69z-28

it depends where you get parts from, condition of parts and also who you know. my dad got a complete original 402 with steel forged crank for like 500 bucks cause he had connections. if you buy stuff new from a warehouse or something you can spend over 10k easily.

Jpack

Follow this exactly and you will beat stock LS1's and smoke GT's. Found this helpful article for ya. Hope this helps.

403 ci Olds stock bottom end
1968 #5 Olds 350 heads, drilled for 1/2 inch head bolts, milled .015, 3 angle valve job with full port and polish.
110/320 valve springs and stainless steel OEM size valves.
Edelbrock #3711 intake port matched to the heads.
Jet stage 1 Q-jet Carb
Pertronix performance HEI kit.
SSI 214/224@ 472/496 lift cam and performance lifters.
Dynagear double roller timing chain.
2 1/2 inch dual exhaust with Dynomax Ultra-flo mufflers
Richmond 3:42 ring and pinion with kit
B&M Shift kit
Total parts cost: $1,661.99


With a minimal investment you can be putting out 300 to 350 hp and tire-frying torque. The 403 responds well to more compression and cam, and like all late 2nd generation T/A's a true dual exhaust. Always check your local emission law before making modifications. The 403 4A Olds head is a 83 cc smog head. The result is a compression ratio of around 8.0:1. Try to find a set of 1968 to 1972 Olds 350 heads. A set of early Olds 350 heads have a 64 cc chamber and will raise compression to around 9.5:1-10:1. Make the effort to clean-up the ports and pockets on your heads. You will see a vast improvement in horsepower. Edelbrock aluminum heads are an option, but that's an extra $1500.00 and their 77 cc chamber will give you 8.5:1 compression.

You will want to add a cam and intake to match the heads. The Edelbrock Performer intake is pretty much an aluminum copy of the factory intake, just a lot lighter. If you bolt on a Performer intake with no other changes you will notice little improvement. The Performer intake is thick enough that it can be port matched to your early Olds heads. If you opt for the Performer RPM intake manifold, overall height will increase causing shaker hood scoop clearance problems... the choice is yours. Any factory style 650 to 750 cfm Q-jet carburetor will fit the Performer manifolds. The factory camshaft should be pulled and a flat tappet cam between 206 and 220 duration @ 0.050 inch lift can be used. You can install a larger cam 214/224 if you change rear end gears to 3:42 or 3:73 and advance the cam 4 degrees. Advancing the cam will lower the 214/224 @ 0.050 inch lift torque range 300 to 500 rpm. This will make your factory torque converter with a 1500 to 1800 rpm stall, usable. You can also consider a stall converter with 2200- 2500 rpm stall and a cam. BY ALL MEANS DEGREE YOUR CAM! I run a 214/224 @ .472/.496 lift with 110/320 lbs valve springs and 3:42 gear on an air-conditioned, daily driver T/A.

Upgrade your HEI to include an 50,000 volt coil, performance advance kit and adjustable vacuum advance. You will need to drop a range or two from the factory 403 spark plug. I run 68 Olds 350 plugs. You may consider dumping the cast iron exhaust manifolds and installing headers. Because I show my car I still run OEM exhaust manifolds... the choice is yours. Doing the above mentioned will help you address the main performance weakness of the 403: the cam and compression. I must stress, the details (degree the cam, port match the intake and heads, performance HEI with curve kit) will maximize your performance gains.

Do these simple and low budget modifications and your 2nd generation T/A will be running mid 13's at the strip on pump gas.

SmallBlockBandit

thanx that does help alot now all i need to do is get tha $$$$ lol

blue89vert

damn jpack where did you find that out

Jpack

GOOGLE 403 olds and see what ya get. I remember reading that awhile back, I may be old but when my brain functions, watch out........lol

blue89vert

lol