68 Cutlass - How Not To Do A Car Project

[olds70supreme]

Hello,

First, I never do this because I am terrible at taking pictures, so I have nothing to share normally. I'm going to try to do better though - it is sort of depressing that I have so few pictures of the projects I have worked on.

So, my first car was a 70 Cutlass Supreme that I drove for 10 years. It was really rusty and we finally had a house w/ a garage to work in so I tore into it. Unfortunately, what I found was overwhelming for my first time doing body work.

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I made a difficult (but rational) decision to part it out and watch for a new project.

About a year later I found my 68 for sale, flew to the west coast and drove it back.

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Fast forward through a home renovation, out of state move, 2nd home renovation, 2nd move, 3rd home renovation, and finally I was able to gain traction on the body work.

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So as it sits now the exterior is done and interior is 90% complete. I took time out to get my garage finished on the inside, so I don't have any excuses any more for taking so long to make progress :).

[olds70supreme]

I've been bouncing back and forth on whether to do drivetrain or suspension next. I had decided to do the engine this winter, but backordered rods caused me to miss my window. Now I'm on the fence on what I want to do next - I might try to at least get a rear gear change done this winter.

The engine will be an Olds 350 w/ upgrades.

Suspension plans include SPC control arms, chassisworks spindle, upgraded brakes (uncertain on what exactly yet). Still have a lot to learn on this.

[andrewb70]

Good looking Olds. I would do the suspension next.

Andrew

[olds70supreme]

Yeah, that is very likely. As an intermediate step when I get time this winter I want to do a rear gear change. Car is a 4 speed and has 2:56 gears now - I want to see how much of a difference 3:23 or 3:42 rear gears make before deciding if how urgent an engine rebuild is. If that wakes it up enough to keep me happy for a year or two I'll focus on suspension in the meantime.

[thumper877]

Going from a 2:56 to a 3:42 will definitely wake it up

[CarlC]

For sure the gears will make a big difference, but if the suspension and brakes are not up to the task, bad things can happen.

It's best to stop before you go.

[68conv455]

Nice 68. Looks like mine but with a hard top. Good luck with the build.

[jetmech442]

Heck yeah on those Chassisworks spindles and SPC arms. You'll fix about 95% of the issues in one go. For brakes, I ran the wilwood D52's in the front and loved them. they are an aluminum bodies, 2 piston version of the stock caliper(same piston area, which is very large). As I started doing more road courses I got worried about overheating the stock 11'ish rotors(to be fair I never experienced any fade), so I saved up some cash and went with the Wilwood Aero6 caliper and 14'' Z06 rotors. Smaller total piston area coupled with larger rotors results in a small braking force gain compared to the D52's, but they should have more thermal mass to dissipate heat than the original setup.

As far as gears, my original BOP 10 bolt ran 3.23's and a TH350 and a 28.5'' tall rear tire to fill out our ( 68/69) wheel arches in back. The big rear tire really eats up rear ratio. From the pics it look like your running a 26-26.5'' rear tire. Before I went crazy with the rear setup, I benchmarked a lot of sports cars like 2006 GTO, 2009 G8GT, BMW 330i, 2018 mustang etc and found that most modern cars(that aren't trying to cheat 0-60 times by leaving the car in first gear) max out first around 40-45mph. With the rocket 350, you might be good with a little less, 35-40mph at 5800 rpm. As long as that balances a decent cruise rpm( say 2500 rpm at 60-70 mph).

I'd be happy to share the gear ratio calculator , or if you share the tire size, shift rpm and gear ratios on the 4 speed, I can just send results. Anywhooo, for a first pass, that's how I optimize rear ratio. More advanced approaches would involve launch RPM and torque, tire compound, % AntiSquat in the rear etc...

[NOT A TA]

Switching from the 2.56 will make a big difference in normal driving. I have a few different ratio rears I can swap in and out of my Firebird. The one I have with 2.56 is good for 1 mile land speed races and long road courses but a dog on the street.

I use these calculators. http://www.wallaceracing.com/Calculators.htm

[olds70supreme]

Thanks for the replies both of you.

I'm 99% sure that my trans is a 2.52 first gear, and tires are 26" tall (too cold to go outside to verify). I haven't been able to work on the car the past week - I need to finish up some under-dash wiring before I move on to the rear end swap.

[jaybee]

I love that you're staying with an Oldsmobile engine. Nice project!

[olds70supreme]

Well, took a turn down a rabbit hole taking care of some wiring issues. Next up is to convert from manual to power steering. I'm sick of having to turn the steering wheel 30 times/second to take a corner at 30mph. I'm on the fence about power steering gear ratios. Choices are 12:1 or variable 13-16:1 gearing. Car will be 99% cruiser, 1% autocrosser. The only thing holding me back from 12:1 is whether it will be too "twitchy" at speed on the highway. Lots of info on the web about this swap, but not a lot of feedback on how noticeable this is, if at all.

[cdrod]

I've owned several Oldsmobiles over the years; '71 Cutlass Supreme convertible, '72 Cutlass Supreme hardtop, '71 Cutlass Supreme hardtop, and currently building a '72 442 convertible. On the '71 hardtop I took my stock Saginaw gear to a local power steering rebuilder here in Houston. He removed the variable ratio guts and rebuilt it with a fixed 12.7:1 ratio. The difference was significant but not at all twitchy. He just rebuilt the pump (no mods) so the amount of assist was still pretty high, but the ratio change made the car so much easier to drive; not as tight as rack & pinion steering but with new bushings and steering gear parts (tie rods, idler arm, etc.) the car drove almost as nice as my wife's 2001 Volvo S60.

Rodney

[68conv455]

I did the Jeep Grand Cherokee power steering box swap on my cutlass. It's 12.7:1 and the steering action is more like a newer car (not like a race car).
You can google an old article from Hot rod mag.
If your not on a budget, lots of options for a brand new box.