Rocker Issue

8

89_WhiteBirdy

Registered User
I think i am having a problem with my rockers. After i torque them down they still seem to be loose...Is this normal? If it helps i got a new ground cam from Dave d with his recommended push rods, maybe he sent me the wrong push rods? and i also have ported heads. Thanks
 
Last edited:
Duffy Floyd said:
Are they all loose? Were all the pushrods the same length?
Click to expand...

I can answer this... I'm working on the engine with him ;)... They are not all loose, and yes the pushrods are all the same length. The loose ones are on the low points of the camshaft, and the tight ones are on the high points of the cam... Do we need to torque them all at the top dead center of the cam?
 
Well according to the shop manual you do the torquing of the rocker fulcrum bolt with the camshaft at the heel (base circle) point of the cam. Obviously you have to turn the crankshaft to do this. Torque spec is max 43 in-lbs. But in this case I am wondering if David knew you were using stock rockers that are essentially not adjustable for lifter preload?????

Perhaps others more knowledgable about this can jump in and help. I just remember watching him adjust preload on my roller rockers.
 
I think my pushrods that i recieved are 7.188in or pretty close to that. So maybe 7.25's will work?

Dave if you read this i sent you an e-mail about getting longer pushrods.
 
If you spin the pushrod with your fingers with the cam at the valve closed position for that valve, they should have slight resistance only. I know that is an objective measurement and not solid numbers, but the hydrolic lifters will adjust for that. BTW, it sounds like that size is for the Chevy LT1 pushrod, which is also the same pushrod used on the SCP roller rockers.
 
I just did the very same thing, and had to swap in springs as well. Make sure you are at the heel of the cam when your torqueing the rockers down. If your not your torqueing against the hydraulic lifter that has a spring and the angle of the rocker against the pedistal.

Also make sure the bolt holes are cleaned out and there is no "debris" between where the rocker base sits in the pedistal.

Frit
 
Yeah we torqued them when they were at the heel of the cam, but there was still a large amount of play in the rockers....Does this sound like i need longer pushrods?
 
Dont do anything different until you have started the engine. If you are using dry lifters, they will not be pumped up. Try that first and then if that does not do it, get a pushrod length checker and see what you need. By loose, do you mean you can shake them (rockers)? If that is all the looser they are, you are good to go. If you can pull up on them and there is space between the rocker and the bolt, how much space is there? Measure the distance and go from there. I would be willing to bet that it is just the lifters being low.

Chris
 
The lifters should be retained against the upper seat by the spring inside them. No need to pump them up to adjust.

Manufacturing differences can lead to differences in rod length. Since you're showing them short, make absolutely certain that nothing is hindering the rocker from sitting in it's pedistal.

With lifter resting on the base circle of the cam, the push rods must have slight tension between the rocker and the lifter cup. This is described as being able twirl the push rod with your finger tips feeling only slight resistance. Loose isn't good. You should be able to see if the lifter top cup is pushing down when you tighten the rocker.
 
The springs in the lifters are not as strong as they "feel" when you have them pumped up. You can easily push them down when they have bled off. It can be misleading as you push on them if it is your first time. What is the lash as they sit?

Chris
 
Mike8675309 said:
With lifter resting on the base circle of the cam, the push rods must have slight tension between the rocker and the lifter cup. This is described as being able twirl the push rod with your finger tips feeling only slight resistance. Loose isn't good. You should be able to see if the lifter top cup is pushing down when you tighten the rocker.
Click to expand...

Yeah, some of them are tight, but there are 2 or 3 on each side that are loose. It seems as if some pushrods are longer than others, but they are all the same length.

seawalkersee said:
What is the lash as they sit?
Chris
Click to expand...

What is lash?
 
Hmmm... ok, well in that case... they wiggle from side to side slightly, and up and down just enough to create a visible gap between the rocker and the push rod. And this is with them torqued down. It seems like if we have slightly longer posh rods, then that gap will go away and everything will be tight...
 
Ok, lets say this.

What SWS is getting at is the lifters are hydraulic, Just like a hydraulic ram per say.
What he thinks is going on is the lifter got dry which means that the oil is no longer in it. Thus in the example of hydraulic ram which has no fluid and is compressed. And when its full of oil, it will extend.

Ok so when he gets oil pressure they "may" pump full of oil and "extend" to take up the slack of the large lash. But then again, who knows whats up:rolleyes:

Hope you understood that

-Tony
 
Yeah I understand. But that is probably not the situation. We put the lifters in this special oil about a month ago... (not sure what it was called, but it was oil to soak lifters in)... And then we forgot to take them out. :rolleyes: So before we put them in the engine, the lifters had been soaking for at least a month. So they are plenty oiled up.
 
Lash is the distance between the rocker tip and the valve stem/pad (whatever you want to call the area where they connect). Can you push down on the "push rod" end of the rocker and have it go down to where you see this "gap"? Or when you push on the rocker is there distance between the rocker and the push rod?

I will break it down like this;
1) Measure the lash with a feeler guage.
2) Be sure all of the valves have the same installed height
3) Be sure all of the push rods are the same length
4) If 2 and 3 are the same, change the lifters from one that is "tight" to one that is "loose" and see what you have then on that valve.

While you have the lifter out, take the push rod and push in on the lifter as it is in your hand. See how far in you can push the ones that are "tight" and compare them to the ones that are "loose".

If everything is good thus far, and changing the lifter changes nothing, then chang the rocker from one to the other to see if you have one that is out. If there is a problem still, you need to have different push rods installed and may as well go to a RR setup since you will have to shim it some of them.

Chris
 
seawalkersee said:
Can you push down on the "push rod" end of the rocker and have it go down to where you see this "gap"? Or when you push on the rocker is there distance between the rocker and the push rod?
Click to expand...

When the push rod end of the rocker is pushed down, yes it will touch the end of the push rod, closing the gap.

Thanks for all the info... we'll try the things you listed and then go from there. :)
 
You must log in or register to reply here.
Back
Top