Valvetrain Power Loss

I spent last summer shaking down my fresh 306. Had a poor dyno session that made like 195rwhp...then did some messing around. It was better but still way soft...messed some more and still soft. At the end of the year I ran a 14.1 @100mph with 26* total timing.

I took it apart this winter and after SLOWLY have been getting my valve train geo. setup proper. I hope to get my adj. PR measured in the next few weeks to get the FINAL number but I kinda rigd' up my dial guage/mag base to see what ballpark I was in or if I was just realy way off with were I was going.

I found that my adj. PR (by the dial/mag base again, not final meas.) is .113 shorter than the stock PR. So basicly I was more than likely REALY floating the valves...

Check out comp cams website...here is a link to some good reading http://www.compcams.com/Technical/Products/Pushrods/

Realy the geo. is not that hard...you are looking for the travel on the valve head. I was told to use a dial and get the cam lobe I am working on to mid lift (like if the lift at the cam is .250 then bring it to .125) and put the rocker on and bolt it down. When the roller is in the center of the valve head your good to go. It gets preaty easy to see. I first did it with no shim and knew it would be off I just wanted to see if I could tell.

Valve float is just that the valve is "floating" off its seat. Basicly the valve train is keeping the valve from fully closing. If your PR are too short then your not going to get the full lift of your cam, and I am not sure of this but I would think it would mess up your dur. as well and cause a not so smooth life for an already important and hard working things as the springs and lifters...

I am using a "solid" lifter as well...well its a stock one made solid.

That is the point I am at with getting my correct length PR actually.

From what I have been told and even checked out its not realy that big of a deal...some people set it to 0 some just work out a pre-load.

I have been going 2 ways with my thinking on the subject.

1. the stock PR on a stock lifter that is made solid at its pumped up state will have that pre load still built in as its a stock PR from ford...right? So if everything is the same in setting it up...why would you realy need to add or subtract any further amount when checking with a adj. PR...after all its going to be related to how much shorter/longer from stock right?

2. should you just add the .020-.030 to the adj. to get that preload back from setting it up with a pumped up lifter? If its fully pumped up and you set it up with 0 lash then to get the correct pre-load amount just add it...right??

anyway this is my thinking on the subject going both ways...maybe Tmoss or some of the others who are wise in this area can jump in...I know Tmoss has been a great help for me so far with this.

A very good point was made to me about the checker PR...I bought the comp Microm. one...its still a very good idea to get it meas. to be sure. If not for the fact you will see and know for sure its length.

blksn955.o said:

Realy the geo. is not that hard...you are looking for the travel on the valve head. I was told to use a dial and get the cam lobe I am working on to mid lift (like if the lift at the cam is .250 then bring it to .125) and put the rocker on and bolt it down. When the roller is in the center of the valve head your good to go. It gets preaty easy to see. I first did it with no shim and knew it would be off I just wanted to see if I could tell.

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you can also use some gear pattern checker paint and place it on the top of the valve and rotate the engine over a few times and remove the rocker. look to see how wide the paint is in the respective areas.

example: if it is wider at the bottom then you have it too far down--pushrod too short.

when i did mine, my pushrods were too short and clattered like crazy. if you had your heads milled then they are likely too long. shim it up a little and then check the geo. as for setting the preload, i like to go until there is no up/down movement of the pushrod for zero lash instead of the rolling in the finger tips method as it may be too tight before you adjust pre-load.

mytight95 said:

2. Does anyone have a link to a step by step tech article etc. on exactly how
to shim up etc. a pedestal mount rocker system.

thanks for the read guys, and any help you can provide.


jason

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i do not have a step-by-step but the basic jist is this: adjust to zero lash like you would on a stud mount set up then turn the ped bolt to achieve proper torque, this turn should be no more than 3/4 turn. if you can turn it more than 1 turn after zero lash then you need to shim untill you get proper torque within the specified range.

I did that on mine too, I used a VERY light coat of grease.

The reason for the mid lift is to know that the roller tip is in the center of the valve at mid lift...if your going threw the whole travel its going to be REALY hard to see that. As the roller body will be in the way of you being able to see the middle, and the travel will be across that plane.

It is a great tip though. I didnt say that since the link went into detail about that.

bimmertech said:

i do not have a step-by-step but the basic jist is this: adjust to zero lash like you would on a stud mount set up then turn the ped bolt to achieve proper torque, this turn should be no more than 3/4 turn. if you can turn it more than 1 turn after zero lash then you need to shim untill you get proper torque within the specified range.

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The problem I had with the shim is that I need a .060 shim (running lash caps for the crane 1.7rr) to get the correct patt. on the valve. Adding another .030 shim would make that travel off, going down to a .030 shim would do the same.

The think with the solid lifter also is that if you try to turn it after 0 lash...your pushing on the solid lifter and not pre-loading one so the trq. will be off, and you not going to be anywere near 1/4 turn. I tried that and it went from hand tight to the trq spec in like 1/4 or less of a turn.

If you have a harbor fraight(sp?) near you pick up a mag. base and a dial guage. Should only be like 30$ or so and set it to mid lift after getting the travel down to be sure.

an hr . Check out summit they are preaty close in price and after gas it may be cheaper to just order it.

I was going to use a buddies but another buddy had it and he is about 1 1/2 2hrs away, so I just said screw it and went to the harbor frieght that is like 5-10min away from my house.

Here is the thing with our lifters that seems to be the tale around here. It may have been misunderstood by me or mis-stated by others but, nonetheless, this is how our lifters work:

The lifter does NOT pump up to the retainer during operation. It will only pump up to contact the pushrod and put a certain (relatively small) amount of force on it. You can calculate that force based on the oil pressure at the lifter and the cross-section area of the lifter plunger. But think of it the opposite way. . . if your valve seat pressure is 100lb, it takes 100lbs to lift the valve from its seat. Multiply that by the rocker ratio (say 1.7) = 170lbs of force required to lift the valve from it's seat via the pushrod. Take that 170lbs and divide by the area of the lifter plunger (~.31 in^2) and you get 554 PSI of oil pressure required to pump the lifter past zero lash, it would take even more to lift it past that point. So if you are checking pushrod length via the solid lifter, make sure you account for a healthy preload with this in mind! Now lets talk about the preload . . .

The preload is there to take advantage of the hydraulic system. As your valvetrain wears out, the lifter will always have a nice zero lash since the lifter can pump up as required. If the pushrod shortens over time by .005", the lifter preload will decrease by .005". This keeps us from having to re-adjust the valve train every so often and it keeps the system quiet. With that said, you want .020-.060 preload as most will tell you. I opt. for the lower of the range, maybe .020-.030" preload.

Once you get the geometry at the valve tip checked out, there are plenty of ways to check the length of the pushrod you already have. I have a trick to doing it accurately on pedestal rockers with bled down lifters. You can easily find your required pushrod by adjusting the checking rod to a firm zero lash and adding .030" to the final length. I would do this with a hacked 'solid' lifter as stated above. Just put washers in it instead of the spring. I had to buy like 3 little bags of small washers at Home Depot to get the perfect combination of thicknesses to get the lifter seat to abut the retainer clip.

So basicly, if you just say 'adjust to zero lash with a solid lifter', you will end up with a shorter pushrod than what you should be using. You'll end up with zero preload which is bad for everything.

On the subject of valve float . . . The disadvantage of the hydraulic roller lifters is that when you go with a pointy-lobe cam, old worn out springs or just rev way to high, the lifter can pump up too much becuase it will float. This happens when the spring can't keep up with the cam. As the lifter rolls off the backside of the lobe, the cam will fall faster than the spring can move and the lifter is left hanging. Every time that roller doesn't touch the cam, the oil pressure pumps it up alittle more and after some more revving, it can in theory pump up to the retainer and it won't bleed down right away. Then before you know it, you have busted valves flying around the cylinders.

Thanks zero, great explain. on the subject .

the only way your gears play a factor in over revving is if you shifted into a wrong gear, missing a shift and revving the bejesus out of it in nuetral is not a factor of your final drive.

long story short--keep your 4.10's.

as for your cam and springs, i run .542 lift on .550 springs and it revs cleanly to 6k. i would not try to go to much further than that with ped rockers.

your stock rev limiter is set at 6200, revving to that may achieve mild float but nothing to drastic. if you keep the R's down you will be ok.

as for doing the good ol 4-2 shift(aka the "money shift") that is a whole nother story.

so i can pretty much solve my vt issue by adjusting a solid lifter to zero lash, and adding .030, which is the desired preload? Am i interpreting that correctly.

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Yeah, as long as your solid lifter has the pushrod seat touching the retainer so you know the seat is at the very top. Even that has some error, but should get you within .005" once you add your preload which should be close enough. I did that then double checked by putting in a bled down lifter, installing everything and dialing it. It was right on the money.

A 3rd way to do it is more straightforward. Say you put 4 washers in the lifter to get it to seat against the retainer, and each washer is .040" thick. So to get .030" to .040" preload, just remove one of the washers and adjust the rod to zero lash and you're done. But it should always be double checked with the dial setup.

Zero Signal said:

So basicly, if you just say 'adjust to zero lash with a solid lifter', you will end up with a shorter pushrod than what you should be using. You'll end up with zero preload which is bad for everything.

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Very true of the pedistal heads - less of an issue with studs. With studs, if you get the length right and do a patern and then add .030" to the length and do another pattern, I found little if any difference.