jim

 

3.73s would be pretty radical gears for the street IMHO. Of course, I am more of a fan of highway gears anyways. I will keep my 2.78s and 3.08s, my 71 98 can pass a Corvette at 70mph and barely break a sweat!

 

I would go wit hthe 350. Like it's been said that 350's are easier to find and any 350 68 to 72 has soild mains, the 403 does not, plus the head choices are better for a 350, unless to need to run emissions on the car

 

both are great engines. the 350 is rumored to be more durable. however, the 403 is a great engine too. it's not nearly as weak as people think it is. you can even strengthen it by adding a forged Olds 330 crank, or an early nodular iron Olds 350 crank, and a set of light 6" small block Chevy rods with a light custom piston (forged of course). I'd go with a set of "worked" Olds 350 #5 heads, instead of the 403's heads. Also, I'd definitely have my 403 treated to a torque plate bore/hone job...

 

I agree with everything except the torque plate bore/hone job. There is a misconception that boring a block with a torque plate will help in some way. Not necessarily true. A torque plate locates off the dowels which are very seldom in the correct spot, therefore your bore location will not necessarily be corrected in the process. The right way is to use a BHJ Bor-Tru plate then hone with a torque plate.

 

If you can find a 403 build it. If not than get a 350 build it. It's as simple as that.

 

Only if you get rid of the 200r4 and go back to a turbo 350 or 400.

As Warhead stated, the rear swap and exhaust would be the easiest way to give your car more get up and go power. After that, if you want more power, then you will need to upgrade the engine and transmission. A 350 with #5 heads would be my choice over a 403. Then you will have to work on the 200r4 as well. It will not hold up without being beefed up to handle the extra torque. Hope that helps.

 

cutlassefi,
that's what I meant :-D.. funny, I bought a 403 specific plate from BHJ.

reesejames,
Yup, try and find a 2004R core out of a Buick GN, they're supposed to have a performance oriented valve body from the factory. you'll definitely want to beef it up to handle the gobs of TORQUE either motor is capable of making.

 

You can use a Monte Carlo SS one too. The both have about the same valve body and governer calibration. Main difference is 2-3 servo, Buick GN is better.

 

I did not find them "radical" for the street, a bit more on the highway.
You do not have an overdrive.

Put a set of 2.41's or a 2.29 gear in that 6000# whaling barge, and we will see what you have to say! I understand your point, but he has a very different scenario.

A 3.23 would be fine for highway driving IF he has a t-350/400.

My opinion.
Jim

 

thanks, for the replies i think i will go with the 350 and th350. of course i will upgrade the gears to 3.73 wit a 2700 stall. what u guys think?
i just want to give the car some *****

 

Personally I would stick with the 200-4R with a performance rebuild. It's really not that expensive and then you'll have the overdrive and lockup capability. That will make for some nice highway cruising even with 3.73s. As for 350/403, I'd go with whichever you can find a good deal on first.

I forget which board I saw it on (might have been a Trans Am board), but a guy posted pictures of a 403 he finally broke after LOTS of hard driving on the street and track. I wish I could remember how much power it was making, but it's safe to say it was way more than what you're shooting for. It took lots of high-RPM abuse before giving up. It did crack some main webs, but again it was a high-effort engine running higher than stock RPM. The dude got his money's worth out of it.

 

X2 on both points. I'd take a built 200-4R over the TH350, and I also believe you'll be hard pressed to break a 403.

 

X3

 

http://72.22.90.30/phpBB2/viewtopic....&highlight=403

There are better ones on this site.
Colormegone has shown a few.

http://www.jsmachineoldsmobile.com/403CARNAGE.html

And I like the 403.
Know your limits.

Jim

 

So in the first example it looks like he had been running 12s for quite a long time before it cracked. What sort of horsepower does it take to run those times?

The pics on the J&S site looked like a lot more violent failure.

Still having a hard time getting an idea how far you can push a 403.