Pics from under my Mazda's valve cover.

[mike1qaz]

Nice looking top end, I only hope my daughters '99 1.6L ZM does as well. We're at 82K+ and I haven't cracked it yet but, through the oil fill everything looks good.

Was the timing belt/water pump replaced at this mileage also?

Was this the first transmission fluid change? I've been draining and replacing about 2.5 qts every 10k since we got her's at 47K. BTW, back in '99 Mazda spec'd MII or DexronII. I wonder if the Mercon V would work in her Protege.

 

[tigrpal]

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That cam is not like an old small block cam. The low side tapers away . The width of the lopes is not constant like old small block cams.

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I find that interesting. I think I can understand making them narrower, but why not narrower all the way the around?

 

[74DartSport]

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I think I can understand making them narrower, but why not narrower all the way the around?

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Think about the pressure the lobe sees as it depresses the valve; as it's opening pressure goes way up so you'd want more surface area to decrease the unit loading.

 

[tigrpal]

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I think I can understand making them narrower, but why not narrower all the way the around?

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Think about the pressure the lobe sees as it depresses the valve; as it's opening pressure goes way up so you'd want more surface area to decrease the unit loading.

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Bear with me please, physics class was 30 years ago.

I guess I was thinking of forces in the other direction - the cam is exerting force on the valve stem. That force is coming out from the cam shaft through the long end(if you will) of the cam. In order to push open the valve, wouldn't you want the force to be concentrated in as small an area as possible and concentrated directly on the end of the valve stem? It seems that a wide cam would spread out those forces.

I'm sure the engineers, designed it right. I'm just trying to understand.

 

[tom slick]

you have a keen eye, the low side gets really skinny. why? weird mazda engineers. you have to remember this comes from the same folks that make engines with spinning pistons.
I guess once the "bump" is away from the shim/valve it no longer makes contact. its not like a v-8 where the lifter is in constant contact.

 

[kgb007stb]

What was the concentration of LC used? I am currently using 10% in one of my vehicles, your results look promising.
What were the driving conditions? Was this engine redlined?

 

[mazduh30]

Very nice...shows that you really take care of your vehicle

 

[ekpolk]

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I think I can understand making them narrower, but why not narrower all the way the around?

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Think about the pressure the lobe sees as it depresses the valve; as it's opening pressure goes way up so you'd want more surface area to decrease the unit loading.

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Bear with me please, physics class was 30 years ago.

I guess I was thinking of forces in the other direction - the cam is exerting force on the valve stem. That force is coming out from the cam shaft through the long end(if you will) of the cam. In order to push open the valve, wouldn't you want the force to be concentrated in as small an area as possible and concentrated directly on the end of the valve stem? It seems that a wide cam would spread out those forces.

I'm sure the engineers, designed it right. I'm just trying to understand.

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Remember that the cam lobe does not act directly upon the valve stem. In a modern engine design, there is some form of device in between the two, a lifter, tappet, etc., depending upon the design. The general idea is to have the relatively thin and hot valve stem acted upon by a purely vertical force. If the lobe itself touched the stem, it would get it's "up and down" vertical push along with significant "bending" force from the rotating lobe.

Now, as to the original point, for the "pushing" contact between the lobe and the lifter, more contact area would presumably (there may be other factors at work in a particular design too) result in less force per area. On the "back" side, with no "pushing" happening.

 

[ekpolk]

Oh yeah, congrats on the successful engine care program. Hard to argue with that. 10w30 clearly isn't the "red-headed step-child" that some seem to feel it has become. . .

 

[tom slick]

LC20 was added at 4 oz per oil change. and an oz here and there as a top up.

 

[92saturnsl2]

By the looks of the pics, it's a bucket type lifter directly underneath the cam... I thought the bucket style lifters were all hydraulic? Why the need to check valve clearance?

FWIW, most heads with this design (cam acting directly on lifter) have the tapered lobes. I've noticed this many, many DOHC designs including Kia, Saturn (1.9L DOHC), Hyundia, Daewoo (now GM), etc. It's to save costs. The idea is to spread the force over a larger area, then taper down where there is no exertion of force.

I imagine if the lobe didn't taper to as large as it does, the oil film wouldn't hold up (too much pressure would literally wipe it away perhaps), and you'd wear grooves right into the surface of the lifter, and perhaps the cam lobe would wear itself.

 

[Max_Wander]

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By the looks of the pics, it's a bucket type lifter directly underneath the cam... I thought the bucket style lifters were all hydraulic? Why the need to check valve clearance?

FWIW, most heads with this design (cam acting directly on lifter) have the tapered lobes. I've noticed this many, many DOHC designs including Kia, Saturn (1.9L DOHC), Hyundia, Daewoo (now GM), etc. It's to save costs. The idea is to spread the force over a larger area, then taper down where there is no exertion of force.

I imagine if the lobe didn't taper to as large as it does, the oil film wouldn't hold up (too much pressure would literally wipe it away perhaps), and you'd wear grooves right into the surface of the lifter, and perhaps the cam lobe would wear itself.

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All Mazda engines 98+ we're mandated solid lifter DAMB (Direct Acting Mechanical Buckets) in North America to eliminate any problems with HLA clogging and collapse due to poor maint. Pre-98 they were Hydraulic without the base circle tapering. The tapered base circle allows oil to to spread over the bucket face when not being held open. This contributes to even less bucket/lobe wear. They are said to be maint. free for the life of the engine, which explains Mr. Slicks findings of within spec measurements.

 

[jbas]

DINO NO: "jbas you too, whats your driving conditions"

Dino no: central Okla., summer temps usually upper 90s, but can get up to 108F couple of days a year; winter's coldest - in single digits. Seldom zero. But wind chills with 30,40 mph gusts makes it seem worse. Only 3 months winter here. I've used 10w30 dino and syn in eights, 4 cyl., and sixes. Of course, A/C running constantly in summers!

 

[tom slick]

this engine has shim in bucket directly on the valve, no hydraulics, hence the clearance check.

 

[Greggy_D]

Wow. Gorgeous pics. Please tell me that's your new dinner table cause you could eat off that sucker!

 

[Jim 5]

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FWIW, most heads with this design (cam acting directly on lifter) have the tapered lobes. I've noticed this many, many DOHC designs including Kia, Saturn (1.9L DOHC), Hyundia, Daewoo (now GM), etc. It's to save costs. The idea is to spread the force over a larger area, then taper down where there is no exertion of force.

I imagine if the lobe didn't taper to as large as it does, the oil film wouldn't hold up (too much pressure would literally wipe it away perhaps), and you'd wear grooves right into the surface of the lifter, and perhaps the cam lobe would wear itself.

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To add to the discussion, I would agree with much of the foregoing, except I might question two points:

1. I don't think the tapered a cam lobe design is to save money. I can't imagine any significant increase in cost of designing a full thickness lobe around the full 360 degrees of the cam. Instead, I'm guessing the tapering (in locations where less lifter pressure occurs on the cam) is to lower internal engine friction/resistance and free up horsepower, without an increased wear penalty; and

2. I don't think the lifters would get a groove unless they were roller lifters (even then I'd question it). A properly designed lifter should be constantly rotating within its bore, and should not stay in one orientation with respect to the cam lobe long enough to have a groove worn into it. I will admit that I've never seen how a shim-in-bucket lifter sits in an engine block, so this comment may be off base.

 

[JAG]

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Nice looking top end...

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That sounds like a decent pick-up line. Single guys may want to consider using it with the ladies.

 

[Doc8404]

haha....I always liked, "You have a beautiful pair.....................of eyes"

 

[BrianWC]

Wow....

 

[sprintman]

tom slicks comment on driving conditions show why it's clean.