Why do so many cars/motorcycles have bad valve guides?

[HardDrive]

Over the years, I have come across many stories of engines with bad valve guides. Everyone can point to a particular make/model of vehicle that was 'known' to have bad guides.

I'll get to the point, is "bad valve guides" just an excuse for shops to charge the hell out of consumers, because they know the consumer has no way of confirming the need for repair themselves?

OR

If many vehicles do have this issue, then why? How could companies like Ferrari, Porsche, Ducati, etc....make engines with bad guides? Is it really THAT hard to find the right material? Are the stresses of high compression motors harder on valve guides, thus leading to issues?

Whats the story here?

[nynor]

this is just a guess: higher stress, higher RPM's, and higher heat for the valve guides in those engines.

[RWebb]

every state needs a law requiring a shop to offer to show removed parts to the car owner

shops I use usually do -- and the guys are happy to talk about them too

[Rusty Heap]

Note that any late 1960s car or earlier, was designed to run on leaded gas.

When I had an older boat, to run on un-leaded gas, you had to run a lead additive, yeah to lube the valve guides


That said, I know my 1980's-2004's Honda Passport / Isuzu Rodeo's in all 2.8 3.2 and 3.5L engines are notorious for ticking and burning oil through valve guides.

So what IS it about valve guides, good question, new hydraulic lifters verses mechanical bump sticks?

[kaisen]

Originally Posted by HardDrive

Over the years, I have come across many stories of engines with bad valve guides. If many vehicles do have this issue, then why? How could companies like Ferrari, Porsche, Ducati, etc....make engines with bad guides? Is it really THAT hard to find the right material? Are the stresses of high compression motors harder on valve guides, thus leading to issues?

Tons of reasons:

Emissions - esp at cold start. Mfrs shoot for faster cylinder head / combustion chamber warm-up for cleaner cold-start emissions. Unfortunately, higher cylinder head temps are not 'good' for valve guides and/or other valvetrain components

Lighter weight components - Lower mass is good for performance and higher revs, but can mean less stability and more flex, leading to quicker wear. Also, less material (i.e. lighter valves) can mean more thermal transfer for hot-spots that lead to wear

Cost savings - Use of powdered / sinter-forged metals in valve seats and guides were a great ideato cut production costs, but were sometimes problematic.

Geometry - Modern combustion chambers and 5 valves-per-cylinder (F355) lead to valvetrain geometry that can/might put some lateral loading on valvestems. Coupled with low-mass valves that can flex, you have a double-whammy for wear.

Friction - rather "low friction" for higher efficiency/performance has lead to materials and coatings that are compromises. Low friction valve guides may be 'looser' and allow more oil to get by and the guide itself may wear faster at the benefit of low friction. Same with the valve stem seals that scrape oil as the valve moves. Letting too much oil by the stem seals can lead to accelerated valve guide wear. Manufacturers want JUST ENOUGH oil to lubricate, but just barely. Too much oil pressure or volume just creates losses. So sometimes the oil available at the valvetrain is compromised, esp if there is another problem, or poor maintenance

Carbon build up and other non-direct issues may LEAD TO issues like valve guide wear. Again, there may be other existing conditions that cause issues down the line. Example, the exhaust manifold issues with the Ferrari F355 can cause hot spots and overheat the exhaust valves which accelerate wear to the valve guides.

If sure there are dozens more reasons.

But some motors are either better engineered, or by luck didn't suffer the issues. I don't think it is just modern high-performance engines. It seems to be hit and miss for many.

[McLovin]

Guiding valves - it's a tough gig.

[Superman]

The guides that came stock in my 911SC were made from a material that is not as good as the guides John Walker installed. Guide technology has apparently advanced.

[ODDJOB UNO]

people were once very mean to "valve guides" they took their womenz, they took their land, they killed all their buffalo.


plain and simple...........valve guides hate YOU and ME!



signed those who have replaced their 911 valve guides.



they even hate AL GORE!

[cgarr]

Here is the start of my second box, the price of bronze gets me several cases of beer!

[kaisen]

Go Copper-Beryllium and you'll not replace a guide again

[nota]

this not Beryllium toxic and super expensive too

I believe Beryllium is banned in F-1

[kaisen]

Originally Posted by nota

this not Beryllium toxic and super expensive too

I believe Beryllium is banned in F-1

Beyllium is toxic, some forms of Beryllium alloys (like CuBe) isn't so much.
Expensive? Sure! But so is rebuilding the heads every few races

[Noah930]

It was banned in ChampCar/CART for cost reasons, mainly. Probably true for F1, as well.

The risks of beryllium exposure aren't inconsequential. I came across an internal memo for a major metal-manufacturing company a couple months ago regarding their beryllium exposure safety measures. I've got it kicking around the office someplace. This company apparently feels OSHA standards are far too lax, and their own company's internal standards are about 10 times as stringent. Plus they've got separate beryllium work areas where employees change clothes to enter/cover shoes/head/etc, shower before going home, vacuum work clothes before they exit the work area and change back into street clothes, and all that jazz.

Wonder what would happen if there were beryllium molecules coming out an exhaust pipe. (I honestly don't know.)

[kaisen]

It's really just during the machining and welding processes working with purer forms of Be that the risks are great.

BTW, my friend James Glickenhaus' Ferrari P4/5 has beryllium roll caging. Expensive, but light and strong.

[Arizona_928]

Bad as in worn? the o2 porsches guides don't last long. My 32V 928; the guides are all worn at 100k .

[LJ851]

The Ducati example i have experience with (a lot). Not all their engines suffer from valve guide issues, the DS line in particular is at fault. I have uncrated and disassembled more than one DS powered Ducati to make a race bike and the valve guides were out of spec. 0 miles on the odometer and needs new valve guides. There is only one thing that causes that and it is called poor machining.