Valve Noise through exhaust?

[Mancave11640]

Hi all,

Quick question. Recently had a full stage 1 kit put through my LS1 VZ SS.

Picked up a good amount of power from it she definately has more punch, however it doesn't sound like any LS1 I have ever heard after stage 1 upgrade.

Took it back to where I had all the work done and was told that the "rattly" noice I can hear through my exhaust is "valve noise" is this a thing?? The bloke took all of about 10 seconds to come up with that diagnosis.

A few issues after the work. My car now sounds like a George Jetson car, sounds like it is sucking in air from somewhere other than the OTR box. When it back fires it makes a rattle sound and I might be going mad here but it sounds like it's backfiring along the exhaust not out the back. Also my Speedo is out by 10ks!!

Anyways if anyone has any ideas I'm all ears. I would like if there are any issues to have them fixed with the guys that did the work but maybe I need to take it somewhere else for a look see.

Any help muchly appreciated

Michael.

 

[99notout]

"Rattly noise" could be disintegrating cats, this could also make your car sound a bit like "George Jetsons"...

 

[Trevor loves holden.]

Holden VZ Commodore: LS1 and L76 V8 engines
Overview
With the exception of the early 5.7-litre LS1 V8 engines, General Motors' LS V8 engines are regarded as being generally reliable. However, they may experience the problems described below.

Hydraulic lifter failure
For GM's LS V8 engines, the hydraulic lifters may fail due to:

• A failed plunger within the lifter itself. When the plunger fails, it cannot maintain oil pressure and remains in a collapsed state – the lifter therefore cannot take up valve lash such that a tapping noise is heard that increases in volume and frequency with engine speed;
• The spring mechanism jamming – this is more common in older engines;
• Inadequate lubrication of the lifter roller wheel surface causing friction on the lobe (this generally results in a squeaking noise);
• Softened valve springs which also require replacement; or,
• Worn lifter buckets.

A failed hydraulic lifter can bend the pushrods which can then fall out of the space between the rocker arm and the top of the lifter. Once a pushrod falls out of that space, it may cause broken rocker arms, broken valves, cracked heads, a damaged cam or total engine failure.

It is recommended that the lifters be replaced every 100,000 kilometres, though failure of the hydraulic lifters is more common in engines with high-lift camshafts because higher spring pressure are required to prevent valve float, putting extra pressure on the lifter. Replacing the lifters requires that the cylinder heads be removed such that new head gaskets and head bolts are required.

Hydraulic lifter noise
From cold start-up, the hydraulic lifters may make a tapping noise. The most common cause of hydraulic lifter noise is particles in the engine oil becoming jammed between the lifter plunger and the lifter body, causing the plunger to become stuck down. The clearances between the plunger and body of a hydraulic lifter can be as little as 3 microns (0.003 mm) such that any particle larger than this in the oil can jam the lifter plunger in its body.

Lifter noise may also be caused by aeration of engine oil in the lifter’s pressure chamber since this increases valve closing velocity. Aeration of engine oil may be caused by:

• air in the higher pressure chamber of the lifter affecting valvetrain lash;
• air that is ingested into the lifter during a cold start due to a suction side leak at the oil pump or oil pump pick-up tube O-ring; or,
• low oil levels and high engine speeds.

Once air gets into the high pressure chamber, it will be slowly expelled through the narrow clearance of the plunger and body.

Rocker bearing failure
The rocker bearings – which sit on top of the valve train and transfer energy from the pushrod to the valve – can develop a sideways slop which can damage the valve tops, the rocker or valve springs. Furthermore, the rocker bearings can split such that the needle bearings fall out and end up in the oil pan.

Trunion bearing upgrade kits can be installed in the factory rockers which reduce sideways movement and provide a better range of vertical movement. Alternatively, after-market roller rockers can be installed which have better geometry than the standard rockers and control the valve more precisely via the centre of the valve tip.

Valve spring failure
The LS engine has 'beehive', single valve-type valve springs (as opposed to a dual valve spring which has a smaller spring inside the primary spring) and, in rare cases, the valve spring may break at its top where the coils are tightly wound. If a single valve-type valve spring breaks, it is common for the valve to be dropped, causing significant engine damage; sometimes, however, the valve may be held up by the valve locks when the spring is breaks. Symptoms of broken valve spring include:

• Engine vibrations;
• Loss of power beyond 4000 rpm;
• Misfire under load; and,
• Constant misfire.

If the vehicle is driven with a broken valve spring, a valve may come into contact with the piston, causing the valve to be bent. Furthermore, if the valve head breaks off, the engine will seize. To fix a failed valve spring, the cylinder heads need to be removed so that a new valve, head gasket and head bolts can be fitted.

For durability, it is recommended that high rpm are avoided when the engine is cold