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Questions tagged [valve]

Refers to engine intake or exhaust valves.

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21 votes
3 answers
18k views

What is valve float and how does it impact engines?

The Wikipedia entry is hard to grok: Valve float is an adverse condition which can occur at high engine speeds when the poppet valves in an internal combustion engine valvetrain do not properly ...
Zaid's user avatar
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19 votes
3 answers
233k views

What exactly is a "burnt valve" and what causes it?

I've come across this term a couple of times in the context of diagnosing engine-related issues, but don't know what it refers to. Here is an example from an automotive forum I frequent: I gotta ...
Zaid's user avatar
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19 votes
2 answers
14k views

Why did Ducati decide to use the desmodromic valve train rather than a more tradition valve train?

Ducati's use a unique method to open and close their valves. It's called the desmodromic valve train. The desmodromic valve system does not use springs to close the valve, it uses the cam and has a ...
DucatiKiller's user avatar
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11 votes
1 answer
3k views

Interference vs non-interference engines

What do people mean when they say that an engine has an interference design? How does it differ from a non-interference engine?
Zaid's user avatar
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11 votes
1 answer
2k views

Tyre Valve Pin Too Far In

I just bought a second-hand car, and when I got it home I tried to check the tyre pressures, with a simple mechanical pressure gauge like this, which I've used for years on previous cars with no issue....
DaveyDaveDave's user avatar
11 votes
1 answer
1k views

"Valve like" noise after modifying camshaft ninja 300

A friend and I bought a modified camshaft for his ninja 300/EX 300. After installing and checking/adjusting valve clearance everything seemed ok. After a few laps on our local track the bike started ...
Aerim's user avatar
  • 235
10 votes
3 answers
10k views

Do straight/short pipes burn out valves?

I have heard that straight/short/custom pipes can burn out valves on an engine. However, with a 4-cylinder Ford Model A engine, I have been told this is not the case because it has such low ...
Jonathan Musso's user avatar
10 votes
1 answer
7k views

What are the various kinds of tappets / lifters and the advantages / disadvantages of each

A previous question about tappets found here: What are Tappets? covers the basics of tappets. If we go the next step, here are my questions: What are the various kinds of tappets / lifters? What ...
cdunn's user avatar
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10 votes
1 answer
2k views

Formula 1 valve trains

There was a statement in a post regarding Formula 1 valve trains being pneumatic or magnetic. Are there valve trains driven magnetically or pneumatically that are on the market? When did they start ...
Ppoggio's user avatar
  • 1,487
9 votes
4 answers
53k views

Effects of leaky exhaust valves

While rebuilding my valves, I noticed that 4 out of 6 exhaust valves on one side of the V6 engine were leaking after lapping and I had to relap them. I determined that by doing a water test. I am ...
amphibient's user avatar
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9 votes
2 answers
10k views

Lapped valves still leak but slowly

Background I did some work on my engine's head valves and their seats. This is a very old engine with very old/abused/invented/adapted parts, etc. Both the valves and seats were in pitiful condition. ...
Aram Alvarez's user avatar
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9 votes
3 answers
4k views

What are the causes of fluctuating intake manifold vacuum

I have a 2005 Honda CBR600 F4i which suffers from occasional hesitation at low rpm when accelerating. I also get occasional fault codes from the ECU indicating a vacuum leak. Today I connected a ...
Ian Oakes's user avatar
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9 votes
1 answer
2k views

Pneumatic Valve Spring Operation in Formula 1

In the 2006 Formula 1 World Championship the rules allowed for pneumatic valvesprings. These engines were required to have a 90° V8 engine with 2.4 liters of displacement, 4-valve-per cylinder layout ...
DucatiKiller's user avatar
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9 votes
1 answer
4k views

Do I risk damaging the valve seat if I lap this valve without removing carbon build-up?

This valve is from my LS1 (Exhaust #3). It's suffered from a lot of carbon build-up due to a history of fueling/spark problems. I've tried cooking it in ethylene glycol. I've tried using abrasion ...
Zaid's user avatar
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9 votes
2 answers
1k views

Can leaky cylinder explain oil loss to burning?

One out of the 6 of my Toyota Tacoma cylinders is mildly leaking, as indicated by a cylinder leakdown test. While other cylinders are leaking only something like 5-10%, this one leaks about 20% of the ...
amphibient's user avatar
  • 6,653
8 votes
3 answers
2k views

Can a valve suddenly break in half? Versys 650 destroyed engine

This week-end, I had to disassemble an engine from a Kawasaki versys 650 (early). The bike lost power while making ugly metal sounds. It never started again. RIP. Context: 108.000km, mostly highway ...
TNCreator's user avatar
  • 340
8 votes
3 answers
9k views

Preventing debris from falling in engine while changing valve cover gasket

I am about to change the valve cover gasket on a 2002 Ford Focus SE Wagon with the DOHC Zetec engine. I have never done this kind of thing before, and although it seems simple, I am concerned after ...
J. Taylor's user avatar
  • 433
8 votes
1 answer
2k views

Roller rockers to a stock valve train

78 Nova but the engine is from a different car; casting # V0707CMH. I have a 350 with 305 heads. Stock valves, pushrods, cam, and lifters. The nuts on my stock rocker arms are in need of replacement; ...
Dee's user avatar
  • 697
7 votes
3 answers
5k views

Do valves rotate over time?

As I was doing my valve servicing, one question came to mind: As valves undergo millions of cycles of reciprocating motion, do they actually rotate or is their position relative to the seal fixed? Or ...
amphibient's user avatar
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7 votes
1 answer
4k views

Why when I turn the front wheels by hand, the crankshaft doesn't rotate?

I'm after head gasket replacement and I'm trying to adjust valve clearance. 2 wheels of a fwd 1995 Renault Twingo are lifted off the ground, the engine is in gear, but the crankshaft doesn't turn ...
ronenfe's user avatar
  • 285
7 votes
2 answers
376 views

Camshaft problem not sure what needs replacing

I'm Looking for a part name and info on what could have caused the problem. So I have an 03 peugoet 206 1.4 HDI and I lost a cylinder after going though them by disconnecting each injector and can ...
Barkermn01's user avatar
7 votes
1 answer
5k views

Stuck valve in lawn tractor Briggs & Stratton OHV

My John Deere LA120 lawn tractor has a Briggs and Stratton 21HP OHV engine that quit suddenly. Bad gas was my first guess. Along the way, I discovered a leaky fuel pump. So far, I have now replaced:...
Peter's user avatar
  • 173
7 votes
1 answer
2k views

SAAB 9-5 wagon throws P1549 Code (Boost control valve)

I called an ASE-certified mechanic. He charged some $60 for the visit and $60 diagnosis and really he didn't quite spot on anything. Left me where I was - work-wise , diagnosis-wise and knowledge-...
user1874594's user avatar
6 votes
2 answers
521 views

What are the characteristics and uses for desmodromic valves?

In an answer to another questions @Ceshion introduced a fascinating kind of valve train that I have never heard of, desmodromic valves, as introduced by Ducatti. That answer is here: What are the ...
cdunn's user avatar
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6 votes
1 answer
12k views

This valve is pitted - what options do I have?

This is that infamous Exhaust Valve #3 after cleanup. The cylinder had a history of fuel/spark-related misfires. As the images show, the lip of the valve is pitted. Here is the back of the valve. I ...
Zaid's user avatar
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6 votes
2 answers
1k views

How come only one piston was damaged?

This is a 2007 Dodge Caliber 2.0 CRD (which uses a VW Golf 5 TDI engine). The valves on only 1 piston have come into contact with the piston, causing chaos in that cylinder. The other three are fine. ...
Mark's user avatar
  • 61
6 votes
2 answers
2k views

Help me diagnose the cause of this intake valve burn

I would like some help diagnosing the probably cause of this intake valve burn as seen in the picture. 167fmm engine. 229cc OHV push rod type. Now here is the rub. this is engine originally 9:1 CR, ...
axa's user avatar
  • 346
5 votes
1 answer
1k views

XJ600 1994 Seca 2

I am wondering if anyone can shed light on an issue we are having with this particular bike. Basically, the bike starts fine cold and warms up and drives perfectly for about 15 minutes ( responsive to ...
user190084's user avatar
5 votes
1 answer
104 views

Why a two-lever valve spring compressor?

I just purchased a valve spring compressor that has a lever on both ends, similar to this one: What is not clear to me is the advantage of having this two-lever setup. What does it have over the ...
Zaid's user avatar
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5 votes
3 answers
4k views

1994 Honda Accord EX (F22B1) - Valves still making a ticking noise

I have a 94 Honda accord Ex (F22B1). When I bought it a few days ago the previous owner mentioned a few of the issues that he could remember. Since I've only ever owned Honda's and have worked on them ...
Robert Snyder's user avatar
5 votes
1 answer
3k views

When should I perform a valve head adjustment?

My 2012 Yamaha R6 has about 12000 miles on it. During that times I've had a couple rough accidents and I think the combination of those two factors it may be a good idea to check my valve clearance ...
davidcondrey's user avatar
5 votes
1 answer
978 views

Stuck valve, loss of pressure. Risky or only poor performance?

I have a 1998 Toyota Tacoma 2.7L 4cyl with 202,000. The engine has been running rough and will occasionally sputter and die when I let off the gas pedal. I had it diagnosed and they think it's a ...
flyinryan's user avatar
5 votes
2 answers
5k views

Reliability of water test for valve seal

I took my valves out, cleaned and lapped them and put them back together. I also put new valve stem seals. At least on one side of my V6 Tacoma. I performed several water tests to check the seal of ...
amphibient's user avatar
  • 6,653
4 votes
4 answers
32k views

Do valve cover gaskets need to be replaced every time you reopen the valve cover?

About two weeks ago, I replaced my cork/rubber valve cover gaskets on my 84 2.8L V6 Ranger since the old ones were leaking pretty badly. I forgot to adjust the valves when I did the gaskets, and now I'...
Kevin Evans's user avatar
  • 1,186
4 votes
3 answers
3k views

Should I lap my valves if I have easy access?

Now that I have my cylinder heads out of my V6 Tacoma, I am considering taking the valves out to inspect them in case they are bent or whatever and grind them. There is no symptoms of valves ...
amphibient's user avatar
  • 6,653
4 votes
1 answer
285 views

Are valve shims re-usable?

I'm in the process of re-shimming the valves on my 1994 Suzuki Katana 600. For the valves where I need to replace the shim, should I save the old shim I removed, or is it considered a disposable item ...
Brian Knoblauch's user avatar
4 votes
1 answer
6k views

Should I care about valve order or are they interchangeable?

So I've just learned how to take valves down and I'm pretty fascinated by the whole mechanism. I got a C-clamp compressor and took two valves out just to try. Went smooth. A question: is it important ...
amphibient's user avatar
  • 6,653
4 votes
2 answers
172 views

Are there any downsides to the Coates valvetrain?

There was a lot of buzz around the Coates valvetrain circa 1995. (Animation is too good to miss) Two decades later, I still don't see mass adoption of this "revolutionary" technology. So what gives? ...
Zaid's user avatar
  • 39.2k
4 votes
1 answer
147 views

Should I be concerned about eccentric valve rotation?

Yup, it's that infamous Exhaust Valve #3 again (that "6" is a misnomer). It's now back from the machine shop, with a freshly-cut valve face as part of a 5-angle valve job. Now that the valve and ...
Zaid's user avatar
  • 39.2k
4 votes
1 answer
24k views

Why is this motorcycle burning oil, and how can I get it to stop?

I have a newbie question for you. I'm considering buying a 2004 Yamaha TTR600RE- a single-cylinder, air-cooled dirt-focused dual-sport bike. It's perfectly set up for adventure touring, which is what ...
bevanb's user avatar
  • 337
4 votes
0 answers
98 views

Light abrasion on the valve stems - is the outlook gloomy?

Background I'm rebuilding my LS1 Chevy. The cylinder heads came back from the machine shop fresh with a 5-angle valve job and mechanically-lapped valve faces and seats. What concerns me is the ...
Zaid's user avatar
  • 39.2k
3 votes
2 answers
3k views

Why are intake valves dirtier than exhaust?

I took my engine apart and one of the things I noticed, on both cylinder heads of my Tacoma V6, is that the intake valves (picture right) are significantly darker (or dirtier) than the exhaust ones (...
amphibient's user avatar
  • 6,653
3 votes
2 answers
752 views

Reusing valve stem seals

I just lapped my valves on a cylinder because they were leaking and reused the stem seals. Should I put new stem seals or is it okay to reuse them?
amphibient's user avatar
  • 6,653
3 votes
4 answers
2k views

Lapping valves by hand - does the compound have to be cleaned off?

I'm hand-lapping valves on the LS1. This is probably a silly question, but I just wanted to confirm that I have to wipe off the lapping compound prior to the hydro test.
Zaid's user avatar
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3 votes
2 answers
8k views

Lapping Valves - Using Water as Test Medium

I've lapped my valves and want to check if they are sealing properly. Everywhere that I've read talks about using stuff like, acetone, gasoline, paint thinner... to fill the exhaust/intake ports and ...
John_911's user avatar
  • 161
3 votes
2 answers
1k views

Compression of valve springs and camshaft rotation

As you know, in most cars it is not easy to turn the intake or exhaust camshaft by hand. You probably need to use both hands, grab the cam sprocket and apply a lot of force to rotate them even with ...
LFY MP7.3's user avatar
  • 946
3 votes
3 answers
989 views

How does excessive undercutting of valves make an engine less streetable?

I don't understand a claim made by Jafro's machinist in this video (around 26:00): (Jafro inspects undercut valve) Machinist: You drive it on the street too, don't you? Jafro: ...
Zaid's user avatar
  • 39.2k
3 votes
1 answer
806 views

Can I use hard tools to remove hardened carbon buildup on valves?

I used a brass brush by hand to clean the carbon off the aluminium head of my BMW R80GS 1991. The valves however are very stubborn, a brass dremel head won't do it either. I started using a soft steel ...
Max's user avatar
  • 358
3 votes
1 answer
356 views

If I'm lapping valves do I need to replace piston rings?

I just removed the head and am lapping valves because of timing problem. If I'm lapping valves, do I need to replace my piston rings too or not? Car: 2010 Passat CC 1.8 TSI, 100,000 km
Fredj A Jad's user avatar
3 votes
2 answers
208 views

Is this valve toast or could I possibly salvage it without tearing into the engine?

I have a 2010 Mustang GT with 4.6L engine that started making a ticking sound which at times is fairly loud. The sound is much less obvious at cold start but becomes apparent after it gets hot. The ...
mark b's user avatar
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