FE investigation continues. I welcome your input.
 

Many of you probably already know that I broke another push rod the other day in my new engine. Only common link between this engine and the last one is the rocker arms and the last engine broke push rods too. This engine is running a milder cam at about .540 lift and 240 duration, less spring pressure than the last, harland sharp rockers & hardened shafts, precision stands, supports, and spacers. Stock 427 type push rods.

Here's what I know and have done to this point:

1. #4 intake push rod broken

2. Removed the manifold and have found all of the big stuff. Took a magnet to every concievable spot to pick up any tiny stuff.

3. Inspected lifter and looks perfect.

4. Did an little leak down test without any sort of gauge. Took a compression tester end and mated a air hose to it and pushed about 100 psi into the cylinder. Wasn't sure what to expect, so tried all four on that side of the engine and they acted about the same. Loose very little to the valves, but most leaks past the rings (not certain if that's supposed to be the case, but it was at least consistent on the 4 I listened to. Engine has about 300 miles, so not sure if everything is fully seated?

5. Interestingly found no additional broken push rods, but these push rods have a grooved top edge of the cup (the top rim of the cup is like a "v" all the way around), but quite a few of them have the very outer edge of the groove is broken off (the outside edge of the v is broken off). I found a couple pieces in the head crevices that matched right up to the push rods. The thing is, I don't see how at any angle the edges would be hitting anything, but....Ideas?

Aside from questions above, are there any other things you would do at this point while I have crap apart? Anyone using Precision Oil Pums rockers? Any other suggestions on parts I should get?

I'm actually at least feeling like I'll be back on the road shortly...I hope.

Just a guess here,but it sounds like the balls on the rockers are bigger (even if a little) than the pushrod sockets. You might need to get pushrods to go with the rockers.

Brent, sorry your having all these problems! I've been there and FE's can be a trick deal with. This is nothing new as I read before that someone had suggested checking the tolerences between I/E valves at full lift and the geometry of the pushrod cup to the bottom of the rocker arm. This could be the cause of the broken pushrod pieces you describe. I'm assuming or don't remember reading whether you have enlarged the pushrod holes in the intake sufficiently to accomadate the pushrods. If they are hitting but still operating you willnotice a small "wear" mark on the pushrods making contact.

Lastly, I will be more than happy to exchange a fresh, test stand only 428 with completely rebuilt 48 IDA webers (tuned and runs well) completely decked with the goodies for your engine, as is.:LOL:

Best of luck and hang in there. Once you finally get it right it will be all worth it - I promise! I just got back from the Atlanta chapter Club mountain drive with 6 other Cobra's.

WDZ, definately planning to get new push rods. Thinking about going with precisions rocker arms which use ball-ball push rods.

Cracker, I'm not seeing any wear marks on the rocker arms, and with the arms off, I can't seem to move the push rods to an angle that touches the arm itself (at least within the proper range of motion)...Hmmm.... Oh, now why the hell would you try to throw a nice 428 with webbers at me. I assume you're joking, but if you're not, well, why the heck are you making me think about stuff like that? :D

Brent,
I had similar experience before I cured push rod breakage problem. I had to do extensive clearancing of the manifold to eliminate all rubs. Secondly, I found stock push rods did not yield correct push rod to rocker geometry because the stock rockers were much higher than the FE MAX roller rockers. Wear patterns should tell the story. If clearance is the problem, choose 5/16 rather than 3/8 dia. rods but must be high strength moly material. Smith supplied mine. You must specify ball/cup diameter and effective length. Use a wire guage to check clearance between push rod and bore before giving it your blessing. It's not hard work but it is tedious. When you get it corrected you will be very pleased to have done it yourself.
Paul

Thanks Paul. I don't see any wear marks on the length of the push rods and the holes in the manifold have been drilled/ground out big.

How big Brent? Much bigger than a snug fit for the push rods?? FEs have some LONG push rods as you are all too well aware. Is there slop in the push rod holes?

Brent,
If the push rods rub the manifold, you will definetly see a rub of about 1/2 inch legth. Other area to watch besides cup to ball contact and geometry is whether the cup is contacting the rocker. This can happen if your adjustment stud is backed out too far. Shorter push rods would be the solution in this case.
Paul

Brent, with the valve covers off, get a buddy, remove the spark plugs and turn the motor over with a socket and pull handle watching everything very
closely. Check for everything, coil bind, rubbing, clearances, measurements ect ect....
Like Paul, I went with Smith Bros. ball to ball push rods, no problems.

Brent Mills Hi Couple of questions? If the edges of the pushrods are broken off you have the wrong size ball for the rocker. I would buy a set of Smith brothers push rods with the correct ends. Are the rockers chewed up under buy the adjuster screw causing a binding of the pushrod to the rocker. If this happens it will push the pushrod end out of the center of the rocker adjuster and possibably cause the valve to hit the piston and hit the valve, causing the pushrod to bend or break. If you know someone with a bore scope look in that cylinder and see if any contact has happened. I donot know of anyother way a pushrod can break. Are the ends of the pushrods blue, burnt , lack of oil to lube the parts. Makebe there is a oiling problem with the rocker shaft oiling holes to #4. Grind all of your rocker by the bodys between the adjuster hole and the rocker body for more lift and clearance for the pushrods full movement without binding on the body of the rocker. What where you doing when the pushrod broke?? cruising, WOT, idleing, hear any change in the motor just before it broke. Do you have limiters in the heads for oil control? I would look at the size of the holes. .080-.090 is what most people are running. I KNOW SOME PEOPLE ARE RUNNING ALOT SMALLER WITH NO PROBLEMS. :eek: Hope this points you in the right direction. I would call George Anderson at Gessford and see if he can help. He has alot of FE knowledge and answers Rick Lake

Brent: Here is a thought......

If the lobe lift on your cam is on the high side I have read of this happening. At maximum (or near maximum lift) the ball on the adjuster (even if it is the correct diameter) loses contact with the pushrod. This happens because the edge of the cup contacts the unthreaded area between the ball and the shank of the adjuster. At that instant the loading its too great for the surface area in actual contact and the edge of the cup fractures because IT is carrying the load. Look for marks on the area immediately above the balls of the respective rocker arms/pushrods in question. Be sure you are using the correct rocker stands for the heads that are being used or the geometry will be off.

Process of elimination

Rick

Rick Lake, the thing is that the inside edge of the cup isn't broken, it's the outside top edge of the cup that seems to be broken or wore down. I don't see where this is happening though....I'll try to get pics.

Rick Parker, I'll look for the contact area you suggest, although I don't think the angle goes to that extreme. Rocker stands are correct.

Brent Mills You didn't say when the problem HAPPENS????:confused: As far I know the pushrod spin a like when the motor is running. Shelby said to check the valve clearance with any cam over .550" lift. I read that some cam builder retart the cams when machined for FE motors. I am not an expert on these motors. George Anderson is STILL the man to ask. If your lifterare hydro's and pump up at 5500 rpm the valve could hit the piston and bend the pushrod. I bent enought pushrods in my jeep turning 6000 rpm in a AMC 304, then 360, and ended with a 390 AMX motor. I had valve float and bent the push rods. Went to chromemoly rods and started bending valves. I would go back to the basics, Put the stock rockers and pushrods in the motor and roadtest for 1/2 hour then pull apart and check for damage. The outside of the edge is hitting the rocker. If I had a digital camera I have a set of Dove rockers with this kind of damage. Stock nonadjustable rocker are 1:73 adjustables are 1:76. Can you take a clear picture of the rocker on the bottom side to see. Your .540 cam is at the limit of checking for valve to piston clearance. Brent give me a call and maybe we can firgure it out. 732-254-3536 EST Something is out of whack Rick Lake:) I will be up till 1:00 a.m. est

Brent, sorry you are having so many problems. Enjoyed talking with you at the Fling. I can heartily endorse the Precision Oil Pump rocker setup. I am using them on my FE with a solid lifter cam and they work great!
Larry:)

OK Brent Mills What is the latest poop on the mistery with the engine???:confused: :confused: :eek: :rolleyes: ;) :) :D Rick Lake ps I can say poop right? I mean type.

Latest is that I have ordered rockers and pushrods from Precision Oil Pumps. You can see the details on them at: http://cgi.ebay.com/ebaymotors/ws/eB...tem=2428128609

Brent,

Pretty nice, didn't see anything about the pushrods though.

...sorry to hear
 

Hi Brent,
it seems you have reached a point of diminishing return after multiple attempts. Sorry to say this, but we all see and feel for what you are going through. It really should not be this difficult.

Time to work with a professional on your FE: (916) 339-0427.

Stupid question, but I know this can happen... What heads are you using?

Are you sure (really sure) the rocker arm stands / rocker arms you are using are right for those heads? C5AE and C3AE units are just different enough to cause your problem. As it has happened twice I am very curious.

I have that setup on my 427 (photos in galllery) ... very nice choice. Did you get a bonus at work??? :LOL: