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I had a chance to pop my valve cover today. I wanted to look things over and check out my lift bolts. Here are some pictures and comments.

I can do a lift bolt changeover writeup if folks are interested. Basically they are a wear item in the cam changeover gizmo and sometimes they break. Once your valve cover is off (10 minutes or so, a trick or two but easy) they just unscrew and you load in the new ones. They cost me 98 cents for the two you need, one bolt per cam. The valve cover goes back on easily, there are a few things to line up, you need a dab of glop near the chain cover and you reuse the rubber gasket.

Lif Bolt: Toyota PN: 90105-06293

Here is the head with the valve cover yanked...clean as a whistle, synthetic oil baby.



Here is a closer view with the lift bolts unscrewed.



New versus old bolts...see the wear pattern? There is a ridge and the wear goes all the way around the bolt.



Another view...



I am glad I changed the lift bolts. If the bolt breaks off it is a pricey repair and you can't hit the big cam in the mean time.

Go for it Stan......by the way can the valve springs be changed while engine is in the car?

Stan da man,
Any idea as to what causes that unusual wear on the bolts? Seems like it would be bad design to me.

Aloha,
Thomas Praetzel
And oh ye, Stan, as usual, as we say on Maui, "you da akamai guy, bruddah!!"

ronin wrote:Go for it Stan......by the way can the valve springs be changed while engine is in the car?

The valve springs? Sure. You just use a spark plug adapted to a compressed air line, or buy an adapter. BTW...when you SC boost a car...the intake valves acts like the springs are weaker...due to the pressure on their back side = lower valve float RPM.

BTW...examine the cam construction in the PICs above. They use a shaft onto which separate lobes are assembled. This is needed because the low and high cams need to be made of different metals from one another. The low cam uses roller lifters, while the high cam uses slippers which slide against the cam. That sliding action leads to high loads per square inch and has wear / lubrication issues.

Underside view of the valvecover. Note the lubrication plumbing designed to aim at the high cam lobes and keep them alive.



A closer view. The tube lives in the corner near the trunk and oil fill cap.

Some high cam lobes have the ? appearance. No pitting or scratching if you test with a fingernail. Maybe that is some remaining coating (see lobe sides). Also note the roller VS slipper concepts. The low cam uses a low friction roller lifter...they are undemanding lubricationwise due to the rolling and not sliding/rubbing action The high cam slipper sees very high rubbing loads, which requires some xtrem pressure (EP) functionality from the oil. Note that such additives have been reduced several times as the API certifications SL, SM, etc have progressed. See: http://www.monkeytuner.com/forum/viewtopic.php?t=554. I'd want to use a proper oil to protect the high cam if I was on it a lot... The API has capped such additives because they suspect that catalytic converters will get coated in about 8-12 years of normal car mileage. Your converter stlll flows, it just cuts pollutants less. The additive issue is more of a concern for nonroller cams and for piston rings in certain cars.

Here is an overall view:

Thanks for another great write-up Stan!

The secondary lobes being slipper type may be one of the reasons Lotus recomends heavier oil for "the track"...

Also, should valve adjustment be checked?

edaddy wrote:Thanks for another great write-up Stan!

The secondary lobes being slipper type may be one of the reasons Lotus recomends heavier oil for "the track"...

Also, should valve adjustment be checked?

Our motor uses the lightweight shim under tappet approach. Little lash caps on top of the valve stems. The roller and slipper are height matched such that both clearances are set when the tip clearance is set. The wear is low, it's a PITA to set as the cams have to come out. But especially if you'll have the cams out reset it all. You check clearances with everything together, writing it all down. Then you disassemble the works and measure the shims, calculating what is needed. After doing any needed, you reassemble and confirm clearances. Some cars use pop out disc shaped shims weighing about an ounce apiece...which are much easer to service...but those weighty shims and their buckets affect high rev operation and required spring rates.

why not buy the cyro'd lift bolts?

Stan da Man,
The whole shim thing brings back some rather bad memories of my 63 Elan, what a pita that setup was, if you had to fuck with it!

Aloha,
Thomas Praetzel

choi0706 wrote:why not buy the cyro'd lift bolts?

Thanks Stan. Do you recomend checking the clearance at any particular interval, i.e. 60K?

choi0706 wrote:why not buy the cyro'd lift bolts?

I think I'll just replace mine in something like 40,000 more miles for 98 cents. That's for a pair of very easily replaced stock bolts of the latest design. I think Toyota / Yamaha designed them to be easily replaceable as well as the item intended to wear out...as opposed to the rocker shaft itself. Cryo treated bolts would likely work fine if you wanted to use them.

edaddy wrote:

choi0706 wrote:why not buy the cyro'd lift bolts?

Thanks Stan. Do you recomend checking the clearance at any particular interval, i.e. 60K?

There is no interval for that, believe it or not. Changing out the lift bolts takes 30-40 minutes, you can check clearances at the same time. Checking is not time consuming, resetting the clearances is though. Maybe 4-5 hours or so. You'd want to have a selection of various shim sizes before starting.

This article is an example of why moremonkey has now become my primary Elise board.