Recently at boost levels of 50-60psi I am hearing a rapid flutter. The closest sound I can compare it to would be when you shuffle/arc a deck of cards while shuffling them. Does that make since?
Could it be a boost leak? Valves "floating"?
IDK! Your help is much appreciated.
Neil

 

At what RPM? I don't think that floating valves have anything to do with boost pressure.

It may be your head lifting. I lifted my head recently, and it sounded like a small machine gun...

 

i'm runnin tnt, so @ 50-60psi and 2600-3200rpm i hear it. in the tnt instructions bob says stiffer springs may be needed with higher boost levels.
its a rapid sound, but not loud like a machine gun. if its lifting what needs to be done? i already have arp's2k's. thanks bro

 

Not saying that is what it was, just giving options. I have to re-torque mine, apparently.

I would not tempt fate. It could also be timing rattle... back off of that timing some and see what happens. I see you are stacking the TST... Timing rattle to me sounds like a pot with a lit on a stove, just about to boil... or the sound my grandma's old 302 valves made when I drove...

 

i have been running timing on 2 and 3 for the last 2 years . but yesterday i switched to timing 4 and man what a difference in spool up. i am very impressed with that find. it's still popping/fluttering though. as far as the TST, i will use it alone or Smarty alone. i learned my lesson a couple of years ago about stacking those two together. i will retorque head bolts and install don's springs and see if that changes anything. i just noticed your in beaufort. i installed all the playgrounds in that base about two years ago and paris island also. thanks again bro.

 

Ha... lots of playgrounds...

Take the truck back to stock and see what happens, then add one, then the other. Just gotta play with it.

 

High boost and stock springs will lead to floating valves. What happens is when the valve is closed and the tappet is off the cam, boost pressure is enough to cause the valve to open... just oh so slightly, enough to break the seal; same with exhaust and excessive back pressure ... high rpms with weak springs will allow the tappets to not fully follow the cam lobe allowing float as well. Both of these "could" be happening. 60psi and ARP 2000's tells me it is unlikely the head is lifting... if it was you would see other signs as well such as overpressurization of the coolant system.

What it does sound like, based on the description-- the rpm range and the sound--and the easiest thing to check, is timing.

Try going to default setting on timing and then use an even numbered SW. If the sound goes away, it is timing. If not... then it could be valve float... and it just could be that and it looks like you have a fix on the way. If you have been running timing 2 with no issues, you should be able to run 3 or 4 with no issues too.

 

Hey Soulezoo,
I just finished replacing stock springs with Don's (wasn't too bad to do). I'm going to be replacing cam tomorrow also. Hopefully I can fire it up tomorrow, definitely Friday and see if the springs were the issue ( I believe they were the problem). If not I'll play with Smarty tuning.
Thanks

 

I don't understand how boost/cylinder pressure pushing outward on all 4 valves can cause any of them to open. Isn't this basic hydraulics and the theory of a check valve? The exhaust back pressure makes sense though.

 

To be perfectly honest, I am not the science guy that can give the detailed engineering explanations necessary; however, I can provide personal opinion based on personal experience.

First, floating from boost can happen the same way it would from exhaust. And it wouldn't be from 4, but only 2 valves at a time as the exhaust and intake ports are obviously separate from one another. (But I suppose it could be argued -- I don't really know-- that it is 12 valves since effectively all the intakes share the same air chamber... but at different times due to the cam) Certainly, given that back pressure in many trucks tends to rapidly escalate above a certain point would tell one that exhaust valves will tend to open first as back, or more correctly drive, pressure usually exceeds boost above a certain point and will therefore overcome spring pressure first. But, float is float. In bigger systems like mine, 80 psi of boost can overcome stock springs pretty easy (and show up as severe flutter in an un-snubbered boost gauge) as the boost pressure overcomes spring pressure. And it doesn't have to be 2 valves... it only takes the weaker of the two springs on the valves to "break the seal". This can happen with intake valves, as I understand it, when cylinder pressure on any stroke, is much lower than the boost pressure needed to overcome spring pressure.

Now high rpms, is simply an effect of time and pressure on springs. As simply as I can put it, if the cam is rotating faster than the spring pressure has the ability to make the tappet follow the lobe, it doesn't close fast enough, and "floats". This then tends to make valves hit pistons. Not good. This is especially evident in cams with high, or fast if you will, ramp rates and improperly matched springs and pushrods (pushrod deflection becomes a real issue if you have heavy springs, a fast ramp rate, high rpms and thin pushrods).

This last phenomenon is why the good folks at smarty insist on at least cam springs for their TNT/r program. Darned good advice there.

 

One last thing, there's been a lot of cam and spring debate of late... especially between manufacturers. I am of the opinion that those mfgs. know their product. If you choose their cam, follow their recommendations concerning springs, pushrods and etc.

 

I understand now. I don't know why my first thought ran to the pressure inside the cylinder. I see now how the boost would be between the compressor and the valve pushing it open, the same as back pressure or drive pressure would do th the other set of valves.

 

Interesting. It seems like if the exhaust valves were opening from drive pressure, they would have to do it on the intake stroke. Or they might just be opening back up, after closing, at the end of the exhaust stroke because of the extreme exhaust pressure as the intake opens.

If the springs and the valve diameters are the same for both intake and exhaust, the exhaust valves would definitely open first because the exhaust pressure is higher. Also, during the exhaust stroke, the cylinder pressure is even higher than the exhaust manifold pressure so it would help keep the intake valves closed. And, of course, on the intake stroke the intakes are open anyway and there is no way they could get blown open on the power or compression strokes.

How much pressure is developed in the exhaust with the exhaust brake on? Is it similar to extreme drive pressure?