Flat tappet question?

[GTO52]

Does a flat tappet camshaft refer to an OHV engine only?

So in otherwards is it safe to use an SM spec oil in any engine with an overhead camshaft?

 

[SteveSRT8]

typically, but many OHC designs actually ride directly on a flattened follower/bucket/adjuster.

So some of them can be affected by the lack of Z in oils, too.

 

[Shannow]

Flat tappet is an old term.

Basically refers to sliding friction in valve trains

 

[HyperJinx]

I agree with Steve's statement. however, for the most part-the ohc design which employs a follower does not suffer to the extent that the flat tappet design does.

Flat tappen refers to the older style valve system. Most went to a quasi-roller lifter 20 something years ago.

 

[JHZR2]

I guess it would be helpful for folks if there were some telltale signs of flat tappets, and maybe known engines that had them...

 

[ARCOgraphite]

Anyone buying a car should research the engine and trans thoroughly first. Most toyota 4 cyl engines use SUB inverted bucket tappet with no hyd lash adjustment. Dealer wanted almost USD$1000.00 for a valve adjustment (6 valve locations out of spec)! Said head head and front engine cover had to be dissassembled and cams removed.

 

[ARCOgraphite]

ASTM D6891 uses a nissan inverted bucket cam mockup. But API cert allow 90 microns wear average MAX which is too much.

 

[bepperb]

"Most toyota 4 cyl engines use SUB inverted bucket tappet with no hyd lash adjustment"

This is true, or was true. The new 2.5/2.7's don't, but the Camry/Highlander/TC 2.4 does have bucket over. And, yes they are a pain to adjust. You need to find the lash, buy a new bucket and install it.

But, for someone to go around considering themselves an expert on all things engines to not be able to perform a valve lash adjustment themselves is beyond ridiculous... The reason that I post here is that ARCO has a habit of referring to these OHC bucket arrangement as flat tappet, but it really isn't. The only similarity is that it's not rollerized, the cam slides on a piece of metal. But the real problem with "flat tappets" is the high amount of moving mass, and the high spring pressures involved. In ARCO's 1000 dollar example, the 2az-fe, the spring pressure is so low you don't even need leverage, you can just push down the valve springs by hand and remove the keepers. Try that on your SBC!

 

[bepperb]

"Most toyota 4 cyl engines use SUB inverted bucket tappet"

Well, it's probably also worth pointing out that prior to the 2000's almost 4 cylinder OHC engines had bucket style valve adjustment, with the exception of Hondas where the VTEC system makes a rollerized valvetrain a necessity. In the 90's I only remember seeing a Mitsubishi with a rollerized system.

Now, many manufacturers are adopting a rollerized system for fuel economy, which usually also involves an easier adjustment mechanism. But, the GEMA engines (Dodge, Jeep, Hyundai, Kia, Mitsubishi) 2.0 and 2.4 are a relatively new design with the bucket system.

 

[ARCOgraphite]

Originally Posted By: bepperb
"Most toyota 4 cyl engines use SUB inverted bucket tappet with no hyd lash adjustment"

....

But, for someone to go around considering themselves an expert on all things engines to not be able to perform a valve lash adjustment themselves is beyond ridiculous...
I think you minimised the work involved. The cam box has to come apart, chains removed and the cams removed to swap out buckets. A MAJOR job not a shade tree job. The lash should be close to spec for 100K miles if there was no undue wear. There was undue wear.

 

[mechtech2]

OHV=overhead valve. This is universal in automotive engines nowadays. Old cars [flatheads] had valves in the block .

OHC= overhead cam. Most are nowadays, but not all.


If an cam does not have roller lifters, it is a flat tappet type.

 

[1999nick]

Originally Posted By: mechtech2
OHV=overhead valve. This is universal in automotive engines nowadays. Old cars [flatheads] had valves in the block .

OHC= overhead cam. Most are nowadays, but not all.


If an cam does not have roller lifters, it is a flat tappet type.





Absolutely right. As I was reading this thread, I was going to respond with this very sentence: If a cam and valve system does not have roller lifters, it is a flat tappet system type.

 

[UNC017]

Originally Posted By: bepperb
The reason that I post here is that ARCO has a habit of referring to these OHC bucket arrangement as flat tappet, but it really isn't. The only similarity is that it's not rollerized, the cam slides on a piece of metal.


I disagree. The part I highlighted is the EXACT definition of "flat tappet." So OHC bucket cam-followers are definitely in the flat-tappet class of designs.

Whether its OHC or pushrods, lightweight valve springs or dual-coil monsters, etc. may make a difference in how *demanding* the particular engine is on extreme pressure lubrication, but it doesn't matter at all to the basic definition of whether or not its got flat (non-rollerized) tappets. There are OHC engines that have higher tappet/lifter peak pressures in their operating profile than some pushrod engines. For example, a Jeep 2.5/4.0 has pushrods, but is not particularly demanding because its a low-revving engine with small valves, modest lift rates, and relatively light springs.

 

[UNC017]

Originally Posted By: bepperb
In the 90's I only remember seeing a Mitsubishi with a rollerized system.


The Chrysler 2.0SOHC/DOHC and 2.4 DOHC family, which first appeared in the 1995 Neon, was rollerized from day 1.

 

[ARCOgraphite]

Not used much today, but there are radiused base (bullnose/bulletnose) tappets that require a different cam profile as does the noisier flat tappet OHC. Most SOHC were/are non-direct acting fully rollerised w/ finger followers. The old Vega 2.3L and fiat 1.0-1.3L come to mind as SOHC with direct acting inverted buckets - the vega had an allen key adjustment port on the tappet. Most older bike ohc were inverted bucket DOHC. Remember when DOHC was a rarity? Those old 1.7L Alfa spyder with SPICA mechanical fuel injection? Quick cars for the day!

 

[rszappa1]

the 318 v8 has rollers in the mid to late 80s...

 

[rszappa1]

It was from 1988 to 2003...

 

[Nick R]

Originally Posted By: mechtech2
OHV=overhead valve. This is universal in automotive engines nowadays. Old cars [flatheads] had valves in the block .

OHC= overhead cam. Most are nowadays, but not all.


If an cam does not have roller lifters, it is a flat tappet type





This is true, but genearlly pushrod engines are referred to as OHV, and OHC engines are SOHC or DOHC depending.

 

[GTO52]

So it should be fine to use SM spec oil in my Toyota 3RZ-FE engine?

I found this in the Tacoma manual:

http://www.ncttora.com/fsm/2003/Repair_Manual/03tacoma/pp/lu2rzfe3/lubr.pdf

http://www.ncttora.com/fsm/2003/Repair_Manual/03tacoma/em2rzfe3/cylhea/comp.pdf (see page 4)

I used Castrol Magnatec 10W40 for years in both my pickups but changed a few months ago to HDEO oil(Delo 400 15W40)but i have noticed my fuel consumption suffered.

So I would like to change to Shell Helix Ultra 5W40 which is SM spec PCMO oil.

Here is the TDS for Helix Ultra(I see it says SL but it must be old as the bottles in the auto spares shops are SM spec)

http://www.epc.shell.com/Docs/GPCDOC_SA_TDS_Helix_Ultra.pdf

My other choice is Castrol Edge 5W40 but it is more expensive and still SL spec.

 

[ARCOgraphite]

The shell helix ultra should be fabulous! SM additive restrictions for PCMO dont apply to non EC HDEO.