Folks,
I REALLY appreciate the valuable (and spirited) technical advice folks are giving me. Here is some data, which might help explain why I insist on taking my chosen path of keeping the factory 307:
- Bought this 1984 Hurst/Olds in May 2023 for $ 28,000. It is an "Unrestored Original". Almost all factory-installed parts, besides tires, brake pads, belts, etc. It has a March, 1984 Build Date, which apparently was the end of the Hurst/Olds run at GM.
- Have already put in $ 7,500 for Service, to just replace worn or aged parts.
- I also invested $ 3,000 in upgrades (UMI chassis braces, Aluminum Driveshaft, Bilstein shocks, etc.)
- So, close to $ 40k for the car, thus far.
Now, here is the preferred sequence for performance upgrades:
- Brakes always first. I have thoroughly researched Wilwood, Baer, and other brake companies. If I want to keep the beautiful chrome Olds Super Stock II 15 inch wheels, there are many limits and constraints on what can be done (sawing off Spindles, widening front track, etc.).
- Suspension: the front and rear suspension really would benefit from upgrades (Coil-overs, larger anti-sway bars, Polyurethane bushing Control Arms, etc.). These improve handling, but hurt the ride quality.
- Then Frame Stiffeners. Not the small UMI braces I have bolted-on, but rather full length, weld-on chassis stiffening.
- Now, only at this juncture are we truly ready to handle lots of extra horsepower and torque. I just blew through about $ 20,000 just to do #1 - #3 above, on a '71 Duster, not counting $ 10k to build (or replace) the 307.
- So, IF after doing all of the above, I would have about $ 70k into a car that would still be outperformed by a ~ two decade old Camaro, Firebird, GTO, Mustang, or Challenger.
Please take a look at these attachments:
- Recent Oil Analysis on the 307 in this car. At 64,000 miles, it barely burns any oil, leaves no blue smoke, starts easily in cold weather, idles well, gives good power up to redline, and decent gas mileage.
- Mondello Oldsmobile technical manual. It is a superb book; I have a copy. See hyperlink below to get one.
- Mondello document on modifying the Olds 403 (which was used on GMC Motorhomes).
The reason that I am bringing up Mondello is that I visited their facility, spoke with their Engine Builder face to face, and he was highly confident that the 307 could be built with "low-to-mid 200's" horsepower with all of my OEM constraints (Olds Air Cleaner, Air Pump, Exhaust Manifolds, Catalytic Converter, etc.). While the Mondelllo company doesn't get quite the rave reviews when Joe Mondello was running things there, they still have a decent operation. You probably count the number of dedicated Oldsmobile engine builders on Planet Earth with one hand, and have fingers leftover.
As for comparing the 403 to the 307, the large bore and narrow piston-to-piston spacing of the 403 means the cylinders are "Siamesed", such that there is no coolant flowing there between cylinders...yikes!
To restate my objective: I am DETERMINED to avoid the dreaded N.O.M. (Non-Original Motor) derogatory label, and maintain the coveted "Numbers Matching" status. Also, if you overly modify the original engine, which often means you just preserve the Engine Block itself, does it even matter that it is "numbers matching" anyway? And in light of the good "grades" the engine just got from the oil analysis, I might just upgrade the externals (performance re-build of the Carburetor, and Extrusion Hone the Exhaust Manifolds, and OEM Aluminum Intake Manifold), and wait until the engine hits 100,000 miles, and THEN reconsider what level of build will be done on the engine.
