My boost gauge "flutter": Source identified.

J

JasonCzerak

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Aug 10, 2006
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You all may thing i'm nutz. Some of you folk suggested that it's the gauge, me being stubborn to just live with it, placement of the pickup (boost bolt). What ever the case.... Well. I'm not nutz! :)

It's in the valve train. Yep. the high iron wear after the new valve springs. the fact that the push rod on cylinder 1 and 2 show .006 low on the intake and .003 low on the exhaust. So most likely the stock cam.

Those of you who suggested that .018 and .020 that there would be no difference.... Think again. I didn't make the connection, because I still had my theories on the wastgate but I did loosen up the lash to .010 and .020. The flutter did get worse...

So tonight I tighten up the lash. to .017 and .008 (couldn't find min .007 gauge). I did each cylinder based on location in the cycle. double checked each, and ran the motor and checked again.

On my test run the boost gauge now just "sits" at 48-ish PSI. I need to turn it down a little now! :) I suspect if you look very closely it does flutter, but like it's only noticeable if you look right at it and not the road. Before you could see it flutter out of the corner of your eye. like someone waving at you.

So my theory here is the cam and it fits. The exhaust note is not as "poppy", just fast sounding at load. Boost picks up faster, runs smoother.

I no long think the gate is an issue, however, one day I may pull it and check just for giggles, just not any time soon unless I'm upgrading the wheel to a 66.

So now I'm even more convinced that getting a cam swapping in is going to be a good thing! :)
 
The difference in diameter of peak lobe from min spec to max spec is about 26 thou, remember there is very little wear ever on the circle.....frankly I can't imagine 6 thou making your guage flutter.

Tell me what tightening up the lash would acomplish? Very slight advance, but still all the same??
 
Joesixpack said:
The difference in diameter of peak lobe from min spec to max spec is about 26 thou, remember there is very little wear ever on the circle.....frankly I can't imagine 6 thou making your guage flutter.

Tell me what tightening up the lash would acomplish? Very slight advance, but still all the same??
Click to expand...


I got to imagine that a tighter lash would bring it back closer to stock lift once on the lobe. I would agree that the the circle it's no different.

But if the lobe wore off .006, then the valve opens later, less and closes earlier. if you bring the rocker close to the valve in the process it should reclaim that time and distance right?

valve train math still makes my head spin a little. If I'm off please show me how the numbers work.

I need to get my hands on a longer arm for my dial gauge and I can get numbers for cylinders 3-6. However the dial gauge reads on the intake .229 and .295 on the exhaust measured from the bowl of the push rod..

Is there a tool I can buy/rent to pull the lifter outa the bore? I'd like to get some pics of the cam and lifter with out pulling the cam. This could really tell a story here.
 
The lifters have to drop out the of the bottom of the bore. No way to get them out with out pulling the cam.
 
What was the Fe content of the oil analysis, and what valve springs did you install?
 
XLR8R said:
What was the Fe content of the oil analysis, and what valve springs did you install?
Click to expand...

Hamilton 110's like a year ago. Go into Hamilton area and look at the zinc threads. I have my reports from a while ago and now.. I'll sample when I'm back from my trip and see if the zinc is working for me. It may be too late.....

On a flutter note... the flutter is back again! All I did was make one full turn counter clockwise of the bullseye to bring the boost back down toward 45 a little. Last night was 55degrees out, today is 80. I did got for an extra long trip down the road to get the motor really warmed up and the flutter did lessen.

I'll need to check the lash again soon and see if everything is where I left them.
 
I am having a simular problem, boost gauge flutter// I have done a lot of new mods, ( don't know where to look first? =) I have made calls to a few shop experts/ I got two things to look at. or try.
1) make sure your intercooler, pipes, and hoses are leak free. you can make a tester tool with a shop air regulator and length of hose / two 4 inch pvc pipe caps and two 30 psi pressure gauges. Go from the boot at the turbo (pressurize).. then the other cap end at intake inlet pipe/ you do not want more than 2-3 psi drop across/ is so spray . all down with dish soap and water look for bubbles/ (leaks) listen for air .
2) make sure exhaust manifold bolts and gaskets are leak free/ also turbo flange gasket.
I will let you know what i find out after this weekend's tests,
 
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