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Discussion Starter #1
I have a new set of Dart Pro One heads with the .520 lift valve springs. My cam has an exhaust lift of .494. If I go to 1.6 rocker arms I have read that I would add approximately .030 to the lift, thereby giving me a theoretical .524 lift. This would exceed the factory valve spring recommendation by .003. Would this be a problem with any clearances?
Or would I have to go up a spring size? I'd like to use 1.6 rockers, but it's not worth returning the heads or replacing brand new springs.

Thanks for any help.
 

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Hammer and a torch
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That should not be a problem but what is the coil bind at...? Just make sure thats not the coil bind point of the springs... Going to the max lift of spring will of course shorten its life as opposed to running a 1.5 rocker to keep the cam at the rated lift...

BTW the gain from using the higher ratio rockers minor as compared to reduced life of the springs... Just my .02 :thumbup:
 

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Discussion Starter #3
Bumpstick said:
That should not be a problem but what is the coil bind at...? Just make sure thats not the coil bind point of the springs... Going to the max lift of spring will of course shorten its life as opposed to running a 1.5 rocker to keep the cam at the rated lift...

BTW the gain from using the higher ratio rockers minor as compared to reduced life of the springs... Just my .02 :thumbup:

Thanks for the info. Yea, I'm not sure if the 1.6 is really going to be worth that much effort on this street motor. especially since I already have brand new 1.5 rockers. I'm just looking into the advice given by a relative who races.
 

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Troll Hunter
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I would back off from say that it is NOT a problem if you haven't done any checking of coil bind or other measurements. There is also the seal within the spring that can get hammered by the retainer. If you do get bind you could minimally bend a pushrod... and that is minimally. I'd check it closely prior to changing the rockers for more lift.
 

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I wouldn't worry about .003, the thickness of a hair, just for a comparisons sake. That's within the adjustment/thickness range of any shims you might need to assemble the valves . But .030 - no.
 

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surfshark said:
I have a new set of Dart Pro One heads with the .520 lift valve springs. My cam has an exhaust lift of .494. If I go to 1.6 rocker arms I have read that I would add approximately .030 to the lift, thereby giving me a theoretical .524 lift. This would exceed the factory valve spring recommendation by .003. Would this be a problem with any clearances?
Or would I have to go up a spring size? I'd like to use 1.6 rockers, but it's not worth returning the heads or replacing brand new springs.

Thanks for any help.
There is only one way to answer that question, and that is to physically remove the springs, and check them for solid height in a vice, then check the installed height as assembled on the heads.

These days, everyone uses large numbers to sell their products, so even if it has a set of "Z-28" style springs, they inflate the numbers to sell the heads.

Check and be sure, and don't try to run a cam that will run your springs close to coil bind.


A spring is just like a coat hanger. The more you work it, the hotter it gets, the easier it will fail.

Larger body springs that are not compressed to the max and have more area to transact applied forces live longer.

The term ".520 lift springs" is a very loose term to be sure.


NAIRB
 

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Save a horse, Ride a Cowboy.
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One thing to consider is........

even if everything clears and the lift is only .003 more than the recommended max.....

but springs that have been run at one lift for a period of time then a larger lift is pushed to them........ sometimes they fatigue and break. :(

Exactly how much damage can you afford to repair?

And IF you can afford to repair it later... why don't you just change springs now and save all the anxiety and work later.
 
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