My 350 tpi keeps breaking the push rod or throwing the push rod threw the rocker arm, but only on piston #1 intake side . the engine was just overhauled and has not been ran much because of the push rod problem. I had a local machine shop vat and bore the block I used the old crank, and rods which was not damaged. Had the new pistons pressed on the rods then took it home and assembled the engine. For the heads I used a set of vortec heads that I Purchased used from a 1997 C1500. Took the heads to the same shop where they put new valve guides and stainless 1 piece valves with a performance spring( don’t know what kind of spring the shop purchased and installed them). Also used a new cam shaft and lifters from comp cams here is the cam


Operating Range:1800-5800 RPM Duration Advertised:268-4° Intake / 276-4° Exhaust Duration @ .050'':222° Intake / 226° Exhaust Valve Lift w/1.5 Rockers:.464'' Intake / .464'' Exhaust Lobe Separation Angle:114° Computer Controlled Hydraulic Flat Tappet Camshaft


I have replaced the same push rod about 10 times testing it. I have changed the lifter out and it still breaks the same push rod after the push rod breaks I can push the valve down so it isn’t stuck . I also know how to adjust the rocker arms and I am not getting it to tight or to lose. On one of the time I changed the pushrod I drove the car for 6 miles before it broke but some times I can change the pushrod and it will break within 15 seconds

Any help would be appreciated

 

Sounds like the retainers are hitting the top of the valve guides.

Take a REAL CLOSE LOOK at the top of the guide whose push rod keeps breaking. I'll bet you'll see a nice smash mark there, from the bottom of the retainer hitting it.

 

what would cause the retainers to hit the top of the valve guides? and what do I need to do to fix it, Also if this is the problem would it run 10 minutes plus then break at random or does that sound like the valve sticking

 

The guides are tall, and the retainers are huge. When the valve moves it can only travel just so far before the bottom of the retainer runs into the top of the guides.

Vortec heads are well and widely known to all who know what they're doing, as being PARTICULARLY afflicted with this. The factory cam in a motor with those heads only has about .430" of lift, so it doesn't matter to the factory. There's no reason, as far as the mfr is concerned, for why they should make them any differently.

The solution is to get your guides cut down.

Alternatively, you MAY be able to use .050" offset keepers and a corresponding amount of shim under each valve spring.

Yes it might run 10 revolutions or 10 minutes or 10 months before the push rod actually breaks, depending on alot of different minor influences. No it is not the valve sticking. No it does not sound like that. It sounds like your retainers are hitting your guides.

 

so if I use the .050" offset keepers should I install them on all the valves or just the one that is breaking the pushrods and also when I go to add the keepers should I change to umbrella seals. thanks very much for the help also where could I order the keepers from

 

If you go that route, use them on all the valves.

You can get them from Summit or Jeg's or those type places, or your local speed shop. Comp, Crane, Lunait, Isky, etc. all supply them.

I'd ditch the umbrella seals, which are ineffective; and put the stock type ones back on, which are "positive" seals. They actually grip the guide and do something. However, they're fairly thick on top; you'll want to check and make sure that the retainer won't smash them because they don't fit, after you get all of whatever you decide to do done.

This is part of the reason why the real right solution is to get the guides cut down.

 

I pulled the spring off the valve that is breaking the push rod and the retainers are not hitting the guides, but I pulled the spring off of one of the vavles that are not breaking push rods and the springs look different. The one that is breaking the push rods has a longer inner spring, when it is placed on the stud it doesnt do down on it without the inner spring resting on top of the stud. So the inner spring is compressed more then the other springs

 

Springs don't go over the stud.... do you mean, on top of the valve guide?

If so, there's your problem. That inner spring (or damper, which is probably what it really is) is stacking up solid.

The solution remains, get the valve guides cut down.

That's another well and widely known issue with those heads. In addition to being taller than what they used in previous heads, the guides are bigger around, down low. They have this funky step shape to them that's ALOT bigger than older ones. So if you try to put better springs on them than the truck junk that they come with, they often won't fit over the guides. Just like the other dimension, it didn't make any difference to the factory, because their parts don't interfere with it; but for anybody trying to turn a set of those into "performance" heads, it's an obstacle that MUST be overcome.

That one spring is ruined, and any others that fit tight to the guide are no better. They need to be replaced when you get the heads repaired. It's interesting that they're not all the same though; which means, there's no telling what you actually have on there.

The standard size to get the guides cut down to, is .530" OD; and their height should be no left at no more than about .625". It's a pretty simple operation. In fact you can buy the tooling to do it yourself, from Manley, Crane, Comp, or Isky. The tools look like this. You'd want whichever of the seat cutters that would go with whatever springs you plan to use, and then the guide cutter that cuts to .530" OD, and use the 503 seals.

 

Sounds like the same problem I had. Take them back to the machine shop, get the guides cut down, use the positive type valve seals and be done with it.

 

Well took the 2 springs to the machine shop and the guy happened to use the wrong spring on the #1 intake vavle the damper was larger on this spring. the damper was binding up and breaking the push rod only on this one valve.

Thanks for the help I would not have found the problem with out all of the help yall have given me