Big Power mods for the 8.1 motor!

[tbyrne]

 

 

 

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.

[tbyrne]

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.

[mxrider4]

I think this would be better than the whipple.Do you know what kind of torque increase you would see? Would the engine still be good for towing? I tow a 36ft 5th wheel that ways 13500 loaded. I have the 2004 2500hd 8.1/allison, and want more power for towing and city racing. I know the whipple has mad torque increases, but if this was comparable i would prefer this set-up. Any idea on cost and smog issues? thanx

[tbyrne]

This package will allow the motor to produce about 500ft-lb torque at 2000 RPMs. Peak torque would be in the 600ft-lb range at 4300 RPMs. The truck would have the same driveability as it does now but with alot more power. A set of mid-length headers should be worth about 25-30hp with this combo. All would be very good for towing.

 

The heads are $2599.99, $2399.99 for the intake, $429.99 for the cam, $284.99 for the 1.8 rockers and just under $400. for all of the upgraded head bolts and gaskets. So your looking at about $6000. for everything. Taking the intake out would drop that down to about $3700. This will be good for about 115hp increase.

[Cool Zr2]

Sweet!!

 

Are there packages like that for my motor?

[tbyrne]

They company only offers them for the 8.1. I believe Accel might have a different intake for your truck.

[Cool Zr2]

They company only offers them for the 8.1. I believe Accel might have a different intake for your truck.

I tried to locate one but no luck, do you have any links?

[tbyrne]

I'll let you know if I come across anything. I believe it's called the SuperRam.

[tbyrne]

Quick update about this intake. The one pictured above is an early prototype so it shows the throttlebody facing straight out. The new will have the correct angle to mate up to the induction. A large billet aluminum with an oval opening will be available in the next 1-2 weeks. This will flow about 1200 cfm. Life is getting good for the 8.1s now! I'll also be installing one of these with the complete package.

 

A few people have called about the 1.8 rockers. These are a direct bolt-on that will fit under your stock valve covers. They can be installed with no other modifications required. You'll see about 12hp from them.

[tbyrne]

I should finally have all of my parts in the next 1-2 weeks. I really want to install a set of 1 7/8" long tube headers at the same time so they might hold up the install for a few weeks. I'm like you guys and girls... I hate waiting for parts to come in!

[CMNTMXR81]

SWEET!!! This is what I had waited for forever with mine. But alas, the fuel economy was terrible as it was, this has to kill it!

[Bud]

Do you need a nice truck to try all of this on?

I volunteer

[tbyrne]

SWEET!!! This is what I had waited for forever with mine. But alas, the fuel economy was terrible as it was, this has to kill it!

 

Mileage should actually go the other way. They expect it to increase by at least 1 MPG.

 

Do you need a nice truck to try all of this on?

I volunteer

 

I'll actually have the first truck running this complete package. They've sold these for marine motors and have had some parts go out for truck motors but nobody is running everything on one.

[CMNTMXR81]

Yes and no.

 

If you're burning your A/F mixture more thoroughly and getting the power benefit from it, then yes you will be more efficient. Seeing as though these are low compression engines, you really have a lot of room to improve combustion.

 

However, the more volumetrice efficiency you add by ported and polished runners, bigger valves, longer ratio rockers as well as bigger lift cam/longer duration cam, you also have to feed it with additional fuel to maintain the proper ratio for power enrichment.

 

Alas, 496 cubes is a lot to feed!

 

Like I said, I loved my 8.1 and was eagerly waiting for aftermarket parts to become available. If money were no object, I'd have been all over it. I guess the question that needs to be answered is if the increased efficiency offsets the increased fuel requirements and only time will tell that.

[Daubs]

Holy crap! This is awesome! We are talking about almost doubling HP in the 8.1 for roughly $6,000.

 

Wondering if the Allison can handle all that torque / HP?

 

NOw if I can just convince the wife...