Ownership Verified: Miami Weiß - My 1989 Chevrolet Corvette C4

Mitchi

Sierras für alle!
DONOR
Joined
Dec 10, 2012
Messages
5,474
Location
Lüneburg
Car(s)
'89 C4
Looong post ahead!

So over the weekend I spent some time in some parts of the lower mountain ranges of central Germany together with Beni.

Plan was just to do some joyful drives on b-roads, which was absolutely wonderful. Cruising with the targa top down on a sunny day feels quite special in this; I enjoyed that a lot.

First, have a pic dump with my pictures first (excuse the instagramness of them), and then Benis wonderful shots - of course together with the Sierra on the hills around Limburg and the Feldberg:











And yes, Beni is actually quicker in the Sierra than I am in the C4. It's of course all down to knowing the roads... I swear.
















I did nearly 1400 kms this weekend with the C4, quite a lot more than I thought, but it behaved quite good.

We did take the chance and hoisted the car up in Benis workshop together with his brother on saturday. This meant we managed to fix two missing screws, one within the wheelwell on the left front, and one underneath the rear bumper, which meant the left side was always hanging a bit. We couldn't really fix the exhaust though, which is sagging a bit on the left side viewed from the back - it's all really solid, no spare movement to be had, but anyway, it doesn't really bother me that much.



The car is loosing a little oil and used about a third of the dipstick since I bought it (so make that about 1800 kms), which I think for a 31 year old US-american car that probably never had its oil seals changed is actually quite good. The oil down at the engine and the gearbox was somewhat fresh, and could be wiped off easily. I will have them done some time soon.



Also see that small pipe directly next to the exhaust? Sadly I forgot to take a picture from the other side, but it's some sort of breather pipe that goes from the exhaust to the engine. Right now, it's not connected, and we couldn't connect it - at least not without moving the exhaust some 5 cms backwards. Probably not even TÜV-or emissions-relevant. I'll do it one day.

There are a couple of things though that need to be done and investigated:

Cooling - I really need that small GM fan actuator that starts cooling the car down at like 15-20°F earlier than now. Even with my bigger cooling fan from the factory, the car likes to get really quite hot. Also, considering the car doesn't really have any opening at the front, I reckon the front lip (greetings) will to a massive job at cooling the car down better, as it'll shovel the cold air right into the radiator. Definitely need to order that front lip!

Tyres - I ordered four of those Nankangs that have been talked about earlier and will get them mounted this friday. I can't wait to be able to drive over 100 kph again without the steering wheel wobbling like hell - and on the way back during pouring rain, the car was literally undriveable at town speeds. And when I say literally, I do mean literally - I aquaplaned too many times, sometimes at bumpy roads at like 30-40 kph, and I needed to stop twice because I couldn't drive in a safe manner at all. I never experienced something like this in my life. During a construction zone on the Autobahn, I was on the right lane holding everyone up, trying to navigate those damn ruts in the road and once almost lost the front end of the car in the barriers at 65ish kph. Luckily I am here sitting at home writing about this, not having crashed the car about a month after the purchase. It was a difference of a few kph and some 40-50 cm's that kept me off the guard rail. The new Nankangs won't be the best in the rain, I know that - but they're going to be somewhat new and fresh, and I hope I won't experience anything like this ever again.

If at a standstill, the car sometimes comes to a stop at 2 kph quite abrupt - as if the car has some sort of a mechanical hill assist, but one that seems to work pretty much all the time. I didn't even know such a thing exists, but Beni told me his old Subaru had one. I have absolutely no idea if the Corvette has such a thing or something comparable - but thinking about it, it does feel exactly like that. It's definitely something mechanical at the rear, very likely within the differential, that does it. When going off, you can feel and hear it still biting until you have enough power to get going. It pretty much does it all the time, except when the car is cold or at least somewhat cool (which isn't often the case). It is actually pretty handy, as you can just let go of the brakes at a lot of smaller hills. Maybe a change of the differential fluid together with a necessary additive will help this. At first I thought the brakes were dragging, but they're not.

If anyone has an idea if the car came with such a thing, please let me know - the internet tells me absolutely nothing about this, it's either a feature everyone knows but doesn't speak about, or something's not quite right with my drivetrain. It's a 3.33 Dana 44 fwiw.

Speaking of something's not quite right with my drivetrain:
The original clutch and dual-mass flywheel for the C4 has been discontinued since 2007 or 2008. Since then, there's a lot of people going for single-mass flywheel conversions and upgraded clutches due to lack of options. At first, I thought my car might have had this done to it already purely due to the noise of the car, considering single-mass flywheels tend to be noisier than dual-mass flywheels (especially with the black tag ZF6 in my car), but I am not sure anymore. Also, apparently pretty much every single aftermarket clutch kit out there is pretty much the same cheap shit from the same factory in China. Unsure how true this is, but oh well. How can it be that it is so tough to find a proper flywheel and clutch for an old Corvette? You'd think the same ones would be used in some pickup truck, a Camaro or something similar.

Anyway, at first I thought my clutch and flywheel are within the last third of its life, but now it seems like they are not. When the car is cold (or just cool in general), setting of is actually quite smooth (except for that diff brake, or whatever it is). When it's hot and you're doing multiple set offs, it's actually really difficult to set off smooth - and it'll generate a feeling of the clutch slipping a little too much, which might come from trying to overcome that differential brake thingy. So trying it with more revs is just making it worse and hotter, trying it with low revs means the car is unwilling to actually move. Personally, this doesn't feel like the clutch is worn out, but rather more I think something's not quite balanced or grabbing properly - maybe the pressure plate or so. Another indicator (which at first I thought might have been the throw out bearing): At a standstill, the clutch will run a little uneven and irregular and produce slight clonking noises. It really kinda hurts me hearing this and doesn't feel good at all, making me press in the clutch at a standstill all the time (bad idea, I know). It all goes away once the clutch is pressed in. Once again, if the car is cold or cooled down enough, this barely happens.

In general - if you google something like "Corvette C4 clutch chatter", "clonking", or similar, there are tons of threads on Corvette forums, but none really say the things I am experiencing.

So yeah - I will try to have a US car shop close to me to take a look at it, but seems that they're closed off in the current situation. Dang.

Again, I appreciate any further help on this. I will also try to create a video with good sound if possible. I think overall the car really enjoyed being driven that much and having proper heat cycles go through it, but it also generates or shows problems like this more easily. Then again, the car probably hasn't been driven like this since forever or maybe actually never.

And now for the somewhat big one:
While taking the wheels off, there was one lug nut that was really tight - turns out, it has been mounted in a kinda crooked way. Ouch. At least I broke it off myself instead of just weakening the bolt and loosing it somewhere on a road, imagine that ...



Now this meant somehow finding another one - which means hopping in the Astra wagon of his brother and trying to source some on a saturday noon before the shops close. Sadly we were unable to locate any, which means Beni and his brother got really creative and took of a somewhat fitting wheel stud off a Volvo V40 and made it fit for the C4 - MacGyver would be proud. Now, this doesn't mean I want to drive around like this forever, but it's still working! I am in the process of sourcing at least one, if not two new wheel lugs - because as you can see at this picture down below, there's been another one that has been changed once. A massive thanks again to Beni and his brother for this awesome work - it was mostly me watching and failing because I am just not that handy and they knew how to get the job done efficiently.



On a positive note - she may be thicc, she may like a good drincc, but she's not that thirsty if you drive with your pinky toe.
On the way back, I managed to do about 8.3 liters per 100 km on the last 200+ kms as per onboard computer - probably 1-1.5 liters less than it actually were, but still, not bad for an engine from 1953 with apparently shitty fuel injection!



Anyway, that's it for now, I hope you had a little bit of fun reading this!
 
Last edited:

93Flareside

Döner Kebab enthusiast
DONOR
Joined
Jul 20, 2009
Messages
17,771
Location
42 miles outside of Chicago
Car(s)
‘18 VW Golf GTI, '87 Mercury Colony Park


Also see that small pipe directly next to the exhaust? Sadly I forgot to take a picture from the other side, but it's some sort of breather pipe that goes from the exhaust to the engine. Right now, it's not connected, and we couldn't connect it - at least not without moving the exhaust some 5 cms backwards. Probably not even TÜV-or emissions-relevant. I'll do it one day.


Anyway, that's it for now, I hope you had a little bit of fun reading this!
That tube most likely is an air injection tube to blow air into a catalytic converter to lower emissions. In the 80s and early 90s that was a piss poor way to reduce emissions and honestly, is still done on an industrial level today. I've heard it done on natural gas boilers when in cities like LA or San Francisco. Somehow more air to dilute is fine provided that NoX reading is below the limit when exhausted to atmosphere. How it's done, isn't a big deal so I imagine it's the same idea. Is it required? Depends on your emissions laws, if it's Tuev'd now, fuck it.
 

Mitchi

Sierras für alle!
DONOR
Joined
Dec 10, 2012
Messages
5,474
Location
Lüneburg
Car(s)
'89 C4
That tube most likely is an air injection tube to blow air into a catalytic converter to lower emissions. In the 80s and early 90s that was a piss poor way to reduce emissions and honestly, is still done on an industrial level today. I've heard it done on natural gas boilers when in cities like LA or San Francisco. Somehow more air to dilute is fine provided that NoX reading is below the limit when exhausted to atmosphere. How it's done, isn't a big deal so I imagine it's the same idea. Is it required? Depends on your emissions laws, if it's Tuev'd now, fuck it.
Yup, fully agree. If I manage to get it in one day (twss), then so be it, otherwise ... who knows, maybe the car even runs better like this.
 

WDWBen

Subaru Killer
Joined
Nov 5, 2007
Messages
1,344
Location
Disney World
Car(s)
2012 MX-5 PRHT
The noise you describe sounds exactly like when I needed a throwout bearing, so I think your assessment is pretty accurate there.

Upside: cheap part!
Downside: all the labor
Upside: Might as well replace the clutch if it's needed while you've got it all cracked open.
 

Dr_Grip

Made from concentrate
Joined
Jul 8, 2008
Messages
14,189
Location
Germany
Car(s)
1979 Opel Kadett | 1972 Ford Country Sedan
I am surprised at how much room there's around the transmission and bellhousing. This will be easy to take out compared to Lucille (since I got a gigantic x-pipe in the way).
 

Mitchi

Sierras für alle!
DONOR
Joined
Dec 10, 2012
Messages
5,474
Location
Lüneburg
Car(s)
'89 C4
I am surprised at how much room there's around the transmission and bellhousing. This will be easy to take out compared to Lucille (since I got a gigantic x-pipe in the way).
... I take that as an offer that we can do that in your garage with a few beers. :D
 

public

Volvomies, volvomies
Joined
Nov 26, 2007
Messages
11,856
Location
Causticity
Car(s)
P26L XC70 D5 and a ton of crap
Obviously something important was glossed over here.

Volvo V40?!
 

Mitchi

Sierras für alle!
DONOR
Joined
Dec 10, 2012
Messages
5,474
Location
Lüneburg
Car(s)
'89 C4
Volvo V40?!
I have forgotten why, but Beni has a red V40 estate stored, yeah. That's where they took the wheel stud off ... from donor car in back.

Here, have a picture of its arse sticking out of the workshop.

 

93Flareside

Döner Kebab enthusiast
DONOR
Joined
Jul 20, 2009
Messages
17,771
Location
42 miles outside of Chicago
Car(s)
‘18 VW Golf GTI, '87 Mercury Colony Park
I have forgotten why, but Beni has a red V40 estate stored, yeah. That's where they took the wheel stud off ... from donor car in back.

Here, have a picture of its arse sticking out of the workshop.

Weird.... I remember the transit that @nicjasno wants to make into a mobile sauna, but that red building doesn’t look familiar at all. Where is this?
 

gaasc

Desperately looking for a title
Joined
Apr 26, 2008
Messages
8,566
Location
Honduras
Car(s)
3 of them
...bullshit that car will go 840km on a tank :p
 

Mitchi

Sierras für alle!
DONOR
Joined
Dec 10, 2012
Messages
5,474
Location
Lüneburg
Car(s)
'89 C4
Only Nankang has the same strategy as Hankook, which is having all tyres from crappy eco tyres to racing slicks under the same brand, instead of splitting them to different sub brands like most big manufacturers do. That said, I've had couple generations of NS-2s in various cars and they are very much adequate. Compared to mid range sportier tyres turn-in feel is a bit soft and there's a bit of lateral movement under heavier cars, but since I doubt you'll be regularly tracking the thing they work perfectly well, both wet and dry.
So I finally got some new rubber because remember kids, always use a fresh rubber and stay safe.



It's amazing how much of a difference new tyres can make. The ride is sooo much smoother and way more comfortable than with the old tyres, and no steering wheel wobble is to be had. So far, I think the tyres are more than sufficient for the car in the dry, let's see how the wet grip is. I guess it will be fine. The now discontinued Michelin PS2's would've cost four times that much, but how much better are they really (yeah I know, running a classic sports car on a budget yadda yadda)?

Sadly the shop didn't do an alignment because they say the bushings are so bad (which I've seen for myself at Benis workshop) - I think I should get new ones, a full poly bushings kit is quite a lot cheaper than for other cars.
I also fail to find standard bushings for the car online, I guess most people just go for these kind of bushings anyway when replacing worn-out original ones.

And for those wondering how I mounted the numberplate at the front - this is how I've done it:


Full on car poser mode. I didn't want to screw of the number plate cover, as it looks really good. This way I can just always take the numberplate off when I want to feel cool. So far, the numberplate has held on up to like 160 kph - the force of the magnets seems to be much higher than the weight of the plate, which is why this works so good. And I didn't even buy super strong magnets as originally planned as I couldn't find that many online. But of course if the wind is strong enough, it might be possible that it grabs underneath it and pushes it into the air. Luckily I don't feel the need to speed on the Autobahn in this car. One disadvantage: Apparently the magnets tend to oxidize rather quickly... dang.

Cue me posting that I've lost my front numberplate or had it stolen in a few weeks. :D



Also see that small pipe directly next to the exhaust? Sadly I forgot to take a picture from the other side, but it's some sort of breather pipe that goes from the exhaust to the engine. Right now, it's not connected, and we couldn't connect it - at least not without moving the exhaust some 5 cms backwards. Probably not even TÜV-or emissions-relevant. I'll do it one day.
Another thing: The disc of the A.I.R. pump is slightly wobbing around, and making some squeaking noises, but not actually moveable by bare hand once the engine is stopped. Nothing to worry about really, it's also not getting worse, and it's not like I would need this emissions stuff to pass TÜV nowadays (there are even delete kits available).





See those small tubes next to the cylinder heads that are blocked off? I fail to understand if this is factory (surely it can't be?), or if it has been blocked off, like some people do when deleting the A.I.R. pump and the EGR (something I might look into one day, too).





I think deleting the EGR is only a good idea once I get into the ECU - have a quote from a corvette forum post:

"If you don't have the vacuum solinoid this could be a problem, there not made anymore although I have seen on here that some others will work.If you delete the EGR you can get a (86-89 TPI Corvette Chip Custom Prom Programming) .. this is what its called and it lets you delete ,egr, air pump and many other things on your engine, You can even change the temperatures that your fans come on. They can set it up anyway that you want.If you go to ebay and do a search under this product name or find the ebay site for (TPI_parts )you will see it on there..This cost $65.00 and is much cheaper than sending in your prom to be reprogramed and from what I hear from other people this works very well...sorry I can't give you the direct link but its not allowed on here...WW
Here is a list of changes you can make and things they can correct for.

VATS Enable/Disable
EGR Enable/Disable
AIR (smog pump) Enable/Disable
Injector Size Specify Size
Fan On/Off Temperatures Specify Desired Temperatures
Speed Limiter Specify Desired Speed
RPM Limiter Specify Desired RPM
Cold Start Injector Enable/Disable"


Speaking of something's not quite right with my drivetrain:
The original clutch and dual-mass flywheel for the C4 has been discontinued since 2007 or 2008. Since then, there's a lot of people going for single-mass flywheel conversions and upgraded clutches due to lack of options. At first, I thought my car might have had this done to it already purely due to the noise of the car, considering single-mass flywheels tend to be noisier than dual-mass flywheels (especially with the black tag ZF6 in my car), but I am not sure anymore. Also, apparently pretty much every single aftermarket clutch kit out there is pretty much the same cheap shit from the same factory in China. Unsure how true this is, but oh well. How can it be that it is so tough to find a proper flywheel and clutch for an old Corvette? You'd think the same ones would be used in some pickup truck, a Camaro or something similar.

Anyway, at first I thought my clutch and flywheel are within the last third of its life, but now it seems like they are not. When the car is cold (or just cool in general), setting of is actually quite smooth (except for that diff brake, or whatever it is). When it's hot and you're doing multiple set offs, it's actually really difficult to set off smooth - and it'll generate a feeling of the clutch slipping a little too much, which might come from trying to overcome that differential brake thingy. So trying it with more revs is just making it worse and hotter, trying it with low revs means the car is unwilling to actually move. Personally, this doesn't feel like the clutch is worn out, but rather more I think something's not quite balanced or grabbing properly - maybe the pressure plate or so. Another indicator (which at first I thought might have been the throw out bearing): At a standstill, the clutch will run a little uneven and irregular and produce slight clonking noises. It really kinda hurts me hearing this and doesn't feel good at all, making me press in the clutch at a standstill all the time (bad idea, I know). It all goes away once the clutch is pressed in. Once again, if the car is cold or cooled down enough, this barely happens.

In general - if you google something like "Corvette C4 clutch chatter", "clonking", or similar, there are tons of threads on Corvette forums, but none really say the things I am experiencing.

So yeah - I will try to have a US car shop close to me to take a look at it, but seems that they're closed off in the current situation. Dang.

Again, I appreciate any further help on this. I will also try to create a video with good sound if possible. I think overall the car really enjoyed being driven that much and having proper heat cycles go through it, but it also generates or shows problems like this more easily. Then again, the car probably hasn't been driven like this since forever or maybe actually never.
I want to change all the fluids in the car soon - which means also the differential fluid together with the much-needed GM Positraction Additive.

"Specifically formulated by General Motors to stop annoying positraction clutch chattering and clunking associated with limited slip differentials. Add one 4oz bottle per Corvette. Use in combination with GM/Delco axle lubricant."

While I am still unsure about his manual hill-holding-assist, I haven't really noticed anything weird with the clutch and the differential recently. Over this week the car has been really quiet and felt much better than on the weekend. I think the car might have just gotten a little too hot and I think the drivetrain really dislikes that. Once the car is warmed up properly the differential does hold me at a hill, but it doesn't really make any chatter once setting off (dito for the clutch), hence my assumption about overheating.
I think in general the car doesn't like a lot of start and stop, which is what the car has done a lot of a weekend ago.

I think a differential fluid change will pretty much eliminate every weird feeling about this. I can imagine the current (probably 31-year-old fluid!) being in completely the wrong state of viscosity and the differential clutch discs biting incorrectly.

Also, I definitely need to source the front lip (greetings) that my car seems to be missing. I thought it was only for aerodynamical stability - turns out, it aids with cooling aswell (and with the Z51 handling package, might even be a little different than the stock three part lip).

On another note - I've ordered the front lip. Apparently there are different sizes for cars with and without Z51 performance package, so mine would have been 4,25" instead of 3,5" (or thereabouts) from the factory anyway. Can't wait to install this and see how much of a difference it makes.
 
Top