You may have heard the term, valve job, because older engines frequently needed their valves reconditioned.
You rarely hear about, valve problems or valve jobs in today’s engines. Because, modern (OHC) engines, have fewer parts to wear out and fail.
That’s why, most modern engines valve trains, are virtually trouble-free. But, after so many miles, any engine could need a valve job.
So, to help prevent, needing a valve job, there are a few things you can do:
- Maintain a clean, efficient cooling system. So, the engine does not run too hot.
- Use good quality fuels. To help prevent carbon build up, on the valve and seats.
Valve work often requires, a certain amount of detective work. Because, to fix a valve problem, you first have to figure out, what caused it in the first place.
Why Would You Need, A Valve Job:
Many engines need a valve job, long before they should, because of valves bending or burning.
Bent Or Broken Valves
So, the most common failure of valves, is bending or breaking, as a result of, contact with the pistons.
The valves contacting the top of a piston, is due to, incorrect engine synchronization. As a result, of timing chain/belt breakage and incorrect fitting, of new belts and chains.
So, burnt valves, is another common type of failure. Essentially, this is caused by, combustion gases escaping, between the valve and valve seat. And, is usually, because of incorrect sealing.
The hot combustion gases, are forced past the valve, which starts to burn away, the edge of the valve. Normally, this type of failure, affects the exhaust valves only. But, it can also damage the intake valves. As a result, you will need a valve job.
Because, these problems are so rare in modern engines, many people don’t recognize the signs early enough.
Here Are Some Of The Common Signs, That You Might Need One:
Ticking Or Popping Noises
Ticking or popping noises, are the most common types of noises you will hear, when you’re valves are leaking.
Blue Smoke From The Tailpipe At Startup
Exhaust smoke is a classic sign, of overall engine trouble and should never be ignored.
Though blue smoke is not specifically a result of valve problems, it is one of the most common signs. Especially, when combined with, ticking and popping noises.
Engine Power Loss
Another sign that you have valve problems is, that you frequently notice a, loss in engine power and performance. If your valve guides and seals are leaking, oil can build up on the top of the valves. Consequently, this can cause it lose its seal. This could cause, compression issues, which lead to poor combustion and power loss.
Broken Timing Belt
If you have a interference engine, it means that the valve and piston’s stroke, take up the same space.
So, the timing belt essentially keeps them, from smashing into each other. Consequently, if the timing belt breaks, they will run into each other, causing bent valves.
So, you need to do, a cylinder leak down test and confirm, valve leakage. If there is, now you know that, the cylinder head has to come off. And then, be sent to a machine shop for inspection.
What Should You Expect From The Machine Shop, In Relation To A Valve Job
So, there is no such thing as a “standard” valve job anymore. Because, every valve job is different. An (OHC) head, may require a lot more time and effort, than a head off a pushrod engine.
There is often no way to tell what a head will need, in terms of repairs, until it has been:
- Completely Inspected
Always, ask for an estimate first, commonly known as a strip and advise cost to repair.
So, it is common to have to replace, exhaust valves and springs.
Valve guides and/or seats may have to be replaced. The head may be warped or cracked, requiring additional repairs. The list of things included in a “complete” valve job will vary, from job to job.
Most common jobs performed, as part of a valve job should include:
- First, a visual inspection, looking for broken and damaged parts.
- Complete disassemble of the head. So, all of the parts can be, cleaned and inspected.
- Inspect the cylinder head casting, for cracks or other damage. The best way would be by, pressure testing.
- Inspect valves, seats, springs, guides, and other valve train parts, for wear and damage.
At this point the shop should be able to come up with, a firm quote for the complete job.
When getting a valve job, what should you expect next:
- Replace any parts, deemed not repairable.
- Install and machine, any worn valve guides and seats.
- Resurface the cylinder head, to assure flatness and a proper, (RMS) finish. This is a must, for today’s gaskets to seal properly.
- Completely re-clean all parts and the cylinder head.
- Reassemble the head, with all the new part machined and installed.
- Do a vacuum test on the head, through the intake and exhaust ports. This will confirm that the valve have been, sealed properly.
- The cylinder head should come back to you, with all the parts needed to finish the job.
Reinstall the cylinder head on engine, with new head gasket and cylinder head bolts. (do not reuse torque-to-yield head bolts). Refer to vehicle service manual for, proper head bolt torque procedure and specs. Also, (OHC) camshaft alignment and timing procedure. Finally, replace all gaskets, along with a new timing belt or timing chain set.
Thank You !