C4 Corvette Front Suspension Description and Tear Down

Time for some tear down work on an early C4 Corvette front suspension. In this video I give a brief description of the C4 aluminum front suspension and detail the individual major components as I disassemble it.
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Thanks for watching👍

[@24theMoney]

If it wasn't for KZbin and this channel, how would anyone ever see something like this? Thumbs up.

[@VetteSource]

Thanks, buddy. Appreciate the positive feedback👍.

[@CREEKSuff]

Thanks for these videos! I have been restoring a 1986 Vette for about 2 years. Bought a wrecked 1987 vette as a donor car (I mainly needed the engine & wire harnesses). I've pulled a lot of parts off the 87 which paid for quite a bit of the restoration but am left to mostly the chassis of the 87 to dismantle and need to work on getting the rest of it stripped down...so thanks for your videos. They have helped A LOT.

[@VetteSource]

No problem, glad I could be of assistance👍

[@TheJimmyCarterFamily]

Do you have the gas tank door or or one that would fit my 86 I also need the hinge

[@fidelarroyo2182]

Thanks much will be installing to 1940 Mercury

[@VetteSource]

Cool, glad to help👍.

[@Max-kk1wf]

Very interesting video as always. I recently got a c4. It would be awesome for me if you did a "get your c4 ready for the season" videos kind of thing. Lubing suspension, what fluids to check/replace, recommended products etc. I live in scandinavia so i keep my c4 tucked away all winter.

[@VetteSource]

Max, glad to hear you enjoyed it. That's an excellent idea, and one that I can explore further as I get the Compettion Yellow LT4 ready for a 2400 mile road trip. If you haven't seen me talk about this car before, here's a link to the playlist kzbin.info/aero/PLAM-V1w3acpiMjpJE5Z26MGUSFdcXdwHh

[@tomallen6073]

Learning a lot of shit fast. Awesome.

[@VetteSource]

Great, glad you enjoyed it👍

[@ronwong7030]

Have a 90 C4. Enjoyed your video. Looks like you are using a 1/2 to 3/8 adapter on your 1/2” drive impact. Suggestion: Next time your are at Home Depot, check out the Milwaukee 2554 impact wrench. It is 3/8 drive and a lot smaller and lighter than the 1/2 drive you are using.

[@VetteSource]

Ron, thanks for the feedback and suggestion. I will check out the 3/8 impact next time I am there. I do like the versatility of the Milwaukee electric tools.

[@justmax36]

Pretty thorough video but i have to say, imo, its so much easier to disassemble before you separate the whole front end assembly from the rest of the frame. i just finished doing this to my 89. all bushings, top and bottom, ball joints stabilizer bar, everything. when you start from the wheels and work inward its not like wrestling an alligator on the ground with the whole assembly loose. just sayin

[@VetteSource]

It all matters on whether or not you're disassembling the entire vehicle. In this case when its being torn down for parts it much easier to keep it complete with the engine and transmission attached at the front crossmember. Most times anyway, the front suspensions are sold to hot rodders and people modifying their car to accept the Corvette front suspension, so it is usually kept together to make it easier for freight shipping, and to ensure the required fasteners aren't misplaced. I only dismantled this one in this manner to illustrate how the tear down is performed and the location of all the hidden fasteners. Thanks for watching👍.

[@jardog16981]

Knowing what you know, do you have a preference between the 84-87 suspension design vs the 88+ design? I've heard many things back and forth defending each about which design actually handles and works better for autocross and track work.

[@VetteSource]

That's a good question and one that gets asked quite often. First thing is that 84-96 Corvette suspensions are all very similar in design and construction, save for some running changes made over the years to accommodate the change to 17" factory wheels, different engine mounts, and the addition of larger brakes. The earlier narrow track 84-87's have very stiff spring rates(especially 84 Z51's) but smaller brake calipers/rotors. The 88-96 wide track suspensions have bigger brakes(13" J55's on 95-96), but softer spring rates. Personally, I like the narrow track 84-87 for autocross and track work due to the very high spring rate that makes it feel like a high powered go kart. However, the 88-96's with the wide track make great open road cars for extended driving, and won't rattle the fillings out of your teeth. I tell people that the decision should rest with the desired use of the car, but boy those 84 Z51 4 speeds sure are fun to drive...

[@jardog16981]

@@VetteSource I personally bought an 85 4+3 Z51 car a few years ago. When I got it, the car was very original even down to the stock exhaust and had 68,000 miles on it. It had been repainted once and the paint isn't in very good shape with some bubbles coming up on the hood in certain spots and it also only had 1000 miles put on it during the 10 years before I got it, so I got it super cheap to be a fun project. The pros of the car were that every power accessory, mechanical component, and electronic component on the car was still in working order. I'm talking about the overdrive shifting perfectly, the dash was working flawlessly with every bulb lighting up, the headlights work, the power seat works in all directions, the power mirrors move in all directions, the heated mirrors still heat up and rear defroster, power antenna and Bose radio are working flawlessly. So although it needed some work and the paint was not perfect, I took a chance and got a really good price on it. So far I've went though and changed all of the fluids, put new calipers and braided stainless brake hoses on it with ebc yellowstuff pads, full tune up with plugs, wires, cap and rotor, module, flowmaster cat back, throttle body coolant bypass, stripped and painted the valve covers, and I've been chasing fluid leaks and bad hoses. I went through and changed all of the intake gaskets down to the base, valve cover gaskets, all of the cooling hoses on the car, and I'm about to do oil pan, rear main, and timing cover gaskets/seals. Also had to put a clutch in it about 1000 miles after I started driving it. Front y pipe rusted from the inside out and started leaking so I replaced that over this past summer. Had the oil pressure switch on the back of the block fail while I was driving and make a mess, so I had to degrease everything underneath and replace that. Lucky I didn't have a fire with that one! I also got it aligned at a local Corvette specialty shop near me which made a huge difference with how it drives. I also sent the original injectors out to be cleaned and serviced. I've done so much to it now that I'm sure I'm forgetting some things. I'm very particular about how I want my car to drive, which is why I've tried to catch up with all the neglected maintenance items from previous owners and be proactive with other things. One problem that I've been chasing so far and haven't figured out what's going on yet is an issue with spark plugs fouling only on cylinders 2 and 4. They'll oil foul every 2-3,000 miles. So far, I've been just replacing those two plugs every 1,000 miles or so to prevent running into any more misfires since the first time they fouled out on me. The car runs so well up to the point when a misfire starts, it doesn't make any sense. It seems to pull strong and have good power. I ran a compression test on all cylinders and got between 170 psi and 174 psi in each, which seems to be right on the money for a, at the time of the compression test, 75,000 mile L98. I also did a leak down test, testing at 100 psi on the input, and all cylinders tested cold between 88 and 94 psi, which seemed really good to me? At first I thought it could be a leaky intake base gasket, because there was a coolant leak on the top of the intake between cylinders 2 and 4, but replacing all of the gaskets didn't make an ounce of difference. Then I went though and replaced all of the valve seals, which also didn't make an ounce of difference. I then switched to mobil 1 15w-50 oil just to see what effect that has, and it did decrease the oil consumption a little bit. It's such an odd problem to me and I was wondering if you've heard about this before on any other 85 cars. Its so weird to me that an engine with such good compression and what I'm assuming to be good valve guides with new seals would burn that much oil to foul the plugs so quick on only two cylinders. The plugs on the other 6 cylinders look completely clean and normal. Have you heard of this happening before on other 85 L98's? I ran this by the owner of the Corvette specialty shop nearby me who did my alignment and he said he's heard of the 85's having a really weird problem with their piston rings aligning in a way that the end gaps get stuck in a line and causes the oil consumption to happen. I don't really buy that theory though. My next course of action before eventually tearing into the bottom end would be to try a special oil that I've heard about in the diesel world. Cummins makes an oil designed to eat carbon away to clean piston ring lands that get stuck from carbon build up in their isx 15 engines. It's a special oil available only from cummins dealers and costs $70 a gallon, but seems worth a try compared to a rebuild, assuming that gunked up and stuck rings are my issue. I was just wondering what you think of the issue I'm having, have you heard about this being a problem with 85's before, and do you have any other suggestions for trying to fix it?? I know that they switched to the cast pistons in 86 and the 84's/5's got the leftover TRW forged pistons. I've driven it pretty often still during the first two years and it's up to 81,000 now. Very stiff ride for the street, but I've been fixing it up little by little getting it ready to eventually do some autocross with it. It's been a blast to drive though so far even with the issues I've ran into! Sorry for the long follow-up but I'm hoping you might be able to shed a little bit of light on the fouling issue.

[@VetteSource]

Very cool, 85's are my favorite early C4 hands down with alot of cool features the later cars don't have. Thanks for the through writeup, that is helpful. It sounds like you may be battling a lower end or head gasket problem with cylinders 2 and 4. Regardless of how well the car was kept, age is now becoming a factor and some of the soft mechanical pieces will start showing failure after 35 years. I would try the special oil you were referring to, but wouldn't count on it for a long term solution. After so many years and heat cycles the engine internals just may need to be freshened up unfortunately. My 2000 Chevy 1 ton 3500 with a Vortec 454 is just now starting to show symptoms of head gasket failure with 225,000 miles on it. I add water once a month, and until I start to see water in the oil, I will just keep driving it since it makes money for me😁. I would recommend driving the car regularly over the next few months to see if the problem remains static or progresses. That way you can see if its something you need to address now, or defer for future maintenance.

[@jardog16981]

@@VetteSource I forget to mention that I also ran a coolant system pressure test after replacing the water pump, intake gaskets, and cooling system hoses. The system held 16 psi perfectly for over a half hour. I also had confirmed when replacing the water pump that the block is numbers matching. I also had gotten a car fax before I bought the car that went back to 1992 on the report with the car at 32,000 miles. Everything I've found says the block is original to the car, hadn't been touched internally, and the mileage seems to be accurate. The service record paperwork that I got with the car confirms that as well. But like you said, it's 35 years old and may be starting to show that. It just has really bothered me trying to track the issue down. It would kill me to rebuild an engine when I'm getting such good compression/leak down numbers and can't seem to find anything wrong. Another potential issue that I've heard about is cracking/porosity issues with the 624 iron heads. I also heard that the later 624 castings that my engine would have come with were improved over the earlier 624 in terms of cracking/porosity, but I'm wondering if somehow there is an oil leak path into the intake tract or combustion chamber because of a cracking issue. Another issue I've heard about is a possible defect somewhere in the intake manifold base itself. Maybe a drilling was performed incorrectly when it was new, or an egr plug was overtightened on the bottom. I'm kicking myself now because when I had it apart I never took the heat shield off the bottom of the intake to check the egr plugs. I also didn't replace the timing cover gasket/front seal when I had the water pump off, so I'm going to have to take that back apart to replace the timing cover gasket. Live and learn. I'm currently a college student studying mechanical engineering and this is my first project car. Like I said, I agree that it's totally possible that it's just going to need to be freshened up due to age. On the flip side of that, it scares me to go into a rebuild without being to identify the actual problem before hand because of the possibility of taking the time and spending the money on a full rebuild that won't fix the problem. Definitely going to try that special oil once I fix the weeping gaskets and seals over the winter. I want to get 5-7,000 miles on it with the special oil next season and see what it does as the last resort before tearing it down. At $70 a gallon, I want to fix all of those leaks first. Haha. As far as effects of the oil consumption while driving around, it does run very well in general and pulls good. I did put a 180° thermostat in, replacing the stock 195°, when I had it torn down last time, so with the oil cooler the oil runs pretty cool most of the time here in New England except for in the heat of the summer. Which might not be a very good thing. While I've had it, I've been replacing the oil more often to compensate for lower oil temps. The engine seems to use more oil as the oil temp increases, again kind of making me think it's a ring issue. Like how the increased viscosity also helped reduce oil consumption while running the 15-50 as an experiment. In the summer when the oil gets into the 210-220 range, I do notice a bit of an oil burning smell from the exhaust while following the car. Also, if I go full throttle after sitting at a light for a minute I'll get a puff of smoke right at the instant when I get on it. Then its fine. Letting off the gas from high rpm is smoke free, kind of making me thing it's not a valve guide or any sort of porosity/crack in the head or intake connecting into the valley. I would think with that, the high vacuum would make it smoke out of the exhaust the most but I'm not seeing any of that. These other symptoms were why I was thinking it's ring related and maybe trying something to free the rings would fix it if that's the case.

[@VetteSource]

It sounds like you've done your homework and are pretty well versed for this being your first project car. Your a step ahead, as most mechanic engineers I know down here around NASA are great at the designing part of things, but couldn't assemble a cardboard box if their life depended on it😁. I would recommend continuing on with your current plan, and seeing how it behaves over the next few months while you drive it as much as possible. I haven't personally heard of porosity problems with the heads, but again anything's possible with 35 year old parts. Remember, half the fun is driving, the other half is tearing into it to rebuild again👍.

[@Orrinwellsbigo]

Where would you find bushings for lower and upper control arms Etc🤔🤔🤔

[@VetteSource]

In the past those were one of the difficult items to locate. However, I think I recently saw them available on rockauto

[@justmax36]

@@VetteSource pretty much anywhere... Prothane, Energy suspension is what i just put in my 89 conv...

[@VetteSource]

Thanks for the info👍

[@TheJimmyCarterFamily]

Do you have the gas tank door that would fit. A 86 also i need the Spring and hinge for an 86 Corvette gas door

[@VetteSource]

Hey Jimbo, sure I have one available. You can find my DM information @VetteSource on IG, or on FB. Let me know if you have any difficulty.

[@pettykash675]

Hello do you know where I can find an 85 Corvette rear knee assembly!?

[@VetteSource]

Sure, I have one available. You can reach me through IG @vettesource or by email [e-mail]

[@HeavenReservation]

Do you know any one that has in stock a oil seal repair kit for the rack and pinion on the 1989 C4 Corvette?

[@VetteSource]

Looks like you can still buy the Dorman repair kit with part #905515 on rockauto.

[@dagrind8710]

Are the unibody cars

[@VetteSource]

Yep, they're unibodies, often referred to as a unitized or unframe chassis. There is a really good MotorWeek retro review video for the 84 Corvette in this playlist - kzbin.info/aero/PLAM-V1w3acpififnUQ8pD5TbW7crzqBcz that goes into detail of how the chassis is constructed. It's pretty interesting the attention to detail that went into them.

[@dagrind8710]

@@VetteSource I've got a 1962 oldsmobile f85 cutlass its unibody in looking into using a c4 to upgrade the suspension

[@VetteSource]

Ok, gotcha. While it's not an impossible conversion, there are a few more challenging aspects that need to be worked out first, namely the mounting points into your unibody structure and determining how the track width will affect tire and rim selection. If you haven't seen it already, I have a video describing the rear suspension construction and mounting points - kzbin.info/www/bejne/nYDIZKF_eM9qh5I

[@dagrind8710]

@@VetteSource thank you I will be watching it ..yes it's going to be a challenge. I haven't made a decision yet just looking at other ideas besides say a s10 frame swap

[@VetteSource]

Sounds good. Let me know if you need anything else👍.

[@goodbonezz1289]

You kept saying front suspension…when you’re working on the rear..at least up to 12:30

[@VetteSource]

Are you sure about that? Those look like front suspensions to me, but what do I know😁? Thanks for the comment👍

[@goodbonezz1289]

At 6:00, that shock you’re taking off is a front shock? Because in the background I’m looking at those aluminum A arms and those are definitely front suspension…the rear suspension is not an unequal length A arm setup. Are we looking at two front suspension’s? I’m definitely no expert but can you see what I’m saying?