Camshaft cover defect causing rocker-arm breakage (P1302)?

[SKYVUE]

Michael:

How many Elises/Exiges have the broken cam parts?
How many are consistently thowing the "infamous" cam codes?

Carl and I will be pulling the valve cover on my '05 Elise cam (30,000 miles including 4000 track miles) Friday. So far, there isn't a problem. This is for prevention and another data point for trying to solve the cam problem.

I hope your Lotus is repaired and hits the road soon.
I know what the feeling is without a Lotus!
GOOD LUCK!

--Hal

[xtn]

Originally Posted by insane

...the valve hits the seat so hard, it malforms and heads up the valve guide (slightly) -- essentially 'stretching' the valve stem.

Boosted is correct; that's a way-common way to kill a valve train. ....but not the only way.

Okay, I get what you mean, but I don't get how that causes valve train damage. I mean so what if the valve stem is elongated? That just means the low point on the cam lobe will be the determining stop instead of the valve seat itself. Just means the valve won't close all the way anymore. Shouldn't put any undue stress on the rocker or cam???

xtn

[Brent Bauman]

Okay, I get what you mean, but I don't get how that causes valve train damage. I mean so what if the valve stem is elongated? That just means the low point on the cam lobe will be the determining stop instead of the valve seat itself. Just means the valve won't close all the way anymore. Shouldn't put any undue stress on the rocker or cam???

When valve adjustment is tight, a valve doesn't sit fully in its seat. Therfore yhe stress and energy from combustion is driven through the valve, stem, rocker then cam. The valve, seat and head are designed to take this combustion stress and spread it accross a larger area; the valvestem, rocker, and cam are designed to push against the valve spring tension. This is much less and over a much smaller area, tip of the valve stem. When valves go tight they can ruin heads, valves, guides, rockers, etc. When they break they ruin even more.

[shay2nak]

what's a mushroomed valve?

[SKYVUE]

Originally Posted by shay2nak

what's a mushroomed valve?

You don't want to know, shay2nak. If you knew what a mushroomed valve is, you'll get nightmares. Marilyn Monroe had mushroom valves before she died.

(I love the emiticon:)

[GTsRasta]

And here you guys are saying "we need low-midrange power adders, NOT top end power adders", yet there's so much rev limit bouncing going on...

See the importance of top end power adders now??? Why milk power out of high rpm use and create more wear and tear to your engine when you can put together a top end oriented setup???

[MaineLotus]

Originally Posted by GTsRasta

I so called that. LIFT can be a killer...

Lift occurs before redline, the two are not related. And I think your initial post asked whether being on cam caused the misalignment of the oil spray - you're still incorrect, it has nothing to do with being on cam. It's a manufacturing flaw.

Originally Posted by GTsRasta

"yet there's so much rev limit bouncing going on..."

How do you know this? Are you riding with everyone experiencing this problem?

[xtn]

Originally Posted by Brent Bauman

When valve adjustment is tight, a valve doesn't sit fully in its seat. Therfore yhe stress and energy from combustion is driven through the valve, stem, rocker then cam. The valve, seat and head are designed to take this combustion stress and spread it accross a larger area; the valvestem, rocker, and cam are designed to push against the valve spring tension. This is much less and over a much smaller area, tip of the valve stem. When valves go tight they can ruin heads, valves, guides, rockers, etc. When they break they ruin even more.

Okay now I understand. Seems like if the valve remains slightly opened during combustion that MOST of that pressure would just pass around it into the intake runner and not really push up on the valve that hard, but I suppose even a small percentage of the total pressure acting upwards on the valve can be too much for the rocker and cam.

But wouldn't there also be signs of intake-side backfire if that was the case?

xtn

[xtn]

Originally Posted by MaineLotus

How do you know this? Are you riding with everyone experiencing this problem?

Personally I hit redline all the time while rowing up through the gears. At least during track outings anyway. But I certainly don't sit there pegged against the limiter just holding it there!

xtn

[GTsRasta]

Originally Posted by MaineLotus

Lift occurs before redline, the two are not related. And I think your initial post asked whether being on cam caused the misalignment of the oil spray - you're still incorrect, it has nothing to do with being on cam. It's a manufacturing flaw.



How do you know this? Are you riding with everyone experiencing this problem?

I guess it's still a manufuacturing problem, but I don't see a point of going into lift if I don't redline it, especially if you want to stay in the cam. It's inherit that some of you guys bounce of the rev limiter, due to the fact you guys have a high rpm/low torque sports car. You expect me to believe you're saving wear and tear in your engines by shifting at 8,000 rpm or something? I know I'm not when I'm hitting the corners.

[insane]

Originally Posted by SKYVUE

Michael:

How many Elises/Exiges have the broken cam parts?
How many are consistently thowing the "infamous" cam codes?...

--Hal

Wish I knew. I think someone may be tracking that in another thread. Somebody may want to start a thread (or solicit PMs to collect names and VINs, or any other pertainant tracking information).

Originally Posted by shay2nak

what's a mushroomed valve?

see post #100... the part about 'malforming' -- not sure about the nomenclature, maybe it looks a little like the top of a 'shroom (never seen it)

[turbophil]

It seems like poor valve adjustment would be a much more likely source of wiping a cam lobe than slightly misalinged oil shower. Too tight will cause undo wear and Pressure on the valvetrain for obvious reasons... Can't you shim the rocker shafts to adjust clearance just like a turbo Buick? Seriously, I think you can ,yes?

Best,

Phil

[Icedog_16]

I've seen a few mentions of valve float, but what's to say that the springs in our engines are sufficient for the increased redline that Lotus has allowed, much less any margin of safety? AFAIK, they didn't upgrade any of the internals.

[Ol'Racer]

Originally Posted by turbophil

It seems like poor valve adjustment would be a much more likely source of wiping a cam lobe than slightly misalinged oil shower. Too tight will cause undo wear and Pressure on the valvetrain for obvious reasons... Can't you shim the rocker shafts to adjust clearance just like a turbo Buick? Seriously, I think you can ,yes?

Best,

Phil

Yes you can. Don't know the procedure though.

[xtn]

Shimming is used for the lash adjustment, but not at the rocker shafts. There is a little spacer shim that rides on the tip of the valve stem itself.

xtn

[Ol'Racer]

I think between the roller on the rocker... right? Between shims and rocker arms? Might need a tool to hold the rocker down...pretty hard with just a finger and the gauge. NO?

[turbophil]

Originally Posted by xtn

Shimming is used for the lash adjustment, but not at the rocker shafts. There is a little spacer shim that rides on the tip of the valve stem itself.

xtn

Are you sure? I think you can shim the rocker shafts to adjust lash even on the 2ZZ. I've broken the rocker shaft on a turbo buick from too little lash. I would think too little or too much lash could cause a broken/wiped valvetrain on the 2ZZ as well...

Has anyone checked it?

Obviously can't check it on the bad ones since it's too late, but what about the good ones? Perhaps there was some greater deflection or machining variances on #3 causing a lash problem... Or perhaps the valve seat is wearing a little faster for some reason (good, bad, or indifferent) causing the lash to tighten up beyond spec... then valves can float or stay in contact with the rocker wiping the oil film off, etc... Obvious problems...

Regarding this oiling issue: I was always under the impression that the 2ZZ had too much oil slopping around in the head and there were even reports that it couldn't drain oil fast enough. Improperly adjusted valvetrain sure seems like the most logical place to start with a cam wiping problem... Disclaimer: I've built and blown up a lot of engines but NOT a 2ZZ, so I can't say for sure on this particular motor...

If it's been checked by everyone, then forget it... just a thought...

Best,

Phil

[ZAMMY1]

re: oiling on the head.
the orifice in the oil feed line looks to be under .075".
there is a hole in the end of the head that's (guessing) abouy 1/2" by 1 1/4" which the oil can drain back into the lower engine.
the idea of the head assembly containing too much oil is not reasonable to me.
if/when i take the xrs apart, i'll photograph it, or if someone has a head open, they could post it.
when i took my elise v/c off, there was no puddled oil apparent.
sam

[Jack]

Originally Posted by turbophil

It seems like poor valve adjustment would be a much more likely source of wiping a cam lobe than slightly misalinged oil shower. Too tight will cause undo wear and Pressure on the valvetrain for obvious reasons... Can't you shim the rocker shafts to adjust clearance just like a turbo Buick? Seriously, I think you can ,yes?

Best,

Phil

Could be the cause -- I doubt it's a defective cam cover oil shower.

Phil, you've got to stop talking to Frank.

[xtn]

Originally Posted by turbophil

Are you sure? I think you can shim the rocker shafts to adjust lash even on the 2ZZ.

Pretty sure. Please note the rocker shafts are continuous, making individual rocker adjustment highly impractical. Consider that if the adjustment was made to the rocker, there would be no adjustment for the individual valves for that cylinder. Also note the "shim" that resides atop the valve stem where the rocker touches it. The engine manual details the procedure to measure the lash and choose the correct shim at this location. I have indicated both the rocker shafts and the valve-top shim on the following image: