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Old 05-12-2010, 08:54 PM
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1:6 Roller Rockers

Is there any gain to changing my stock rockers to 1:6 rockers on a stock ZZ-4.
Will I need to change the valve springs and is there enough clearance for the stock tin valve covers?

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Old 05-13-2010, 08:22 AM
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changin rockers

if thats all your going to do ??? save your money.
u don't need to change springs and there should be enough room for them... but again, ain't worth it..
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Old 05-13-2010, 08:40 AM
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Quote:
Originally Posted by solidaxel
Is there any gain to changing my stock rockers to 1:6 rockers on a stock ZZ-4.
Will I need to change the valve springs and is there enough clearance for the stock tin valve covers?
According to info in the GMPP catalog, 1.6 rockers cannot be used with the ZZ4 cam because the valve springs cannot take the increased lift. Because the intake lift is less than the exhaust lift, the problem should be only on the exhaust side, but I'd replace them all to be safe.

There might be clearance issues between the retainer and guide boss/seal, as well.

There are stock diameter "drop in" springs available that have specs that will allow the use of 1.6 rockers, but the guide boss to retainer still needs to be verified, along w/P to V, etc.

Last edited by cobalt327; 05-13-2010 at 08:45 AM.
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Old 05-13-2010, 08:45 AM
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Quote:
Originally Posted by cobalt327
According to info in the GMPP catalog, 1.6 rockers cannot be used with the ZZ4 cam because the valve springs cannot take the increased lift. There might be clearance issues between the retainer and guide boss/seal, as well.

There are stock diameter "drop in" springs available that have specs that will allow the use of 1.6 rockers, but the guide boss to retainer still needs to be verified, along w/P to V, etc.

100% dead on correct.

I'd like to add that a cam swap instead of a rocker change is about the same cost, and will produce more dramatic results.
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Old 05-13-2010, 08:47 AM
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A cheap cam upgrade is the HOT cam, often found in like-new condition when guys swap them out for aftermarket cams. Still a "factory" cam, but not a bad one, IMHO.

(Added "FWIW") For L98 engines 1995 and before, the dowel pin in the end of the camshaft must be pushed in so extension from end of cam is 0.300" +/-0.010", the same as the production part.

The HOT cam specs calls for 1.6 rockers. With 1.6 rockers, the cam should be worth about 25-30 HP over the ZZ4 cam.

HOT Cam Specs:
218°/228° duration @ 0.050"
.492"/.492" with 1.5's rockers or .525"/.525" with 1.6's
112° LSA

ZZ4 Cam Specs:
208°/221° duration @ 0.050"
.474"/.510" lift with 1.5's rockers
112°LSA

HERE's a build w/Vortec heads and the HOT cam that made 422 HP w/a 355 SBC. This was w/a Super Vic intake, the dual plane was down 10 HP peak from the single plane intake. Because the dual plane was a GM Performance Parts dual-plane Vortec intake manifold, using an RPM intake instead would likely do better than either of the tested intakes.

Last edited by cobalt327; 05-13-2010 at 09:37 AM. Reason: Add link.
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Old 05-13-2010, 11:01 AM
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Quote:
Originally Posted by solidaxel
Is there any gain to changing my stock rockers to 1:6 rockers on a stock ZZ-4.
Will I need to change the valve springs and is there enough clearance for the stock tin valve covers?
The 1.6 rockers will build around an additional 15 horses on the top end. They're actually pretty good for a street driven under headed engine like the ZZ4. The L98 head isn't a real good breather, this is where 1.6's really shine as they tend to pick up the mid lift faster than a 1.5 which is where the L98 head will take advantage of the greater amount of lift at that point. The stock L98 port is running out of steam by the time the valve gets to max lift so it really can't take as much advantage of the flow potential offered to it by the more wide open valve. This brings one to the argument for a cam with more duration with these heads, as this also offers the benefit of more and fatter lift thru the mid lift zone. This can also offer the benefit of not adding much if any lift over the nose since the unported L98 can't use it anyway, so this alleviates the need for solving the valve spring problems.

Both solutions 1.6 rockers and certainly to a greater extent a longer duration cam both work better against more compression, another ZZ4 point of needed improvement. While a piston change would be highly desirable in the ZZ4 to a D dish piston to improve squish/quench, simply building the compression up a bit is helpful. This can be accomplished using a Victor Reniz gasket at .026 inch thick instead of GM's .053 inch gasket http://www.cnc-motorsports.com/produ...08&CtgID=16808
This will work with aluminum heads, it will raise your compression about .6 of a point.

Bogie
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