Is there a common fix/ solution to frame rail flex on the driver side under the hood? Does someone make a bracket or something? Been having clutch issues. Where the pivot for the z bar mounts (mechanical clutch) on the frame rail there is a crazy amount of flex to the point where my brake booster is moving a bit. 😶

thanks in advance!

Bo

 

If the brake booster is moving you likely have an issue w rust or cracking around the booster mount on the fire wall or somewhere around there. The frame shouldn't be moving in relation to your z bar. The pivot for the z bar bolts to the frame directly. That area is pretty thick. I wonder if your pedals are moving because of firewall issues.

 

What you are experiencing is common with these cars and is actually not the frame flexing, that is a separate weak point on these cars. The firewalls are not that strong, which is why GM added extra material around the clutch master cylinder opening in the firewall. It is common to see the brake booster "flex" when applying the clutch and or brakes. There is a member here who put a camera in his engine bay to help characterize the magnitude of this movement, but his name escapes my memory at the moment.

 

I wanted to come up with a support brace knowing that there is a considerable amount of movement in factory form, and pay no attention to the squirting of dirty brake fluid
What a came up with works well for the elevation rise but not so much for the horizontal movement, later on I may revise the support brace to help here.

 

Best fix I know of, is to change it over to hydraulics.

I did that to my 83 L69 back in about 86; THE INSTANT I first came across one of those setups in a junkyard (wrecked 84 L69 car). Haven't regretted it ever in the least.

 

sofa, can you go into more details on that, I’m not familiar?

 

I took out the Z-bar and put in hydraulics.

Seriously, I did have to cut the oval-ish hole for the MC. I got the pedal assy, hydraulics, & BH out of the 84, and just swapped em in once that was done. Piece o cake. Took less than a weekend. Everything worked when I was through; cruise control, starter safety switch, everything. And of course the car drove 10 times better at least.

 

Ok, blond moment, you went from a mechanical clutch to a hydraulic assist clutch

 

I sell a brake master brace that removes a lot of firewall flex on a 3rd gen.
it's not the end all solution, but it helps a lot
ultimately the 3rd gen fire wall is weak.
That's why the 4th gens are nearly 2x as strong.

I also have a video on my channel:

eBay Link:
https://www.ebay.com/itm/175555281751

 

I purchased this brace and it helped. I also have something similar for the clutch master. My 82 firewall wasn't rusted or cracked but flimsy as hell. I placed these braces in and it made a pretty big difference. When I removed the mechanical linkage I thought about making a bracket that went from the frame mounting points of the linkage to where the master cylinder/booster bolts are. I still may but it's a busy area and the plates I put in helped quite a bit.

 

With the hydraulic system, the braces you need most of all, are the ones that connect the pedal assy to the MC. That's the axis on which the force is mostly applied. If THAT connection is secure, the firewall deal is almost just incidental. Let's say, 80% of "perfect", and you're done.

NOT that I'm saying "you shouldn't stiffen the firewall"; NOT saying "firewall stiffness doesn't matter"; only, that (Pareto Principle) for MOST of us, the factory's braces, properly installed, are adequate. Now, if you go doing something abusive like autocross or road-course racing, you get into a whole other envelope, where you need every bit of perfection you can get. For that matter, even for street driving, if you want REALLY CRISP clutch action, as PERFECT as you can get, then added stiffness there will help. It takes some individual discretion, it's not a "one size fits all".

 

I made this little piece and welded it to my STB.

 

I wanted to do something like this but HSR + stock Firebird hood = no STB

 

I like the one you made, it just needs a piece welded in the front part. Maybe with a similar bolt to stop against the MC.

 

He asked about the clutch and the z-bar, not the brakes.

Although it's not impossible that bracing the brake MC would also help the clutch MC, by making the whole firewall more stable. Probably a minimal effect, but w/e, an effect is an effect, at the end of the day.

Butt, unless I can't read (always a possibility), he's asking about the CLUTCH, not the brakes.

 

To be honest, when you push the clutch pedal, it's essentially a lever and the fulcrum is the pedal mount. So stiffening the pedal mount on the fire wall will help w flex/movement of the fulcrum. All the different types of master cylinder stabilization will help prevent movement. This will ultimately help the clutch release. The flimsy 82-83 tinfoil firewall could use all the help it can get. I'd still be looking for cracks/rust and other issues but it may be as simple as some flexible/thin metal. After working on mine, I'd put all the bracing in possible, it's pretty sad.

 

He did say the "brake booster is moving a bit". Just saying, but does one not have to push the brake pedal sometimes when applying the clutch?

 

I considered welding a nut and plate to mine to use a something similar to what you're using on yours, I have some concern with how much pressure would be put on that mounting stud.

 

You mean the one on the strut? You could put a second stud on the strut plate to reinforce it. Could also keep the MC from wanting to push the bracket forward, if you welded a plate in front of the MC.

 

The z-bar ball stud doesn't mount to the firewall or the strut tower. It's on a little bracket that mounts on top of the "frame" rail, a few inches in front of the firewall.

His problem isn't just "firewall flex", per se; it's that the WHOLE CAR around the WHOLE SYSTEM, is inadequate for it. It's as though they designed a car with complete other goals and constraints and criteria in mind, and then at the last possible minute before issuing the production documentation, somebody said "oh crap this thing has to get a clutch installed in it somehow" and that was their "solution". Granted, the firewall DOES flex; but it's in 2 directions: the act of pressing on the pedal pushes it INTO the engine compartment, but the force trying to compress the pedal-to-z-bar link tries to push the firewall RERWARDS. The whole thing tries to twist. It's a disaster. You can put a protractor or something on top of the "frame" rail, and watch the firewall literally try to bend INTO THE PASSENGER CABIN at the point where it meets the "frame" while the upper part of it, where the pedal bracket is, tries to go toward the engine.

Having a 83 car myself with that crap, I TOTALLY get what he's dealing with. All of that is just ALTOGETHER TOO LITTLE METAL all around there in the first place for what's being asked of it, in shapes that aren't optimized for forces in the directions the clutch puts on it. That whole system was bad enough in BOF cars; speaking strictly as someone that drove 50s and 60s cars with 4-speeds for MANY years, and then suffered through the same unibody CRAP when I bought a 79 Z28 4-speed (which was the car I traded in on my 83).

Which is why I converted my car to the hydraulic system. No amount of "bracing the firewall" will cure what ails that crappy mechanical linkage setup. Talking about "bracing the firewall" won't do the OP a damn bit of good.

 

Yeah, but if the booster is moving a bit when the clutch is actuated then there's an issue. Imagine how much flex there is when braking.
Both my 82s had mechanical clutches and didn't have these issues. I swapped D/T a t 56 swap. My point is if there's that much movement of the master there is likely an issue at the firewall. A few millimeters of lost travel/flex in the linkage will cause an issue w release.

Stabilizing the firewall may be a safety issue. It's worth looking into.

it's also worth loosing at the tabs on the z bar, they bend/crack.

The question was about bracing/support. It will likely help in multiple ways and is the smart thing to investigate.

PS: if/when you switch to a hydraulic releases system you will also need to add support/bracing. All the supports I put in made a difference in stability.

 

The issue is mainly the flimsy firewall as mentioned. If it were me i would incorporate all of the suggestions mentioned here. FWIW there is another thread on this issue posted that is more in depth.

 

The hydraulic system is MUCH easier to "reinforce", since the whole clutch system isn't trying to split the car in half, the way the z-bar CRAP does. For hydraulics, all you hafta do, is make sure that the pedal pressure doesn't have too much effect. TOTALLY DIFFERENT from the dynamics of the z-bar CRAP.

So yeah, "reinforcing" the firewall is no doubt A Good Idea, always, no matter what clutch system you have, and offers benefits to the brakes too; butt DOES NOT overcome the FAILURES of the z-bar CRAP at the fundamental design level. It will NOT "fix" the z-bar CRAP and turn its chicken s*** into chicken salad. It is USELESS to harp on this as some kind of "solution" to the z-bar CRAP being ... CRAP. It WILL NOT make it right. EVER.