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Anyone have experience setting up the valvetrain on gt40p heads? Im running a TFS1 cam, scorpion 1.6 rockers and I have what sounds like a noisy lifter with some vibration. The valvetrain is VERY noisy... you can literally hear the rocker arms...considering im running a full exhaust with no cats and dumps... this is crazy! So, Im going back in... The car runs solid at WOT...but im sure there is more in it. Anyway.. has anyone noticed a particular pre load adjustment with these heads?? I have always just got the roller tip in the middle of the valve stem and tq. to spec... and its worked for a while... but considering the current issue... Im surfing for answers. Thanks.
 

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Welcome to the forums, Rob! I need to know:

  • Pedestal rockers (I assume) or modified heads with studs?
  • When installing, what fraction of a turn was necessary between zero lash and final torque (pedestal)?
  • Did you install the TFS valve spring package, or something else?
  • Did you verify zero interference from retainers to rockers through two engine revolutions?
  • Did you use the original pedestal alignment channels?
  • Were any preload shims added or removed?
I am also assuming the engine made no noises before this, and that you have 'normal' oil pressure?

David
 

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Hey David, thanks for the quick reply... Here lies the issue. The car was bought with all this already installed. My last 5 liter had milled, o-ring'd, professionally ported (bennett racing) screw in stud converted GT40 heads and they did require the normal shim to fit etc install. These heads im currently using look like (assuming) stock GT40p's.... the car came with build pictures, block, heads, cam, etc. The valvesprings are in a bag labeled "1.780" target installed height - GT40P Hyd. Roller". The assembled pic shows a shim under the pedestal mounted rocker arm but there are no specs to the actual size of the shim. Or is there any clue to what size pushrod they are using. Just pics (which they say pictures are worth a 1000 words, but... not really.)

So to do this over again, starting with new lifters, I am hesitant to use the old set up considering this was all done in march of 11 and things are already coming unglued. Granted it could have been over-revved at one point, or there maybe some other issue that caused it... but bottom line I just want to hear what you guys do with "non adjustable" pedestal mount valvetrain when setting it up. Im going to be taking this thing apart to look for a fault somewhere but since I have limited time, im trying to nail down any and all parts so I can put it back together without much down time. I really appreciate the help :)

Rob
 

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Well, Rob, the scheme is that the rockers are set to best geometry, and then the pushrod length is measured and chosen for closest fit (steps of .050"), and then shims used to bring it to proper final geometry at preload. Performance preload is generally .020-.030" initial. So, you'll have to essentially pull the valve train down and do the setup from scratch to be sure it's right, and I'm sure you have no issue with that.

Oddly enough, I can see in the pics that the spring package has already been changed from stock, so I'm not sure what the second set (or the first for that matter) is for, or how they are different. They both appear to be singles with damper. So, if it were me, I'd be testing spring pressures and rates while it's apart to determine which set you should run - if either. Keep in-mind the installed set will be a bit softer than new, so allow for that when comparing sets. Also, if you're not aware, the tip length is different for the intakes and exhausts, so keep track of your locks (some may be offset) and any shims so you know what you have now and how it was set-up to hit desired installed height.

David
 
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