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Discussion Starter · #1 ·

Are you thinking about doing more than just upgrading your 8.1's induction and exhaust? If so we have some Big Power mods for you! Raylar Engines now has their Big Power series of modifications available for the late model GM big block. These include a set of aluminum cylinder heads that will increase horsepower and take about 100lbs off the front of your truck. Combining these with their Cool Gap intake and cam will get you into the 500 horsepower range!

Cylinder head specifications

Applications: GM 8.1 liter 8100 vortec (L18) engines

Mercury Marine 496MAG or 496HO

GM vortec Marine HP1, HP2, HP3 versions

Materials: Lightweight a356T56 Alcoa alloy aluminum

Heat treated and hard anodized for marine use

Method: Smooth cast

Machining: all required machining on 5 axis CNC centers

Valve seats: super alloy hardened high strength steel

Valve guides: manganese silicon bronze

Valve seals: super viton in steel "top hat" bodies

Valves: stainless steel EV8 with 11/32" stems, high flow necked stems with

black nitride strength treatment after fabrication.

Valve sizes: Intake valve 2.20" x 12degree w/11/32" stems

Exhaust valve 1.725" x 20 degree w/11/32" stems

(Optional Inconel 1.725 exhaust valve x 20 degree avail.)

Rocker arm studs: Hardened steel with 8MM x 1.0 threaded top with

thrust nut base for mounting stock rocker arms with stock nuts, or

(optional) Raylar Stainless roller rocker arms with "all the way down"

adjusting nuts.

Intake Ports: 315cc. High velocity-High flow smooth ports

Exhaust Ports: 135cc.High velocity-High flow smooth ports

Complete Assembly: Includes:

Valves-intake & exhaust

Springs, retainers and locks

Valve stem seals, valve guides

Rocker studs and guide plates

Complete 5-angle valve job with

Back cut valves with special margins and radiuses.

The "Cool Gap" manifold is engineered to maximize the horsepower and torque levels of the 496-8.1 engine in high performance use with our "BigPower" aluminum cylinder heads and camshafts. The stock manifold was designed for low RPM and emissions use, and even with expensive modifications cannot meet the higher air flow demands of this engine in performance use. The "Cool Gap" manifold is the best answer to the 496-8.1 engine's intake manifold breathing problems. This new manifold incorporates long high velocity runners to provide excellent low and mid range torque levels and a large volume plenum to satisfy this engine's demand for more air at higher RPMs.

The "Cool Gap" manifold gets its name from two air gaps one between the engine lifter valley and the manifold runners and one between the runners and the plenum. These keep the incoming air fuel mixtures cool and dense, additionally producing more power and torque over the entire RPM band.

The "Cool Gap" also features a design that allows it to bolt on in the same space as the stock manifold, and accepts all standard fittings, sensors, brackets, injectors, fuel rails, and accessories without additional modifications to the engine or its wiring.

Each of these products can be found on our website. There is also new 1.8 ratio rockers, upgraded 8.1 piston and accessories to go along with the heads.

· Registered
1,889 Posts
Discussion Starter · #2 ·
I went over some more details about these products this morning. All of these mods can be done by themselves or as a package. You'll see about 75hp from the heads and a set of 1.8 rockers. The intake is good for about 30hp by itself. The mild cam will produce about 25hp over stock while the big one will show you about a 50hp increase. Orders placed now should be ablle to ship in about 2 weeks. I might go with the complete package instead of the Whipple that I was planning for my Silverado HD.
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