The Money Pit

I pulled the intake Saturday in hopes to begin my Vic Jr swap. As the intake came off, much to my shock and surprize, I found two broken pushrods,and the corresponding lifters laying in the valley.I noticed the break in one of the pushrods right at pushrod guideplate.The pushrods were Comp Magnums,and were supposedly hardened for use with guideplates.The broken pushrods show no abnormal wear at the guideplate area,and in fact the other push rod broke in the center,nowhere near the guideplate.My springs are AFR supplied 120lbs on the seat,300 lbs open,and I don't think I've hit the piston,but will pull the heads to see for sure.(Kinda sounds like the solid cam is coming sooner than I thaught)
Question is what else could cause this to happen. I flattened a lobe on the first cam and saw pushrod spaghetti,and now this time the lifter bottoms look perfect,but the pushrods broke. I have tipped 6500 rpms with it once in a while, but it's a toy,not a race car,so those rpms aren't all that common.

CFI-EFI

Coil bind? Retainers hitting the tops of the valve guides? Rocker arms hitting the studs, inside the slot? It sounds like some kind of interference, somewhere.

RACE ON!!!

Ironcross

Good advice, follow it and you will probably find the answer so it wont happen again.

SmokedTires

That's a bummer but at least you found it now before something worse could have happened.

I pulled my intake and heads Saturday which gave me a good chance to look at everything. Looks like the bronze distributor gear wears really fast

MotorHead

If you replace the cam with a roller get an adjustable pushrod checker. WIth the intake off you want to turn the motor over by hand on watch the valve geometry. You look at everything mentioned above to see where your problem is, could be pushrods rubbing the block, guide plates, coil bind etc.

You can also check your piston to valve clearance if you get some light checking springs and a dial indicator since you will have to change the springs anyway for the new cam. I am not specifically talking about you but too many people just bolt this aftermarket stuff on and go without checking clearances, sometimes it works sometimes it doesn't

The Money Pit

This cam has around 15-20,000 miles on it.I checked everything mentioned when I put it in,but will look at the old parts closely when I pull it apart. Should be able to see where it bound up if it is a clearance issue. I was wondering if maybe it was a bad pushrod.I thaught Comp made some good stuff,and am concidering their top of the line pushrods this time.

MotorHead

Go with the .080 wall Hi Tech pushrods, that's what is in mine they are hard to break

The Money Pit

The Comp HyTech pushrods are on the list already,but now I struggle with the cam. I was planning on a solid,originally (Comp 294S with 1.60 rockers)Then I start looking at the lobe specs and find the XE-294 has more area under the curve than the solid. It's a new design hydraulic with 250/256 degrees@.050, and with my 1.60 rocker will lift .554/.558. I'm thinking no valve lashing and a cam that should pull high 6 grand rpms easy.
Am I crazy or should one of you smack some sense into me?

SmokedTires

Money Pit I was thinking about this post last night and I'm assuming that you have screens in your block to keep the debris from doing further damage?

Being that my top half is currently off, it's probably a good idea to epoxy some screens in just in case I have a similar situation someday.

ZD75blue

Mike...

That looks like a big block valley, but the rest of it looks like a small block? ! Aftermarket?

SmokedTires

Yeah it's a Dart small block. Being that it has the BB like valley, I'm now concerned that it could easily swallow broken metal pieces into it

The Money Pit

Both broken pushrods were still in the valley with the lifters,and I do not have a screen installed. I never had an engine break parts like this one,but I guess when the hp goes up, so does the breakage.May want to concider the screen now that you mentioned it.

88-406

AFR springs are JUNK

My guess is that it pumped up the lifters and then I wouldn't reuse any of them without a very carefull inspection. What was you coil-bind clearance?

Have the springs from the affected cyl's measured for pressure at your current install height/lift. They may come up short as most AFR springs do.

Hyd's can be made to work at 6500 but you have to have the required clearances incase things get out of hand.

km

The Money Pit

The AFR site lists the bind height at about 1.09" which leaves almost .700 for the cam. They recommend .550 max lift,and even with the 1.60 rockers I'm only at .544.I haven't pulled the engine yet(maybe Saturday),but when I do I'll be looking under a microscope at what caused the problem. Truth is I seldom run the snot out of it,but look out when I do.I've come up on cars in the fast lane so fast I've had to lock up the brakes to keep from climbing into their trunks.

KyRP2NITe Corvette

Valve train geometry is critical! One thing I ran into some time ago was that the Valve Cover I was using had some extra baffle directly above the rocker arm ( I guess to deflect oil down ) anyway those little bastards cleared the arms at idle but once I rev'd it up they would hit and kept breaking pushrods. I never really heard a tapping noise either so I checked everything over and over except looking up at the inside of the cover until I happened upon it as I flung it across the garage in a fit of rage

71coupe

Reg wall pushrods are a safety net. Installing stronger pushrods will cause something more expensive to break

Matt Gruber

all the above
plus
get a rev limiter w/solid cam

comp

Hmmmm i'm watching this one

The Money Pit

Crower's tech support called me back today and once I explained the rpm range of what I wanted and what not,he immediately said a solid was the only real choice. He said for my application something in the 245/250 degree@.050 and with a 108 LC(circle track cam) and offered to custum grind one if need be.I found that promising,but with all the catalog's I've got laying around,somebody's already ground one like that I'm sure.Why do custom?
I grabbed the micrometer from work and will check soup to nuts this Saturday the valve train to see why my pushrods broke in the first place. The rebuild will commence shortly,and don't worry guys... there will be plenty of beer.

comp

did you order it ???? what part # ??