More balls for my 83 H/O

[bored030over]

Guys,

I'm new to the site. I just purchased an 83 H/O. Runs great, but weak in the performance department. For the winter months I thought of getting a 350 or a 403 and dropping it in my car for next year. Out of all the reading that I have done, the Olds 350 is a real gem...but if I went with the 403, it could be even better due to the 403 winding up much quicker. I read all about the block being siamese in configuration and the oiling problems over 5,000 rpms. But if you change the heads to the heads from an Olds 350,( 72 being the best year ) and adding an Edelbrock intake, Edelbrock Avenger 770 carb and MSD electronics...you could really have a beast on your hands.
Is this true? Are there any aftermarket headers for a 403? What more do I need to know about the 403 over the Olds 350?

Tony
83 H/O

 

[olds307 and 403]

The 403 fits exactly the same parts as 350 or 307. They are harder to cool due to the Siamese bore. Get a 3 core aluminum rad, high flow thermostat, 7 blade clutch or good dual electric fans. Add a mild cam, early 350 heads( makes 9 to 1), if the stock bottom end is good. Otherwise KB, Arias or Diamond, if overbore is needed. Edelbrock just redid their RPM head better flow and chamber. Needs the RPM intake with it. The 403, has much more torque than the 350 but is a direct fit unlike the 455. The 350 Olds is also a great engine, very reliable. The 455 is a torque monster will fit but some things need modified. All SBO are the same 307,350 or 403, Sanderson rear dump shorties or Hedman Elite full length are good and fit. The stainless American Racing headers are the best but around $900 a set. Add a big trans cooler for your 2004r, hardened pump rings and performance spring, Good HD shift kit with the bigger boost valves, billet servo, deep pan and 700r4 filter. You can run 12's with a 403 in your with the 350 heads, others have.

 

[88hurstolds]

That's a myth, the 455 drops right in with very little mods unlike a Chevy BB (technically the 400-455 is not a big block, just has a taller deck height of 1.2", that's it). There's not allot that needs to be done to do so...
You can use all the same brackets, mounts, non CCC HEI Distributor, Water Pump, fuel pump, and even the stock 455 exhaust manifolds will bolt right up to the existing exhaust so long as the exit is 90* like the 307s.
If you wanted to go with headers you will need to run Hooker super comps and run s tube over the frame rail.
If your keeping your AC then you will need to extend one of the bracket tabs with a piece of scrap or cut and weld an extension but that's about it.
I dropped a complete stock '73 455 right in with stock exhaust and used all my 307 brackets, just needed a spacer between the Alt/ PS bracket to compensate for the taller deck height.

 

[olds307 and 403]

Yes, the 455 "bolts in", not a hard swap at all but NOT direct.

 

[bored030over]

Olds 307 and 403.

Thanks for all the information on the 403...this all sounds exciting to me and I am ready for this fall to see what I can get into with all this! Curious though. Will the headers fit without any problems...I was told that the left header might have to be dimpled do to the suspension on the left side? Hooking up my true dual exhaust with X pipe should fall right into place without any major problems?

Tony
83 H/O