big hammer

When it comes to cams and Cam theory, Darth is veryregarded.

DietCoke

iTrader: (18)

Yes, my simple math skills factor in rocker ratio vs lobe lift. 1.7 rocker * .050 lobe lift = .085 valve lift, or .015 into the piston where you may have had .070 clearance.

Simple math. It works when you know what you're talking about

tech@WS6store

iTrader: (2)

You dont measure ptv in lobe lift. You measure it in ACTUAL lift. So i took your words as literal "when you add .050 lift right there" to mean exactly...adding .050 lift RIGHT THERE. It helps when you type in a clear concise manner. Typing what you mean helps. No one is a mind reader esp thinking as small as you are.

Your rebuttals are all about IF'S
If IFs and BUTs were candy and nuts we would all have a Merry Christmas.

Adding max LOBE lift wont always increase lift "everywhere else" so it sure WONT effect ptv "everywhere else". That is a fact, not some over complicated and over simplified blanket theory.

Duntov1967

iTrader: (22)

I think there is some disconnect going on here. DietCoke is trying to say if there are no other variables except lift, whether at the lobe or valve. "Everywhere" I am interpreting to be any degree of crankshaft rotation. Except on the base circle of course.

Help me out here Mike as I am must be missing something. If the cam specs are exactly the same except for lobe lift increasing (ie duration, cl, lsa and ramp rate stay the same), not changing the advance on the sprockets, pushrods are same length (as a different length can change rocker ratio), the total effect should be the valve drops further into the cylynder and thus closer to the piston. The only variable I can forsee is that the higher lift will also give more duration under the curve but this would make the valve closer to the piston for a broader degree span. How could this not effect the PTV being a tighter clearance?

Edit: Actually using the same length pushrod with a diferent cam lift will change the rocker ratio slightly.

tech@WS6store

iTrader: (2)

He was saying that when you change cam lift ptv goes down "everywhere" vs the original cam lift. Which is half wrong and half right. It obviously can change at any point above the original cam lift but he uses a broad definition of ptv and a narrow definition of lift. No one puts 2 inches of clay on the piston to check ptv at half way up the cylinder.

What you are saying would be true only if the cam were actually in a range where ptv would even be relevant. Otherwise its just an argument about nothing really. That is dependent on cam timing also and not just lift though. If it were never close or the intake lobe were retarded enough etc then even adding more lift would be meaningless like Darth said.

Splitting hairs even further duration is just a measure of lift. So even increasing duration but keeping max lobe lift the same could decrease ptv clearance...but he never made that point. It does in essence add "lift" on the front side or the back side of the lobe, but that is such an obscure way to try and define it that no one does it. Sometimes it is calculated with lobe area or ramp rate, but no one takes the time to map all of that out for every lobe every single time either.
The separate is true though as you are using the piston as a frame of reference so to speak and move the valve as the variable, then you can also use the valve as the frame of reference and move the piston as the variable. Top down and bottom up. Ptv will increase or decrease on 2 separate engines also with different ptd clearances regardless of lift. If you are dealing with a stationary plane only the first would be true, but you arent.
Then there is every other variable on top of that. Ho far down the rabbit hole do you want to go is the issue i guess.

Its all splitting ridiculous hairs for no other reason than for one person to say they are right.

DietCoke

iTrader: (18)

Jesus christ, PTV is measured in actual lift, but you can't add actual lift to a camshaft, now can you? You add to the lobe lift, which effects the end result.

Did you eat paint chips as a child?

DietCoke

iTrader: (18)

No, I didn't.

Keep trying, through.

tech@WS6store

iTrader: (2)

If you actually had coherent posts, no one would have to guess if you mean lobe lift or valve lift.
You were all over Darth for just saying lift not "peak lift" but you say add .050 lift here and everyone automatically knows lobe lift?
Spit it out junior is it lobe lift or valve lift?
Yet you still gloss over other factual info just to add more redundant and snowflakey insults.

Im not sorry i fed the troll, but maybe you should find another bridge

tech@WS6store

iTrader: (2)

Then preach on that Rev Coke. Bless us with your infinite lift knowledge. Since you skipped over it every other time i mentioned it, address it.

Or are you going to keep quoting Tommy Boy?

DietCoke

iTrader: (18)

No one knows what you're asking, nor is there anything to guess. How much longer do you think you're going to be able to troll the community with non-knowledge before you're banned from this site?

G Atsma

DietCoke, just an outside observer here. I have read all of the interchange between you and Tech@WS6store. Tech makes a lot of good sense, does not speak inflammatorily, and besides all that is a vendor/sponsor here. You do the opposite. So before you speak of someone getting banned from here, I'd watch your own *** first.

Duntov1967

iTrader: (22)

Seriously? I don't agree with your assessment at all.

G Atsma

OK. Tech@WS6store has been trying to get a point across (a CORRECT one) that DietCoke refuses to recognize. But instead of putting in some good reasoning, he just badmouths Tech and leaves it at that. He can't see the trees for the forest. Tech is right. DietCoke is wrong.

Duntov1967

iTrader: (22)

They are both right. But tech goes off on tangents. There isn't just one factor that effects piston to valve clearance. That is a fact and to say one factor doesn't directly effect PTV is crazy as they all do. I am not defending DC for any of his comments but Tech has a propensity to talk down and use name calling in many threads and on other forums. Being a sponsor does not give one a pass for that and it very unprofessional. He has much knowledge but so do others but perhaps needs to harness his need to butt heads.

G Atsma

Good points! And for the most part you are right. The PTV factor here in the purest sense is "where is the valve when the piston is at Point X?" And TOTAL lift is really not as much a factor as one would think. By the time either valve is wide open, the piston is WELL down the cylinder! And the wider the LSA, the less chance of interference. When BOTH valves are open during overlap is the problem. So lift AT THAT POINT should be considered, obviously. And it's LIFT AT THE VALVE that's considered. DietCoke kept on about lobe lift and "adding lift". Well, obviously that's done thru ratio rockers. But he got picky about the terminology. And hung onto it when it was not necessary.
All that aside, we all have faults. Well, except for you and I, right? LOL Have a great New Year!

Duntov1967

iTrader: (22)

Right!

But seriously, take a cam, any cam and check the closest piston to valve clearance. Note the degree. Now add to the total lift of the valve. It doesn't matter where the lift comes from. The piston to valve clearance will be closer. This isn't rocket science. Get out your degree wheel and micrometer and prove it to yourself if need be. Or to be simple just take your feeler guage and insert it between the rocker and valve stem and see what happens. PTV is nothing more than a distance measuremet and may or may not be an interference issue.

It is unbelievable that this is being debated at all. Changing cam specs only changes at what degree the closest piston to valve clearance will occur.

Now, we all meet up at the bar and laugh this one off. Except I will be drinking bourbon.

tech@WS6store

iTrader: (2)

Consider me bowed out of the thread.
Enjoy the new years!

DietCoke

iTrader: (18)

Every change that was talked about was a cam size change, which is lobe lift. Not valve lift. I can only talk sense about the reality of the situation.

DietCoke

iTrader: (18)

Correct. The only point I've been trying to make in this useless thread. At any given point, no matter what, if lift increases, PTV decreases.