Knocking in valve cover
#1
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Join Date: May 2003
Location: Riverdale, GA
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Car: 86 Trans Am
Engine: 350 Roch-4bbl
Transmission: 700R4
Axle/Gears: Normal
Knocking in valve cover
Hello,
I have rough Idle and stalling. checked and fixed vacuum leaks, adjusted carb, tested ECU, knock sensor, replaced cap rotor, sparkplugs and tested wires, all works great. Car stills Idles rough, and hard to start.
I went to Harbor Freight tools for some more inexpensive Chinese tools and purchased a automotive stethoscope. got home and started poking around and was amazed at how great this **** works. got to the passenger side of engine listening to the sounds threw valve cover and I hear a tapping(knock) over the second cylinder and I think I found the problem.
I need help! I fixed alot of stuff on this car but never took off the cover so i'm a little intimidated here.
Do you think it's a rocker issue or a rod issue?
is it easy to repair just that part or do I have to do all rockers rods and spring?
Do I have to replace the heads?
Is there any math involved?
Thanks much Yall!
I have rough Idle and stalling. checked and fixed vacuum leaks, adjusted carb, tested ECU, knock sensor, replaced cap rotor, sparkplugs and tested wires, all works great. Car stills Idles rough, and hard to start.
I went to Harbor Freight tools for some more inexpensive Chinese tools and purchased a automotive stethoscope. got home and started poking around and was amazed at how great this **** works. got to the passenger side of engine listening to the sounds threw valve cover and I hear a tapping(knock) over the second cylinder and I think I found the problem.
I need help! I fixed alot of stuff on this car but never took off the cover so i'm a little intimidated here.
Do you think it's a rocker issue or a rod issue?
is it easy to repair just that part or do I have to do all rockers rods and spring?
Do I have to replace the heads?
Is there any math involved?
Thanks much Yall!
#2
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Location: Cary, North Carolina
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Car: 1992 RS
Engine: Carbed 350
Transmission: 700R4
Axle/Gears: 3.42 posi
Re: Knocking in valve cover
Easy stuff - first open the cover, and look to make sure pushrod is not bent or lost - if all looks OK, then check rocker for loose, and see if the rocker has a hole worn in it from slapping the pushrod and/or valve stem. If all that looks ok, then search here for "valve lash" and read on how to set valve lash.
#3
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Car: 91 RS and 88 IROC-Z
Engine: 305 TBI and 383 Carb
Transmission: 700R4/2200 stall & 700R4/3500 stall
Axle/Gears: 3.42 posi and 4.11 posi
Re: Knocking in valve cover
Check out the valve springs. Sometimes it's hard to tell when a section has broken off. I had one break on me with my old heads and amost past it up when looking for the problem.
#4
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Car: 87camaro 357ci
Engine: xe294,scat crank,6" rods,Dartheads
Transmission: th-350 3000 stall
Axle/Gears: 4th gen rear 4.10 gears
Re: Knocking in valve cover
I agree with mike. My brother had the same problem on his 87 trans am and it turned out to be a broken valve spring. Sometimes they can be hard to find when the head is on the car.
#5
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Car: 86 Trans Am
Engine: 350 Roch-4bbl
Transmission: 700R4
Axle/Gears: Normal
Re: Knocking in valve cover
Ok Thanks will check it out. BTW, if a spring is broken, can I buy one spring at; like autozone? or do I have to change all spring to be the same tension?
#6
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Car: 87camaro 357ci
Engine: xe294,scat crank,6" rods,Dartheads
Transmission: th-350 3000 stall
Axle/Gears: 4th gen rear 4.10 gears
Re: Knocking in valve cover
I would replace all 16.. although spring breakage can often be caused by a stress riser when someone scratches or gouges a spring due to rough technique when installing them.. if this was the case..and no other springs were damaged, then just replace the one.. but its not east to inspect them all properly while installed. Most likely since your car is all stock the springs are just tired and your other springs are close behind.
An old trick to changing springs on the car is to take the plugs out, put the piston down the bottom of its travel, fill the cylinder with rope by feeding it in the plughole, then squish it up hard into the combustion chamber, this holds the valve closed well enough to change out the springs.
Remember to leave the tail of the rope out.
An old trick to changing springs on the car is to take the plugs out, put the piston down the bottom of its travel, fill the cylinder with rope by feeding it in the plughole, then squish it up hard into the combustion chamber, this holds the valve closed well enough to change out the springs.
Remember to leave the tail of the rope out.
#7
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Car: 84 z28
Engine: 5.7 tpi
Transmission: t5
Axle/Gears: not sure
Re: Knocking in valve cover
I had a tapping inside of my valve cover it was/is my rocker arm it was destroyed like the bottom of it was broken off which I payed 4 bucks at oreillys for a new one went ahead and changed out the gasket while I was at it which was around 10 bucks so maybe your lucky and thats all ?
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#8
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Car: 91 RS and 88 IROC-Z
Engine: 305 TBI and 383 Carb
Transmission: 700R4/2200 stall & 700R4/3500 stall
Axle/Gears: 3.42 posi and 4.11 posi
Re: Knocking in valve cover
If you do change your valve springs, you can use and air compressor and get a fitting to thread into you spark plug hole and it keeps the valves closed so they don't fall into the cylinder when you go to change it.
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