Here's a picture of what it looks like: https://drive.google.com/fi...ut8/view?usp=sharing

Anyone have advice on if you think this could be patched if I weld a plate in there with a hole and use a longer bolt? Limited welding skills and I have another cradle on a parts car but this one is already almost ready for paint and I'm not sure the other one is much better. Would rather not have to pull that one off, remove bushings, clean up etc.

[This message has been edited by BadNewsBrendan (edited 11-03-2018).]

As long as other areas on the cradle are sound; if you are good with a mig it appears that that area can be replaced.

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Have you checked the rear upper frame rails for rust? Here's a video just to give an example of how bad it can get.

Yeah thanks Patrick, I took a glance at them a while back when i saw a post about how to repair them and one side is pretty rusted but not nearly that bad. Might have to cut some out and weld some support in down the road but not as concerned about that right now. The purpose of the rear frame rails is just to connect the rear bumper to the rest of the chassis right?

quote Originally posted by BadNewsBrendan: The purpose of the rear frame rails is just to connect the rear bumper to the rest of the chassis right?

Geez, I don't think I'd wish to trivialize the importance of the rear upper frame rails to that degree. If nothing else, you don't want your engine up by your dashboard after a rear-ender... simply because nothing (of any substance) was holding the rear bumper in place.

Perhaps someone with a good understanding of the Fiero chassis could chime in and comment on this.

[This message has been edited by Patrick (edited 11-04-2018).]

Hahaha fair enough. This thing is probably months away from the first test drive post engine swap but before I ever consider driving it for more than a spin around the block I will make sure to look into it some more.

Rear cradle should be replace IF that's the only problem. You can't go on just 1 picture to say if fixing the rust you easy see will solve the issue. You can't just weld a piece either. Welding suspension is not simple.
1. Bad welds or crap cradle can fail w/o any warning and if/when the failure is same area the wheel can slam sideways then steer you into a wall to head on traffic at highway speeds.
2. More metal means bolts won't compress the metal to inner sleeve right letting inner sleeve to move and wear the metal and bolt. Or the bolt can break the welds when tighten to crush the metal to the inner sleeve. Most suspension bushing bolts are Class 10.9 (~ Equiv to SAE Grade 8) or higher and easily bend/break softer frame metals. Either leaves you back to # 1.

All front and rear frame etc are crush zone parts make to fail in a rear/front end crash.
Many claim can "fix" this after rusting out etc are only fooling themselves. The "repair" is ether way too weak or way to strong.
Weak and engine and everything can be push thru the firewalls.
Strong repair parts can do same thing or break off and do little, nothing, or become shrapnel even if the engine etc isn't push thru the FW.
Even more problems, These iffy "repairs" and frame can/will flex even driving normally and can fail w/o warning.

Youtube have many crash test videos but few knows what their watching and have no clue what is happening.
Example: Most people have no clue why the Fiero hood fails w/o going thru the windshield. Most hoods won't even break the glass in a wreck.

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Thanks for all the insight. I will start checking the other cradle. I'm not planning on doing much or any highway driving with this car but I will take this all into consideration. This will probably be mostly driven around town and maybe some autocross and track days. I don't think any engine swapped car will ever be as safe in a wreck as it would be the day it was driven off the line especially if the swap is done by an amateur like me in my little garage. Would also argue that almost no car that is 20 or more years old is as safe as it was the day it was driven off the line even if it wasn't swapped and any car built in the 80's is going to be significantly less safe the day it was driven off the line than any car built in the last 10 years.

I am not going to scrap this car because it might kill me in a wreck because that is always a risk anyway. A suspension component breaking and sending me into oncoming traffic puts others at risk and not just myself so I will try to make sure that doesn't happen. I will get some more pictures on here of the other cradle after i clean it up and the frame rails when I get a chance and would appreciate it if you could take a look and see how dangerous it is/ what the best course of action to minimize risk moving forward.

Thanks again for the advice and don't hesitate to tell me if I am way of base here.

big problem is cradle/frame areas are hollow and often rot from inside out.
So frame may look normal outside but be so weak and steel is so thin as current Al soda cans.
Is why many tow truck drivers in "rust belt" states have a 1-2# hammer to hit an area of frame before attaching hooks. You tell by sound or if hammer dents the frame easy.

Cars can be as safe as came off factory decades later and even better but not in rust belt states and some other areas mainly because of above.
My Fiero and many others still have most of or all factory rust coating on the bottom of car.
Then add who's maintaining and install new parts. Examples:
A real brake job cost money even for DIY people but many believe BS that the car needs an "upgrade" or can use front calipers on rear axle.
Using better pads like Wagner TQ and Monroe/Gabriel Gas shocks/struts are better that factory parts even when many cars has WS6 etc options.

I would agree that you should replace that cradle. It is very hard to tell if any other areas are not in better shape. Too many hidden areas.
The rust I have seen on Fieros happen (by what I have seen) 3 different ways. The unsuspecting way, is water running down from the top into the frame rails. This happens when they sit outside. Worse with leaves and debris, help hold the moisture, letting it drip down slowly.
The most common way. Road salts, kicked up into the strut tower, frame rails and trunk.
And then the times when cars are sat on dirt and grass and grass grows up into the cradle/subframes, and floor, rotting them out.
Most are complaining of "salt belt" cars. Here we are seeing issues with even 5 year old cars due to the "stick on snow removal chems". They have been using that stuff for about 4 years here. Had a 2014 F250 with 42,000 miles in about 3 weeks ago. It looks like it had been parked in 2 feet of ocean water. Mind you, it looks new from outside. Under it, it looks 20 years old.
It is unfortunate for me that I have to use my Fiero as a daily driver. But I do clean the stuff off often. You can't just hose it off. You have to wet it, agitate with a stiff brush, then rinse it off. Then I touch up any spots that need it. I'm due to pretreat/paint/undercaoting before the state starts going crazy with the salts again. And I do have an another rear cradle for it when it will need it.

I’m with most here, do not try to repair that cradle. Especially with limited fabrication skills. As others have mentioned the rust can start from the inside out leaving a bad area for weld penetration=Blowthrough and porosity.

As the ogre stated getting the mounting points and sleeves dead nuts is absolutely critical in longevity and safety, this takes a large amount of time and experience to do correctly.

As for any other rust areas that need repair the only way to do it 100% properly is a butt weld (end to end no overlap) with tight gap, medium heat, lots of cooling time between stitches. and stress relief of the weld area to counteract the potential of shrinkage. The patch material must also be the same thickness and type (cold vs hot rolled) and must be placed all the way back to “new” metal

Has anyone considered fabrication of a new cradle from aluminum? Newer GM cars use aluminum for cradles and it seems that the weight savings is significant, not to mention no rust.

I would think an aluminum cradle/ chassis would need to be cast. Welding aluminum makes it very brittle and welds crack and would fatigue under very low cycles. Casting would take a lot of work and equipment. Could potentially cast a solid version of the steel frame bout would be probably just as heavy and who knows how strong. To get similar strength and durability out of cast aluminum you'd need to do a lot of engineering and stress/ fatigue analysis and completely redesign it. Not worth the weight savings IMO.

I’m gonna have to correct the misconception that welded aluminum cracks....the only welded aluminum that cracks is poorly welded aluminum the strength is definitely better welded vs cast. The cast aluminum that get welded on will crack like glass, take some good alloyed stock and weld it together and you wouldn’t have a problem.

Considering that commercial fishing boats, military patrol boats etc are strictly welded aluminum I’m pretty sure it doesn’t crack. Those guys beat the living crap outta their boats.

Not trying to get into an argument over a topic that has nothing to do with the original but I work at a company that does rigorous physical testing on aluminum products and we have completely gone away from any welding due to it always being the failure point and adhesive being able to withstand at times over 100 times more force and even more times the cycles. Yes welding aluminum can work, especially very long welds along aluminum sheet where the force is very spread out like you talk about on boats but I doubt you find it very often on load bearing support structures and when it is used its done by professionals or more likely very precise robots for mass production and not in someones garage. If you know anything about material properties you know heat makes aluminum brittle. That is not something you can argue. It might feel strong when you weld some bar stock together but if you know anything about fatigue stress you know something that can withstand a single load cant always withstand that load 10,000 times especially aluminum. So don't tell me you are going to "correct" me buy giving one example of where it is done and tell me aluminum welds don't crack. If you instead said "There are applications when done professionally where aluminum is welded and doesn't crack" I would have agreed and we could have a nice discussion on the topic.

[This message has been edited by BadNewsBrendan (edited 11-09-2018).]

The steel in the cradle is a lot thicker than the frame rails and the way it is bent and folded before welding results in a lot of places being double thickness. If that is the only damage to your cradle I would just fill in the holes with a mig welder. I have never seen a billet aluminum engine block. They are usually sand cast or cast using the lost foam method. Maybe top fuel engine builder use billet blocks? I don't know. Here is a thread where a member built his own AL cradle. It is for a stretch chassis but same principal involved. https://www.fiero.nl/forum/Forum3/HTML/000137.html

[This message has been edited by wftb (edited 11-09-2018).]

BNB: I believe we both read too much into each others posts. I had ASSumed that you were implying on that all welded aluminum regardless of type/preparation would crack, where my experience is that the ones I see the most failures on are poorly attempted casting repairs or that god awful aluminum arc electrode, hence the statement of my reply.

That said you had also wrongly assumed that I was saying anyone can go out and build an engine cradle with aluminum, I was really trying to convey that it can be and has in fact been done. I had assumed anyone that would take this on would have ALOT of exp with welding aluminum. As I would hope it could be assumed I was speaking that professionals can in fact weld structural aluminum. I can understand how this came across in my post as aggressive that was not my intention I was typing quickly and skimped on details, I guess it reads aggressively.

All that boils down to a couple of key points:
Yes you are absolutely correct about the HAZ (actually relivent to the topic at hand)
I never knew about adhesive properties on alu so thanks for that info
Aluminum is a tricky SOB to weld correctly and should be left to pros for a critical piece
An Alu cradle is possible but IMO the ROI is low (time spent vs weight saved).

Hope that clears things up a bit.
ps billet block are in fact used in top fuel cars and in cars where people have a LOT of money.

God the rust is so bad back east. I live here in reno an went to the local pick u pull an looked at 4 fieros from 85 to 88 an none of them had a spot of rust on the frames, still black paint an oil, only if we could get these cars back east ! it makes me sick to see them get smashed up

Just for reference, the 88 rear cradle by itself is 50 lbs, so even if someone did make one from aluminum, it would likely still be about 35 lbs. So the opportunity to shed weight is about 10-15 lbs. There are a lot easier and less expensive ways to drop 15 lbs from the rear of the Fiero.

Aluminum cradles/subframe are pretty much the norm for GM and many OEs and they use a variety of methods from castings to weldments using extruded and formed pieces. However, very few DIYers know how to or have the capability to weld aluminum, fewer still could do it right (design of component, placements of the welds, and quality welds).

Typical GM midsize (W-body and similar) FWD engine cradle


C5 front suspension subframe:

Didn't mean to open a can of worms, but the cradle on my donor car was pretty light and judging from the severity of the crash and the slight damage it had, aluminum seems like a good idea. If someone started professionally producing them for our Fieros, I would expect that they would build a quality product. I know that limited production products are fabricated from aluminum. Boat trailers come to mind.

Sorry I ranted, was one of those days. This is a very cool discussion. As said its hard to see it being worth it to switch to aluminum just for weight savings but after dealing with all the rust problems with my car i think it might have instances where it could be worth it.

Update on the original post: I decided to switch to the spare parts car's cradle after inspecting it and although it has less paint remaining, it is mostly just surface rust and nothing deep. Also I think I might consider starting my own custom front bushing business. $20 a set, pm me. https://drive.google.com/op...sc3WedYVUsRvKS-HSTzh Who wants to be on if they will crack when I put the car back on the ground?
The car is likely going to be trailered to the scrap yard unless anyone wants to give me $100 for it.

[This message has been edited by BadNewsBrendan (edited 11-18-2018).]