CorvetteForum - Chevrolet Corvette Forum Discussion - C4 Tech/Performance

New C4 owner please help with supercharger issue

Canyon.C5 — Thu, 21 May 2026 20:46:46 GMT

Hello,
I just recently purchased this supercharged 88 corvette, and am running into a crank case pressure issue that I need help with.

the car spewed oil out of the dipstick so I took it to a mechanic and had a full inspection done and the only the issue the car has is that there�s too much pressure in the crank case and to my understanding I need a source for a negative pressure because:

positive + crank case pressure combined with (normally) negative - intake vacuum creates an equilibrium but because this car is supercharged that creates

positive + crank case pressure combined with + supercharged intake pressure causing this issue.

I would like to fix it by removing the pcv tubing and capping the intake side while adding a filtered ventilator to the top of the valve cover so that the engine can safely ventilate to atmosphere.

is this the correct solution and if it is, what parts would you all recommend?

thank you all for your help!

What Hyd Slave Cylinders for the ZF Snout ?

Gale Banks 80' — Thu, 21 May 2026 16:26:16 GMT

This is for the aftermarket internal Slave Cylinders and not for a replacement stock external reverse pull clutch set up. I currently have the Ram one and when switching to the Dual Disc 9.5 they want the Spiral Lock removed and when that is done the slave falls apart when the Trans is removed. The Piston then falls and gets scratched which ruins the O-Rings. In the past I have had good luck with the Tilton brand but that was 20 years ago, and a lot has come along the market since. I will only consider dual line design. What have You used in the last 10 years or so that has worked?

93 front brakes lost something

radar502 — Thu, 21 May 2026 01:12:49 GMT

My 93 front brakes just lost grip ,rotter's like new Halk ceramic pads stainless lines all around, now the rub the pads been installed for 7-years but only have 10,000 miles ,is there a thing just time the pads got old and not what they used to be ,they worked good till about 6 month back the stop right now grip gone ,??? any suggestions ,Changing pads no big deal to what ???

1989 wide band

the blur — Wed, 20 May 2026 19:40:04 GMT

What's the best way to do a temporary wide band?
1989 100% stock. I had to replace the Multitec's with Delphi's. Car runs nice, but I want to see how it is in open loop, and also, from idle, all the way to red line.

when I'm done scanning, I'll remove it and plug the bung hole with 1/2" pipe plug.

Vats system behind center dash

Jeam1010 — Wed, 20 May 2026 02:04:20 GMT

Looking for exact same way to bypass vats system behind center dash. Please,help!!!!

Engine oil Dipstick reading

Kole kat — Tue, 19 May 2026 18:46:34 GMT

New 92 ZR1 owner, coming from an s2000 and other previous sports cars. For context, the s2000 dipstick had a problem where people would only read the top side which was higher than the bottom side of the stick. So they were actually running it low. Then they would run it out and blow the engine. So idk if there's a quirk with the dipstick on the LT5, especially since the filter sits at the top and the oil slowly drains back into the pan. Does the LT5 have any weird "features" when it comes to the fluids? Any advice/help would be greatly appreciated.

Strange Issue with 95

CorvetteRules — Tue, 19 May 2026 18:00:30 GMT

Last Sunday I was driving my 95 home after picking up window screening from Home Depot and it just stopped running. Pulled to the side of the road and it would just crank with no indication of firing. First thing that came to mind was opti- spark but the SES light never came on. Also thought of the fuel pump. It was too noisy on road side to hear if pump did run to prime.

Of course sitting on side of road I had no access to my fuel pressure gauge and code reader. Called AAA and had it towed to garage I use for my vehicles. Was originally going to have it dropped at my house so I could play with it but decided garage was best in case it was something that needed diagnostic equipment I don't have.

Now the mystery is that when they went to start it Monday it fired right up and ran perfect. They allowed it to run for about 15 minutes without issue until they turned the A/C on it just died. It was getting late in the day when they did this so didn't have time to do any diagnostic testing. Told them to play with it for a few days and we'd talk about end of the week. I will add that when it died on me the A/C was running.

Any thoughts from any of you as to what the issue may be? Prior to this issue it was running perfect.

1993 AC compressor clutch shim kit part #

steve40th — Tue, 19 May 2026 16:54:51 GMT

Anyone have the part number for our air compressor? I need one for new pulley etc.

88 Vette Courtesy Fuse

M0TLEYCRUE — Tue, 19 May 2026 02:21:35 GMT

Just bought a really clean 88 Corvette given to the guys wife from estate and she sold to me. Seems he was trying to track down some sort of power backfeeding through the courtesy clock fuse, there was nothing in its place when I got the car. I put a 15 amp fuse in the slot and without the key being in the ignition every single accessory powered by that circuit came on and killed the battery instantly. The only aftermarket thing I can find is a pioneer cd changer was installed at some point, unsure if it is bad will be unplugging tomorrow and checking again on that. Factory delco bose radio and speakers, not sure of any other areas that could possibly feed power like that if anyone has had this problem before any help would be greatly appreciated, thanks.

1995 vette, drops rpm for a second

JETDAWG — Tue, 19 May 2026 00:59:59 GMT

Hello, just bought a 95, 6 speed car, 50k miles, super clean. On hard acceleration sometimes at about 4500 rpm or so it drops rpm for a split second and then comes back on. Also, I noticed sometimes hard to start, especially when it is hot. Should I get a code reader? If so, which one? Any ideas what is the root of the problems I am having. It runs awesome. Awesome car. Thanks a lot everyone

86� corvette MAF mystery issue code 33

Managed — Tue, 19 May 2026 00:48:44 GMT

1986 Corvette C4 L98 TPI automatic

Getting persistent Code 33 and unplugging the MAF causes absolutely no idle/drivability change at all. Engine still idles smoothly around 600 RPM and runs surprisingly well otherwise.

Things already checked/tested

- Timing properly set to 6� BTDC with EST bypass disconnected
- Engine mechanically seems healthy
- Stable idle/oil pressure/temp
- No major vacuum leak symptoms
- MAF relay and burn-off relay both appear to function correctly
- Grounds tested good with continuity to chassis
- Connector power/ground seems present

Connector readings with engine running:
- Purple wire: ~14.4V
- Both black wires: ground
- Green middle wire fluctuates around ~3.5V idle and rises toward ~5V with revs

Original MAF behaved this way and replacement MAF behaves IDENTICALLY. Both sensors produce:
- Code 33
- no idle change when unplugged.

I have a Delphi AF10320 on the way, but I�m trying to determine whether this points more toward a signal wire issue, ECM/PROM issue, ECM permanently in fallback mode, or a known 1986 PROM/calibration problem

Any help from someone familiar with early GM/Bosch hot-wire MAF systems would be greatly appreciated.

1984 Pop-Up Headlights

mhhanson — Mon, 18 May 2026 19:48:01 GMT

Ok, I'm sure I'm late to this thread. I have a C3, and my son bought a 1984 C4 last year. As is common, his headlights quit lifting up. We never had grinding or the skipping of the gears, however we did re-build one gear boxes (passenger side). After doing this, we discovered we had not made any advances with the lights not lifting, so we then replaced the relays..... Now his lights lift with no issues.........but the drivers side will not go down unless I either: 1.) start to manually twist the **** on the bottom of the motor(It then takes over and goes down with no issues. or 2.) I gently persuade it with some downward pressure when the hood is closed, and then it again goes down as it should.

I'm looking for guidance. It feels like the motor is under a load or slightly bound up preventing it from closing.

Help needed, Climate control won�t switch off of defrost

C4Breaker — Mon, 18 May 2026 16:13:19 GMT

Hi everyone,
I�m working on my C4 and can�t get the climate control to switch off of defrost. Online says this is usually caused by a vacuum leak somewhere. I�m trying to use a smoke tester but can�t seem to find the best place to plug my hose in.

Does anyone know where I should put it?

Transmission Leak

llapine — Mon, 18 May 2026 11:54:59 GMT

I noticed some leakage on the garage floor from my 1994 C4 e3quipped with the 6-speed manual transmission. I cannot see where it is coming from, although it seems to be farther back than expected. Any ideas?

Control Rod Orientation Question

criceo — Mon, 18 May 2026 06:34:05 GMT

Like a genius, I removed all of the strut and control rod bushings at once without noting which direction the rods were oriented. I put the left and right suspensions in different boxes; so, no worries there. Are the upper and lower control and strut rods directional? By that I mean are there front and rear/left and right ends of the rods? I know there are front and rear bushings, and I know which are which. I just don't know which ends to press them into. Thanks