Wiped cam poll

[BlackBandit]

I'll try and keep this simple and to the point. I'm curious what boost conditions people were operating under when they wiped there cams. I know additives get blames allot for the cam wiping but what about the fact that it's gotten exponentially easier to run more boost (thanks to our vendors ) As cool as that is I don't think I've ever seen anyone post about using a stiffer spring on a new engine because they're planning on running high boost. If you think about it the stocker ran 15 psi so it took about 15 pounds off of the intake spring rate (while under boost) and probably close to 30 off of the exhaust. Now if you turn the wick up to 25 psi your basically reducing your intake spring rate by 25# and the exhaust by (total guess) ~40-50#. That's allot less pressure coming over the nose and usually that happens at higher rpms when the lifter has the most inertia the spring needs to overcome. So please poll up and lets see if boost can be linked to wiped cams.

Edit:I forgot to put it in the poll but if you don't mind post whether you had intake or exhaust valves wiped or wiping.

 

[jhanson1750]

I think there is a not the effect on the exhaust like you stated. The increase in boost (and cylinder pressure) makes the exhaust valve harder to unseat. There are some other pressure diffrential issues that will effect the airflow and the force needed to overcome pressures. Jon Hanson

 

[86 TR]

Luckily Ive never had a lobe go flat in any of my engines. Ive always used either EOS or ZDDP as an additive and broke the cam in as your supposed to.

Im building another engine right now and went with a roller. I guess just for a piece of mind and to make some more power with my combination.

 

[84BuickGNYorkPA]

Also would have been interesting to know how many wiped a cam with a additive to the oil. Ok I see, this could have went on and on....
Good poll.
I'm running 1/2 container of EOS and Rotella

Chuck

 

[BetMinesFaster]

I belive I read somewhere that the 3.8 has 1 lifter bore that is not properly centered above the cam lobe and thats the common one to flatten out???? Dont hold me to it But something about that is in my head......

 

[Black Power]

It seems like it's one of the bores of #3 Ryan.

 

[X Ray]

So far so good....no issues:biggrin:

 

[BlackBandit]

Yes, the number three exhaust lifter bore is not quite as it should be and to compensate Buick reversed the taper on that one lope so it would spin faster. That doesn't explain the other lopes wiping though. Also, in response to jhanson, I see what you're saying but if you think about it the spring pressures are spec'd the same as a NA engine and has the higher pressures working on them like I said, so I really do think it makes a difference.

 

[kingots2004]

i thought while opening it made a sealed valve harder to open not easier instead of taking away 15lbs it adds 15lbs to the lifter while opening then when the chamber is full its 15lbs harder to close than without boost.i know on my turbo dragbike i had to run stiffer springs because at full boost it would try to hold the valve open or so the bike shop told me anyway.so the intake opening i can see being easier, but the exhaust opening being harder and the intake closing being harder

 

[BlackBandit]

i thought while opening it made a sealed valve harder to open not easier instead of taking away 15lbs it adds 15lbs to the lifter while opening then when the chamber is full its 15lbs harder to close than without boost.i know on my turbo dragbike i had to run stiffer springs because at full boost it would try to hold the valve open or so the bike shop told me anyway.so the intake opening i can see being easier, but the exhaust opening being harder and the intake closing being harder

The simple way to look at it is that boost and back pressure act on top of the valve. The spring is pulling up on the valve. So the boost/backpressure are fighting the springs. Hence the shop telling you to run a stiffer spring.

 

[dr_frankenstein]

I dont know if this applys,

But I have a particular 4.1 that has never been boosted and has eaten 2 cams. One was a stock grind and the other was an Erson - both Flat tappets. It does have oversize valves and heaver springs (Z28's), but not much more than that to the valvetrain.

A.j.

 

[BetMinesFaster]

It seems like it's one of the bores of #3 Ryan.

That is what I recall, #3 exhaust!

 

[cool 84]

I've never wiped a cam but I had a friend that wiped 3 different cams. He finally went with a different block and hasn't had a problem since.

 

[gossamer]

Haven't wiped one out yet, knock on wood for luck!