Rocker Clarification is up!!!

[Tom keedle]

Originally Posted by Alan Roehrich

Unless the rule has changed, a 1.6:1 rocker arm on an engine that came with a 1.5:1 rocker arm is illegal in Stock Eliminator.

what about vice-versa?

[X-TECH MAN]

Originally Posted by Alan Roehrich

Unless the rule has changed, a 1.6:1 rocker arm on an engine that came with a 1.5:1 rocker arm is illegal in Stock Eliminator.

Correct-A-Mondo............Alan is 1000% correct......brush up on your stocker racing history. Remember the Crane stamped steel rocker that came in 1.6 for the small block chevys. Several big name stocker racers were DQ'ed many years ago by NHRA for using these even though the lift checked correct at the retainer. It changes the rate of lift and produces more flow as the valve rises off the seat. Its DUMB to even think you could use rocker ratios greater than what the engine spec. book calls for. Stop trying to reinvent the wheel.

[X-TECH MAN]

Originally Posted by Tom keedle

what about vice-versa?

Less would gain you nothing unless you had some major piston to valve clearence or geometry problems with some odd ball engine. The OEM stock steel stamped rockers are way less to begin with.

[novassdude]

If the stock stamped rockers were less and all the cam makers know this. What are the odds that just switching to a aftermarket roller rocker will bump the lift at the retainer over the allowed limit?

[Tom keedle]

Originally Posted by X-TECH MAN

Less would gain you nothing unless you had some major piston to valve clearence or geometry problems with some odd ball engine. The OEM stock steel stamped rockers are way less to begin with.

exactly my issue....
and while we're at it, is it legal to run less lift than spec?

[X-TECH MAN]

Originally Posted by Tom keedle

exactly my issue....
and while we're at it, is it legal to run less lift than spec?

Yes.....some do to gain piston to valve clearence and use more duration. Duration and overlap is more important than valve lift. Maybe not so much with the bogus aftermarket pistons of today which give you more piston to valve clearence than the OEM unit.

[Rick Leininger Jr.]

[QUOTE=X-TECH MAN;305163 Remember the Crane stamped steel rocker that came in 1.6 for the small block chevys. Several big name stocker racers were DQ'ed many years ago by NHRA for using these even though the lift checked correct at the retainer.[/QUOTE]

How does NHRA check rocker ratio at teardown?

[69Cobra]

I don't know how NHRA does it but I would think the easiest and most accurate way would be cam lift divided by valve lift.

[Stocker 2]

Originally Posted by novassdude

If the stock stamped rockers were less and all the cam makers know this. What are the odds that just switching to a aftermarket roller rocker will bump the lift at the retainer over the allowed limit?

That's right! Anyone making the switch to roller rockers will need a new cam ground. Sounds like the cam manufacturers were all for allowing aftermarker roller rockers.

[Alan Roehrich]

Originally Posted by ss wannabee

Don't see why ratio would matter as long as valve lift spec wasn't exceeded...Again, the spring pressure deal "opened" up this can of worms...

Would think though...that MOST stocker cam lobe profiles were created with the STOCK rocker arm ratio in mind....notice that I said MOST...but not ALL...

It's called "area under the curve". Making the rocker move the valve faster than the lobe can with the stock rocker ratio gives you more area under the lift curve.