super charged valve spring pressure

[mike7570]

True, but Physics and math don't lie. If our "experience" doesn't match the math and physics, then we're not looking at the experience correctly
[/quote]

Or the math and physics are not refined enough to allow for the variables of a running engine.

[scott foxwell]

True, but Physics and math don't lie. If our "experience" doesn't match the math and physics, then we're not looking at the experience correctly

Or the math and physics are not refined enough to allow for the variables of a running engine.

I'd say some of the guys I work with -who are WAY above my pay grade- and the engineers at the Big 3 might not agree with that statement.
The physics and math that applied to some of the very first steam engines a hundred years ago are still the same today. Before anything, an engine is just an air pump.

[mbrunson427]

I've been watching everyone go back and forth and it's been a pretty interesting conversation, one that I have no idea the answer to. I got a call this morning from a friend about something unrelated and figured he was the perfect person to ask what the deal is here. He builds elite level tractor pull engines. Which means, he'll build 600-700 cube Hemi-headed NA motors, and at the same time build inline 6 tractor motors with 3 turbos that build 100-140 pounds of boost.

I asked him about this and I got kind of a chuckle. He said yes this is a familiar conversation. If you think through the cycles theoretically, boost won't have an effect on valvetrain control. HOWEVER, this is only for one particular point in the RPM range where everything is performing exactly as expected and the cylinder is filing just as you want it. If you're setting the cam up for a street driven engine, you're likely compromising away from that optimal point as well.

There's no quantitative answer here, but I think what this means is the answer is not zero added spring pressure, but it's not boost pressure multiplied by valve surface area added spring pressure either. There's a point somewhere in between that needs to be found, which can take care of those shoulder situations where things aren't perfect. The generic answer I got was "we don't go crazy with spring pressure".

And in an attempt to make things more kumbaya..... I will say that I've had the chance to talk with quite a few people from this forum, outside of this forum, and there are some real good guys floating around here. Even though Scott may have the keyboard personality of Niki Lauda sometimes, I don't think Niki Lauda is a bad guy.

[scott foxwell]

I've been watching everyone go back and forth and it's been a pretty interesting conversation, one that I have no idea the answer to. I got a call this morning from a friend about something unrelated and figured he was the perfect person to ask what the deal is here. He builds elite level tractor pull engines. Which means, he'll build 600-700 cube Hemi-headed NA motors, and at the same time build inline 6 tractor motors with 3 turbos that build 100-140 pounds of boost.

I asked him about this and I got kind of a chuckle. He said yes this is a familiar conversation. If you think through the cycles theoretically, boost won't have an effect on valvetrain control. HOWEVER, this is only for one particular point in the RPM range where everything is performing exactly as expected and the cylinder is filing just as you want it. If you're setting the cam up for a street driven engine, you're likely compromising away from that optimal point as well.

There's no quantitative answer here, but I think what this means is the answer is not zero added spring pressure, but it's not boost pressure multiplied by valve surface area added spring pressure either. There's a point somewhere in between that needs to be found, which can take care of those shoulder situations where things aren't perfect. The generic answer I got was "we don't go crazy with spring pressure".

And in an attempt to make things more kumbaya..... I will say that I've had the chance to talk with quite a few people from this forum, outside of this forum, and there are some real good guys floating around here. Even though Scott may have the keyboard personality of Niki Lauda sometimes, I don't think Niki Lauda is a bad guy.

IMO that was a real good answer from your friend.
LOL...I don't mind being compared to Niki Lauda. I'll almost take that as a compliment.
Sometimes "we" respond harshly to those who don't respond objectively to us. I'm a work in progress. Always will be.

[plovett]

My opinion is that the better analogy to use is billiard balls, or marbles, rather than a freight train.  A freight train starts and stops VERY slowly.  What's happening in an intake manifold is lightning quick and very chaotic.   That's what I think anyway.  I don't have any real empirical evidence to back that up.  It's still think it better describes what is going on.  Okay, maybe a long line of billiard balls which is kind of like a train.   

JMO,

paulie

[Leny Mason]

OK most of you are way above my knowledge of valve events so does the weight  of my valves matter a lot thanks Leny Mason

[turbohunter]

Lol, Leny I'd love to have a beer with you.

[scott foxwell]

OK most of you are way above my knowledge of valve events so does the weight  of my valves matter a lot thanks Leny Mason

Valve weight always matters....however, you're not breaking new ground here. Unless you're planning on turning some crazy rpm where very gram counts, I'd just stick with teh recommendations of the guys who have worked with these heads and know what to expect. If this was a pushrod engine with rocker arms, I could give you a recommendation but I have zero experience with overhead cam valve train like this. I deal with big (2.35"), heavy, stainless valves, big 7/16 to 1/2" pushrods and rockerarms with >.800" lift and run that setup past 7500rpm with all the right parts. THAT is a heavy valve train.

[FElony]

So, let me summarize pages and pages of high-falootin' monkey talk thusly. I should rebuild a 360 with stock crank, rods, and pistons. Add a GT/CJ cam with 120 pounds on the seat just for giggles. Streetmaster, turbo at 10 lbs. Finished. Go out and beat on it profusely while you rich guys with Cammers discuss physics. I got that right?

[plovett]

My monkey can beat up your monkey.  Just sayin...

paulie

[cammerfe]

Speaking of how stuff moves around in an intake manifold, we pulled the head off an intake valve years ago in the TP, during a pass at Milan. Part of the valve head beat up #6 cylinder, and part of it was jammed through the top of the piston in #2. Yet #6 fires AFTER #2 and it was #6 that lost the valve.

KS

[machoneman]

How true! It is somewhat amazing when losing a valve where all the parts and pieces end up. Often, the wasted intake pieces end up in another cylinder or two, proving just how turbulent the intake tract can be. I've wondered if it's also more a ricochet 
effect than air moving the broken pieces.

Speaking of how stuff moves around in an intake manifold, we pulled the head off an intake valve years ago in the TP, during a pass at Milan. Part of the valve head beat up #6 cylinder, and part of it was jammed through the top of the piston in #2. Yet #6 fires AFTER #2 and it was #6 that lost the valve.

KS

[Leny Mason]

So, let me summarize pages and pages of high-falootin' monkey talk thusly. I should rebuild a 360 with stock crank, rods, and pistons. Add a GT/CJ cam with 120 pounds on the seat just for giggles. Streetmaster, turbo at 10 lbs. Finished. Go out and beat on it profusely while you rich guys with Cammers discuss physics. I got that right?

FElony, I am not a rich guy it has taken a good part of my life to get the parts to do this that is why I would like to get it right, I know little of what is being argued here I just want it to hold up, sorry you think I am some sort of a rich snob I am far from that, I think most of us are in the same boat, I have a small auto-Machine shop in East Helena Montana that should tell you something. Leny Mason

[Leny Mason]

Lol, Leny I'd love to have a beer with you.

Cool, it is a little early here but I guess that would be fine, let me know when and where. Leny Mason

[turbohunter]

Next time I make it to Montana which I do every so often.