"Burnt Valve" ??
#1
"Burnt Valve" ??
Oh mighty gurus--
Enlightenment please??---
How do you know if you have a "burnt valve"??
Hear it tossed around, mostly by drag racers, but confused by what it means & the symptoms!!
Also, what is the likelyhood of it occuring to a daily driver??
( edit )
Thank You for any education you can pass!!
Enlightenment please??---
How do you know if you have a "burnt valve"??
Hear it tossed around, mostly by drag racers, but confused by what it means & the symptoms!!
Also, what is the likelyhood of it occuring to a daily driver??
( edit )
Thank You for any education you can pass!!
Last edited by t-top havoc; 11-07-2010 at 04:42 PM. Reason: Add Thanks
#2
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Car: 1984 Z28 Hardtop
Engine: 383 Carb
Transmission: 4L60
Axle/Gears: 3.54 Dana 44
Re: "Burnt Valve" ??
Do a compression test, or better yet, a leakdown test, and if you have low compression and you narrow the cause down to a leaky valve, then you have a "burnt" valve.
The odds of it happening in an unabused daily driver are relatively low.
The odds of it happening in an unabused daily driver are relatively low.
#3
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Car: 92 Jamaican Yellow Firebird
Engine: 305 TBI
Transmission: 700R4
Axle/Gears: 3.42
Re: "Burnt Valve" ??
Years ago (mid 70's) there was a vacuum gauge that would indicate if there was a burnt valve. I am not certain if that applies to more modern engines. Never run into one.
#5
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Car: 92 Jamaican Yellow Firebird
Engine: 305 TBI
Transmission: 700R4
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Re: "Burnt Valve" ??
No you just hooked the gauge up, and the scale gave an indication the valve was burnt.
#7
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Car: 89 K3500 Fleetside
Engine: RAT *tbi* EBL
Transmission: TH400
Axle/Gears: 3.73-Dana 60
Re: "Burnt Valve" ??
t-top,
A vacuum gauge connected to an intake manifold vacuum port will indicate some of the problems that relate to intake valves.
A crude test that can (or not lol) reveal a burnt exhaust valve is try to hold a stiff piece of paper against your tailpipe & watch for the engine to suck it back toward the pipe.
Both tests are done w/the engine running.
Leak down tests are much more conclusive but require special tools.
A vacuum gauge connected to an intake manifold vacuum port will indicate some of the problems that relate to intake valves.
A crude test that can (or not lol) reveal a burnt exhaust valve is try to hold a stiff piece of paper against your tailpipe & watch for the engine to suck it back toward the pipe.
Both tests are done w/the engine running.
Leak down tests are much more conclusive but require special tools.
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#8
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Car: 92 Jamaican Yellow Firebird
Engine: 305 TBI
Transmission: 700R4
Axle/Gears: 3.42
Re: "Burnt Valve" ??
t-top,
A vacuum gauge connected to an intake manifold vacuum port will indicate some of the problems that relate to intake valves.
A crude test that can (or not lol) reveal a burnt exhaust valve is try to hold a stiff piece of paper against your tailpipe & watch for the engine to suck it back toward the pipe.
Both tests are done w/the engine running.
Leak down tests are much more conclusive but require special tools.
A vacuum gauge connected to an intake manifold vacuum port will indicate some of the problems that relate to intake valves.
A crude test that can (or not lol) reveal a burnt exhaust valve is try to hold a stiff piece of paper against your tailpipe & watch for the engine to suck it back toward the pipe.
Both tests are done w/the engine running.
Leak down tests are much more conclusive but require special tools.
#10
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Car: 1984 Z28 Hardtop
Engine: 383 Carb
Transmission: 4L60
Axle/Gears: 3.54 Dana 44
Re: "Burnt Valve" ??
A vacuum gauge might work on a 4 cylinder tractor idling at 400 RPM, otherwise it's pretty hard to see a problem in an individual cylinder, especially with a large plenum.
#11
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Car: 92 Jamaican Yellow Firebird
Engine: 305 TBI
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Re: "Burnt Valve" ??
I agree. We didn't use it often, and you are correct, only once or twice on a car/truck engine. I forget the spec, but you would look for the drop whenever the burnt valve operated. If you had a hot cam, you'd never find it with the vac gauge. Just a different method that I learned on years ago.
#12
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Car: 89 K3500 Fleetside
Engine: RAT *tbi* EBL
Transmission: TH400
Axle/Gears: 3.73-Dana 60
Re: "Burnt Valve" ??
The dip & flutter of a vacuum gauge attached to the intake of an engine with a bad intake valve is distinct & obvious.
Elvis has left
#13
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Re: "Burnt Valve" ??
That is what I have heard as a cause, a leaking exhaust manifold. I've seen burnt valves, but not on SBC motors. Usually the Dodge V6's, and some older foreign (Japanese) stuff.
#14
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Car: 1984 Z28 Hardtop
Engine: 383 Carb
Transmission: 4L60
Axle/Gears: 3.54 Dana 44
Re: "Burnt Valve" ??
Distinct and obvious when everything is agreeable, like the grind of the cam, engine speed, plenum volume, responsiveness of the gauge, length of the tubing, exactly how badly the valve leaks...
#15
Re: "Burnt Valve" ??
Not a jack!! That Q does fit, & not a bad 1 at that!!
(edit)
Along the lines of Moe87--
How do you know when? What symptom(s) are looked at?
Way down on power all of a sudden? Knocking or ticking? {I mean not like a valve tick or header // manifold gasket leak tick} Smoke erraticly, such as when said cylinder(s) are on the exhaust stroke?
Last edited by t-top havoc; 11-08-2010 at 07:42 PM. Reason: No need to make a new post#??
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