Re: Rocker Ratios. 1.5 or 1.6?
[Re: MoparDonny]
#1902060
08/29/15 09:04 PM
08/29/15 09:04 PM
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Joined: Jun 2003
Posts: 52,972 Romeo MI
MR_P_BODY
Master
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Master
Joined: Jun 2003
Posts: 52,972
Romeo MI
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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 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
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Re: Rocker Ratios. 1.5 or 1.6?
[Re: MoparDonny]
#1902209
08/30/15 01:24 AM
08/30/15 01:24 AM
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Joined: Oct 2003
Posts: 21,345 Marysville, O-H-I-O
70Cuda383
Too Many Posts
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Too Many Posts
Joined: Oct 2003
Posts: 21,345
Marysville, O-H-I-O
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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.
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Re: Rocker Ratios. 1.5 or 1.6?
[Re: MoparDonny]
#1902371
08/30/15 12:13 PM
08/30/15 12:13 PM
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Joined: Aug 2009
Posts: 304 Portland, Oregon
Digger73
enthusiast
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enthusiast
Joined: Aug 2009
Posts: 304
Portland, Oregon
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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)
I live with fear everyday but, sometimes she lets me race!
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Re: Rocker Ratios. 1.5 or 1.6?
[Re: ahy]
#1902491
08/30/15 03:55 PM
08/30/15 03:55 PM
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Joined: Jan 2003
Posts: 15,439 Val-haul-ass... eventually
BradH
Taking time off to work on my car
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Taking time off to work on my car
Joined: Jan 2003
Posts: 15,439
Val-haul-ass... eventually
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... 1.6's may get you into a marginal valve spring/stability situation. 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.
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Re: Rocker Ratios. 1.5 or 1.6?
[Re: justinp61]
#1902973
08/31/15 05:11 AM
08/31/15 05:11 AM
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Joined: Nov 2004
Posts: 1,760 Port Alberni, British Columbia
MoparDonny
OP
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OP
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Joined: Nov 2004
Posts: 1,760
Port Alberni, British Columbia
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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. I do very much plan on stepping up the power. But I will look into the Hughes Rockers.
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Re: Rocker Ratios. 1.5 or 1.6?
[Re: MoparDonny]
#1903060
08/31/15 11:57 AM
08/31/15 11:57 AM
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Joined: Jul 2007
Posts: 732 eastern,Ky
70RT Charger
super stock
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super stock
Joined: Jul 2007
Posts: 732
eastern,Ky
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Heads would be a cheaper upgrade that the rockers !! My heads shouldn't fail though. My rockers arent really ideal for a 500+ hp engine. 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.
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Re: Rocker Ratios. 1.5 or 1.6?
[Re: Stanton]
#1903257
08/31/15 04:44 PM
08/31/15 04:44 PM
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Joined: Jan 2013
Posts: 126 Oregon
Jamie McGrath
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member
Joined: Jan 2013
Posts: 126
Oregon
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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.
Last edited by Jamie McGrath; 08/31/15 04:46 PM.
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Re: Rocker Ratios. 1.5 or 1.6?
[Re: Jamie McGrath]
#1903319
08/31/15 06:20 PM
08/31/15 06:20 PM
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Joined: Sep 2004
Posts: 6,906 IL, Aurora
ademon
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master
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IL, Aurora
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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.
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