TraMotorsports

iTrader: (1)

1999 camaro ss.
On startup the car has a loud popping noise from the exhaust only on the drivers side (true duals). Diagnostic check reads cylinder 1 misfire. The misfire and popping goes away after the car finally warms up. Did a compression test and cylinder one only got up to 60psi.

The exhaust: Stock manifolds with straight pipes exiting each side of the car in front of rear tires. no cats or mufflers.

Im figuring it would be a burned up or bent valve due to the exhaust being so open and cool air sucking back up and hitting the hot valve. But i have also heard that the ls1 is notorious for bending pushrods.

Any help is greatly appreciated.
thanks.

GuitsBoy

iTrader: (4)

Hmm, Lots of people race open headers, and many more run cutouts up front without problems. Your exhaust dosnt sound like cool air reversion would fry your valve. Its true that in many cases when a motor is mechanically overrevved, the pushrods bend before the valves do. I bent pushrod probably wont hold a valve open though, it will do the opposite and keep the valve from opening completely. While only getting 60 # on the compression test seems like a problem, unless you compared it to other good cylinders, you dont know for sure. You could have a miscalibrated gauge or a leaking hose or fitting that keeps it reading low. If they all hit around 60, a valve might not be your problem.

technical

Bent valve or torched piston. I'd say check the plug but you had the compression tester in there so that wouldn't be it.

SILVER TA

Yeah I Also Had This Problem. Piston#5 Only Had 60 Psi And All The Other Ones Had About 190. I Had Over Rev The Car, So I Bend A Rod. I Replace It And Still Have The Same Problem. So I Assume That I Also Bend The Valve.

ArcticZ28

iTrader: (14)

If u're losing compression it's a bent valve or the piston rings are toast.

nasty ss

iTrader: (1)

I would also check for a broken valve spring. I have seen this many times and it showed the exact same symptoms. I doubt that it is a pushrod. Pull a valve cover and check it out. If things check out run a compression and a leak down test.

SILVER TA

if it was a piston rings there would be oil in the cylinder, correct?

Adrenaline_Z

Do you actually believe you can create enough heat from running an open
header to bend a valve?

Don't forget about the 02 sensors which will add fuel to relieve a lean condition.

Valve guides, cooling systems, valve seats and oil systems are responsible
for removing heat from the exhaust valve.

Open headers don't bent valves. You must have high combustion temperatures
due to an improper air/fuel ratio errored on the lean side.

99Fbody99

I would really take a look at the valve spring.. Hopefully its just a spring and hasnt gotten the valve into the piston.
Takes a few minutes to pull the coils and covers and inspect.

Dave

technical

This is the crux of the problem. There's only a few things that will cause this such as a bent valve, broken piston, or bad rings. If it was a valve spring, the popping noise won't go away after the engine warms up. Which leads me to believe that the rings are bad more so than a bent valve.

TraMotorsports

iTrader: (1)

thanks for the help guys.

Lvmyz28

iTrader: (1)

so pretty much from what everyone has said, pull the valve cover, pull the rockers for that cylinder, check the rockers to be sure they aren't cracked, pull the pushrods and run them on a piece of glass or a mirror to be sure they aren't bent, look at the valve spring and check to see if it's broken, with both rockers off put pressure in the cylinder and see if it holds pressure, if everything checks out ok then it's the rings or possibly a colapsed lifter. if not you'll find out what it is along the way!