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.

 

[enginesrus]

That's like asking me for data of airbag problems before it became so widespread that the manufacture finally had to admit there was a problem. That is pretty much how problems with cars are dealt with. Like the BMW failures of the past.
Or the Porsche problems, or the Toyota problems, many just swept under the rug.
It is not like extracting data from a dyno run.

 

[LadaTrouble]

[ I don't think Honda has ever built a pushrod engine for automotive or motorcycle applications.]

Ooops....The first C50 was a pushrod engine, the CG110 and 125 were very popular, and of course the CX already mentioned. They also made a high cam engine in quads, similar to BMW, where the cam is in the head, but opperates pushrods. Engines converted from pushrod to OHC (Volvo, Ford Falcon) are much taller engines...that's not exactly going to get frontal area down.

 

[SwinnyGG]

That's like asking me for data of airbag problems before it became so widespread that the manufacture finally had to admit there was a problem.

Do you realize that cars have been on the road with overhead cams for more than a century?

I mean... did you know that? Seriously? This isn't new.

 

[enginesrus]

I've got 4 that do have OHC. They are great for repair shops, a head pull means dealing with cam drive and timing along with the normal things needed on a push rod engine. Cam drive was never an issue on say an old chevy 6, and they out lasted many modern engines of now days. Just so many 10,000 to 20,000 dollar disposable auto engines now. Has anyone here ever worked on a W8 VW engine? I have, and how much fun is dealing with the cam drive system on that engine?

https://www.youtube.com/watch?v=slQ9E1s1FuQ

W8 is very similar to this cam drive at about 4:00.

Disposable

https://www.youtube.com/watch?v=c2g6H3u9B8o

 

[SwinnyGG]

an old chevy 6, and they out lasted many modern engines of now days.

They lasted longer?

You sure?

Have any data that says so?

Something other than a youtube video?

Something other than your opinion?

 

[btrueblood]

Don't cite a VW engine as an example of engine design. Just don't.

and, "or the Toyota problems, many just swept under the rug. " Hunh? Toyota has run so many voluntary recalls on their products it makes your head swim. Voluntary recalls are a sign of a healthy company, willing to fix things so their customer base stays loyal and happy.

 

[BrianPetersen]

The W8's maintenance nightmare (which it was), wasn't the fault of it being OHC.

I've had the cylinder head off a few motorcycle engines, all OHC, and the fact that you have to disconnect the timing chain tensioner and remove the camshafts as part of the procedure is a relatively trivial part of the overall job.

 

[enginesrus]

Brian, then just use the Mercedes as a OHC maintenance nightmare, or maybe the subarus, or BMW's. And when the cam drive system goes out, its most always a front cover removal to access the plastic chain guides. Except for the rear timing chain engines like the W8.
Data on the old chev 6's out lasting the newer engines? Data? Where would you even begin to find such data?
The OEM's for all the failed modern engines will not release such info, and they will be the only source for it, because even when out of warranty they will still be the number one point of first contact in hopes of help. Maybe attorneys would have the info. And to be fair the data would have to only compare the number of failed engines with in 1 year when the warranty runs out. There would be little if any data available beyond that.
jgKRI if you trust the other sources on the net there is data of the modern engine failures, in the form of consumer complaints, there will be none on the old stuff.

 

[SwinnyGG]

Data on the old chev 6's out lasting the newer engines? Data? Where would you even begin to find such data?

I have no idea where you would find this data. And....

That's my point exactly. You're making a baseless claim.

If there's no data available, where did your opinion that the old 'chevy 6' is the paragon of gasoline engine reliability come from??

I can tell you one data point that doesn't support your case- look at the history of automotive warranties offered by Big 3 OEMs.

In the 60's there was a 'warranty war' as all three major players added years and mileage to their warranty programs, in an effort to outmarket each other and boost sales. Lincoln's BIG PLAY early on was to offer a 2 year, 24,000 mile warranty. If that was the 'halo' warranty offering from any major non-luxury manufacturer now, they likely wouldn't sell very many cars.

By the early 70s, these warranty programs had sank back down to single year with low mileage limits- because the cars of the late 60s were built with such varied quality that the warranty war cost the big 3 massive amounts of money.

Engines today are categorically better that the 'chevy 6' you reference and it is not close. They are lighter, they last longer on average by a large multiple, they produce a LOT more power from smaller packages, they are much less expensive to own over the long term, they are made in larger numbers with much better manufacturing consistency, they are better for the environment... they are literally better in every single conceivable way. The fact that they use technology that you don't understand or don't like is not a valid argument for much of anything, let alone for why we should all be pining for slant sixes iron heads and single barrel carbs.

You're worshiping an era that no one wants back, and making a wild claim that you, by your own admission, can't support. And you do this same routine in seemingly every thread you start... I'm not sure why.

 

[enginesrus]

Thank you for the help.

 

[JayMaechtlen]

Seems to me there are lots of interesting tradeoffs. (initial cost, bulk vs weight vs power per liter, etc...)
If emissions standards weren't mandated, cat converters wouldn't be needed, and priorities of engine development would have been quite different.
However - seems to me that power and economy would still have driven fuel injection and related developments.
I sure don't have the answers - don't even have all the questions!
It certainly would be fun to know more about statistical reliability of various engines. Consumer Reports ratings of new and used cars offers some clues, perhaps.
Two of the cars I had in the past were downrated (by CR) for fuel injector problems - Buick 3300 V6 pushrod motors.
I put lots of miles on the cars I had (two 3300s, one older 3.8, and a 3800) with never a hint of FI issues.
But three vehicles out of millions - not statistically meaningful.
Another data point re repairability - most 3800 enthusiasts consider the motor not worth rebuilding, as it is easier to find a good used motor with only 100k miles or so, and run it!
And that is an iron block, iron head pushrod motor.
Yeah, the Ford spark plugs are a bit scary - need to have some care getting them out to avoid a cyl head R&R.




Jay Maechtlen

http://www.laserpubs.com/techcomm

 

[GregLocock]

Wasn't the push towards OHCs vs pushrods more to do with weight reduction and fuel economy, as it was easier to design light, small capacity, high power engines with DOHC at the time? That's not to say that in retrospect it was the right decision, compare the DOHC LT5 Corvette engine and its pushrod successors, LS1 and LS6.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

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[3DDave]

The Ford plugs were a perfect storm - neck down the plug to a tiny section; make it from a low-expansion material and drop it into a close-fit hole made with high expansion metal; then introduce fuel which won't combust well in the narrow gap, depositing carbon; tell people they don't have to mess with the plugs for 60 or 80 thousand miles and, finally, tell people they have to change the plugs when the heads are cold, so that differential expansion gets the tightest grip the head can possibly have on the carbon coated plug.

If they had changed any of those things there would have been few to no problems.

 

[Lou Scannon]

The Ford plugs were a perfect storm... finally, tell people they have to change the plugs when the heads are cold, so that differential expansion gets the tightest grip the head can possibly have on the carbon coated plug.

That is interesting. I just acquired a 2003 Grand Marquis, and was warned by my mechanic brother to R&R the plugs sooner rather than later. But the hot vs cold, I get the differential thermal expansion, so is there also data supporting that removal hot is better than removal cold?

"Schiefgehen wird, was schiefgehen kann" - das Murphygesetz

 

[MikeHalloran]

I'm not sure that hot/cold matters, because by the time you get the first one out, the engine will be cold anyway.

My mechanic friend suggests applying PB Blaster (or Kroil if you have it) to each plug for several days in a row, then working slowly and carefully to ease them out.



Mike Halloran
Pembroke Pines, FL, USA

 

[GregLocock]

Well, you could do one, take the car for a spin, do the next one, rinse and repeat.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

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[Lou Scannon]

I meant to include in my post, only 50,000 original miles, so the assumption is the plugs are original (undisturbed) also.
@MikeHalloran, I was thinking along those lines myself.
Does anyone know a maximum safe removal torque?


"Schiefgehen wird, was schiefgehen kann" - das Murphygesetz

 

[3DDave]

How long does it take to remove a plug? Anyway, if the engine cools before they are all out, put in the new ones and toast it up again, just don't over torque the replacements; wait for the engine to cool before setting the final torque. Differential thermal expansion is one of the things a person can count on. It looks like the eventual recommendation was to use impact tools on the spark plugs; maybe it fractures the carbon.

Not sure how the Kroil gets past the threads to where the interference is. This isn't the threads binding in the head, it's the probe that feeds into a tight passage that breaks off because of jamming with carbon.

http://www.fordproblems.com/trends/spark-plug-stuck/

That probe is swaged to the threaded body, so it twists off and then breaks the ceramic and electrode off.

I think the rate for changing plugs was between $50 and $100 each for labor to make up the cost of removing the stub, but if it got bad it seems some were charging closer to $5000 per head to remove the fragments. Obviously better to avoid injury lawsuits from mechanics getting burned on hot engine components than worry that changing a set of plugs might cost the the customer a thousand dollars or more.

I found the original recommendation was 100k miles interval, but the class action settlement prevented anyone from claiming if they had more than 80k. Most of the checks were under $100. It is now 65k, but I think most owners are going for 35k to be safe.

 

[RodRico]

Wikipedia has a compilation of the 10 "best" engines selected by Ward's Autoworld magazine since 1995:

https://en.wikipedia.org/wiki/Ward's_10_Best_Engines

 

[btrueblood]

Popularity/beauty contest for engines? No mention of serviceability or reliability there...