Hey guys. I'm going to upgrade from my original rockers to some rollers. I'm pretty set on Harland Sharps but in a 1.5 or 1.6 ratio? Would appreciate some info on why or why not a 1,6 ratio. I figure if I'm gonna buy rockers, might as well get .030 more lift for the extra few bucks. Been awhile since I've posted here so here's my combo.
451 low deck stroker
Comp xe284h cam (241/247@.050 & 507/510 lift)
Stock Stealth heads with comp 925-16 springs.
Stock rockers & pushrods
Torker intake
Q850 carb
1-3/4 headers with 3" exhaust

11.6 -7 quarter times at 116mph in my Challenger.

i wouldn't hessitate & go with the 1.6 ratio. it'll make you cam think it's bigger when you stab your foot on the loud pedal. all my motors have 1.6 ratio, never seen a bad point on running them. the HS rockers may cause you to loose oil pressure a little when hot but thats what you get with roller bearing rocker arms. go for it, don't look back.

I wouldnt just say yes.. do the heads need more cam... yours
are stock.. will you have the clearance to the pistons.. will
the spring go into coil bind.... and I believe your talking
a street car... so those are things to check... yeah we all
like a big cam.. but if the system isnt balanced your just
spending money

Maybe what I have is not balanced.

In theory, the higher ratio is more stable at higher rpm. Adding ratio will increase you "@.050" lift numbers, because you get to .050" of lift sooner. So you gain a few degrees of 'useful' duration as well as total lift. It's more stable because you're moving the valve further without moving the heavy parts further. Heavy parts have more inertia. A .600" lift cam with 1.5 ratio rockets will valve float sooner than .600" lift cam with 1.6 ratio rockers with the same valve spring pressures. Am I making sense here?

That said, the rest of the combo has to be able to take the extra lift. As said, valve to piston clearances, coil bind, and locks/retainers to guide clearances need to be able to take the added lift when you take one combo and just toss the higher ratio rocker at it.

There's also the debate on side loading the valve stems, and swept area of the valve stem. The higher ratio will sweep further to the edges of the stem, and can add extra side loading

The EFI magnum engines all left the factory with 1.6 ratio rockers.

I run a set of Ed heads on a 496 with fast rate cam and 1.5 rockers (243@.050, .55" lift). With the 1.6's yours would be similar. I think I am near the limit for a standard single spring. You probably spin your engine faster... 1.6's may get you into a marginal valve spring/stability situation.

I am planning to upgrade springs on mine a bit as I am running it on the road track and pushing the RPM more.

Something also to think about. The intake push rods will have to have extra clearance in the heads. A buddy of mine runs 1.6 rockers on Stealth heads. He had to grind additional clearance because the intake push rods rubbed the heads.

Digger73 (Mike)

Or, maybe a NOT so marginal stability situation. Those COMP Xtreme hydraulic lobes aren't known for the best high-RPM valve train control; adding more ratio can cause the issue to occur earlier in the rev range.

I'm not one bit concerned with piston to valve clearance and last year I put comp 925–16 springs in place of the stock stealth head springs, I haven't checked coil bind but they must be able to take .540 lift at the valve. I would check to be sure of course. I would expect pushrods to hit, they do on Eddy heads with a 1.5 rocker and smith bros pushrods. Any issues that could arise regarding side loading and such, can't be any worse with a $1000 set of Harland Sharp rollers vs my stock rockers that I've been buzzing to 6300 rpm for 5 years now.

Anybody know the best place to get Harland Sharps through Moparts? Being Western Canadian takes its toll on exchange rates and duty charges so any savings would be sweet.
Don.

Are you planning on stepping up the power? IMO a set of Hughes rockers would be more than adequate for your combo, it would save a bunch of money too.

Heads would be a cheaper upgrade that the rockers !!

No "duty" on auto parts due to NAFTA.

Summit or Jegs are probably your best deal for rockers. They'll even ship free if you want to pop over the border to pick them up but I guess a ferry ride, etc. doesn't really make it all that worthwhile !! The nice thing about Summit or Jegs is they have their act together for international shipping ... some vendors couldn`t find Canada on a north american map!

I do very much plan on stepping up the power. But I will look into the Hughes Rockers.

My heads shouldn't fail though. My rockers arent really ideal for a 500+ hp engine.

I have the Harlan Sharp 1.6:1 rockers on my Stealth heads. I have not had any problems with them. I am using the 5/16" smith brothers pushrods. I think 3/8" pushrods will require more clearance in the pushrod holes. I would even double check with the 5/16" pushrods as the higher ratio moves the pushrod/adjuster closer to the rocker shaft.
I don't think you will have any problems with the springs you have.
They coil bind at 1.18" or 0.725" valve lift if installed at 1.900".
Not sure your install height, but a bit less would add a bit more seat pressure (only 111 lbs @ 1.900".)
The retainer to valve guide clearance will be fine.
Not sure about Piston to valve clearance, but if the pistons have valve notches I'm pretty sure your good.

I'm just wondering why your rockers wouldn't be suitable for 500+ HP. Guys have been running them for years that way and how much HP do you actually gain by running a roller setup backed up by Dyno Sheets. I'm also trying to figure out do I really want to spend that much money for a roller setup and it's just for a cruiser too.

I'd run the numbers on something like desktop dyno. It won't be dead accurate but it would give a pretty good idea of what you could expect a) from a head swap or b) from a rocker swap.

If you do a rocker swap its a complete cash outlay with virtually no return from your old stuff. You still have to pull the heads to grind for pushrod clearance.

A head upgrade would yield a return on your existing heads. All your current hardware can be moved over to those.

FWIW I have a chart of a bunch of different heads and the difference between the stock stealth and ported stealth is somewhere between 80 and 100 HP at .500 lift. Can you hope to get even close to that with a rocker swap ?!?!?

I'm surprised no one has mentioned this so I will.... The stock rockers although fool proof are rated at 1.5, but that's there not there true rocker ratio. I think there closer too 1.42-1.45 so there all over the place. Your not getting the lift that you think you are. You will see a improvement with a trued ratio alone, anything extra on top of that is a bonus.

If your head moves more air at the higher lift, then the 1.6 would really help because its also moving more air under the curve as well. This is provided you have the clearances too take advantage.

Might be even closer to 1.40, plus a lot more flex than a good rocker.

Harland Sharp makes a great rocker, unfortunately his rockers are too long for the heads. There have been some great discussions here in the past year. Do some research. There are rockers out there that fit better.



R.

Thanks for the replies. I'm not exactly looking for a bunch more power at this point, this is not my current goal. My goal is to replace the stock rockers with something more stable and durable and just better all around than the 50 year old stamped type. I figure that 1.6's vs 1.5's would give me a bit more lift and duration@.050 without the negative drivability effects of a larger cam. Not looking to spend 2 or 3000 on heads until I'm ready for that. By that time the rest of my valvetrain should be decent stuff.
Don.