90C4sRule

You guys are great and have helped me out a lot.

I have been cleaning and painting parts while I finished replacing my fuel injectors in my 90 c4. While I was at it I added an adjustable fuel pressure regulator, fuel filter, roller rockers, oxygen sensor and ported the plenum and runners so it could breath a little better. I adjusted the valves according to the FSM but when I tried to start it it would not fire unless I gave it gas. Then it sounded like It was only hitting on four cylinders. So I took my freshly painted valve covers back off and backed the valves out until the engine would idle. Then I adjusted them the messy way with the motor running and rags draped over the rocker arms to keep the oil from squirting everywhere. After i got the valves quieted down I was hearing a knock that sounds like something banging under the car. So I got out my stethoscope and found that the knock is the loudest on the bell housing and in the transmission (6 speed). If I push the clutch in the knock quiets down quite a bit. And if I put it in gear (car is up on jacks) and let out the clutch the noise transfers back all the way to the rear-end. Almost like the noise you would hear if you lug and surge the motor. Could the clutch be making this banging sound? I checked the timing and it is at 10 BTDC. I was hoping to make it to the rally this weekend and the parade the weekend after but right now it is not looking to promising.

Any suggestions would be appreciated.

Thank you

Z51JEFF

Why would you have to adjust the valves on a 1990 Corvette?Did the motor come apart for maintenance?

racebum

clutch issue of some sort, i've seen this happen personally from loose flywheel bolts and a disc that was starting to come apart. loose flywheel bolts are rare if ever something that just come up unless it's right after a clutch job. the disc is often from a spring that pops out BUT there are no springs on a DM flywheel setup. unless you have bottom end knock that sounds similar it's highly likely the transmission will be coming out

96GS#007

Sounds like the dual mass flywheel is on it's way out.

Btw...Did you add 1.6 ratio roller rockers? If so, did you change the valve springs or make sure the current springs could support the added lift? If not, you need to check/verify before you bind a spring and drop a valve. Never mind if you kept 1.5 ratio rockers.

90C4sRule

I used 1.5 roller rockers so I could keep the stock valve covers. New plugs, cap, rotor, wires, fuel filter, 22# Bosch injectors from FIC, egr valve, pcv. It still sounds like there is something is not quite right, slight miss, but I think your right about the dual mass flywheel. If I shift hard or decel and accel after it has been driven for a while it sounds like I have a bad u-joint in the drive train. I checked it out while the car is up on jacks and the drive train seems solid.

The car only has 53 thousand on it.

Any suggestions for the new clutch? I would like to go aluminum.

cv67

Check out Carolina Clutch.
Why are you choosing an aluminum?

90C4sRule

More HP and faster rev.