bent pushrods rocker arms jumping off

1982 350 sbc + 0.30 new pistons,crank job all new .mild cam in.420 ex.443 lift ,hydraulic lifters.new alloy heads( unknown make ) 64 cc com chambers ,stock length valves ,stock valve springs ,stock pushrods (7.794 ") screw in studs ,guide plate, 1.50 rocker arms have used stock arms and a set of roller rockers .when engine started ran for about a minute began to rattle pulled the valve covers to find bent pushrods and roller rocker arms off valves (about 5 pushrods and arms ) swapped to stock rocker arms same thing happened again ,pulled head off made an old lifter soild refit 1 head with gasket, set valve lash to find that valve spring is binding what could be the problem ????

come on boys help

 

valve springs binding cause bent pushrods? yes!

but how are they binding with that mild lift cam? are you setting the valves correctly?

 

Valve spring binding.
Spring pocket not deep enough, spring to tall, valves not long enough, wrong keeper/retainers....

 

Sounds like a walking cam. Try a cam button.

 

Something odd is going on there. Post some pix of the valve train, it should help with the diagnosis. My 1st thought would be to try 1.6 ratio rocker arms, but the cam lift is pretty conservative. Look under the rockers to see if they've been rubbing on the valve spring retainers.

Were all the valve train parts bought as a kit? This is how I prefer to buy them myself.

Bob

 

Might check valve guide height.

 

some aftermarket aluminum heads come with .200 longer valves. Your valve train geometry is probably way off.

 

Valve train did not come as a kit ,just bare heads ,all other parts picked up after

 

Most alloy heads like Patriot and Pro-Comp require pushrods 100" longer than stock.Just to be safe this is a cheap investment: http://streetperformanceusa.com/i-8...er-tool.html?gclid=CNyyoLOr-bUCFYpDMgod82UAlQ

 

Does this apply to the SB Ford heads as well?

 

thanks boys

 

Sounds like Spring coil bind you should have .030 between at least 3 coils at full lift or not enought retainer to guide clearance.

 

There have been quite a few reports of valvetrain misalignment on some of the off brand alloy heads. I've seen it on SBF and SBC. Shortened and inconsistent distance between rocker stud and valve tip is very common. One "fix" was using longer valves but incorrect sweep of the rockers still posed problems. Tweaked pushrods is a certainty with the above problems. Alot of folks have spent a good chunk repairing these flaws or switched to a reputable head.

 

Sounds like the pushrods may interfere with the hole in the heads where they come up through the head Check one Int/Exh with the valves adjusted to see if the push rod is hitting the head at that point, turn over by hand, then as others said check your rocker tip to valve for length problems with the pushrods
Good luck!

 

The OP needs to look everything over carefully to see what was contacting what. There should be some trace of physical contact on something.

Or reassemble one cylinder's worth of components, perform the initial valve adjustment, rotate it around and watch closely.

Bob

 

Valve Train Geometry
As cam profiles continue to get more aggressive and valve springs pressure increase, the importance of pushrod knowledge has never been more critical. Here are some answers to the most common questions that you might have for COMP Cams® tech support about pushrods.

Pushrod Length & Rocker Arm Geometry

A large number of variables are involved in determining the correct length pushrod for your application. Pushrod length is affected by any of the following:

• Block deck height
• Head deck height
• Head stud boss height
• Rocker arm brand/design
• Cam base circle size
• Lifter design/brand/pushrod seat height
• Valve stem length​

Don’t assume anything when determining the right pushrod for your new engine. A pushrod that fits one engine may not necessarily work in another. Any number of items can be different on your engine, requiring you to use a different pushrod length. Following the steps below will streamline the pushrod selection process, ensuring that you get the right parts the first time.

1. Buy a checking pushrod.

Do not buy pushrods when you buy the cam, lifters and other valve train components. As much as we would like to sell you pushrods at this time, nobody can predict ahead of time what length a given engine needs, unless it is bone stock.

Instead, invest in a checking pushrod at this time. They are available in two different designs, with the more expensive of the two being easier to measure once you have it adjusted to the proper length for your valve train. Neither is particularly expensive if you consider time lost and freight costs when returning pushrods.

Other companies offer their own versions of pushrod length checking devices, funny little plastic things with complicated instructions to calculate the length. The main disadvantage with these is that you have to order the pushrods and receive them before you know if your calculations are correct. With a checking pushrod, you can actually rotate the motor over and check the rocker arm/valve tip relationship as you adjust the pushrod length. When you get the correct geometry, it is a simple matter then to measure the length and place an order. COMP Cams® carries a large number of various length and diameter pushrods so you get the correct length the first time.

2. Determine correct valve train geometry.

What is the correct length pushrod for your application? The one that produces correct valve train geometry. What is correct valve train geometry? When the rocker arm roller tip rolls from the intake side of the valve tip, across the center of the tip (at approximately mid-lift), to the exhaust side of the valve tip (at full lift) and back. See Diagram A.

3. Measure the resulting pushrod.

Measuring the length of a pushrod is a simple process. The most important thing to remember is that different manufacturers measure pushrods differently. Not all pushrods of a stated length will measure exactly the same. The three most common pushrod measurements are shown in Diagram B.

Theoretical Length: This assumes that the pushrod has no oil hole in the end of it. Therefore, the radius at either end is complete, which lengthens the pushrod approximately .017" in the case of a 5/16" pushrod with .100" diameter oil holes, minimally chamfered.

Actual Length: This is what you would measure if you had a set of calipers large enough to measure over the oil holes at each end of the pushrod. This is the measurement that most people can relate to. Unfortunately, this measurement is affected not only by the diameter of the oil holes but also by the entrance chamfer for each oil hole.

Gauge Length: Although the most difficult to measure (it requires a special length checking gauge), this measurement is the most reliable. This is because the oil holes and their chamfers are eliminated from the measurement. The only problem is that not all companies use the same gauge diameter. COMP Cams® uses a .140" gauge diameter. All Magnum and Hi-Tech™ Pushrods listed in this catalog are measured using this technique. See Diagram B on the following page.

4. Simple measurement techniques.

We realize that most people don’t have access to the special gauge required for these measurements or even a dial caliper large enough for most pushrods. We’ve developed two techniques to help you determine exact pushrod length so that the perfect valve train geometry is achieved in your engine.

​

Pushrod Measurement Techniques

Technique #1

This technique requires the use of a COMP Cams® Hi-Tech™ Pushrod Length Checker. These are marked with a standard length stamped in them. This number represents the gauge length of the part (.140" gauge diameter) with the two halves screwed completely together. Extending the pushrod one rotation lengthens the gauge length .050". For example, a pushrod stamped 7.800 and screwed apart one rotation would be 7.800" + .050" = 7.850" gauge length. Therefore you would order the part number from the catalog that matches this gauge length, since gauge length is how they are listed.

Technique #2

This technique requires one of our Magnum Pushrod Length Checkers. Once fixed, you don’t need to have an expensive gauge or a pair of calipers to measure it. You just need a pushrod of a known length to compare it to (a standard). Then use a pair of common 6" calipers to measure the difference between the standard and yours.

Here are a few final hints about pushrods in general. It is always a good idea to buy a few spares when purchasing a set of custom length pushrods, and stick them in your toolbox. If one ever fails at the track and you need a replacement, it would be nearly impossible to borrow one from a fellow racer.

Another hint involves cup end pushrods. Measuring them for length is especially difficult, no matter which technique above you choose to use. The size and shape of the cup end varies greatly from manufacturer to manufacturer, so measuring from the ball end to the cup end over the cup surface is a dangerous practice. The best strategy is to drop a 5/16" diameter steel ball into the cup end, and do all measuring over this ball, subtracting the 5/16" diameter (.3125") to figure the length.

​

 

Obviously the pushrod bent and then the rocker came off. The pushrod bent because:
1. Coil bind
2. Retainer hit the top of the valve guide
3. Valve hit the piston
4. Valve hit the block
5. Cam is installed ass backwards

 

In the original post you said stock pushrods( and you may have meant just stock length) but make sure you use hardened pushrods with guide plates when you get this sorted out.

 

thank you exracer 64 ---good tech even i could follow...

 

Exact same thing happened to me: somebody had decked the block .020 in a previous rebuild.

The gang's right: that mild a cam shouldn't be eating pushrods.

 

Installed height minus lift (minus lash also) should be .050 larger than coil bind spec.



All you need to figure out pushrod length is a sharpie marker, adjustable pushrod.



1 The first step is to install a solid lifter and an adjustable pushrod. Mark the tip of the valve with a marker.


2 Install your rocker arm and set it up with zero lash. Rotate the crankshaft clockwise several times. Remove the rocker arm. The contact pattern of the rocker tip will be where the marker has been wiped away from the valve tip. The pattern should be centered on the valve tip, and as narrow as possible. If it is not, experiment with varying the pushrod length to yield the best pattern.


3 Rotate the crankshaft clockwise several times. Remove the rocker arm. The contact pattern of the rocker tip will be where the marker has been wiped away from the valve tip. The pattern should be centered on the valve tip, and as narrow as possible. If it is not, experiment with varying the pushrod length to yield the best pattern.


4aPushrod Too Long: Notice how the pattern is wide, and shifted to the exhaust side of the valve tip


4bPushrod Too Short: Notice how the pattern is wide, and shifted to the intake side of the valve tip.


4cPushrod Length Correct: Notice how the pattern is narrow and is centered on the valve tip



Once you do it, itll be a snap next time.

 

You guys are amazing.

 

That happened on my Edsel...collapsed lifter so then the pushrod fell out from under the rocker. The lifter then came apart. I was able to collect all of the lifter pieces, then put a new lifter and pushrods and she runs fine.

 

Are you sure your cam is lined up correctly?

Sounds like piston to valve contact.

I have been there...

 

I've seen that happen when guides were put in crooked then the seats were finished to match.
check everything mentioned and good luck with it!

 

Sometimes the solution is the simplist! Are you sure the timing chain gears are on the correct keys? I've had a few come in with the exact same problem and the timing chain crank gear was on the wrong key slot. I've also come across at least one chain, (Chinese), that was incorrectly marked.

A simple way to check......

With no.1 at TDC, and the cam sprocket marks aligned together in the center, The keyway on the crank should be at approximatly 2:00. If not you have the sprocket on wrong or the chain set is mis marked.

 

cam timing is bang on ,looking to machine spring pocket or .100 longer valves ,just working out which will be the best

 

Did you replace the stock rotator cup with aftermarket keepers and retainors?

 

I would lean tword the longer valve because you would have to guess how much material is under the spring pocket.

 

Kept the stock valve length ,retainers from the cast stock heads ,will go with longer valves