Can to much preload cause valve float.

[forcefed86]

So I set up custom pushrods for at .034 preload on my recent build. This was this a .060 HG. I have since replaced the HG with a .033 SS shim type HG. So now the preload should be .061 or darn close. That is the top of spec. Originally I was running a .020 spacer under the rocker assy. to compensate and was able to rev the engine to 6200. After breaking the rocker assy I recently removed the shims and installed studs and braces on my rocker assy. Now the engine has problems reving over 5k? Sounds like valve float to me. Springs tested at around 100# installed height which is higher than the suggested springs by comp cams for this 218/218 cam. So my question is would .020 preload difference cause this issue? I’m thinking I have issues elsewhere. .061 is on the tight side, but should be nowhere near bottoming out the lifters? (running replacement lifters from TTA perf,)

 

[Just a Six??]

I’m thinking I have issues elsewhere. .061 is on the tight side, but should be nowhere near bottoming out the lifters?

I agree. They are not bottomed out unless by some chance they are stuck?
I would check then look elsewhere. Take off the valve cover & watch them as it idles.

 

[bison]

100# at the seat is not enough for that grind if you are running high boost. Order the correct length pushrods to take away any question with preload.

 

[forcefed86]

What would u suggest spring wise? Comp suggested 980 which are lower press than my current springs. Last week when I broke the rocker assy. I went 12.22 @ 133 on 30psi or so. This was with the .020 shim installed. Same springs though. Even at 17 psi im having issues.

Ill order up some pushrods anyway. Probably springs as well.

Thanks.

 

[BlackBandit]

edit: used my 4th grade education to actually read the post which rendered what I typed useless drivel. What kind of lifters do you have? Maybe they're pumping up and causing your valves to hang.

 

[forcefed86]

Running the TTA performance lifters.

Hydraulic Lifters, V6 HYDRAULIC LIFTER, TA_V1405 | TAPerformance.com

Wouldn't you want your lifters to pump up?

 

[BlackBandit]

At higher RPM's if when a lifter comes over the nose the pressure being placed on it drops and the pluger can move up in it's bore. It happends more at high rpms because oil pressure is higher and everything is happening faster.If it doesn't have enough time to bleed pressure as this happes it can start to hang your valves open. I'm not saying this is definetely what's going on but I could see how increasing preload would manifest this as the plunger has further to "move up" and therefore more potential to hang open the valves. This is also why manufacturers have a max rpm rating on lifters (usually) and one reason the really high rpm guys run solid lifters.

 

[forcefed86]

At higher RPM's if when a lifter comes over the nose the pressure being placed on it drops and the pluger can move up in it's bore. It happends more at high rpms because oil pressure is higher and everything is happening faster.If it doesn't have enough time to bleed pressure as this happes it can start to hang your valves open. I'm not saying this is definetely what's going on but I could see how increasing preload would manifest this as the plunger has further to "move up" and therefore more potential to hang open the valves. This is also why manufacturers have a max rpm rating on lifters (usually) and one reason the really high rpm guys run solid lifters.

Ah I gotcha. Well I was turning 6300 or so a few weeks ago when I made my best pass. I have since installed 28" tires (prev. 26") to try and keep the rpms down. Oddly enough my "valve floating" happens around 5k rpm. And has only since happened with the removal of the .020 shim. Could be unrelated. I may have an ign issue.

 

[A2000RICH]

So I set up custom pushrods for at .034 preload on my recent build. This was this a .060 HG. I have since replaced the HG with a .033 SS shim type HG. So now the preload should be .061 or darn close. That is the top of spec. Originally I was running a .020 spacer under the rocker assy. to compensate and was able to rev the engine to 6200. After breaking the rocker assy I recently removed the shims and installed studs and braces on my rocker assy. Now the engine has problems reving over 5k? Sounds like valve float to me. Springs tested at around 100# installed height which is higher than the suggested springs by comp cams for this 218/218 cam. So my question is would .020 preload difference cause this issue? I’m thinking I have issues elsewhere. .061 is on the tight side, but should be nowhere near bottoming out the lifters? (running replacement lifters from TTA perf,)

in all the engines that i have built i have always targeted about 030 for preload since thats what most folks seem to recommend------a couple years ago i carefully measured the preload in a brand new Vin 7 factory crate long block-------don't have the exact data with me at the moment but memory says that it varied from about 060 to 080 throughout the engine---------i clearly remember the plunger travel in the OEM lifter is .190"------this could allow for more safe preload which would allow for more wear/longer life in normal operation----------plunger travel in most aftermarket lifters that i have measured has always seemed to be much less than .190--------food for thought ................RC

 

[forcefed86]

Thanks for the info, I'll drop an email to the TA performance guys.

 

[hiboom]

springs

I remember reading on this site when you start getting in the 500 lift area there was a concern with spring binding unless you cut the steams down someone can probley help a little more on this I had the 212/218 with new 980's never could get it to rev over 5300 put in a 204/210 now it go to 5800 and keeps going maybe the shims gave you the extra clearance may not have anything to do with it just putting it out there to think about?

 

[forcefed86]

Ta performance wrote me back a two-worder. ".300 travel" Seems like a whole lot. I don't think they understood the question.

 

[87GN_70GS]

Removing the .020 shims does not equate to .020 more preload. You have to factor in rocker arm geometry - specifically rocker arm ratio.

 

[forcefed86]

Why? The fulcrum point is the same it's just raised? The rocker length was not altered? (not arguing... I'm sure I'm wrong, just tryint to wrap my head around it.) How much of a difference are we talking about?

I put the eng at TDC, then marked the pushrod with a straight edge leveled on the head (just light finger pressure on the rod). Then tightened the rocker assy down and marked the push rod again. Then measured the distance between marks. Was suppose to be .035. Was closer to .034. I did not measure this again after changing HG's, spacers, etc.

thanks!

 

[bison]

The bolts that retain the rocker assembly are 3/8-16. Just back them off and go to zero lash/preload with the lobe on the base circle and measure how many turns till the bolts are torqued. Post the number of turns and I can easily give you a fairly accurate preload number. I would want a verified 110lbs on the seat. Comp 980's won't cut it on that cam.

 

[forcefed86]

The bolts that retain the rocker assembly are 3/8-16. Just back them off and go to zero lash/preload with the lobe on the base circle and measure how many turns till the bolts are torqued. Post the number of turns and I can easily give you a fairly accurate preload number. I would want a verified 110lbs on the seat. Comp 980's won't cut it on that cam.

I'll reinstall the bolts when I get home and check. Or I can just measure the studs?

Thanks.

 

[bison]

I'll reinstall the bolts when I get home and check. Or I can just measure the studs?

Thanks.

Just give me the thread pitch and number of turns till it pulls the shaft down. Don't torque it down. Stop as soon as the shaft hits the pedestal.

 

[Mike Licht]

the preload is fine there. 90% of the "these crappy lifters are noisy" posts are caused by not enough preload. We really dont spin these motors enough to pump the lifters. The springs are too weak.
Mike

 

[87GN_70GS]

Why? The fulcrum point is the same it's just raised? The rocker length was not altered? (not arguing... I'm sure I'm wrong, just tryint to wrap my head around it.) How much of a difference are we talking about?

Look at it this way. With the shims in and then taken out, the valve and spring doesnt move, so the rocker must move downward (in essence, it is pivoting about the valve/rocker tip junction). It moves downward at the pedestal by .020. But at the end of the rocker (pushrod cup) it moves downward even more, since its the end of a lever which is further away from the pivot point (valve/tip). This downward motion is multiplied by the arm geometry: it will be overall_length _of_rocker / length_from_rocker_tip_to_center or 2.55/1.55 or 1.645 . Multiply that by 0.020" and you get 0.033"

Whether or not that is enough to cause the results you are seeing is questionable.

 

[forcefed86]

the preload is fine there. 90% of the "these crappy lifters are noisy" posts are caused by not enough preload. We really dont spin these motors enough to pump the lifters. The springs are too weak.
Mike

I understand your thinking, and I can't imagine pre-load is the culprit here either. If the springs were indeed to loose how would you explain my last clean pass of 6200+rpm at nearly 30psi prior to the rocker assy failure? If it was a constant I'd be all over changing springs. I may anyway. I also am not running spring cups. Any suggestions PN's for a 110-112 # springs?

On a side not I ordered a custom set of 5/16 rods. I'll have a known preload of .035. The 3/8th pushrods also scared me little. I don't think they are necessary and they were darn close to rubbing. Although I saw no indication of contact on the rods.