OVERVIEW

This purpose of this thread is to document multiple planned performance upgrades to my 1968 Cutlass S and bounce ideas off fellow CO members in those areas where I’m not already committed by already having parts on-hand. This will be the biggest project I’ve attempted on any car I’ve owned, primarily since I’ve been “saving up” for it prior to retirement. This project includes an engine rebuild, suspension and wheels upgrade, and a front-disk brake conversion. I’ll be lucky to get it all done this summer season, but I do plan on having it back on the road by summer of ‘27. Prior modifications made that support these new upgrades have either been documented in separate threads here on CO (see my signature for links) or were performed prior to my joining CO. Please feel free to chime in if you think I’m heading down a dark alley with any of my approaches.



BACKGROUND

I’ve owned this Cutlass since 1981 when I purchased it from dad for $100 because “I needed transportation for a job”. He was the 2nd owner who purchased it in ‘74 with ~27,000 miles on it from its original owner, who was his next door neighbor (a Magnavox retiree). It had not seen any salty winters until then, but being dad’s only 2-door coupe since his ‘48 Plymouth, he took extra care of it by making it mom’s car (which sat in the garage most days of the week) while he drove a ‘74 Ventura as his daily. Mom loved her Cutlass since it had “so much pep” that it “moves without hardly thinking about it”. I learned how to drive and took my driver’s test in this car. Dad added an under-dash A/C unit in ‘76. All I knew is that it looked a lot like a 442 and I had to have it. So a years-long campaign to pressure dad to eventually sell ME this car ensued. By the time I took ownership with ~75,xxx miles, rust was starting to bubble through behind each wheel well, and it suffered only one minor hood-bender at my hands when I drove it in high-school. It wasn’t until I got a copy of Casteele’s 442: A Source Book that I was introduced to Dr. Olds and all the W-machines. I was mostly intrigued by the W31s that used a high-winding 350 and had always wished I had one of those. Eventually my vision for my Cutlass became a homage to the ‘68 W31s by sticking with a SBO and adding the OAI, although I won’t ever put any Ram-Rod decals on the fenders.



It survived 3 years of use and mild abuse while I was in college (seating for 6 meant it was a popular road-trip ride). During the first winter following graduation, I got in a fender-bender on the way to work that pushed in the RR quarter panel. One of my senior co-workers talked me into taking an auto body shop class in the evenings (4 hrs every Wednesday for ~9 weeks), during which I was able to repair the RR quarter (pulled-pounded-and-filled) as well as welding in patch panels behind each wheel. I finished priming and paint prep in dad’s garage and took it to a “pro” to lay down the original Scarlet w/ clear-coat. It looked OK for what I paid, but the shiny clear reveals the less-than-perfect bodywork I did underneath, making it a 20-footer that at least looks MUCH better than it did. My theory was that if it stays off the salt and doesn’t get wet except for washes, rust should be avoided for decades (which has been true in this case). Later in the ‘80s I swapped the hub-capped steelies for a well-used set of 14” SSIs. I also rebuilt the front suspension w/ poly-graphite bushings.



By 1996, a leak had developed in the rear axle, drenching the rear brake shoes. That made it un-driveable, and I was tight on money for repairs at the time. So at ~113,xxx miles I put it on jack stands, fogged the cylinders and put it to bed for nearly 10 years. In 2006 I undertook a rebuild of the 2.78 open type-O axle, “future-proofing” it by putting in a Supercars Unlimited posi and 3.90 gears. While I was at it, I installed Edlebrock adjustable UCAs and SSM lift bars in place of the LCAs to enhance traction and be able to adjust pinion angle. The new gear woke-up the launch quite a bit, but without an OD in the Jetaway, it was spinning the 350 a lot faster than I’d like on the highway. At this point in time, I noted that the timing was getting pretty sloppy, so in went a new timing set.



In 2014 (~118,000 miles) I swapped the Jetaway for a 200-4R built by CK Performance. Its “rated” for 500 HP / 500 ft-lbs, which at the time seemed more than adequate for my then ~400 HP aspirations for a rebuild on my 350. This trans swap solved the highway RPM discomfort and made shifts MUCH more noticeable. In 2019 I installed a complete repro OAI system (using a spacer on my 2GC). Nothing is cooler looking under the hood than these factory-designed OAI systems.



Since my eventual engine rebuild plans include LT headers, the column shift linkage was going to be in the way, so in 2025 I swapped my bench for aftermarket buckets and a floor shifter, adding 3-point belts in the process.



The old A/C system hasn’t worked in years, so I yanked it a few years ago and plan on keeping it a non-A/C car. Although I did acquire some driver-side alternator brackets to allow a Vintage Air compressor to be mounted on the passenger side if I decide later to go that route.



What I had not initially planned on was having an opportunity to get in on one of cutlassefi’s SBO stroker cranks. Since his ~7.0L builds, be it with iron or alum heads, crank out numbers in the 500 HP / TQ neighborhood, it raised a momentary concern that my built 200-4R might not be able to handle it. Then I figured YOLO, there’s always more stout transmissions out there, its not everyday you can nab a SBO stroker crank, so out went the check.



At ~124,000 miles, the 350 still runs OK. No smoke on startup (or when putting the spurs to it) and it runs pretty good. But the lifters are getting noisier (its always had a tic at idle since dad purchased it in ‘74) and I feels like the cam isn’t what it used to be. So it is time. Since this will most likely be my only opportunity to do these performance upgrades, making it a budget-driven rebuild is not the priority. As of this posting, I’ve yet to park the car and begin disassembly, but that should commence within 2 weeks.

 

THE ENGINE PLAN:

I’ve committed to rebuilding the numbers-matching 350 myself in my garage (leaving the trans in the car). Mark also sold me pistons and rods to go with the crank (which results in the same bore/stroke as the LS7 or 428 ci). Other than the block, valve covers and timing cover, pretty much everything else will be new.



Block: ‘68 350 bored to 4.125”, align bored crank and cam journals, decked as required



(Parts on-hand)

Crankshaft: 4340 billet, 4.00 stroke, SBO crank journals, SBC rod journals

Heads: Edlebrock 61025 (new BBO w/ springs for roller cam)

Intake: Edlebrock 7111 Performer RPM (Mark’s advice was that the Victor would be less limiting for these larger cubes, but I still need to squeeze the OAI system under the hood and I know the RPM will fit)

Pistons: Mahle 198008425

Rods: Eagle FSI 61250

ARP Main & Head Studs (184-5401, 180-3700)

Freeze Plugs: Milodon 697-34045

Oil Pan: Canton 15-502

- Pickup: Canton 15-503

Damper: ATI 917840

Flex Plate: ATI 915564

Oil Pump: Melling 689-M22FHV

Timing Chain: Cloyes 9-3513X9

Gaskets / Seals / Valley Pan: Fel-Pro 260-1008 / BS6141 / MS 96027



(Parts to acquire)

Head Gasket: Cometic, thickness as required to achieve ~10:1 CR

Starter: RobbMc 3004 w/ 2025 pinion support kit

Headers: Headman 58066

Exhaust System: Pypes SGA14R (3” 409SS w/ X-over, cutouts and Race-Pro mufflers)

- Collectors: Pypes PVR10S

Bearings: Clevite sized as required

Roller Rockers: Harland Sharp 5016 (I think I’ll need to use 3/8” spacers to fit these under my stock covers)

Pushrods: Smith Brothers sized as required

Roller Cam / Lifters: TBD

Fuel Delivery: TBD (Leaning towards Sniper 2 EFI w/ HyperSpark distributor, but may consider using carb initially for break-in and adding EFI later)



I’m sure there are many additional incidental parts I’ll need along the way to complete this, but these are the biggies. I’m wide open for suggestions on cam/lifter selection and fuel delivery options. Since I’m no longer trying to spin it to 6500 RPM to get 400 HP from 350 ci, my cam doesn’t need to be too crazy. But a little lump in the idle won’t bother me at all either. I do have to get decent idle vacuum for the power brakes though, and want to be able to run on 92-93 octane. I’m confident this will be much easier to achieve w/ more cubes and less strenuous RPMs.



THE SUSPENSION PLAN:

Other than new springs, shocks and sway bar to match the planned front suspension mods, the rear suspension will remain the same. I’ve wanted to correct the front suspension geometry for a long time, and with nearly twice the HP I have now, I want this car to handle as good as I can get it without going too overboard. Also, my old SSIs have lug holes that are shot and BFGs that are >12 y/o, so new tires & wheels are in order.



(Parts on-hand)

UCA: UMI 4056-1 (+ 4003 hardware kit)

LCA: UMI 4032 (+ 4001 hardware kit)

Tall-Spindles: UMI 910-3500B

F/R Sway Bar Kit: OPGI RP01722

Front Coil-Over Kit: UMI A204-550S (+ bearings & spanner wrench)

Rear Springs: UMI 4050R

Rear Shocks: UMI B230

Steering Box: Lares 10972

Steering Coupler: Lares 201



(Parts to acquire)

Center Link: Moog DS749

Idler Arm: Moog K5143

Tie-Rod Sleeves: Moog ES2032S

Tie-Rod Inners: Moog ES681N

Tie-Rod Outers: Moog ES333RL

Power Steering Pump: Lares 12039

Wheels: 17x8 / 17x9 Staggered SSI rims from Year One (includes center caps and lug nuts) are on back-order

Tires: 255-40-17s front, 275-40-17s rear (possibly Nitto NT555)



I really wanted Y/O’s staggered 17” silver SSII rim kit but those appear to be discontinued.



THE BRAKES PLAN:

The stock power 4-drum brake system needs upgrades to keep pace with the expected HP increase and more aggressive handling capabilities. So I want to go a bit larger than stock discs in the front. I’m a believer that rear discs are overkill on these cars, so I’m staying with stock drums in the rear. It costs nothing to try the drums and I can always “upgrade” to rear discs later if I want to. While I’m planning on accommodating 17” rims, choosing front brakes that can accommodate a 15” rim has advantages in case I’m forced to change my mind about wheels.



Seems that the trickiest part of a brake upgrade project is determining the optimum size of the master cylinder piston. Many sources indicate a desired line pressure of 1200-1500 PSI for emergency braking conditions. Several sources recommend ~100 lbs of pedal pressure to achieve that. So using some rough calculations:



Booster Ratio: 2.0 (typ for 9” vac booster)

Pedal Ratio: 3.43 (as measured on my pedal)



Desired MC Piston Area = 100 lbs * 2.0 * 3.43 / 1200 PSI = 0.572 in^2 → 0.853” dia piston



The smallest piston MC Wilwood offers in their standard tandem line is 7/8” (0.88”), so I’d have to increase the pedal force to 106 lbs to achieve 1209 PSI line pressure with a 7/8” MC piston (132 lbs needed to achieve 1505 PSI). Close enough, I think. I do plan on confirming my booster size and recalculating as required before ordering parts. I may still call Wilwood to confirm I’m barking up the right tree with this combination. My thinking is that the smaller MC piston will make it easier to modulate braking force. I’m wide open for other opinions on this. Since stopping force is ultimately limited by the tires, weight transfer and road surface, its much more straight-forward to target a range of line pressures vs. pedal force. Also, if I end up being way off with the feel of the smallest MC piston I can always change that component.



(Parts on-hand)

nothing yet



(Parts to acquire)

Front Disk brake kit: Wilwood 140-7675DR (12.19” drilled/slotted rotors, 4-piston calipers)

- Brake Lines: Wilwood 220-7056

Master Cylinder & Adjustable Proportioning Valve Kit: Wilwood 261-13271P

Residual Pressure Valve: Wilwood 260-13784



Wilwood recommends the 10-PSI RPV on the rear drums to offset the shoe return springs. Its cheap and can be removed easily if it doesn’t work as expected.



I may also install a line-lock while I’m at it. I do plan on validating the HP achieved at the drag strip some day. Unless I screw-up the cam selection and tuning, I don’t have much of an excuse to not hit at least one of the 500 marks.

 

Why the big block heads with the 77cc chambers? Wouldn't it be better to run the SBO Edlebrock head? This way you also don't have a ton of work on port matching the intake manifold.

 

Good stuff Johnny, focused on your first post more than the second as the latter is out of my league. But I am excited for you. Looking forward to how it turns out.

Love it.

Can you remember how many miles you put on her yourself? I think we've talked track performance before, but I've spent a lot of time on other social media platform's of late and cant lock in fully... Have you baselined her performance and have you tested her with all mods up to date ? With regards to tick I have some also that seems to come and go. I don't remember hearing it when I first got her. But one time at Island Dragway I was manually shifting and heard a loud pop... My understanding I may have overrevved her and caused valve float on a 100,000 mile plus engine. Was worried I hurt something but she felt fine afterwards. And eventually ended up going much faster than I ever went at Island. Maybe its just normal wear and tear ... But no more manually shifting...

Maybe your then ultra low mileage 350 was overrevved once as well...

 

Good question, I was initially assuming that I'd need to use the (anxiously awaited) new SBO heads for this stroker build, but Mark pointed out that with 428 ci, the smaller SBO chambers would result in too-high CR unless I used a really thick head gasket. The BBO heads are a better fit to 428 ci.

 

My (electronic) maintenance records only date back to 1984 when it had 84,000 miles on it. I lost the paper records I kept for the 1st 3 years of ownership, but IIRC it was in the high 7x,xxxx mile range, so almost 50,000 miles. I keep a plot going that shows mileage vs. date (which shows it was my daily before I repainted it, and the big pause when the rear brakes were FUBAR'd):



I've not had this car to the track, but I do distinctly remember racing my buddy w/ a '89 Quad-4 Calais and we were neck-and-neck up to ~100 MPH (this was when the drivetrain was bone stock except for the dual exhaust and turbo mufflers I installed in the late 1980s).

Regarding the lifter tick, the original owner never impressed me as an auto abuser, I remember him describing to me how he liked how smooth it shifted as he lifted slightly between gears. When he sold it to dad, his replacement car was a (gasp!) Pinto (this was 1974 after all). However, I do recall one event where mom was having a hard time getting it started one morning and asked me for help. I jumped in, mashed the gas to prime and choke it, then let off (standard startup proceedure). Instead of firing up normally, it revved to the moon and I turned off the ignition as fast as I could. I popped the hood and found that the carb linkage was all bent out of shape and jammed the throttle wide open. My conclusion is that it had been the victim of vandalism, most likely the day prior when mom drove me to my Wildcat baseball game in it and there were some "hoodlums" hanging out that day. Just grateful that it didn't jam on the way home from the game when mom was behind the wheel. I fixed the linkage, but that was the only "over-rev" indicent I can recall. Of course, I also had 2 younger sisters who drove it too before I took ownership. In any case, it never seemed to affect performance, and the tick does come and go. I think its just a lazy lifter as the tick is barely noticible above ~1200 RPM. There are other (newer) noises it makes above ~4000 RPM that is much worse and keeps me from a full-out pull down the 1/4 mile. I'm thinking possible weakened valve springs from sitting on blocks for ~10 years.

 

Holy ambitious build, nice. You will be testing CK's 2004R with the stroker small block, nice and should stop and handle like a modern car, nice keeping your parents car alive.

 

Excellent plan. Very meticulous and you've obviously put a lot of thought into it. I'll be paying close attention as I have a '69 Cutlass S also with the 350/2GC combo. My future engine upgrade plan is similar to yours. Mine only has about 80k miles and was well maintained so the thing runs and idles incredibly well. It has manual steering/brakes and factory 4 speed so I should be able to get a little more radical on cam than you're restricted to.
I dropped a Remmel built 455 into my '69 442 about a year and a half ago. I put Hooker long tubes on it and Hedmann makes collectors with welded in bungs for O2 sensors. I'd highly recommend adding these to your exhaust plan and installing a wideband gauge. Simple install and you wouldn't believe how much more you're able to understand what the engine is actually doing under the hood under all driving conditions.
Best of luck!

 

So, I have the UMI 4056 upper control arms, and I'm not sure I'd really recommend them. I've had to replace the rod ends a few times and they aren't particularly easy to adjust. My newest set of rod ends is holding up, but for a bit, I was seriously considering swapping those arms out for the standard mounting setup.

I'd also think very long and hard about the lowers. I have those as well and wish I had gone with the corner max version to give me more options with coilovers. But that's because I was tossing the car pretty hard around an autocross circuit on sticky tires and finding everything to be too soft. The ability to step up to a true coilover with way more than 550 lbs/in springs would be very welcome. If you're just cruising around on the street, you'll be fine, but something to think about.

 

Thanks for the feedback. Yes, I've been looking towards future potential engine performance when I selected the 3.90 rear gear back in '06. I even used an old DOS performance simulator called CarTest to zero-in on that (and the 200-4R) solution:



This modeling probably doesn't correlate accurately to the real world, but I was focused more on the changes from the mods, which I think is still useful. Back then I was using Edlebrock's "Top-End Kit" performance curves as inputs to this model (397HP). What I liked about the 200-4R and 3.90 solution is that crusing RPM at 70 MPH was actually lower than stock (+/- TC slip) I've not re-run this for the stroker solution, but I won't be surprised if down the road I'm going to wish I used a 3.42 gear. I'd rather not rely on a shift to 4th to get through the 1/4-mile.

(Note: With the 4.10 gear, the stock engine exceeded its "redline" before the car reached the 1/4 mile, so the simulation stopped there. Also, I believe the model started predicting wheelspin w/ 3.90 gears and stock engine which explains why the 0-60 times increased vs. 3.42s & 2.78s).

YES, welded bungs for O2 sensors will be added whether or not I use a carb or go EFI. I'm a big advocate of future-proofing, especially if the added labor is small compared to putting it off to a later (most likely less accessable) configuration.

Good info on the UMI control arms. I think at the time I selected the lowers, I was still on the fence on whether I'd use springs or coil-overs. The 4032s allow either. Fingers crossed on the longevity of the UCA pivot points.

 

You've done a great planning job and you are one of those rare individuals who is open to suggestions. And good that you've preserved a family vehicle.

So, why did you pick a non-standard 9" power brake diaphragm size? A standard size would assure repair options remain in the future.

 

Thanks, I try to stay open minded because I don't know everything. I certainly couldn't remember the booster size I installed. But now you forced me go and find the receipt from 2015 that shows I installed a 10.45" booster (Cardone 54-71106). Based on the same table used to determine the boost ratio for the 9", I used numbers for an 11" booster and scaled it (by ratios of areas) down to 10.45" This gave me a new boost ratio of 2.15. Putting this back into the calculations above, I find that I can increase the MC piston size to 15/16" and still achive 1200 PSI with 112.4 lbs of pedal force and 1500 PSI with 140.5 lbs of pedal force. Similar ball park ranges as before. So this exercise leads me to change to a 15/16" dia MC piston, which is probably better anyway because now if I need to tweak it for feel, I have two directions to go instead of one. THANKS!!