DOHC basic respect 101:
Double over head cam respect , that is what you have ,when you learn
that most are INTERFERENCE, ENGINES. Not
a complete list is here.
So, if your engine stalls, don't just keep cranking away, and bend over
all those head valves or worse. THINK ABOUT what you have there!
CAM drive failure:
The timing belts snaps slips or? shreds? oops.
The cam chain jumps off the sprocket, by only one hydraulic chain
tensioner failure (ignoring its cry, was your doom and very $$$$ thin
DOHC +VVT , IS DOUBLE TROUBLE, you can Google and read about that for weeks, (lots of sad owners, world wide)
Some DOHC are safe, like Mazda's fabulous 1.8L liter engines. But all Honda's smash.
Interference engine 101.
Short and sweet, it's not new information .
The FSM or all cars (chapter on your engines, covers this topic 100% read it) It may be at alldata.com too.
Why does DOHC do this and SOHC engines not. (mostly)
engines are designed from maximum performance per liter
displacement. (this ,magic timing gets more exhaust out of the
cylinders, and makes compression more effective during the intake
As does valve overlap.
This means it may have 4 or more valves per cylinder and a
2nd cam, and VVT and now the key part, to get max pumping efficiencies
This tricky timing, makes the piston chase the exhaust valve closed, closely, so close
in fact, that if the cam drive fails, the piston will hit the valves
and bend them.
(some are lucky and it just stalls, and no bend,
pure raw luck)
Luck happens, like walking across a turn pike , blind folded?
(getting killed), what is the point of discussing pure luck, as
so many do. Silly to the extreme , IMO.
The comment, gee my chain can't fail, below 200k miles design limits,
really? with oil filthy oil , running 20k on oil changes for SYN oil
hype, and did you know the hydraulic tensioner on many engines
don't last 200k?
See VVT failures (cause and effects) Google that when bored.
No matter what, the savvy mechanic, hand turns the crank (wrench) and
does a cylinder leak down test to make sure the valves are not hitting
and that they are not bent leaking like mad.
Cranking it willy nilly only bends more valves, or far worse, there is no limit to the damage caused, if you try harder.
Some engines not inference can bend valves, if the lash is set wrong, or that and engine overheated.
They have like 0.020" clearance, and if lash is wrong, off by that amount , bam you bend valves.
So there are lots of ways to mess up a soup sandwich, no? (a comedy of errors by DIY mech.'s can happen (timed wrong and lash way off?)
Keep in mind cold engines work different that hot or too hot. (thermal expansions , and pure physics)
That is all I have on this topic, but I do respect all DOHC engines. (leak down tests done or valve drive noise big time)
Keep in mind 2, that some engines,world wide run a differnent cam
profile and are different than yours (height of lobes and timing) So, respect them all, and win.
- Not cranking a dead DOHC like crazy !
- Using hand turned crank leak down tool readings to find out damage now. First do no harm, or first why make it worse?
- Not guessing at cam drive timing or using internet rumor to get
facts, get your own facts off OEM FSM Or at least alldata.com
- Setting lash by guess. and or not using TDC rules for same, per FSM.