Most common is a sticking hydraulic lifter which can end up with enough of a gap between the top of the lifter and the push rod that the push rod can get sideways and end up bent. The reason being that if a pushrod is severely bent or it breaks, the pushrod could dislodge itself from between the valve lifter and the rocker arm and fall through the engine into the oil pan. It is not enough to just replace the pushrod. Yes, you repair them by going to your favorite auto parts store and ordering a new set.
You also need to figure out why they are bent. Pushrods are long, slender metal rods that are used in overhead valve engines to transfer motion from the camshaft located in the engine block to the valves located in the cylinder head. The bottom end of a pushrod is fitted with a lifter, upon which the camshaft makes contact. Photograph of the failed rocker arm shaft. One of the major causes of component failure is faulty manufacturing.
This includes all effects that increase brittleness or those inducing cracks and or stress raisers in the component. Valve seals prevent oil from entering the combustion chambers through the valve guides.
The valve seals fit over the valve stems and keep oil from entering through the clearance between the stem and guides. Usually, the job consists of replacing the seals, gaskets, connecting rod bearings, cylinder head bolts, and flushing out the engine and cooler lines. If you do not take action quickly enough, you might need to replace the engine entirely. As for driving the car with a rod knocking or it could be a worn out big end bearing expect the situation to get worse until the engine suffers catastrophic failure,at which point its time to scrap the car..
I bought a Porsche that had a rod knock which I interpreted to be bolts loose on the crank pulley. Bent or broken intake valves will cause the engine to have a misfire and create a popping sound in the intake. This can damage any sensor located in the intake system and burn the air filter. Bent or broken exhaust valves will cause the engine to have a misfire and create a popping sound in the exhaust.
From the spark plugs to the ignition coils, many different things can cause an engine to misfire. The most common causes of misfires are worn, improperly installed, and mishandled spark plugs, malfunctioning ignition coils, carbon tracking, faulty spark plug wires and vacuum leaks. What is the difference between stud mount and pedestal mount rockers? What is a shaft rocker? What do rocker arm stud girdles do? How do you measure pushrod length with shaft rockers?
What happens if pushrods are too short? Which pushrod is longer intake or exhaust? What happens if pushrods are too long? How do I know if my push rods are too short? What is the difference between 1. What causes push rod failure? How can you tell if a push rod is bad? Can a bad lifter bent a pushrod? Before I say anymore, keep in mind every setup is different, which is the reason to check it anytime you change cam, head, rocker arm combination, etc.
When changing to 1. I have put several cams in with stock heads using 1. Just keep in mind when checking, the ideal geometry is for the center of the rocker tip that contacts the valve to be centered on the valve tip at mid-lift. If you need shims, Ford Racing sells them for this particular purpose that you should be able to pick up at a Ford dealership that is also a Ford Racing dealer.
Best bet is to just check it. The main thing to take away is that if you torque down the rocker bolt, and the rocker is still loose, you need longer pushrods see end on determining pushrod length. If you are able to torque in the suggested range, you should be ok on tip alignment, but check it anyway: 1 test fit your rocker and get the proper shims needed, etc. The center of the valve tip should be free of marking, with the outside edges front and back of the rocker's roller still having marker showing.
IF you aren't centered, then your pushrod length needs to be adjusted. I ended up with 6. Re: Stud Mount vs Pedestal Mount rockers Quote Post by cgrey8 » Wed Dec 23, pm Once you've found what makes the rocker roll over the center of the valve and gives you the pattern you want, do you have to do this for each and every rocker or can you trust that the tolerances from position to position are close enough that if one aligns, all will align with the same configuration?
Re: Stud Mount vs Pedestal Mount rockers Quote Post by stang » Wed Dec 23, pm cgrey8 wrote: Once you've found what makes the rocker roll over the center of the valve and gives you the pattern you want, do you have to do this for each and every rocker or can you trust that the tolerances from position to position are close enough that if one aligns, all will align with the same configuration? What you want is the narrowest wittiness mark you can get.
The narrowest mark will have the least side loading on the valve. Less valve guild wear. Shoot for a. Adding or subtracting push rod length will do two things. Change the width of the witness mark and move the mark.
A longer push rod will move it to the exhaust. Shorter will go to the intake. The valve and the stud are not in the same plane. Good luck. The wittiness mark is more controlled by the lift of the cam. Check out the link below from comp cams. Soooo Wrong. Sorry but it is. Midlift has nothing to do with the center of the valve. Well maybe with a shaft setup like I have.
Did you look at the link? Looking at from the wittiness mark standpoint, let's take this to extreme cases for a better picture. Say you have a cam with only a.
If you try to get the. Re: Stud Mount vs Pedestal Mount rockers Quote Post by cgrey8 » Thu Dec 24, am You aren't the 1st one I've heard from that says the Comp Cams method of setting up rockers is wrong, or is not the best way to do it. It may be 1 way to do it, but not the best. So detail out how you setup an engine, As for lifting the rocker, I think I see what you mean. But with pedestal mount rockers, do you have as much control over how tall the rocker is vs the valve?
I can see how a shim will locate the roller tip on the valve. But with pedestal rockers, how much control do you have on controlling the witness mark thickness? The good news is it sounds like based on other's comments that with 1. Another thing I'm hoping I can do is reuse the stock Explorer valve covers. They are very low profile and fit in my engine bay with fairly minimal interference with the AC box. Notice here, the AC Box has an indention, but the indention doesn't go in enough and doesn't go in at all at the bottom of the box If I have to run a taller valve cover to clear the roller rockers and the higher lift the cam will be pushing, I'll have to revisit that AC box To get your ideal setup, you need to use a combination of shims and pushrod length.
Once you determine your pushrod length may have to average between a couple cylinders , then you shim each rocker accordingly when installing to get your correct preload. The best method would be to measure each pushrod length individually, however that's not practical, as you usually get them in sets of Factory tolerances, weak lifters, etc, not sure.
For a street, lower RPM engine, I don't think your witness mark width is nearly as critical, as you're not looking at as bad of guide wear. Really if you're witness mark is on center on the valve head, you should be ok. With higher RPM performance engines, then you'd want as narrow of witness mark as possible as Bender stated, but again you'd likely be running stud or shaft type rockers and this is easier to accomplish. Also it's rare that roller rockers will work with stock covers, but I've seen a few sets advertised that say they will.
Just check closely when buying. It doesn't matter for an engine that doesn't get raced and rarely hits high RPMs. There is a right way and a wrong way. With a pedestal mount you are limited. I'd probably still shim up a little. If the factory geometry was close adding lift will require raising the rocker. Or a valve job could also because the valve tip is now higher.
I'd shim. In your application I feel preload will be way more important to get right. As you said, valve jobs, etc, will change valve height and necessary rocker height.
So on a performance motor where you'd want that proper geometry on every valve to minimize wear, supposing that every valve is at least slightly different in height, What's the best way to achieve that?
Re: Stud Mount vs Pedestal Mount rockers Quote Post by stang » Thu Dec 24, am I do not totally agree with the way comp cams says to do this, I was mainly referring to to picture about midlift. The one thing I don't like on the comp cam instructions is they do not mention lifter preload.
In any case, the main point I was getting at is for a street application, it is not difficult at all to do this and with a street application, I can't see a reason where you need different specs on each valve. And if they are not my Suiox will get them there. More often than not the narrowest wittiness mark is not going to be in the center of the valve tip. The best alternative for a pedestal type rocker would be a comp These give an adjustment on the pushrod side for WAY more accurate preload adjustment after the rocker is torqued down thus eliminating the need for different length pushrods or different shimming per rocker.
IMO either way a pedestal mount is a compromise even on a mild setup. Re: Stud Mount vs Pedestal Mount rockers Quote Post by bender » Thu Dec 24, pm Side loading the valve happens when the roller tip on the rocker rolls itself across the valve tip.
The bigger the mark the more side loading regardless of where the mark is to a certain point. A narrow mark close to center will have less side loading than a wide mark in the center.
Plus rocker geometry is going to be better with the narrow mark. For your setup if your using a stock stamped rocker I would just shim up. Then concentrate more on your preload. Basically for you and what you are using more gains to be had with the preload set right.
Re: Stud Mount vs Pedestal Mount rockers Quote Post by dualdj1 » Thu Dec 24, pm So really, if you're going to be using the pedestal setup, you're best off with a rocker that had adjustable preload pushrod socket , so you can use a static shim height across the board or according to your valve height if there is variance there.
Using fixed socket rockers, you sacrifice either preload or geometry if using a static shim height same. This makes much more sense now, wish I would've gotten into this a little more before getting the rockers I currently have.
But again, for a lower rpm more street motor, it shouldn't kill my motor, and should last until I upgrade heads down the road. One more question, is it better to have roughly the same shim height across the board on a fixed socket rocker, even if that means preloading the lifter more? Or does it really depend on your witness mark as in should I check every rocker? I wanted to go back and recheck everything in my valvetrain anyway, so want to get the best possible setup I can while doing so. That comp rocker I suggested makes things so much easier.
But if I was stuck using stock rockers here is what I would do if it was my stuff. Start with a. With an adjustable pushrod find zero lash on all 16 rockers and record the different pushrod lengths. Don't mix up rockers, stands or shims. Look at the data and find the longest pushrod measurement and add. This is your new push rod length order the push rods.
Next get your self a hand full of. Set your adjustable push rod to the longest measurement found be for.
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