Topic: Olds 403 Build

[TheKid]

Hey ya'll,
I'm just a few days away from having my 403 out of my TATA and ready to overhaul. I have decided on keeping the original 403, and don't really want to change my mind. I've read some great builds and talked to a few folks here and there that have helped with a few things, but just want to get an idea of what you guys here think as you've never steered me wrong!

The block appears to be in good shape, and I love the Quadrajets (not to mention, it's a number matched car) so I'd like to keep the Q-Jet also.

To help others who are building a 403, I'll include a list of the parts I've purchased for the build as I start acquiring them.  The reasoning for purchasing each individual part can be found throughout many discussions in this thread so if folks are wondering what to use and why, read through these pages!

As far as the build goes, here is a list of the parts I've purchased for the build:

Erson Cam (specs on Page 11)
Full roller lifters
Ga heads (BBO)
ARP Rod Bolts


Rebuild transmission also.

I'm not looking for huge power, I read a build similar to this that put down the numbers I want, which was in the 430hp and 450tq range. Something streetable, fun, and quick.

This seems like the standard for making power out of a 403, up the CR, let it breath better, and add a little more cam to it.

I'm open to all input, except for "ditch the 403 and just build a 400." I'm really wanting to build the 403 and don't want 50 posts saying it's useless.

Thanks for reading guys! This project is coming along slowly but surely.

JJ

View page:
6- Shaker fitment with RPM intake

[Maryland Bandit]

If you can, keep the over bore to .20", might just need the walls touched up. The 4A stock heads are fine, maybe some light polishing work in the intake runners. The largest cam you can stuff in it with the stock non adjustabke valve train is 214/224@ 50" 472"/474" lift. It will still have good manners at idle. Qjet, your going to need to enlarge the internal fuel idle tubes, down channels and a few other passages to handle the need for more fuel at part throttle, no biggie.  Have the distributor recurved by someone thats knowledgable. You want all your power in by 3500 rpms. Keep away from 4500 rpms due to the webbed mains and weak bottom end.  Cooling is critical with the siamesed bores and no water jackets in the middle. Stay away from getting on it until its warmed up completly and keep the temp below 220.  O ringing the heads is overkill, save your money here.  Watch running any oil pan dry with extended full throttle runs. 

[72blackbird]

JJ,
Olds 403's are decent for stock output or mildly warmed-up builds, but as you can see from the Bandit's post the 403 has design flaws that won't be wished away by good thoughts or solved by main cap girdles. But I don't consider them useless by any means- here in Socal many TA's came with the 403, and many owners do prefer to stay with the original engine.

Some 403 owners also wish to make more horsepower, and despite the warnings some do attempt to build a higher hp version of the 403. There are a few out there that are still running and making good power, but there are far more that have grenaded due to the excessive flexing of the block and tossed rods. Naturally it's your engine and you're free to do as you wish, but consider that your 403 is the original numbers-matching block, and once you blow it you will loose a very valuable part of your car's value. You're better off finding another 403 block and building that, and storing the original block.

Geno

[joe d]

i have to stress the importance of the heads, spend the time or money porting the heads properly, a good cam and intake, beef up the lower end for stability and run it, i have heard the same things about the 403 so rather than try to create a mountain motor make some serious hp wih an outstanding head job, rough swirled intake ports and mirror finished exhaust ports

[TheKid]

I'm still kind of up in the air. I don't want to destroy this block, but I honestly feel like 400hp will survive just fine with it. And about the cams, I was going to switch to and adjustable setup.

[TheKid]

The guys doing the resto-job for me also said they get great deals on crates, and can do a crate motor, installed, for 3,000. That's not a terrible option either.

[Wallington]

You have nothing to worry about on a street motor with 300-400hp, the girdle is cheap insurance which goes for any similar blocks. As MB said, if you can get by with a minimal bore then you could use pistons to suit and build a combination that makes the most of the low compression.

Otherwise, if using KB's they have odd-sized piston bore like .024" over so you really need to have your build sorted before you start to prepare for it. Once they pull it down you should have a few more ideas of the condition, although if in good condition it may make the decision harder by leaving all options still available!

You also need to work out if going to use headers and taller intake or keep it easy for shakers at stock height, that all affects which cam will be used. And look to have exhaust crossover filled and electric choke fitted for a few extra gains. And hopefully you don't need to pass smog checks!

If it were me I'd be looking to keep the 'stock' appearance under the hood for a TATA with all the extras in place. You may forfeit a few ponies here and there but it's more of a challenge and easier to work from when you already know what limits are there, although that mainly applies to intake, and to a lesser extent the headers or manifolds. If yours has cruise control you may want to check out that also, some intakes don't cater for them, but usually it's the taller RPM type due to having extended runners in the way, and they don't tend to worry too much about cruising anyway!

[TheKid]

Thanks for the reply! I was planning on running a new intake, adjustable setup, and full exhaust. And as far as the KB's go, they do have the .024 over bore, which is what I would have my motor guy take the block to.

[oldskoolubr]

You have nothing to worry about on a street motor with 300-400hp, the girdle is cheap insurance which goes for any similar blocks. As MB said, if you can get by with a minimal bore then you could use pistons to suit and build a combination that makes the most of the low compression.

Otherwise, if using KB's they have odd-sized piston bore like .024" over so you really need to have your build sorted before you start to prepare for it. Once they pull it down you should have a few more ideas of the condition, although if in good condition it may make the decision harder by leaving all options still available!

You also need to work out if going to use headers and taller intake or keep it easy for shakers at stock height, that all affects which cam will be used. And look to have exhaust crossover filled and electric choke fitted for a few extra gains. And hopefully you don't need to pass smog checks!

If it were me I'd be looking to keep the 'stock' appearance under the hood for a TATA with all the extras in place. You may forfeit a few ponies here and there but it's more of a challenge and easier to work from when you already know what limits are there, although that mainly applies to intake, and to a lesser extent the headers or manifolds. If yours has cruise control you may want to check out that also, some intakes don't cater for them, but usually it's the taller RPM type due to having extended runners in the way, and they don't tend to worry too much about cruising anyway!

Thank You Aus!!!  Cmon Geno Don't make this another Poncho versus Olds Debate?!  Sounds like everything you said is great "Kid"  just don't recommend the same cam Bandit said bcuz it IS an older grind!  It really depends on your compression as well, get the people who are doing the work to figure the Compression so you can make a more educated decision!  The cam he suggested is the exact same grind I was going to use until My Machinist told me why wouldn't you want to get to the peak duration faster?  Plus that cam has a .496 on the exhaust not .474 as stated I really don't think you need that wide of a split if you will be doing all the other mods you mentioned.  Your rear gearing and stall will help dictate that as well?!
  I still challenge anyone to show me a 403 bottom end that personally blew up on them?!  It is what it is and as "Aus" stated in another thread there were plenty of 'Web" motors being built during the same time frame!  Keep at it "Kid" and you will be happy with the result as long as you can trust the people doing the work!

[TheKid]

There's an old guy down here in South GA, Tony, that knows his stuff when it comes to motors. He's the definition of an old timer motor builder. Runs one of the best machine shops in the south east, and he's the guy I'm working with. I'm just going to let this engine build unfold as I go along and talk to as many folks as possible about it. Was just trying to get a good starting point and input here. I'm going to stick with the 403, mine is VERY strong as it is and I think it will serve as a great platform.

[oldskoolubr]

GOOD 4 You!

[SC79TransAm]

The guys doing the resto-job for me also said they get great deals on crates, and can do a crate motor, installed, for 3,000. That's not a terrible option either.

Talk to Geno 72BlackBird he builds 400's and 455 but also has some good info on 403's.  He is a ditch the 403 guy but very knowledgeable too if you need additional input...he blew my mind the other day with what he gets out of a motor HP wise.

[SC79TransAm]

The guys doing the resto-job for me also said they get great deals on crates, and can do a crate motor, installed, for 3,000. That's not a terrible option either.

Talk to Geno 72BlackBird he builds 400's and 455 but also has some good info on 403's.  He is a ditch the 403 guy but very knowledgeable too if you need additional input...he blew my mind the other day with what he gets out of a motor HP wise.

doh just re-read and saw he posted already.....hah!

[uk79transam]

I wouldn`t worry too much about reving the 403 to 5500-5800 with newer lighter pistons in it. When mine was stock I used to floor it past 5500 regulary.

Have fun.

[72blackbird]

Guys,
Do me a favor and don't put words in my mouth. Nowhere in my first post did I even suggest replacing the 403 with a 400- if the OP wants to build up his 403, there are enough parts available to do so. I've built both more than enough times to know their strengths and weaknesses- there's no point in even discussing it since experience will teach you better than anyone's advice can.

I will agree that the main cap girdle and oiling restrictors are key in keeping a performance 403 alive- forget these and the possibility of your 403 hi-po build having issues goes up considerably. The 403 also responds to all the usual hi-performance engine build upgrades- forged pistons and rods, ARP fasteners, rotating assembly balanced, oil clearances blueprinted, etc. The 350 Olds head upgrade is also a worthwhile upgrade, and that head will make a noticeable improvement in power, especially when larger valves are fitted and a street port is done. Unfortunately this head upgrade won't work for a smog-spec 403, as it increases emissions too much to pass the sniffer.

Geno