if you have the stock cam, then get the 1.6:1 rockers, they'll give you longer duration. Port your exhaust manifolds when you do this to see the most improvement.
1.6 ratio rockers do NOT give a longer duration plus they screw up the valve geometry. If you want more duration or lift, buy a cam that has what you want. Trying to make the wrong cam work by changing rocker ratio is not the way to go. The correct cam is out there or it can be custom ground for pretty much the same cost (more).The 1.6 ratio puts the pushrod a lot closer to the stud, grinding clearance on the pushrod hole makes it fit well enough to put a sideload on the stud. The extra lift translates directly into increased load on the cam lobe, lifter face, and the lifter bores. All without changing the duration. The right cam installed correctly makes for a happy engine.
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12:30 AM
Dr Vinculum Member
Posts: 43 From: York, PA. USA Registered: Dec 2003
I do agree, a camshaft change is the best way to change your valve timing to exactly what you are looking for. However it is alot more labor than just changing the rockers. If i had my valve covers off for some other reason, i would not hesitate to swap in some 1.6 ratio rockers. With the correct length pushrods, your valvetrain geometry will be acceptable. Its common knowledge that going from a 1.5 to a 1.6 ratio rocker DOES change your duration by a few degrees, altho that doesnt seem like much, it is a change and will affect how your engine runs. There are many helpful articles online that talk about physics of valvetrain geometry.
Dr V
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04:54 AM
Tugboat Member
Posts: 1669 From: Goodview, VA Registered: Jan 2004
A couple points here. Roller tips don't do much to help. Edelbrock did a motion study years ago that found that roller tips don't roll at some RPMs and at other RPMs they work BACKWARDS. Although the ball and socket pivot isn't too bad, bearings there reduce friction and heat some. Crane even has high dollar roller pivot rockers with a pad to contact the valve, like a stock rocker.
1.6 rockers give a bit more lift and a couple degrees duration. You might get a couple HP difference. The extra load on the cam isn't an issue, a little more valve spring pressure would have the same effect. It might be 10%. Going from stock to performance springs would be a much bigger difference. If you can handle the extra lift, there's little reason not to use them.
Do NOT put 1.6 rockers on the stock Fiero valve springs! The stock springs are only rated up to .420 lift, 1.6 rockers will push the cam lift beyond that. I agree with the others about the fact that it's always better to use a bigger cam then a larger rocker arm but, if all you're doing is messing with the heads and keeping the stock cam, it's a good way to add a little extra power. If you are doing a rebuild and putting in a new cam then it's far wiser to just go with a bigger cam and leave the rocker ratio alone.
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10:30 AM
rodmcneill Member
Posts: 1616 From: Indiana USA Registered: Oct 2000
Some things I have read about stock rockers and push rods over the years: Some car magazines measured stock rocker arm ratios years ago and came up with anywhere from 1.45-1.49 just because of production differences. Also stock pushrods will flex at higher rpms. The Comp Cams rockers(1.52) and good quality chromoly pushrods will both have less flex at higher rpms thus giving more valve opening.
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01:31 PM
PFF
System Bot
Tugboat Member
Posts: 1669 From: Goodview, VA Registered: Jan 2004
One thing to think about when looking at those articles: who pays the writers salary? Ever see a bad write-up for an advertised product?
If you're worried about RPM, take the weight of those things into consideration. Valve float (or lifter pumpup) is caused by the inability of the spring to control the other parts.
GL
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03:41 PM
NotAFieroAnyLonger Member
Posts: 4413 From: 75762/Texas/USA Registered: Dec 2003
I have the CraneGold full roller rockers in a stock size with their 2030 cam. My old engine had the roller tip rockers. The new engine is also bored and stroke to 3.4 and definitely is more powerful.
[This message has been edited by avengador1 (edited 02-25-2004).]
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07:32 PM
Tugboat Member
Posts: 1669 From: Goodview, VA Registered: Jan 2004
You may want to save your money for something else. Yeah they're cool, but roller rockers really pay-off with high rpm engines, which the 2.8 is not. I could think of a lot of other mods that will bring better results for the money.
"I would rather be hatefully remembered, then just forgotten!!"
My old engine had the roller tip rockers. The new engine is also bored and stroke to 3.4 and definitely is more powerful.
