Over head cam 8

[enginesrus]

I am having difficulty seeing the logic in using that tech for average everyday cars, especially in the past before the advent of VVT tech. It is such an expensive way to accomplish the task. Expensive to manufacture and when needing repairs due to warped heads, worn cam drive systems and the like. But in this day of disposable engines it makes things a bit more logical. Problem is these all seem to be over priced inexpensively built engines, so that makes the disposability a bit hard to take in the pocket book. For racing and performance its a go, not for grocery store cars.

 

[NormPeterson]

How long does it take to remove a plug?

Spark plugs at least in the early 3-valve Ford modular engines are notorious for breaking during removal, so it's apt to involve more than simply removing the coil-on-plug assembly and unscrewing the plug. There are special "broken spark plug remover" tools available from a number of sources, as it's apparently that common.


Norm

 

[dgallup]

Been reading the Wards 10 best for decades, didn't know there was a wiki summary. Wards do not take serviceability or reliability into account. Frequently the engines are brand new designs so no reliability data would be available. About the only outfit I'm aware of that compiles reliability data is Consumers Report and I have my doubts about their data since I believe the vast majority comes from members and is thus skewed by the bias of what kind of cars their members buy.

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The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

 

[TugboatEng]

I'm not sure that hot/cold matters, because by the time you get the first one

Our engine manufacturer wants us to set valve lash and injector timing on a "cold" engine. We have determined any engine that isn't running is "cold" regardless of the actual temperature.

 

[MikeHalloran]

. We have determined any engine that isn't running is "cold" regardless of the actual temperature.

NASCAR says it's something 3 hours after shutdown. Engine builders for that series can set the bore to come down to size after 2:45 or so.
My motorcycle mechanic friends insisted on letting a Kawasaki ZL-1 sit overnight before measuring the valve clearances.
I worked on a Kawi racer warranty claim, and measured the piston bore clearance every way I could think of. After three hours, it finally settled down to just barely tight enough.
On a big marine Diesel, it might take three hours just to get the works exposed enough to begin measuring the valve lash, so I'd agree that 'not running' is practically appropriate.



Mike Halloran
Pembroke Pines, FL, USA

 

[Lou Scannon]

Well, I found and read the TSB (08-7-6) on the Ford modular engine spark plug issue. Interestingly, it only refers to specific models and years, which do not include my vehicle. Since it is not an overhead cam specific issue, but rather a spark plug design issue, I'll discontinue the hijack.

"Schiefgehen wird, was schiefgehen kann" - das Murphygesetz

 

[LadaTrouble]

''Available in the US market''....I wondered why it was so biased.

 

[NormPeterson]

I guess not many here have turned a wrench on push rod vs DOHC engines since there seems to be a lack of knowledge of what is required to say remove a head from one or the other.

Actually, I have (at various times, all three - pushrod, SOHC, and DOHC), and I think you're cherry-picking particularly difficult/more involved examples with your German car and Subaru examples. The German mfrs have a reputation for taking the complex way out, and a boxer engine manages to hide most everything (especially when turbocharged and there's an intercooler sitting on top burying the engine itself under yet another layer).


Norm

 

[dgallup]

I am having difficulty seeing the logic in using that tech for average everyday cars, especially in the past before the advent of VVT tech. It is such an expensive way to accomplish the task. Expensive to manufacture and when needing repairs due to warped heads, worn cam drive systems and the like. But in this day of disposable engines it makes things a bit more logical. Problem is these all seem to be over priced inexpensively built engines, so that makes the disposability a bit hard to take in the pocket book. For racing and performance its a go, not for grocery store cars.

VVT is not exclusive to DOHC engines. I believe the Dodge/RAM hemi has had it since 2009, it's definitely in my '14 RAM 1500 5.7 liter push rod hemi. GM finally got around to introducing similar technology in the 2014 LT1 6.2 liter C7 Corvette motor (not sure what they use in their pickups).

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The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

 

[SwinnyGG]

(not sure what they use in their pickups).

Every V8-powered GM truck sold since MY 2010 has had VVT.

 

[NormPeterson]

Doesn't GM's pushrod VVT affect cam phasing relative to the crank without being able to vary intake to exhaust timing? Kind of a halfway step.


Norm

 

[BrianPetersen]

Yes, that's how VVT on the GM pushrod engines work. The entire cam is phased. Fortunately, in the circumstances where you want to run partial Atkinson cycle, delaying intake closing in order to intentionally reduce VE also delays exhaust opening so that it makes more use of the expansion stroke, and delaying exhaust closure (and valve overlap) to after TDC also produces "internal EGR" which is usually favorable in that scenario.