1991 Mazda Miata Restoration! - NEED ADVICE/HELP!

[Redin]

Hello everyone, I'd like to mention this is my first time on this forum so if I posted this in the wrong location my apologies! I posted a video on YouTube because I am in need of some opinions and help! Please see the link below and follow along if you may.
https://www.youtube.com/watch?v=ncmktoDdsMU

0:45 -
So right from the start I've been having an electoral issue where the battery kept dying even though the alternator was giving proper amount of volts with my multimeter. Once I took the dashboard off and seen the amount of aftermarket BS they had I thought to myself this could be the problem (The reason I bought a new harness) Does this sound about right? The aftermarket stuff was spliced into almost every factory wire.

1:50 -
Is the small spot where I've already grinded down good enough to do the next steps, Use rust converter or remover and then paint overtop of it. Does anyone have products that they would recommend for these steps?
(I'm going to regrind the surface rust that has formed before painting)

2:55 -
Is the rust past repair on the inside of the rocker panel? Could I grind down and the strong spots and repair the weak? I am hoping to continue removing any damaged areas that I find.

3:54-
In regards to welding in a new frame rail, should I go with a more thicker metal as the stock metal is known for crumbling? Should I weld the new frame rails in line with the previous frame rails or can I just cap it over the remaining frame rails still having it bud up against the bottom of the new floor pan for spot welds?
*Also side note if anyone can recommend product/steps to painting the underbody, I've seen that people don't like using the rubber spray stuff but I wanted some opinions!

4:40-
The small spot on the exterior rocker panel that the previous owner repaired, is this a worry? Should I grind more out to see in behind or is it safe to just repair the one location?

5:03-
For the pinch weld on the bottom of the rocker, my plan was to hammer it out and make it straight again then add some more metal to strengthen it up for future jacking. Is this a good idea?

5:20 - 7:10-
Is there any spots that people can see that concerns them, something I might've missed? (I do see the leaked fluid on the transmission, I believe it was from the valve cover gasket leak I had that I fixed. I could be wrong though.)

5:50-
Now the scariest part of it all is the rotting frame rail up towards the engine bay, How much of a worry is this and how would I even go about fixing it?

To anyone who can help me with any of my problems I much appreciate it! I've been scratching my head at this car for over a year and I want to hold onto it so I can say I fixed it instead of rolling over and getting a new one. But if it comes down to it and for it just makes the most sense to get a new one so be it.

EDIT: So I've been thinking on what I'm going to do with this thing, Lot's of people say to just get a new one but I think I've came to the conclusion that I am going to keep it for now. Use this as a project to learn welding on and see if I can have some fun learning manual with it. Maybe I can keep it for a year or two before I send it off. With that being said all my questions still stand as I'd like to learn what to do in these situations. I just got in from working on it and was able to grind all the rust in the driver footwell out. also opened up the rockers from both sides to get a better look and it seems to be pretty good inside, a bit of surface rust. I also removed the driver door and the driver side fender, Behind looks quiet good except some surface rust by the rocker. Regrettably I didn't take any photos to share but I think I'm going to be back out there tomorrow morning.

Thank you again!

[Bloo]

Hello from another Miata owner. Mine is a 1990 and is at 330k miles or so. Great cars.

 

I started to type out responses to the timestamps you posted, but as I continued to watch.... Holy ^&$$#. Ive never even seen one that rusty. I hate to be a wet blanket, but.. wow. There are people out in Minnesota who have fixed bodies that bad (and I am envious of their skills), but here in WA you literally could not find another Miata that rusty if you searched for years. I'm thinking you could buy another car on Seattle Craigslist with minimal or no rust, and ship it, for a small fraction of what that is going to cost to fix. Especially if you buy a car with some problem nobody wants to deal with (like an exploded differential, or a bad motor, or minor crash damage). It would undoubtedly have better doors too.

 

If you are gonna fix the car, then yes, replace the wiring harness, It is the easiest way.

 

As for the semi-rusty areas, it is always worse than it looks. Rust converter may slow it down but you cant stop the rust unless you cut it all out and replace. The trouble is, at some point there is nothing holding the car together and you are going to have sag-twist-alignment problems when you try to weld it all back together. An early Miata isn't the stiffest car ever made in the first place. You have already cut out more than I thought you could probably get away with without building some kind of support structure inside the tub.

 

Regarding oil leaks, the most common one is the o-ring on the distributor-like (CAS?) sensor on the back of the head. I have replaced that o-ring countless times,and it is leaking again. If you have not replaced it, you probably still have an oil leak. It isn't a big deal to change.

 

Best of luck whatever you do, and welcome to the forum!

 

[Redin]

3 minutes ago, Bloo said:

Hello from another Miata owner. Mine is a 1990 and is at 330k miles or so. Great cars.

 

I started to type out responses to the timestamps you posted, but as I continued to watch.... Holy ^&$$#. Ive never even seen one that rusty. I hate to be a wet blanket, but.. wow. There are people out in Minnesota who have fixed bodies that bad (and I am envious of their skills), but here in WA you literally could not find another Miata that rusty if you searched for years. I'm thinking you could buy another car on Seattle Craigslist with minimal or no rust, and ship it, for a small fraction of what that is going to cost to fix. Especially if you buy a car with some problem nobody wants to deal with (like an exploded differential, or a bad motor, or minor crash damage). It would undoubtedly have better doors too.

 

If you are gonna fix the car, then yes, replace the wiring harness, It is the easiest way.

 

As for the semi-rusty areas, it is always worse than it looks. Rust converter may slow it down but you cant stop the rust unless you cut it all out and replace. The trouble is, at some point there is nothing holding the car together and you are going to have sag-twist-alignment problems when you try to weld it all back together. An early Miata isn't the stiffest car ever made in the first place. You have already cut out more than I thought you could probably get away with without building some kind of support structure inside the tub.

 

Regarding oil leaks, the most common one is the o-ring on the distributor-like (CAS?) sensor on the back of the head. I have replaced that o-ring countless times,and it is leaking again. If you have not replaced it, you probably still have an oil leak. It isn't a big deal to change.

 

Best of luck whatever you do, and welcome to the forum!

 

Hey! Thanks so much for the response, I'm from Ontario Canada and rusty cars are quite common unfortunately but I think mine takes the cake haha, I think I am going to keep it and just learn off of it. I never even thought about the "sag-twist-alignment problems" How will these effect me and how can I prevent them? I think I'm going to repair whatever rust I can get at and once it creeps bad on me I'll scrap the thing. Thanks for the info on the other subjects. I'll keep those in mind whenever I get around to them haha!

Side note: If you have any products and or steps I should take when I do grind them down to bare metal I'd love to hear them!

 

Thanks

[Redin]

I decided to bite the bullet and go outside to take some photos, Here is what I got done today!

Photo 1 - This is inside the rocker panel

Photo 2 - This is from below the rocker panel

Photo 3 - This is from the outside of the car looking at the rocker panel

Photo 4 - This is the driver side footwell

Photo 5 - I started to grind down the edges

Photo 6 - The rocker panel from the inside

[Bloo]

 

WOW! Looks like it's coming along.

 

 

Edited December 9, 2020 by Bloo (see edit history)

[ojh]

I have restored worse metal and the 1st thing I'd do is get it on a rotisserie and stabilize it.  I pull the dash and windshield out of a roadster and run a substantial brace (1 1/2" square tube 11ga) across it from drivers' side to passenger side (the structure that holds the wondshield is what I'd be bolting the brace to, very stout that), from the brace I run diagonals out to each 'B' pillar door post attaching to the structural members of the top mechanism and record the measurements.  I make the diagonals from 1" round tube with LH & RH 1/2" heims at each end so you can preload them.  That rocker box and transtunnel are the frame, I'd get the doors back on it and adjust the diagonals so the door gaps are correct and tighten the diagonals.  Then I'd load the rotisserie on a rollback and send it to the media blaster to have them strip the car to bare metal so you can see exactly what you're up against.

 

[Redin]

1 hour ago, ojh said:

I have restored worse metal and the 1st thing I'd do is get it on a rotisserie and stabilize it.  I pull the dash and windshield out of a roadster and run a substantial brace (1 1/2" square tube 11ga) across it from drivers' side to passenger side (the structure that holds the wondshield is what I'd be bolting the brace to, very stout that), from the brace I run diagonals out to each 'B' pillar door post attaching to the structural members of the top mechanism and record the measurements.  I make the diagonals from 1" round tube with LH & RH 1/2" heims at each end so you can preload them.  That rocker box and transtunnel are the frame, I'd get the doors back on it and adjust the diagonals so the door gaps are correct and tighten the diagonals.  Then I'd load the rotisserie on a rollback and send it to the media blaster to have them strip the car to bare metal so you can see exactly what you're up against.

 

Thanks for the reply! I'll look into this, Do you think I might've already messed up the diagonals? How would I go about fixing this?

[Redin]

8 hours ago, Bloo said:

 

WOW! Looks like it's coming along.

 

 

Thanks!

[ojh]

22 hours ago, Redin said:

Thanks for the reply! I'll look into this, Do you think I might've already messed up the diagonals? How would I go about fixing this?

I have photo files on another computer, I'll copy them and post them up.  Its easy to check with the door gaps.  On a car with a frame you can be a bit 'off' on body alignment and correct it with shimming.  Not so with your car.  Once I gte them back from media blasting I make a proper frame jig for it and get it off the rotisserie.  Once you have it on the frame jig it'll be secure enough to hammer, beat, pound, cut & grind without the diagonals - they'd be in the way.  Every now and then check the measurements you originally wrote down (I use sharpie and mark them adjacent to measuring points, this might be a 2 year project and don't rely on your memory of where you measured to & from).  You'll be working from the top and when near done you'll get it back on the rotisserie to do the outside of the rockers panels and the underneath, by them it'll be back to rigid and the diagonals be able to easily bolt right back in.

[ojh]

Heres a few pictures, the body stabilized on the rotisserie before media blasting:

After the media blasting, dash area where the lateral bolts to the windshield brackets and diagonals origin:

The rear of the drivers' compartment where they terminate:

Before & after media blasting pics:

[Redin]

3 minutes ago, ojh said:

Heres a few pictures, the body stabilized on the rotisserie before media blasting:

After the media blasting, dash area where the lateral bolts to the windshield brackets and diagonals origin:

The rear of the drivers' compartment where they terminate:

Before & after media blasting pics:

Thanks for the photos! Very interesting!

[Graham Man]

I am also a Miata fan, lots of fun to drive.  For the sane owner, this car is toast but I have repaired worse.  If you want to save it or just have some inexpensive fun... it will never be a perfect car... why not try to save her?   Sheet metal is inexpensive...  a cheap MIG welder is all you need and lots of free time and hard work.  The floor panels are available apparently from Mazda?  I would start with those.  OJH is correct you need to stabilize the car before you go any further, or it will literally fold in half.  Place the car back on the wheels, take lots of measurements to make sure it is still straight, weld or bolt in supports or both.  The drivers side is always worse, they put salt in the center of the road.  

    Practice your welding skills and have fun, the patches should be under $500.  This car is more or less junk at this time, it will make great learning project (hopefully you got it cheap?).   If you win, great!  if not you are out a couple bucks and you get to keep the welder.  Hope you have some fun