keep researching...
the only way that pushrods will make any change to lift is if they bend and flex a LOT.

 

Even on the older small blocks I ran less pre-load than was common. Many have been done with the stockers and I haven't ran into issue's without the longer pushrods. To get the correct pre-load on the lifter you should have the correct length pushrods. I'm hoping that I can pick up a little hp by putting in the 7.4's. I'm interested if the less pre-load is helping my fuel milage though. My last trip out I was getting around 21-22mpg on the highway.

 

Are you serious? This is why I hate the internet. Maybe you should call Scoggin Dicky and run that by them. A 2002 and later ZO6 cam needs 7.450 pushrods. And yes genius total valve lift will be effected by trying to run stock length rods. 7.4 rods will probably work at the expense of lifter durability. I think you should go be an engineer for GM cause if you woulda told em that their standard 7.4 length pushrods were fine they could have saved millions in engineering and parts manufacturing expenses.

 

i say, do it right the first time.


if you're willing to do a cam swap, be ready to spend the money.

 

Just how long are the stock 5.3 pushrods? Every thread I have found concerning this subject comes back with the same mixed results. Some use stock with no problems, 7.4 will probally work, and 7.425 are needed because the ls6 cams base circle is .050 smaller. Thanks for the replys.

 

Call SDPC they will set you up with what you need.

 

I am serious. I love the internet. SDPC is in the business to sell you stuff...

You are way off base(circle) in your statement that lift will be affected by the pushrod length.

Lift is determined by how much off the base circle lobes push lifters up times the rocker arm ratio. The only way that pushrods have anything to do with lift is when they flex. Consider the pushrod is simply a link between the lifter and the rocker. It also serves as a passage for oil to the top of the head.

Listen when people try to tell you about lifter preload, especially in higher RPM applications.

And by the way, the engineers at GM did decide to stay with 7.400" pushrods when they changed the base circle for higher lift. To make up the difference, they used longer valves.

 

best way to do this is to buy a "pushrod lenght checker"..... has anyone tried this with a LS6cam??

old bull, i just bought one at Texas Perfomance, close to hobby airport..... they are cheap and the best way to figure out the RIGHT pushrod...

 

If you believe that pushrod length has no effect on valve lift, try running, let's say, a 7.000" pushrod in a LS1 or LS6 and tell me how much the valve will open.

That length is an exaggeration of too short, but it's just an example of what a change can make.

 

AP has an answer that should appease all sides.