GM 3800 Series II Motor


In this article I will consolidate all of the information I have gathered about the motor I am currently running in my buggy.  It has proven to be a compact yet powerful motor and would be a great choice for buggies weighing 4000bs and under. 

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L67 Motor

  This motor comes in a normally aspirated version (L36) and a Supercharged version (L67), I am going to concentrate on the L67 since it is the supercharger that makes this motor so special.  The supercharged Series II 3800 V6 motor can be found in all sorts of GM cars as listed below:

  • 1996-2005 Buick Park Avenue Ultra

  • 1997.5-2003 Buick Regal GS

  • 1996-1999 Buick Riviera (opt 1996-97, std. 1998-99)

  • 2004-2005 Chevrolet Impala SS

  • 2004-2005 Chevrolet Monte Carlo SS

  • 1996-2004 Holden Commodore

  • 1996-2003 Pontiac Bonneville SSEi

  • 1997-2003 Pontiac Grand Prix GTP

This article details some of the internal engine differences on the later versions (95+).

Thanks to it's Eaton generation 3 M90 blower this 3.8l (231cu. in.) motor produces an estimated 240hp and 280 ft-lb of torque, up from the 205hp and 230 ft-lb of torque from the normally aspirated version.  The one downside is weight, thanks to the cast iron block and heads I'd guess this motor weighs close to 400lbs (I have yet to find anyone that actually weighed one although I did see a reference on a tuners website that claimed about 400lbs).  Aluminum cylinder heads are on the horizon which will reduce the engine weight greatly, details here. You can also shave a bit of weight (roughly 9lbs) by eliminating some of the brackets that are no needed on the engine (torque arm and engine lifting brackets). You can also swiss cheese the coil pack mounting bracket and shave off another 5lbs.

Stock Dyno chart from

Drivetrain Dimensions (approximate)

Crank to Flywheel = 24" long>

Crank to Flywheel = 24" long

Widest Point = 22" wide

Oil pan to highest point on S/C = 26" Tall

TF-904 = 16" long

Tail housing = 6.5" long

D300 = 12" long

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Unneeded Brackets on the left.


As stated above the L67 uses an Eaton generation 3 M90 blower with a 3.8" diameter pulley. Horsepower gains are seen by replacing the blower pulley with a smaller unit, this increase maximum boost and shortens the time it takes for the supercharger to produce boost by spinning the blower faster than stock. Several places sell pulleys that extend all the way down to 2.5" in diameter.  Realistically unless you are running race gas you need to be a little conservative with your choice in pulley diameter. From what I have read a 3.4" diameter pulley is a good starting point along with some sort of air filter upgrade and cooler spark plugs. 


This is the part I hate.  I can wire stuff but I am not fast and it is frustrating.  This time I had Jim's Performance modify my stock wiring harness so I only had to hook up a few wires (6 wires).  He labeled everything and included a nice 4 panel fuse box to run the PCM.  Jim also re-programmed my PCM to eliminate the missing security, transmission and emission related code.  I did find quite a few places that could handle the PCM re-programming but the few that I contacted asked me what codes I wanted eliminated.  Being as I had never used this motor before I had no idea what needed to be eliminated.  Jim's Performance has done the programming for a few rockcrawling competitors so he knows what needs to be eliminated so the motor will work in a rock buggy. 

From what I have read the stock plug wires and coil packs are not a weak link on this motor and have a reputation as being more reliable than aftermarket parts on this motor.

 Make sure the alternator is working good at WOT.  Mine appeared fine showing 12-13 volts in most situations but at wide open throttle (WOT) the voltage would sag to 10v or less causing the engine to sputter.

You should not need a VSS (I am not running one) if you are running a "dumb" manual shift automatic transmission or manual. You'll need to keep the first oxygen sensor but the second one can be faked with a simulator.

Do not use teflon tape on any of the sensors that screw into the block (especially the knock sensors).  A lot of the sensors ground thru the block.

One last thing on the wiring, this motor seems pretty picky about it's grounding.  I had lingering hesitation issues for over a year and finally got rid of them by running a ground wire from the battery negative terminal to every grounding point on the motor and chassis.


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There are two options, run the stock stuff or headers. The L67 has a cast iron exhaust manifold on the drivers side (or front of the original FWD car) and a tubular exhaust manifold on the passenger side. There is a crossover pipe that runs along the back side of the motor that dumps the drivers side exhaust gasses into the passenger side manifold.  From there the exhaust heads to a large collector complete with a large spring loaded misalignment joint.  I used some 2.5" header bends to start the exhaust routing from there. 

Performance wise I have heard a set of headers in a dual exhaust configuration will easily gain you 30hp but also requires enough room to route the exhaust pipes on both sides of the buggy. Most of the guys I know running dual exhaust and custom headers with this motor have rear engine cars.  For a front engine car I think the stock setup makes for very easy exhaust routing since everything dumps to one side. For performance gains with the stock exhaust routing you can get stock headers for roughly $700 or get nearly the same benefit with ported stock exhaust manifolds for almost a fourth the price. 

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Upon further research I discovered ZZ Performance makes a "power log" which replaces the cast iron exhaust manifold on the drivers side (front) with a tubular version.  The benefits to this exhaust manifold are a  5lbs weight savings and the elimination a huge flow bottleneck by increasing the ID of the collector tube by 30% over the stock manifold. The passenger side (rear) manifold doesn't have this restriction. The power log is a bolt in piece and runs only $119 with no core charge.  A ported passenger side (rear) manifold runs an extra $95 + core. 

Another bottleneck lies in the stock flex coupler that bolts up to the passenger side exhaust manifold, all of the exhaust gasses merge here at the flange which has a 3" ID.  The problem lies in the fact that the flex joint (shown on the right) chokes the exhaust path down to a 2.125" ID.  On the left you can see I welded a 3" ID tube to the flange which will eliminate the bottleneck. The 3 inch tube fit really well after I ran a 3" hole saw thru the flange to clean up the bore.

If you do want to make custom headers I found header flanges for sale at West Coast Fiero.

Update 11-20-10

Camaro V6 headers (Pacesetter shown) fit perfectly.  I simply ditched the supplied crossover pipe and have a cheap set of block hugger headers for half the price of a set of FWD headers.

Passenger side view.

Drivers side view.


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The location of the intake is the reason you won't see this motor become a common swap. As seen above the intake is to the rear of the motor which would put it right into the firewall of a standard vehicle or the dash of a custom tube vehicle.

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The above cobra head intake hose was the best way to minimize cab intrusion of the intake hose.  I found the above head at  Utilizing this adapter puts the rear most point of the intake hose 12" behind the bell housing mounting face. 

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I made a small hole in the cobra head adapter to mount the intake air sensor.

If you like finding exotic parts there is an intake that bolts to the M90 blower from an Australia Holden Commodore that points the intake tube towards the front of the motor. Pictures can be seen here.

Motor Upgrades

Here is a list of some of the engine performance upgrades I have stumbled across that would pertain to use in a buggy. 

Aluminum Roller Rockers - good for up to 25hp gain.  Aluminum means less rotating mass.  Roller rocker install write-up.

Electric Water Pump - Frees up about 7hp. -

Oil Volume Kit - Increases the engine oil pressure.

Ported Throttle Body -  TB ported from 69mm to 72mm. there is also a new billet 78mm TB in the works.

Aluminum Heads - Lighter weight and re-designed ports and combustion chambers.

Ported Stock Heads - ZZP, Gessler, Intense Racing

Nitrous Kits - 55, 65 and 75hp shots.

Supercharger Pulleys - ZZP, Intense Racing

PCV Valve

You'll want to plug this in order to keep it from sucking oil into the engine when off camber towards the passenger side of the car. The picture above shows the PCV valve home in the top of the Supercharger housing and you can see the hole that leads into the intake.  This hole needs to be plugged. I chose to just fill my PCV valve with some oil resistant RTV, then I re-installed the PCV valve.

Now I needed a new vent for the valve cover so I drilled and tapped the oil fill cap for a 3/8" NPT fitting with a 1/2" hose barb on it.  Shown is a 45" fitting but as it turns out I need a 90 degree fitting to clear the coolant hose that runs above the filler cap. Basically I'll run the 1/2" line over, down, under and back up the side of the motor to create a plumbers trap, then cap the hose off with a small air filter.

Oil Filter

There are several different oil filter mounts that came on the different cars this engine is found in, West Coast Fiero has some shown here.  I mention this because you may run inter interference issues between the oil filter and front upper links since the oil filter sticks out in font of the engine off to the passenger side. I have also heard an oil filter from a 4.3L Chevy (Found in S-10 trucks, blazers and Chevy Astro vans) has the same diameter and thread but is 1" longer (for more oil capacity).

Power Steering Pump

The L67 motor uses a Saginaw CB style pump.  This pump is a dead ringer for the TC style pumps except for one less mounting ear and a larger output shaft.  I opted to send my pump off to PSC to have it modified for more flow and pressure.


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I went with a 26 x 19 dual pass aluminum radiator from Ron Davis.  The radiator has Ford style outlets which puts both on the drivers side.  I also had Ron Davis install a fan shroud and dual fans.  The fans are controlled by my PCM (via a relay), Jim at Jim's Performance setup the first fan to come on at 150 deg and the second one at 180 degrees. I have never seen the water temperature go above 180 degrees with this setup.

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I also had to make a custom thermostat housing to get the upper radiator hose pointing away from the firewall and towards the radiator. The tubing shown above is1.5" diameter from a 180 degree header bend.

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The radiator was connected to the motor with a stainless steel hose kit I picked up off of E-bay.  You can get these kits form Summit Racing as well. I used a 48" kit which came with enough hose, clamps and adapters to plumb both intake and return lines. For reference the radiator ports were both 1.75" diameter, the motor intake port was 1.5" diameter and the motor return was 1.375" dia. 


The L67 has a 60 degree GM bell housing pattern.  A 700r4 from an S-10 that had a 2.8l V6 will bolt right up to it as well as a TF 904/999 from a 4WD that had the same 2.8l motor (Cherokee's came with a 904 for a short while, 84-86 I believe).  The nice thing about going the 904/999 route is you can get the tail housing from a CJ that had a D300, shorten the tail shaft on the 904, attach the tail housing and then bolt up a D300 with no adapters required. I have also seen a powerglide attached to this motor on some competition rigs, I suspect an adapter was used. 

I saw a post on a message forum that mentioned an adapter that would convert the 60 degree pattern to a regular 90 degree pattern. I never confirmed this.


Edit 11-1-07 While looking thru some classifieds I found a reference to a TH350 adapter plate, sure  enough it is sold by Speedway Motors:,444_Chevy-4-and-V6-to-TH-350.html , #91628907 .

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TF-904 Bellhousing notched for the L67 starter

With the TF 904/999 transmissions the bell housing must be notched on the drivers side to utilize the engines starter.  I also added a tie plate to reinforce the bellhousing where it was notched.

The one thing I am not clear on is the torque converter (TC).  I had thought my setup originally had a Cherokee TC but later I discovered the Cherokee TC pilot was too large to engage into the L67. I don't think the original L67 TC was used because the flex plate on my motor was re-drilled for a new hole pattern and .25" spacers were used to space the TC away from the flex plate. Since I originally bought my motor/transmission/transfer case combo as a unit it is possible that the previous owner had a custom converter built.  If I learn more on this topic I will update.

Information Resources

Pirate 4x4 3800 Bible - More tech than you can shake a stick at.

More 3800 Tech from pirate 4x4

3800 Performance - L67 Parts and Accessories

3800 Pro.Com - Message Forum

Club GP - Message Forum

Full Throttle V6 - Message board covering various GM V6 engines.

Intense Racing - L67 Parts and accessories.

Morad Parts Company - Need a used stock part? Try e-mailing this guy. - Message forum covering motor swaps, check out the RWD section.

ZZ Performance - L67 parts, accessories and tech articles.