Frequently Asked Questions
Find answers to Frequently Asked Questions for First Generation Firebirds that have been asked and answered on FGF. Special thanks needs to be given to all the FGF members who took the time to respond to other member's questions.
Body - Chassis
Short answer: The factory front-end alignment specs (from the 1969 Factory Service Manual, page 3-18) are below. For modern radial tires, adding caster beyond the factory ½° helps noticeably.
| Setting | Spec |
|---|---|
| Caster | +½° |
| Camber | +¼° |
| Toe-in | ⅛” to ¼” |
| SAI (steering axis inclination) | 8¾° at ½° camber |
| Toe-out on turns | 2° (left-to-right, at 20° turn of the inside wheel) |
Notes: Aftermarket sources list caster and camber as a range (each ±½°). Match settings side-to-side, with a slight offset to compensate for road crown if needed.
For radial tires: The industry practice when switching from bias to radials was to add about 2° of caster over spec. You usually cannot get a full +2½° positive caster on a 67–69 F-car without offset control-arm shafts, but anything over ½° helps a lot with radials, especially wider tires. Keep camber and toe-in minimal with wider tires for longer tread life.
Any proposed updates, changes, pictures, and/or corrections, please use our comment section below (may need to click on permalink to access comments feature). Information is subject to change and offered as is without any warranties or guarantees. Please review our Term's Of Use for more information.
Content last modified: June 13, 2026 at 10:06 am
Short answer: You can replace the radiator-support bushings (and the other four body bushings) without disassembling the car — support the body at the front ends of the rocker panels and lower the subframe on a floor jack, doing it carefully step by step.
Procedure:
- Disconnect the steering coupler (makes the bushing nearest the steering box much easier). Pulling the battery tray makes the passenger-side radiator-support bushing easier too.
- Remove the radiator-support bushing bolts and the bumper-support bracket bolts that connect the brackets to the subframe (2 bolts each side).
- Raise the rear of the car (ramps or jackstands) so it ends up level, then jack up the front using the cross-member.
- Place jackstands at the very front ends of the rocker panels (a stand whose pad matches the flat rectangular area there works well).
- Loosen — but do not remove — the four remaining subframe bushing bolts. Slowly lower the jack just far enough for the radiator-support bushings to clear the support. Recover all hardware (various washers, etc.).
- Install the new bushings (coax the lip through the subframe holes — a small flathead screwdriver helps), then slowly jack the subframe back up. Install bolts but do not tighten.
- With the jack still supporting the subframe, replace the remaining bushings one at a time. Snug all 6 bolts, lower the car, then torque everything with the car on the ground.
Tip: The upper half of the bushing below the driver’s floor pan can be tight — it is the steering column/box connection fighting you. After installing the thicker new bushing you may need to loosen and re-tighten the bolts holding the steering column plate to the firewall to fix any column binding.
With all new bushings the car feels transformed — squeaks and rattles gone and handling much improved, especially combined with fresh suspension, shocks, and motor mounts.
Any proposed updates, changes, pictures, and/or corrections, please use our comment section below (may need to click on permalink to access comments feature). Information is subject to change and offered as is without any warranties or guarantees. Please review our Term's Of Use for more information.
Content last modified: June 13, 2026 at 10:06 am
Short answer: There is a ~⅝” alignment hole in the front bushing mounting platform that lines up with a matching hole in the body. Slide a pipe or tire iron through both holes to vertically align the subframe when reinstalling it.
If you are only replacing the bushings without removing the subframe, this is not necessary — doing one side at a time with the front fenders bolted in place keeps the frame in the correct position, so alignment is not affected.
Any proposed updates, changes, pictures, and/or corrections, please use our comment section below (may need to click on permalink to access comments feature). Information is subject to change and offered as is without any warranties or guarantees. Please review our Term's Of Use for more information.
Content last modified: June 13, 2026 at 10:06 am
Short answer: Replacing deteriorated body mounts is a doable DIY job. Inspect the frame perches first — rusted or cracked perches must be repaired before new bushings go in — then work one side at a time with a hydraulic jack and patience. Break all four bushing bolts loose first, lift the body at the front of the rocker panel about ¾”, and swap each two-piece bushing. Never remove both bolts on one side at once, and don’t fully tighten any bolt until all are installed.
Before you start — check the perches: On rusty cars the perches the mounts sit on can be rusted paper-thin and cracked, which is unsafe until rewelded and reinforced. A common repair is to “sandwich” the frame with large washers tack-welded in place. Jagged or rusty metal will quickly chew up new bushings.
Getting the bolts loose:
- Soak the threads for a couple of days first — many prefer Liquid Wrench (a true penetrant that cuts rust) over WD-40 (more of a lubricant).
- Rock the wrench back and forth rather than using brute force in the “off” direction only; a breaker bar with a pipe extension helps.
- A few hammer taps on the bolt head can help break things loose.
- The subframe bolts are at the base of the firewall and under the front seat pedestal. Remove the front seats and fold back the carpet to reach/soak the rear ones; if you have a torch, heat the captured nuts in the seat-pedestal area before removing those bolts.
- Expect some bolts to come out only half-intact — that is common.
Procedure (one side at a time):
- Break loose all four body-bushing bolts.
- Put a piece of 2×6 on the jack to spread the load and lift the body at the front of the rocker panel until the frame separates about ¾” — a pry bar can help.
- Remove one bolt completely (leave the other on that side loose with its nut on), support the body on jackstands (with wide 2″-thick wood between the stand and floor), and pull the bushing.
- Now is the time to apply POR-15 or another rust inhibitor to the bushing seats on the subframe and body — these areas are prone to rust. The new bushing is two pieces: one sandwiched between body and subframe, the other under the bolt head on the underside of the subframe.
- Install the new bushing and bolts (not tight), do the other bushing on the same side, then repeat on the other side.
- Only after all four are in place, tighten them down.
Realigning the subframe holes with the floor can take some fiddling — the subframe arms may need to be squeezed together slightly to match. Doing this with the engine and front clip in place adds some difficulty but is still manageable.
On frame/subframe connectors: bolt-on connectors can be welded in (but you’ll lose access to 4 of the 6 cage nuts that retain the leaf springs); the manufacturer recommends cross-drilling where the subframe meets the connector and bolting each with four ½” bolts; and they will not fit a convertible without notching either the connectors or the offending brace under the car.
Any proposed updates, changes, pictures, and/or corrections, please use our comment section below (may need to click on permalink to access comments feature). Information is subject to change and offered as is without any warranties or guarantees. Please review our Term's Of Use for more information.
Content last modified: June 13, 2026 at 10:06 am
Short answer: For all-around comfort, the original rubber bushings work best. Steel/nylon bushings trade a little comfort for a noticeable handling gain. Polyurethane is not recommended.
From members’ experience: Polyurethane made the car almost as stiff as a hard-tailed motorcycle and squeaked constantly — the same problem turned up on a polyurethane-bushed ’66 GTO restoration. Graphite-loaded products (e.g. PST Polygraphite) are a hard sell for the same reason. Original rubber is the comfort choice; steel/nylon is worth it if you want sharper handling.
Any proposed updates, changes, pictures, and/or corrections, please use our comment section below (may need to click on permalink to access comments feature). Information is subject to change and offered as is without any warranties or guarantees. Please review our Term's Of Use for more information.
Content last modified: June 13, 2026 at 10:06 am
Short answer: There is no single “best” body-bushing material — it is a trade-off between deflection (handling) and NVH (noise, vibration, harshness). Rubber rides best, polyurethane sharpens handling cheaply but adds NVH and can squeak, and steel/nylon eliminates deflection but adds the most NVH.
NVH stands for Noise, Vibration, and Harshness — what an engineer tries to limit in a street car, and what a racer worries about least.
Rubber
Measured in durometer (hardness). Most stock bushings are fairly soft — a compromise for reasonable handling with a smooth ride, since the factory sold to both enthusiasts and buyers who would dislike a harsh ride. (Pontiac used harder-durometer rubber on later WS6 cars to limit deflection.) Downside: rubber decays and wears out, especially under hard road or drag use.
Polyurethane
A relatively inexpensive upgrade that limits deflection; users accept more NVH for better performance driving. Downsides: prone to squeaking and sometimes binding (drill the shells for grease fittings and lube regularly to limit it), and “cold flow” — under hard use over time the material can slowly deform and eventually need replacement. Expect increased harshness.
Steel/nylon or aluminum/nylon (Duralum)
A sure-fire way to eliminate deflection — companies like Global West and VSE tout it for “slot-car” handling, and it is popular on dedicated road-race cars. Downside: the most increased NVH. Try to ride in a car already equipped before committing; some owners love it, others cannot live with it.
The writer’s own choice for a convertible (to cut squeaks and rattles) was stock replacement rubber (TRW), accepting some deflection for a nicer ride. Bottom line: decide what you want from the car and what you are willing to trade off, and the choice gets clearer.
Any proposed updates, changes, pictures, and/or corrections, please use our comment section below (may need to click on permalink to access comments feature). Information is subject to change and offered as is without any warranties or guarantees. Please review our Term's Of Use for more information.
Content last modified: June 13, 2026 at 10:06 am
Short answer: The firewall and engine-compartment sheet metal are semi-gloss / eggshell black (not body color). Restoration-grade paint from suppliers like AMES or Year One works well; period-correct mixing formulas are below.
Eggshell black lacquer — firewall, inner radiator support, and other engine-compartment sheet metal (from a 30th-anniversary Camaro article, believed to also apply to the Firebird):
PPG (Pittsburgh Paints): 2 qt “mixing black” #386 · 1 qt “universal flattening agent” · 1 qt “mixing clear” #310 · use PPG #DDL-16 or DuPont #3608S.
or DuPont: 2 qt “mixing black” #406 · 1 qt “universal flattening agent” 850 · 1 qt “mixing clear” #465 · DuPont #3608S.
Enamel — undercarriage, frame, and suspension (easier to wipe clean for show):
PPG Delstar or DuPont Centari · 3 qt mixing black (sometimes called “strong black”) · 1 qt flattening agent · use PPG DTR601 quick-dry reducer.
The above is for purists wanting the exact shade. A simpler approach that has worked well: three parts cheap chassis black to one part universal flattening agent — it comes out semi-flat and looks great on the firewall and chassis. You can also contact the paint manufacturers (online or by phone) with your color and year for codes or base/clear equivalents.
Any proposed updates, changes, pictures, and/or corrections, please use our comment section below (may need to click on permalink to access comments feature). Information is subject to change and offered as is without any warranties or guarantees. Please review our Term's Of Use for more information.
Content last modified: June 13, 2026 at 10:06 am
Short answer: A few weeks’ gap between an engine’s date code and the Fisher Body trim-tag date is completely normal — nothing to worry about. The rule of thumb for drivetrain parts is roughly 2 weeks to 3 months before the body build date (about 6 weeks is the usual maximum), and generally not after, though exceptions exist.
- The trim-tag date is when the body shell was assembled at Fisher Body — not final assembly. The final date is the “Invoice Date” on the Billing History (when the car was certified to ship).
- Worked example: a body shell scheduled the 4th week of October 1967 (the 23rd–27th), with a “WK” block (date code I177) cast Oct. 17, 1967 — cast on a Tuesday, likely assembled around the 20th–23rd, then a couple more days to reach Lordstown for final assembly. So it could easily have gone into a body built that same week.
- Low-production cars were often built in batches, so many of the same model/color/engine ran through within the same period.
As always with date codes, there are no absolutes — inventory control 30 years ago wasn’t what it is today.
Any proposed updates, changes, pictures, and/or corrections, please use our comment section below (may need to click on permalink to access comments feature). Information is subject to change and offered as is without any warranties or guarantees. Please review our Term's Of Use for more information.
Content last modified: June 13, 2026 at 10:06 am
Short answer: The half of the bushing with the metal sleeve goes between the frame and the radiator support, sleeve pointing up. The plain rubber half sits on top of the support over the sleeve — install it with its large hole facing down.
Assembly: Use two large washers (one on top, one under the frame), plus a medium washer, a lock washer, and a nut. Push the bolt in from above with one large washer; the remaining washers go on the bottom.
Note: some reproduction bushings are slightly large for the radiator-support hole and need trimming/filing, and the bolt can be too short. GM bushings are correctly sized and come with correct-length bolts.
Any proposed updates, changes, pictures, and/or corrections, please use our comment section below (may need to click on permalink to access comments feature). Information is subject to change and offered as is without any warranties or guarantees. Please review our Term's Of Use for more information.
Content last modified: June 13, 2026 at 10:06 am
Short answer: Before modifying or welding any body mounts, align the body to the subframe using two 3/4″-diameter rods slid up into the alignment holes in the lower cowl section from underneath the car. When correctly aligned, the rod sits perpendicular to the frame.
A small lengthwise discrepancy of about 2/10″ is minor, but the rod-and-cowl-hole method is the reliable way to check and correct the alignment.
Any proposed updates, changes, pictures, and/or corrections, please use our comment section below (may need to click on permalink to access comments feature). Information is subject to change and offered as is without any warranties or guarantees. Please review our Term's Of Use for more information.
Content last modified: June 13, 2026 at 10:06 am
Short answer: You do not need to measure anything — the easiest tell is the steering linkage. The 1967 Firebird was the only year to position the linkage behind the front wheels; 1968 and later moved it in front.
Any proposed updates, changes, pictures, and/or corrections, please use our comment section below (may need to click on permalink to access comments feature). Information is subject to change and offered as is without any warranties or guarantees. Please review our Term's Of Use for more information.
Content last modified: June 13, 2026 at 10:06 am
Short answer: The 1967–69 subframes have subtle differences but will functionally interchange. All three years differ in the steering linkage — not just 1969.
Any proposed updates, changes, pictures, and/or corrections, please use our comment section below (may need to click on permalink to access comments feature). Information is subject to change and offered as is without any warranties or guarantees. Please review our Term's Of Use for more information.
Content last modified: June 13, 2026 at 10:06 am
Short answer: The correct factory look for the underside is black with low gloss — eggshell-black lacquer for the firewall and engine-compartment sheet metal, and a more durable black enamel (or a modern urethane) for the frame, suspension, and undercarriage.
PPG mixing formulas:
Firewall, inner radiator support, engine-compartment sheet metal: 2 qt “mixing black” #386 · 1 qt “universal flattening agent” · 1 qt “mixing clear” #310 · use PPG #DDL-16 quick-dry thinner or DuPont #3608S.
Undercarriage, frame, suspension (eggshell black enamel): 3 qt mixing black · 1 qt flattening agent · use PPG DTR601 quick-dry reducer.
Enamel is used here because it is more durable than lacquer and wipes clean for showing.
Modern alternative: Many good urethanes outperform enamel or lacquer for chip resistance and general wear, and have flattening agents to dial in the right dullness (test your flattener-vs-gloss mix). Paint the underside before the body so you get the factory-style overspray onto the rockers and into the cowl — and carefully mask the frame, leaf springs, and all lines/cables.
Any proposed updates, changes, pictures, and/or corrections, please use our comment section below (may need to click on permalink to access comments feature). Information is subject to change and offered as is without any warranties or guarantees. Please review our Term's Of Use for more information.
Content last modified: June 13, 2026 at 10:06 am
Short answer: To remove the old black tar-like undercoating, heat it with a propane torch just until soft, then scrape it off in strips with a cheap scraper whose corners you have rounded so it will not gouge the metal. Finish with a Scotch-Brite pad, mineral spirits, and a rag.
It is a nasty job — wear gloves and goggles.
Any proposed updates, changes, pictures, and/or corrections, please use our comment section below (may need to click on permalink to access comments feature). Information is subject to change and offered as is without any warranties or guarantees. Please review our Term's Of Use for more information.
Content last modified: June 13, 2026 at 10:06 am
Short answer: From the factory the underside was painted (semi-gloss black on everything except body-color overspray). Full-underside undercoating was a dealer-installed option, not factory — GM did not offer factory rust-prevention/undercoating until the 1980s.
Two exceptions worth knowing:
- The neatly masked undercoating at each wheel well is factory — used mainly as a sound deadener rather than rust-proofing. Its texture is hard to duplicate, so if it is not rusting underneath, leave it alone.
- Dealer add-ons existed early: one 1968 Sprint came with a dealer undercoating plus a “Ming Paint Treatment.” That undercoating was a yellowish, waxy paraffin (like beeswax) and came off with rags and mineral spirits rather than scraping.
On the GTO, a factory option let you delete the sound deadener and body sealer (“dum dum”) to save a little under 100 lbs — mainly for drag racers.
Any proposed updates, changes, pictures, and/or corrections, please use our comment section below (may need to click on permalink to access comments feature). Information is subject to change and offered as is without any warranties or guarantees. Please review our Term's Of Use for more information.
Content last modified: June 13, 2026 at 10:06 am
Short answer: The wheel-well plug part number is GM #0480-5844.
The only difference between the original and the new plug is that the original had the part number molded into its back side; otherwise they are identical.
Any proposed updates, changes, pictures, and/or corrections, please use our comment section below (may need to click on permalink to access comments feature). Information is subject to change and offered as is without any warranties or guarantees. Please review our Term's Of Use for more information.
Content last modified: June 13, 2026 at 10:06 am
Content last modified: June 9, 2026 at 7:10 am
