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Premium Member
8,416 Posts
Discussion Starter #221
Dyno Testing 7 Popular LT1 Engine Modifications

From SuperChevy April 2013:

Note that this is on an engine dyno without drivetrain and assesories which sap engine power. Furthermore, it is a magazine that sells advertisement for performance parts.

Dyno Testing 7 Popular LT1 Engine Modifications

We learned a lot of things from these tests. Clearly all of the little tricks will only add up to so much when the motor is still restricted by the factory exhaust, throttle body, intake, heads, and valvetrain. The common wisdom of 10hp from this and 10hp from that equals 20hp, just isn't true. The engine is an air pump, but more than that it is a system of interacting parts – each one affecting the other. When you modify your engine, you should do so with purpose and intent. For example, don't bother upgrading the throttle body and heads if you still have a stock air intake. Don't add octane booster or race gas unless you are running high compression or boost that requires you to pull timing. Knowing that our LT1 still has a few restrictions in it, we'd like to uncork it a bit more to pull out its potential before we start opening it up to see how far we can push a stock cube motor"

Premium Member
8,416 Posts
Discussion Starter #223
Alex's Parts Valve Spring Kit

Valve Spring Kit for stock iron heads

Product Description
Drop in fit, .550" Lift, SBC Iron Vortec
Valve Spring Kit for SB Chevy Vortec
High Performance Hydraulic Roller Cams, up to .550" Lift w/ 130 Lbs seat pressure

Our Vortec kits are engineered specifically for Iron Vortec & 96 Iron LT1 heads. (not aluminum LT1)

That's right, no machine work required to set up a pair of these heads.

We engineered this kit with all the right parts so Vortec head owners won't have to machine the spring seats or valve guides to run up to .550" lift.

Great for engines with 1.6, high ratio rockers.

Yes, works with self aligning rockers as well as heads w/ screw in studs and guide plates and std, non self aligning rockers.

As some of you know, Vortec heads have a problem w/ retainer to seal clearance. The stock retainers and springs do not allow for more then around .460" lift.

This kit is specially engineered to allow for up to .550" lift, all with parts which fit the heads without additional machine work.

We use a special retainer and spring combination which solves two vortec head problems.

The retainer to seal clearance issue.

Spring base diameter issue (vortec heads will not accept std SBC springs)

The issue with clearance between the retainer and seal was solved by producing a special retainer which offers maximum clearance between
the bottom side of retainer and the top of the seal. The bottom of the retainer is pretty much "flush" with the bottom edge of the locks. This
design offers maximum clearance without compromising strength or requiring the guides to be shortened.

Our springs are a perfect fit on the stock Vortec spring base.

Both problems solved!

Stock valves have .260" IN/.289" EX Tip lengths which will generally allow for up to .550" lift.

It it durable? Yes!

We have sold thousands of our vortec spring kits to customers world wide!

Kit Includes:

Sixteen- High Output Drop In Fit Valve Springs
Sixteen- Chrome Moly Retainers, 7 degree
Sixteen- 7 Degree Hardened Valve Locks

For 130 Lb seat pressure, we recommend purchasing a shim kit to facilitate setting up the proper installed height.

To obtain optimum performance, installed heights must be measured and shimmed as required.

Each kit comes with it's own installed height specification card. Always use the specification card included with your kit.


Outside Diameter- 1.270"
Inside Diameter- .880"
130 Lbs @ 1.780"
340 Lbs @ .550" lift
Rate- 365
Average Coil Bind 1.150"
Beehive Spring? - No
High Perf Replacement Spring? -Yes

Kits for High Performance Hydraulic Flat Tappet (110 Lbs Seat) or smaller Hyd Roller (120 Lbs Seat) cams can be found by entering VSK4H50
and VSK4h52 into the search engine.

Suitable for most hyd roller cams w/ up to 244 degrees duration @ .050"

Requirements- Valve Seal replacement is highly suggested. It's important for the installer to make 100% sure the seals are fully seated down
onto the guide. Seals which are not fully seated will reduce maximum lift capacity. We recommend measurements are taken between retainer
bottom edge and the seal top to verify there is at least .030" clearance exists.

OE GM Vortec heads normally use: 11/32" X .552" seals. Be aware some aftermarket heads (such as engine-quest) have different guide diameters.
If you have aftermarket iron heads, it is advised to measure the guide before ordering seals.

NOTE-1- Spring installed height must be checked and shimmed as necessary.

NOTE-2- Not for Gen III LS series aluminum Vortec. Check our other spring kits for late model Gen 3 applications

NOTE-3- We do not recommend the use of "HOWARDS" brand self aligning rockers. Due to their bulky design, clearance between rocker and retainer
is either limited or non existent. The same goes for some older Crane self aligning rockers. Most other brands of self aligning rockers work fine.
Each builder should check for rocker interferance upon assembly.
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