Strength of Stock Push Rods

[mopowers]

Is there a rule of thumb for how much valve spring pressure stock pushrods can handle? I'm assuming probably not much.

How much camshaft have you successfully run stock pushrods with?

 

[moparstud440]

I've ran a .533 hydraulic cam in both a 360 and a 440 with stock rockers. The 360 had OOTB Edelbrock heads and the 440 had OOTB 440 stealth heads. Ran each for several years in my race car. Shifted at 6000, went thru the traps 6200-6400 and never had an issue.

 

[dart_68]

I've got the same question and including the stock rocker arms. I want to put a new cam in my 360 but having to replace the entire rocker train is a bit expensive. New cam will absolutely require new springs. So the question then is...how much spring pressure can I go with stock rocker arms and push rods?

 

[flyfish]

Is there a rule of thumb for how much valve spring pressure stock pushrods can handle? I'm assuming probably not much.

How much camshaft have you successfully run stock pushrods with?

This is one of those areas that I never wanted to fine out the hard way...because if you do have a pushrod bend/break you could loose 10x the cost of new pushrods, or more in engine parts.

With that said, if you contact the folks at Smith Brothers pushrods, they should be able to tell you what wall thickness pushrod goes with what spring pressure.

 

[dart_68]

This is one of those areas that I never wanted to fine out the hard way...because if you do have a pushrod bend/break you could loose 10x the cost of new pushrods, or more in engine parts.

Very true...

 

[Wyrmrider]

inspect your stock rocker for wear at cup and valve tip
I've run .550 but not a lot of spring pressure over the nose
I've had customers with their rockers pushed through by the pushrods
usually with pushrods too long or too short or putting a bigger cam in on worn rockers
Magnum lifters and oil through the pushrods helps on cup wear

 

[mopowers]

Where do stock push rods typically fail? Do the balls break off before they bend/break, or vise versa?

 

[MopaR&D]

Where do stock push rods typically fail? Do the balls break off before they bend/break, or vise versa?

Typically they just bend, it's mostly a function of RPM and spring pressure. Common issue is to get bent pushrods when the engine is overrevved. From what I've seen usually what causes a ball end to fail is poor lubrication/overheating of the tips at the rocker arms.

FWIW I'm running stock replacement-type hollow pushrods with 350# open spring pressure and almost .550" lift (.542" IIRC) on stock LA stamped rockers, had it up to 6 grand a couple times now and no issues, yet... I do intend to upgrade to roller rockers and stronger pushrods though.

 

[Krooser]

The springs in my SB are around 425# open pressure for a solid FT cam running about 7,000 rpm's in an endurance application. The pushrods are stock diameter but I think they are thicker than stock.

Using a stiff pushrod helps you maintain cam lift by preventing loss of lift when the PR bends ever so slightly...

 

[Krooser]

The springs in my SB are around 425# open pressure for a solid FT cam running about 7,000 rpm's in an endurance application. The pushrods are stock diameter but I think they are thicker than stock.

Using a stiff pushrod helps you maintain cam lift by preventing loss of lift when the PR bends ever so slightly...

 

[4spdragtop]

If you are worried about stock push rods, the factory stamped rockers are a gamble as well. Seen many on here wore/pushed thru.

 

[mopowers]

If you are worried about stock push rods, the factory stamped rockers are a gamble as well. Seen many on here wore/pushed thru.

I don't use factory stamped rockers. I'm just curious what the limitations of stock pushrods are since I've never seen a failure first hand - albeit my experience is much less than many here.

 

[Wyrmrider]

miss a shift and find out
if you are running high spring pressure/ high revs it's a whole different ball game
larger dia pushrods, block and head grinding etc