1989 C4 Functional Restoration

[SirReal63]

I am interested in duplicating my CorvetteForum build thread on this old car, as a backup in case something happens and I lose over a years worth of work there. I have done several build threads over the past couple of decades, all but two have gone away with the forum going away. This place is stable and unlikely to go away and I seem to spend as much time here as anywhere else.

If there is any interest in seeing my obsessive disorder on restoration in the cheapest way possible, I will dupe it here if I can figure out an easy way to copy it without messing it up.

 

[Big Mama]

There are lots of Vette enthusiasts here. Copy and paste my man. If it’s not acting right on your phone do it on your computer.

 

[SirReal63]

Thanks, it isn't a phone problem, but a BBS software issue, I use my PC, I have a phone, I look at it at least once a day.

This will be a functional restoration, not a Concourse restoration. I will refurbish what I can rescue instead of just buying new or re-pop. The value of these cars just does not warrant a full on restoration.

I have been wanting a C4 since 1983, it didn't happen since there wasn't an 83.

When I saw my first 84 I wasn't exactly "in love", more like eh, technological advancement I can do without, that changed with the L98 which I was truly impressed with. I got my first real job in 1976 doing whatever my mechanic boss wanted, usually that meant under a car doing what his fat old body didn't want to do.

I had just turned 13 and was actually hired to clean dead alternators and starters and rebuild them, which was my boss's real business. The time I spent there was educational, though my family had been drag racing since the early 60's my Dad wasn't much of a teacher and the mechanic that hired me was a good friend of my Dad's. I learned a lot, in fact I can count on one hand the number of times I have hired someone to work on my vehicles. I am not a mechanic, my career was as far from that line of work as imaginable, but I still enjoy turning wrenches when have time. I have restored many vehicles over the years, never show quality but good driver quality. This brings me to the C4, a car I have wanted for a long time but never bought for some reason. Having just sold my restored 1994 F350 4wd CCLB IDI Turbo 5-speed I needed something to keep my hands busy. (Not really, my wife and I are retired and have a small hobby farm with the 3500 sq ft 2 story Barndo I built with my own hands, I stay plenty busy.) Time to find another project.

I have been searching for a C4 for over a year now, I had decided on a 91 with a 6 speed. Turns out that is a hard find, it seems a lot of people want the L98 with the updated interior and exterior, not just me. I found several but the condition was not good or the price objectionable. I found one here in Texas but the transmission was a huge question mark, I did not want to be dealing with needing a rebuilt ZF right off the bat. The rest of the car was in decent shape but owned by a kid and I avoid buying kid owned vehicles, I was a kid once, I know what I did.

The next possible option was an 89 or 90 but it was mostly the same story, too expensive or in too bad of shape. I was trying to talk myself into flying to Vegas for a beautiful 89 six speed car that had a lot of performance goodies on it but driving back 1300 miles with an untested car was asking a lot, and the car owner agreed, he and my wife eventually talked me out of it. I kept looking and one turned up 30 minutes from the farm, a, 89 six speed convertible. I wasn't looking for a convertible but I also wasn't not looking for one. The price was the same as the one in Vegas but the condition a little worse. I did the math, a flight from Austin to Vegas, gas, hotels, tolls and the huge question of if the car would make it made the decision. It was vastly cheaper to get the one I could drive home and put that extra money into the car, both needed interior work and paint work. Turns out the vert was a good buy, mostly. The engine is strong and the tranny shifts right, just a little sloppy. I should not have to pull this engine, a huge plus.

Here is what I started with...

 

[SirReal63]

The good, and there is some good. One of the 6 previous owners loved and cared for this car, perhaps more than one, but at least one. When I started working on the convertible top, which is original including the rear vinyl window falling out of it, I noticed a huge sub woofer box and 6x9's taking a lot of space. Somewhere in the late 90's a really nice and expensive stereo system was installed. There was a Kenwood KDC-PS7009 head unit, a Rockford Fosgate Punch 360.6 and Boston Acoustics drivers, front and rear. This was excellent equipment at the time and everything worked except the head unit. I removed the huge box, all the wiring started over. The top just barely fit so the box and sub needed to go. I moved the amp to the rear wall, the 6x9's to the cubby holes after removing the Bose pieces that were still there. Looks much better, and neater with actual room to put the top and/or the usual small overnight bag.

The amp was kind of a big deal in the day, it had configurable crossovers that could be adjusted with changing the resisters on the X-Cards. Low tech today but not when it was made.

I did not clean the carpet, it will get replaced with "something" before long.

 

[SirReal63]

The car itself is nothing special, no special handling packages but it does have tire pressure monitoring that does not work. It is a late year model build, with a few nice features. I really wanted a better rear axle ratio, but the 3:33's will be just fine.

 

[SirReal63]

The paint is great from 75' away but closer and you start to see the flaws. At some point it was repainted...mostly. The hood and rear of the car had been repainted but somehow the doors were not. How does that even happen? I do not understand the decision to not paint the doors, but they were not painted. The paint job were it was repainted was not very good work. There are bubbles, cracks, orange peel and a few whiskey scrapes and bumps. These will need to be fixed and I have never done auto paint in my life. I have corrected paint, but never applied it. I may have to attempt it.

Some of the worst areas...

I have a decent compressor, drier, gun and sanders, polishers and buffers. There are some fantastic videos from Paint Society that make this look doable for someone with limited experience.

 

[SirReal63]

The convertible top was a bargaining chip I used to my advantage. I got the price significantly lower because the rear "glass" was coming out and it was raining when I picked up the car. I researched how to repair the vinyl window and clean the horrid haze off of it. I ended up going with Weldwood Contact Cement after failing with 3M VHB double sided tape and adhesion promoter. The double sided tape failed because the cloth portion was disintegrating, nothing sticks to powder but the powder does come off and stick to the tape rendering it useless. The contact cement allowed adhesion by soaking in to the cloth fiber that was still intact. This method worked beautifully while it was cool outside but one day in the sun and it began to let loose in some areas.

It was always my intention to replace the top, I just wanted to buy some time as there are so many areas that need attention. I could leave the car in the "shop" though it was full of our farming related items, numerous 3-point implements, cement mixer, table saw, welder and accessories, the 97 Suzuki Carry that needs clutch work etc. etc. It took me a week to clean out and organize the shop enough to get the C4 in there and have room to work on it. Many items went outside until I can ***** a shelter for them. I have never done a convertible top before so I researched that.

I am a frugal man at heart, I built our house instead of writing a check, I fix our vehicles when they need it instead of writing a check. We rarely hire anyone to help with the farm chores and infrastructure construction, well, at least until I had my heart attack, now some of that gets "farmed" out to a high school kid. When it came to the top I knew I would be doing it myself, without a clue of how. I hated the thought of putting a vinyl window and top back into this car but learned a glass window version from a newer model could be made to work, they even made a kit for it. Off shopping I went, the kit, no longer available, the actual cloth top much more expensive than the vinyl one and there is very limited C4 specific instructions and tips on doing this job. While browsing FB ScammerPlace for vehicles in the past I knew there was a Corvette specific wrecking yard a couple hours away from me. He actually had a 91 vert on his lot he was parting out. I asked him about the top and it's real condition, but it was about the same as what I had. He did however have a black top off a 95 that was in good physical condition but dirty and faded with the frame still attached. The price was right, more than right. I fired off an email to Mirrock to see if this was as easy as it appeared, they assured me it was a direct bolt on. Now we have a plan, remove the entire frame and top from an 89 and replace it with the entire frame and top from a 95.

The problem...

The solution...as it was before I got it home, really dirty.

I ended up with it for less than asking price which was about a third of the price of just the canvas cloth top. I cleaned this top like a piece of cloth that was dirty, Woolite, OxyClean and a horse brush. I managed to get all of the dirt out of it but it was still faded and stained. I have ordered some Renovo Reviver and Ultraproofer to make it black again. I am keeping my fingers crossed it works. If it does work, then I have the glass window I want, on a frame designed to work with it and mostly my labor as an expense. I went ahead and ordered weatherstrip from Top Flight for the top and Corvette Rubber Latex for the A-pillar. The weatherstrip was bad, on the car and both top.

An interesting thing to me...the top from the 89 appears to be original. The correct screws, placement and length of screws, correct adhesive and the hinges only show one set of witness marks. I don't believe it has ever been replaced. The 95 top by contrast has a mix of hardware, some even correct but most not, 4 different adhesives and the actual fabric is still firm and not worn and looks to have been replaced. I swapped the headliner out of the 89 into the 95 as it was in near perfect condition and the 95 one was tattered.

I do not mind the color change to black, I think it looks better than the Saddle top.

 

[SirReal63]

It took me a week to clean off the old glue, weatherstrip adhesive, contact cement and silicone off the 95 weatherstrip channels. It is done as of today and weatherstrip gets delivered next week. I rust converted the screws and painted them, where the screw holes were wallowed out too big for screws I used black pop rivets, though they will never be seen. I used as much of the correct hardware from the 89 as would fit though many of them had to go back with the incorrect screws I took out.

The agenda for when the top is finished is to figure out a speedometer and hope it is the charred wiring in the console and not the discontinued parts like VSS and plastic gears. I know I will be calling for help when that time comes as though I can handle mechanical things, electrical is not as easy for me. I did get a new shop manual and it will be immeasurably helpful once I learn the layout of it. It does not seem very intuitive at first but I will learn to use it.

 

[SirReal63]

The replacement top is on! Putting it back in the car was about as easy as it gets. I had read it was a difficult task but I found it easy. The weatherstrip were not so easy, they were actually difficult. The rear bow went on like a dream which gave me a false sense of hope when it came to the other 6 pieces. I glued in the rear bow after a test fit and it popped right into place. I did not glue all of the side pieces, I did the risers for the window because they slipped right into place. The two top side did not want to be pushed into place doing the test fit. I wasn't sure I would be able to get them in the channel properly with the adhesive on them. I did manage to force them into place with no adhesive to hold them in, but I do not believe the adhesive would make any difference, these 4 pieces cannot fall out, I am not sure I can take them out without destroying them. The A-Pillar weatherstrip came in today but I am going to wait a little while before putting it on.

The 95 top appears to have shrunk a lot since it was removed from the car it was originally on. I am sure my washing it and letting it dry while not stretched out on a car helped with shrinkage. It took a lot of pulling, tugging and cussing to get the rear pushed down and the top fastened. The hinge plates have a good amount of adjustment so I loosened them up and managed to get the top in place.

I need to find instructions for adjusting the convertible top, and hoping I can find some.

My car is equipped with the proper dash switch and wiring for the rear defroster/side mirrors defrosters but there is an additional harness that I do not have. If anyone knows what it looks like or can snap a pic of theirs, I would appreciate it.

The Renovo should be here this weekend and I will get the top dyed next week. It is actually in good condition, but I cannot get the stains out. I was trying to figure out how to get the canvas to stretch when I remembered we have a really nice Euro-Pro steamer. I steamed the top, in hopes of lightening the stains and loosening the drum tight canvas. It didn't really work on the stains but it appears it did loosen up the canvas.

From 10 feet away you cannot see the stains but the camera really picks them up. It is still wet in these pics and looks worse than it really is...

After drying from several feet away...needs to be dyed.

 

[SirReal63]

I had a perfect day to dye the roof, it rained this morning to settle the dust and then the sun came out and warmed everything right up. I ordered a liter of the Renovo Restorer, thinking I would need all of it, perhaps I will need a second treatment but i only used about a third of the container for the first coat. The first coat really soaked in so if I need subsequent coats it should not take as much.

Getting everything masked off, probably overkill but easy enough to do so why not.

This stuff is amazing...

I will check back when it is dry and determine if a second coat in needed.

 

[SirReal63]

I believed I mentioned I was frugal/cheap/whatever.

When I bought the car the center caps were not on it. I found the center cap bolts, well, I found 3 of them and no wrench. These are unique to the 88 and 89 I believe and the 4 bolts and wrench are available for $129.00 Yeah, no way I am paying that for 4 cap screws in stainless and a wrench that may get lost again some day. I pulled out my tap and die master set and found the thread pitch, diameter and length and ordered 10-M10x35mm 304 stainless socket head cap screws for $10.00 and I have plenty of orphaned hex keys. Problem solved. The 0-rings on the center caps were either missing or disintegrating, I used my caliper to measure the groove and ordered 10-150mm OD, 143mm, 3.5mm thick Nitrile O-rings for $7.99 which gives me 6 extra cap screws and 6 extra O-rings, sounds like a plan to me. I ran a tap through the screw hole because they were filled with debris and dirt. The new cap screws fit like a glove.

Out with old and missing...

In with new new and functional...

I am not really worried about someone stealing my wheels, they are old and ugly. I am also not worried because we are remote enough and in a relatively crime free area. We only lock our doors if we are going away overnight but we have a farm, we don't usually have the luxury of overnight trips. If someone should try and they get past the dogs, the security cameras will pick them up and the insurance money will get me some new wheels.

I will polish out the stamped writing on the cap screws when I refinish the wheels.

 

[SirReal63]

It is going to take another coat or two in some places, mainly where the stains are the worst...the flash really brings it out, it isn't as bad with eyeballs.

 

[SirReal63]

That is about as good as I can get it for now. It isn't perfect and has a sheen to it. Perhaps a little time in the sun will help, or at least show me it needs another coat.

 

[SirReal63]

I decided to tackle the front weather strip over the windshield. I had a feeling this one was going to be difficult, and it was. The outer layer looked mostly intact, supple and did not leak. The ends where it goes down the door frame from the windshield was the worst looking part, obviously flaking and brittle so I had ordered a latex replacement.

Yes, it was really bad once I got into taking it off.

I found yellow w/s adhesive, black w/s adhesive, silicone caulk and what looks like Gorilla glue holding it down. It was slightly frustrating taking it off. I have used the 3M adhesive remover in the past and wasn't really impressed with it for removing adhesive residue and had zero faith it would soften the mess I was dealing with. The top strip was the worst, I ended up with a small wire wheel on a drill to get the bulk of the concrete hard adhesive off. I hated doing it as I meant I would need to repaint that part but after closer examination it needed to be repainted anyway.. Once I had the bulk off I decided to try brake cleaner soaked paper towels. Surprisingly, that worked really well, I just had to keep the paper towels moist for about half an hour and it softened it up enough to scrape/brush/pull/roll it off.

The brake cleaner had a nice reaction with the latex remains and the adhesive remains. I got about 90% of it off and out of the grooves with this method. It took exactly one can of brake clean to do the job.

The final results. It only needs a little touchup with the plastic scraper to get it ready for the new w/s

 

[SirReal63]

It has been a busy few days. The front windshield weatherstrip is done, my local hardware store was out of flat black and so was I. I can/will paint the windshield trim at a later date, the way the weatherstrip fits I can still do it without getting pint all over it. The w/s slid into place like it should.

I decided to work on the interior as I need to go over the wiring in the burn zone and the interior will be in the way of that. Most of it came out with absolute ease. It was surprisingly clean for the age and the jute was even in great shape, which was a surprise on a convertible as they have more of a tendency to leak, but this one appears to not have a massive leak. I vacuumed the carpet prior to removing it but have not cleaned the floorpan in these pics, not a bad amount of dirt/debris for 34 years.

We will get to that ugly duct tape in a little bit, as well as the Bubba surprise under it.

 

[SirReal63]

I have been guilty of not doing things as well as they can be done in the past/present/future, sometimes we make poor decisions to get things done and onto something else. I am the 7th owner of this car so really not a lot will surprise me but I have to admit surprise with this one. I knew there was duct tape in the center console and assumed it was related to the burn spot. The cupholder door did not open all of the way as the duct tape blocked it from having a full range of motion.

I started peeling back the layers...

Under the duct tape was a foil covered butyl rubber sheet very much like Boom Mat that had been cut into strips and molded in place of and on top of the rubber shifter boot. This butyl is very similar to mass loading you would use to stop panel vibration or sound deadening. This was the stickiest stuff I have tried to remove in a long time. I probably would have gone a different direction on that repair but other than the cupholder lid not working correctly, it did the job. The shifter knob is hacked up pretty bad, I may have to find another shifter mechanism or try to make this one right again.

 

[SirReal63]

Finding this was a real bummer, trying to source parts now.

Missing shifter guides and shims which explains the side to side slop in the shifter. If I cannot find the correct ones I will have to machine them out of Delrin. I have a new boot on the way so after I get the shifter issues worked out I will be able to seal it up.

 

[SirReal63]

It has been a busy few days here.

I began working on the tranny tunnel burn zone. It was way worse than I expected. After getting the interior completely out, the areas that were black were also very fragile, like you could push your finger through them fragile. I mixed up the last of my clear penetrating epoxy and went to work saturating all of the dark areas that had got hot and crispy. This worked great at stabilizing the fragile pieces and making them strong enough to glass. Unfortunately I could not get to the backside of the area, to massage it back into the proper shape, I would have to remove a lot of things to get to the area and I wasn't ready to drop any of that yet.

This is the area in question, the hole was the least of my concerns as it was the easiest to patch.

I have played with fiberglass off and on for over 40 years and this was the ugliest repair I have ever done, it is shameful and embarrassing but I admit to the bad right along with the good.

One layer of biaxial glass and two layers of .75 oz chop gave me the structure back and I tried pulling the collapsed areas back in from the only side I could get to but it didn't really work as intended so I mixed up a batch of thickened epoxy to try and smooth out the uneven areas and after curing I sanded a little to get the highest bumps out. I got concerned about weakening the area with aggressive sanding and chose to leave it ugly and strong instead of smooth and potentially weakened. I can only imagine what the backside of this looks like. Not pretty but I can pound on it with my fist and it is strong, just embarrassingly ugly. It was cold enough in the shop that the epoxy had a hard time kicking, even with a heater blowing directly on it everything wanted to sag which made additional layers of glass an issue that wasn't needed for strength.

Next I moved on to the floorboard cracks. They were not as bad as I expected, the upper seam and L Channel was intact but the junction of the floorboard to the beam was cracked. A little grinding, sanding chopstrand and bonding later and it was repaired on both sides. I used aluminum duct tape along the bottom to keep the epoxy from running put which allowed it to soak in nicely and will get cleaned up at a later date. A little thickened epoxy and formed fillet and the area was repaired. was still fighting the weather and over 24 hour setup times with the epoxy which made all of this way more fun than it needed to be. Absolutely ugly but also not visible so only my pride is injured as there is zero need in grinding and fairing here.

I covered the repair and the rest of the floor pan that was corroded in topside paint for added protection.

I absolutely could have spent a week of grinding and glassing to make this look near perfect but I did not see the point. I will live with the guilt of these pics for the rest of my life but no one will fall through and water will not get in from the bottom. lol

 

[SirReal63]

The shifter was my next problem. The guide bushings were long gone and the shifts were sloppy, well, actually the 3-4 and 4-5 shifts were sloppy, the 1-2, 3-4 and 5-6 shifts were ok, just moving the gate side to side was really sloppy. After discovering the missing bushings it was obvious why.

These bushings are not available, I looked everywhere and I am usually pretty good at finding obscure things. I did find bushings for other ZF transmissions and the design is very close on them. You can still get the bushings for Ford's ZF trannys used in light and medium duty trucks so I reached out to a seller of these bushings for some measurements in hopes they would either work or could be modified to work.

The S6-650 bushings are the same design but with a crucial difference, the hole size for the pin that fits in them. The S6-650 uses an approx. 10.2mm hole and the S6-40 uses an approx. 11.95 hole. I had hoped I could bore it out to the correct size but that doesn't work, there are little voids around the hole that weaken it if bored out.

I had on hand some 3/4" Delrin rod which fits perfectly in the channel the bushing fits in. I decided to bore out the rod to press fit the pins, but the alignment would be slightly off, based on the dimensions from the S6-650 bushing. I drilled the hole off center to get the pis as close to the correct position as I could. I undersized the hole and had to use a c-clamp to press the pins on in hopes it won't rotate with time. I cut the S6 bushings to fill in the top of the rod and melted some Delrin shavings to fill in the void. Melting Delrin or any UHMW plastic isn't as easy as it sounds, it does melt right before it ignites, so it it was a challenge to get it melted and capped before it cooled. I did manage it with many attempts. The repair should be good and hopefully it lasts. If it does not last I can get a sheet of Delrin and mill it to the correct shape but I used what I had on hand. The shifts are now precise and the slop removed.

This is not a perfect repair, but it is acceptable and massively better than what it was before.

 

[SirReal63]

Time to start getting the interior back in this poor old car.

I bought 36 sq ft of Kilmat to mass load the drum like panels on the car. I know this car will never approach the level of quietness that our other vehicles have, and being a convertible makes it even worse. The best I can hope for is help reduce road noise a little and add some insulation to help as well.

It is not necessary to cover every square inch of surface but the more the better.

36 sq ft went farther than I expected.

Next comes insulation...