Anyone use 1.7 ratio rocker arms???

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mopowers

mopowers

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I'm curious if anyone runs (or has tried to run) 1.7 rockers on their low deck big block with Edelbrock RPM heads. Are there any push rod clearance issues? I'd imagine it would require some clearancing, but figured I'd ask in hopes someone out there has tried this combo.
 
Sorry this isn't answering your question but I have 1.6 rockers and realized I shot myself in the foot trying to find a cam that is what I want for lift, so I'll have to have a custom cam made eventually
 
MOPARMAGA said:
Sorry this isn't answering your question but I have 1.6 rockers and realized I shot myself in the foot trying to find a cam that is what I want for lift, so I'll have to have a custom cam made eventually
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Thanks and no problem. Pretty much anything I build anymore is likely going to have a custom cam anyway, so that's not a problem. I'm just not as familiar with big block Edelbrock heads. I've seen folks run 1.7's on some of the Indy stuff, but I'm wondering what level of clearancing is necessary to run 1.7's on Eddelbrock RPM heads.
 
How much lift are you trying to acheive? I'm running 1.6's with the Hughes 250/254 solid cam, with my rockers I am at .640 lift on the exhaust and .627 on the intake. Your valve springs are gonna have to be pretty stout if you are looking for more lift on a street motor.
 
petethekiller said:
How much lift are you trying to acheive? I'm running 1.6's with the Hughes 250/254 solid cam, with my rockers I am at .640 lift on the exhaust and .627 on the intake. Your valve springs are gonna have to be pretty stout if you are looking for more lift on a street motor.
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It'll likely end up somewhere around 260*@.050" and around .650" valve lift.

Did you have any pushrod clearance issues with the 1.6's? What heads are you running.
 
I'm running a set of heavily ported ProMaxx castings that have epoxy in some areas including in the pushrod pockets. I am running 3/8 push rods I have good clearance.
 
Sometimes u end up like this. 1 welded set and 1 epoxied set. Kim

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What are you trying to accomplish? Why not run 1.5s and just choose or have a cam ground accordingly? There'll be no power difference and you'll have less chance of having to clearance the heads.
 
MOPAROFFICIAL said:
Run what ever you want.
At the adjuster is the change.
Let us know how it works. I like learning.
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I love learnin too, but "NORMALLY" you run a higher ratio rocker, because you have a camshaft already that you want more lift on. It's not normal practice to choose a higher ratio rocker at the beginning of a build without already having the camshaft. In that instance, you can choose or have ground whatever lift camshaft you want for the 1.5 stock ratio. ........in other words, I wanna know what the advantage is doing it one way over the other if there is one.
 
Plus, higher ratio rockers create two new problems:
- stronger springs reqd to control the valvetrain
- stronger prods that will not flex with the stronger springs. Bigger diam is stronger/better v same diam with thicker wall, but could be a nightmare to set up, as in the above post.

Agree with RRR. 1.7 rockers would add about 3-4*@ 050 of effective duration, so have a cam ground accordingly for use with 1.5 rockers.
 
RustyRatRod said:
I love learnin too, but "NORMALLY" you run a higher ratio rocker, because you have a camshaft already that you want more lift on. It's not normal practice to choose a higher ratio rocker at the beginning of a build without already having the camshaft. In that instance, you can choose or have ground whatever lift camshaft you want for the 1.5 stock ratio. ........in other words, I wanna know what the advantage is doing it one way over the other if there is one.
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There are times when you can’t get the lift you want and still have a lobe with some durability. At that point you use a higher rocker ratio.

As an example if I have .620 (gross) lift and a 1.6 rocker I need a .3875 lobe. For the same lift on a 1.5 rocker you’ll need a .4133 lobe. That bigger lobe won’t have near the life as the smaller lobe with the same diameter lifter.
 
Bewy said:
Plus, higher ratio rockers create two new problems:
- stronger springs reqd to control the valvetrain
- stronger prods that will not flex with the stronger springs. Bigger diam is stronger/better v same diam with thicker wall, but could be a nightmare to set up, as in the above post.

Agree with RRR. 1.7 rockers would add about 3-4*@ 050 of effective duration, so have a cam ground accordingly for use with 1.5 rockers.
Click to expand...

Most everyone uses pushrods that are far undersized anyway so it is what it is. As for spring load and rate, the change is minimal.

You not only gain some area under the curve, the higher rocker ratio will change how fast the valve moves off the seat. That means you can use a slower lobe and use rocker ratio to speed up the valve.

Never underestimate the valve of valve speed.
 
Half the problem is finding that camshaft that meets all the specs you want.
 
More seat, not so much open is what will control that. No need to slow a roller lobe, flat..sure...maybe for life span.
Think 'triple springs'
 
Rat Bastid said:
There are times when you can’t get the lift you want and still have a lobe with some durability. At that point you use a higher rocker ratio.

As an example if I have .620 (gross) lift and a 1.6 rocker I need a .3875 lobe. For the same lift on a 1.5 rocker you’ll need a .4133 lobe. That bigger lobe won’t have near the life as the smaller lobe with the same diameter lifter.
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Now that makes sense. The bigger lobe for the 1.5 rocker has to be more aggressive to achieve the same lift as a less aggressive lobe ground for the 1.7 ratio rocker. Thanks.
 
Ahhhhhh, camshaft games… so much fun!
 
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