Installing a supercharger on a NA engine - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


Performance When the race track beckons, find out how to mod your car, supercharge your GM engine, and start "Winning"

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Old 02-23-2009, 06:27 PM   #1
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This question is asked over and over again, and here is REAL definite answer...

Can i Supercharge my Non Supercharged Car?? Short answer yes...Long answer Read on...

You cannot simply bolt on an Eaton M90 blower onto a L36 and make it work. Most importantly, the heads are different. The fuel injectors on a L67 are placed into the heads, while on a L36, they go into the intake manifold. While the supercharged L67 heads and the L36 normally aspirated heads were identical in 97-98, the injector bosses are not machined out to accept the injectors. In '99 and newer, the L36 heads went to a different casting, and these injector bosses no longer exist.....that being said you still can make it work

Ok so you have a L36 or L26 in your current vehicle, and you want to mod it, and your not happy being NA so why not supercharge it, the other vehicle platforms have it

here are the specs for L36
Type:
3.8L V6 (L36)
Displacement:
3791cc

Compression Ratio:
9.4:1

Valve Configuration:
Overhead Valves (2 valves per cylinder)

Assembly Site:
Flint, Mich.

Valve Lifters:
Hydraulic Roller

Firing Order:
1 - 6 - 5 - 4 - 3 - 2

Bore x Stroke:
96.52 x 86.36mm

Fuel System:
Sequential Fuel Injection

Horsepower:
205 @ 5200 rpm

Torque (lb-ft):
230 @ 4000 rpm

Fuel Shut Off:
6000 rpm

Emissions Controls:
Evaporative System
Catalytic Converter
Exhaust Gas Recirculation
Positive Crankcase Ventilation
Air Injection Reaction (CA and NE States)

MATERIALS
Block:
Cast Iron
Cylinder Head:
Cast Iron

Intake Manifold:
Cast Aluminum Lower
Composite Upper

Main Bearing Caps:
Powder Metal

Crankshaft:
Cast Iron

Camshaft:
Steel

Connecting Rods:
Cast Iron

Additional Features:
Extended Life Spark Plugs
Extended Life Coolant
Oil Level Sensor
Oil Life System

and here are the specs for the L67 engine

Type:
3.8L V6
Displacement:
3791cc

Compression Ratio:
8.5:1

Valve Configuration:
Overhead Valves (2 valves per cylinder)

Assembly Site:
Flint, Mich.

Valve Lifters:
Hydraulic Roller

Firing Order:
1 - 6 - 5 - 4 - 3 - 2

Bore x Stroke:
96.52 x 86.36mm

Fuel System:
Sequential Fuel Injection

Horsepower:
240 @ 5200 rpm

Torque (lb-ft):
280 @ 3600 rpm

Fuel Shut Off:
6000 rpm

Emissions Controls:
Evaporative System
Catalytic Converter
Exhaust Gas Recirculation
Positive Crankcase Ventilation

MATERIALS
Block:
Cast Iron
Cylinder Head:
Cast Iron

Intake Manifold:
Cast Aluminum - Lower

Main Bearing Caps:
Powder Metal

Crankshaft:
Cast Iron

Camshaft:
Steel

Connecting Rods:
Cast Iron

Additional Features:
Extended Life Spark Plugs
Extended Life Coolant
Oil Level Sensor
Oil Life System


Now there is also the L26 and the L32 that are the 04+ motors. These are physically the same as the earlier versions, except that the connecting rods are now a stronger powerd metal,

so looking at the specs we know that the CR of the motors is different, and that subject will come into play later, but otherwise the motors appear very similar on paper.

Now lets discuss what is really different between the 2 or 4 motors

The crank, Block, and Cam are the same between the NA and SC motors of the same year range (L67 and L36 share their parts, and the L32 and L26 share their parts)

The connecting rods should be the same length, but the wrist pin ends are different, so it may measure different since they measure connecting rods center to center

the connecting rods are smaller on the L36 than they are on the L67. This allows the rotating assembly to be lighter but also weaker in terms or strength.

The L67 and L32 have a 8.5 to 1 compression ratio
The L36 and L26 have a 9.4 to 1 compression ratio

The L67 and L32 have the fuel injector bosses in the heads
The L36 and L26 have the fuel injector bosses in the LIM(lower intake manifold)

The L32 and L26 have an Electronically Controlled Throttle
The L67 and L36 have a Cable Controlled Throttle

The L67 has a Gen III M90
The L32 has a Gen V M90(the gen V is considered much more efficient)
****The Stock Pulley for both Gen III and Gen V is 3.8 inches in Diameter

The NA motors have the cam timing off one degree from the factory

The SC pistons have more space between the piston top and top compression ring than the NA pistons

The L32 and L26 engines have Powder Forged connecting rods and Moly Coated Piston skirts

The L32 and L26 engines' heads flow slightly better than the Series II heads
(thanks to slightly bigger valves and slightly better port design)

ok so we have our differences. now lets start talking about the swap

A top swap motor has higher compresion giving it about 5% more power at the same mod level as its originaly SC cousin

It can be less costly than a motor swap, and you get to change many engine gaskets, possibly ones that need to be replaced

Now you have read this and decide you want to do it......awesome, here are the parts your gonna need
Heads from SC motor (Either Series will do, all the blocks are the came so all the heads can be interchanged)
Head Bolts, can be OEM replacements or Studs, up to you(Stock are Torque to Yield(one time use)
Thread Sealer (the head bolts go into the coolant jacket, and if they aren't sealed, they will weap coolant out)
Head Gaskets
Rocker boltsSame reason as the head bolts
Valve Cover Gaskets
Harmonic Balancer From the SC motor
Tensioner for SC belt
Idlers for Sc beltThese require bolts that aren't on the L26/L36
Coil Pack BracketThe tensioner and one of the idlers bolt to the SC Coil bracket (some 97 and 98 cars may not need a different bracket)
Lower Intake Manifold from the SC motor(The bolts are the same, so you can use your old LIM bolts if needed)
Lower intake Manifold Gaskets(the Aluminum ones are the Best)
Fuel Rail(you need the one that matches your fuel system, 97-03 gets the standard rail, while 04+ needs the return-less)
Fuel InjectorsAre not a requirement, but you should run the SC injectors or better flowing units
**Injector connectors may be required on some years
Supercharger
Supercharger Gasket(If you use a Gen III M90 you need O-rings as well)
Supercharger Belt
Throttle Body from SC motor(This isn't required but recommended)
Throttle Body Gasket
Colder Thermostat I Recommend 180*, but that is all personal preference
1 Step Cooler Spark PlugsUsually recommended for the Top Swap
Fluids Oil(a change needs to be done after Swap and before engine is started) Coolant(you will loose a good amount doing the Swap
Oil FilterFor above change
Tuned PCM Stock Gt settings are way too aggressive for a SC application, I suggest a tuner, but if you don't have time, a Canned tune can work
Exhaust Manifold Gaskets (optional)


here are some FAQ'*
How much Power do I gain?
General Consencus is that you will have 5% more power than a L67 with identical mods, so stock vs stock, you should have about 252HP at the crank (Stock 240hp * 1.05(5%)).... A stock GTP is somewhere between 185 - 195WHP, so expect similar like 185-200whp if you Dyno your car.....

How Much Faster Does the Car Get?
The usual Gain is 1 full second from where you are now, I gained .89 seconds on my custom tune(which isn't very good) So a full second to 1.2 seconds seems right (this Depends on mods though)

Does It Affect Fuel Mileage?
That Depends if you can stay out of boost, If your going WOT every time your car moves, then of course you fuel mileage is gonna drop, I noticed a gain in Gas Mileage in my car, driving the same as I did before the Swap.

How Long Does The Swap Take To do?
It took me about 11 hours of work from start to finish, but this all depends on how good you are with a wrench and how much patience you have

Will it Kill my Trans?
If your trans is already weak/abused then this may very well kill it, anytime you up engine power you increase the stress on the trans. Now, a well maintained trans will last well(If you don't beat on it and drive like a madman) with a Swap, but in our cars the Trans is the weak link, so sadly there is no guarantee( many Na motors have destroyed their Transmisions) that the added 40 - 60 Hp won't kill the Trans


ok regarding the trans. there is only a few differences between the 4T65 and the 4T65-Heavy Duty. Here is the list

Gear ratio, the 65 will have a 3.05 or a 3.29 FDR, the HD will have a 2.93 FDR
the Differental, and the Differental Tail housing
the passenger side axle.

You can convert your Trans from the Non HD to the HD with the Diff Diff housing and the Pass.Side axle


There are literally hunderds of thousands of miles that have been driven on swapped cars along the W body community with out any issues reported

There you have it, get to Top Swapping
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