Olds small block rebuild ?'s

[John Larkin]

My '76 Olds Cutlass 2-door 350 with a TH350 got 21 highway. This was stock longblock, dual exhaust, and a Holley economizer 450. Car had 2:41 rear and a 3 speed automatic. Had it been equipped with OD, I could imagine 25mpg+. Incredible isn't it that 30 years ago, sedans could get just as good mileage as today's high-tech ones. Kinda validates the saying "you can't get 10 gallons in a 5 gallon bucket". Only so much efficiency can be attained.

 

[83hurstguy]

I am in Calefour I A so we have very strict smog with visual and treadmill. I will have to look into mega squirt but sure that will blow the budget idea.
The HO has 167k miles and looks better in the pics but I already have a lot of what it needs.

ooooo... that's gonna hurt a bit. Ok, it's still doable.

PropJoe here went 12.9's on the CCC system. I'll PM him today to see if I can get you in touch with him. He would know how to do it. He took the car off the computer and still got it to pass the IM240 Illinois dyno emissions test, which was VERY hard to get by.

Realoldspower.com :: View topic - No trailer queen Mid twelves 403 powered g-body

Can you run headers or no? If not, they are going to start repopping a dual exhaust manifold set that would help you out more than stock manifolds (worst part of an Olds small block for trying to make any power... stock exhaust is TERRIBLE).

Of course now my question is why don't more people build Olds 403 engines...???

I can believe the 403 having some grunt as that's what they were designed for. They aren't much of an upper rpm engine to my understanding.

Learn something new everyday.....perhaps someone can give me a secret recipe of making a 307 Olds engine pull 11 second 1/4 mile times in a G body and manage to get 35 mpgs...???

There are quite a few of them in the Olds community, with more being built. Most of the guys are getting a touch over 20 mpg with 3.73 rear gears and an OD transmission. The builds for them didn't really get popular until several years ago. There was little aftermarket support in terms of pistons, which made it very hard to build one. Now KB, Arias, and Diamond all make pistons for the 403. Some people shift them just below 6k, others are going towards 7k, and the SuperStock racers (voodoo doctors) are well over that. The weak part is the bottom end, so keeping the RPM's low tends to be a safer bet.

307's, while possible of doing 11's in SuperStock form, require 5.xx rear gears and a lot of work Gotta remember that the only difference in all Olds small blocks is bore size, all have the same stroke. Getting a 307 to breathe can be tricky. The 403 has a 4.351 bore :biggrin:

 

[INEEDAGN]

I guess I don't get the 403 thing either. You need a girdle to rev them very high, unless you have one of the magical nonexistant solid main web blocks. I would think a better street engine design would a have a longer stroke to help the low end torque. An interesting note is that the mopar 400 is basically identical in both bore and stroke. It is a hair shy on both measurements which accounts for the lack of the 3 cubic inches.

The buddy I mentioned in the first post that has my 350 is using it because he scattered his 403. Again.

 

[83hurstguy]

The buddy I mentioned in the first post that has my 350 is using it because he scattered his 403. Again.

what is he doing to them?

 

[olds443]

Luckily, these are getting pretty scarce so I could probably run headers as long as I retain catalytic converter and O2 sensors, and the tech may not notice. I actually considered trying to dummy up some the sensors and smog stuff so it is present but all that hassle I may as well do it right.

I have seen alot about High HP and stregnth, etc but I want to remind everyone this will be a street car primarily so 7k rpm shifts and 800 hp AREN'T NECESSARY. It may make it to the strip but not often. I will have a turbo car for going fast.

 

[INEEDAGN]

what is he doing to them?

Last time around it was not the block's fault, but rather a flat tappet cam that went south. He has cracked a 403 block in the past though, and for some reason he keeps trying to make it last.

I suppose the reason I wouldn't do it is because I wouldn't put serious money in a design that is noticeably weaker than a different small block. If I were to do an olds with a goal for real power, it'd be a diesel block. I'm sure it's fine for a street engine though so I will back off my soapbox now.

 

[olds443]

Hey 83Hurstguy, where can I get pistons for these motors? Would Hypers be ok for a mild build?
I assume I could get pistons to bump up the compression and keep the 4A heads? Would the heads then be ok or should I just find some 5a or other heads?

I checked and I think my time is worth the cost of the machine work so I will probably take it all the way down and do it right rather than cheap out and have to do it twice.
Thanks,
Jason

 

[83hurstguy]

hypers would be great for a mild build. You can use the stock 4A's or go with a big block head. I plan to use big block heads on mine... the exhaust side of the 4A's is really bad with a 1.50 valve. You can work the heads, but it's usually more cost effective to just go the BB route.

Call Terry at FCR Performance (www.fcrparts.com). He's the 403 street car guru and a really nice guy. He played a part in developing the KB's, and I believe sells them for around $300. Not a bad deal. Overbore and a rebalance, and you are right there. Slap some BB heads on there with big valves and tear it up

 

[olds443]

Right on, Thanks!BTW the Hurst was built in Feb. (My Family's B-days are mostly in Feb including mine and my significant others) and the car is #2030. It was one of 12 (?) owned by GM for it's employees but that is all I know now.

 

[83hurstguy]

Right on, Thanks!BTW the Hurst was built in Feb. (My Family's B-days are mostly in Feb including mine and my significant others) and the car is #2030. It was one of 12 (?) owned by GM for it's employees but that is all I know now.

Interesting! Mine was a March car, built last day of production (#2974 IIRC). Interesting that it was a GM car. Fully optioned? Posi? You can tell if it's a posi by the size spare in the trunk... a limited slip car will have a 16" spare.

 

[olds443]

Well it had a rough life so I'm not sure what the original spare was. Sent you a PM on the rest.

I checked out the websit for fprparts.om and dropped him an email, just need to call him now.
Thanks,
Jason

 

[Pronto]

Here's my old T/A. index page 2 has the build. I like the 403. I wouldn't mind doing one again.