Guys,

Still chasing the idle misfire...

Suppose I had a bent valve (be it intake or exhaust). Would it always show up on a leak down test or compression test? Is there any chance it could pass the test, but act up during engine operation?

All cylinders have passed the test when I conducted them last year, but I started wondering about it when someone suggested it to me the other day. AFR already checked the heads out, but I'm not certain to what extent the inspected them before saying everything was AOK.

------------------
Pro-Touring 71

1996 LT4 Corvette Wheels are 17x8.5 front, 17x9.5 rear
Wheel adapters are 2.0" front, 2.5" rear
Baer Brakes four wheel discs
Fuel Injected ZZ4, custom burned EPROM, AFR heads, TPIS Mini-Ram intake,
Comp Camshaft, TH700R4 Transmission.
God Bless the USA
Project Photos on ULTM8Z project photo album (http://photos.yahoo.com/ultm8z)
See me in Chevy High Performance (http://chevyhiperformance.com/featuredvehicles/86018/)
ULTM8Z Website (http://www.ultm8z.com)

Nah, a bent valve is a bent valve. It would show up on a compression test or leakdown test.

If you had bent a valve to the point where it caused even a small missfire over time the exscaping combustion gasses would torch the valve. If it was an intake valve you would get back fires into the plenum, if it was an exhaust valve it mightnot show up till the valve was completely burnt but still it would get worse over time.

<font face="Arial,Verdana" size="2">Originally posted by Joekool:
If it was an intake valve you would get back fires into the plenum, </font>

On a regular basis I would assume?

Very rarely I'll get one happening if I crack the throttle extremely quickly, but I'm attributing that to not-optimized tuning.

------------------
Pro-Touring 71

1996 LT4 Corvette Wheels are 17x8.5 front, 17x9.5 rear
Wheel adapters are 2.0" front, 2.5" rear
Baer Brakes four wheel discs
Fuel Injected ZZ4, custom burned EPROM, AFR heads, TPIS Mini-Ram intake,
Comp Camshaft, TH700R4 Transmission.
God Bless the USA
Project Photos on ULTM8Z project photo album (http://photos.yahoo.com/ultm8z)
See me in Chevy High Performance (http://chevyhiperformance.com/featuredvehicles/86018/)
ULTM8Z Website (http://www.ultm8z.com)

Do the compression test. It'll take less time than posting symptoms on the internet and asking what-if questions. If it's bent it'll be VERY obvious from the compression results.

Damon, I did do the test...


<font face="Arial,Verdana" size="2">Originally posted by ULTM8Z:

All cylinders have passed the test when I conducted them last year,
</font>

I was posting because I was curious about the validity of test to rule out a possible bent valve.

------------------
Pro-Touring 71

1996 LT4 Corvette Wheels are 17x8.5 front, 17x9.5 rear
Wheel adapters are 2.0" front, 2.5" rear
Baer Brakes four wheel discs
Fuel Injected ZZ4, custom burned EPROM, AFR heads, TPIS Mini-Ram intake,
Comp Camshaft, TH700R4 Transmission.
God Bless the USA
Project Photos on ULTM8Z project photo album (http://photos.yahoo.com/ultm8z)
See me in Chevy High Performance (http://chevyhiperformance.com/featuredvehicles/86018/)
ULTM8Z Website (http://www.ultm8z.com)