Don Zeigler's 1965 MGB with Pontiac 3800 V6
as published in British V8 Newsletter, Volume XI Issue 3, September 2003
Owner: Don Zeigler
City: Idyllwild, CA
Model: 1965 MGB Roadster
Engine: 3800 GM V6
Conversion performed by: Owner
|Engine:||GM 3800 Series II from a 1996 Pontiac firebird. Custom idler pulleys were
required to replace the power steering pump and the A/C unit. A custom adapter
plate allowed for a remote oil filter, mounted to the frame between the sway
bar and the radiator. New engine mounts were fabricated and mounted to the
|Fuel System:||An external fuel pump producing 45 PSI (NAPA European replacement) was mounted
after a filter in the right battery compartment. The original fuel line was used
for return and a new 3/8" pressure line added. The return line enters the tank
just to the right of the sending unit. The later fuel tanks may have a port available
for return. I am in the process of building a small tank to fit in the right battery
compartment, which will be fed by the stock MGB pump with a return to the main tank.
The high Pressure pump will circulate through this tank.
|Intake:||A K&N air filter is placed to the right of the radiator behind the grill.
|Engine electrical:||The PCM and Body Control computers are mounted on the passenger kickpanel. The donor
vehicle had a Pass Key II system. A resistor to match the key was connected to the Body
Control Module. The BCM sends a signal to the PCM to enable the ignition. Without the
enable signal the engine will start, run for 4 seconds and shutdown. The starter system
PCM controls are bypassed. The MG ignition switch still operates the MG solenoid which
acts as an interposing relay to the GM starter solenoid.
|Cooling:||A 1965 Falcon radiator was mounted as far forward as possible, requiring cutting of the
body panel in front of the original radiator position. The radiator cap was removed, inlet
and outlet ports were relocated to the left side and ports to a Sunbird expansion tank
which was mounted on the right side firewall shelf. A14" electric fan just fits between
the radiator and the 7/8" sway bar.
|Exhaust:||Completely custom fabricated including flanges (nothing aftermarket was available at the
time). 3/8" flanges, 1 5/8" tubing out the fender wells into 2.50" collectors. 2" exhaust
pipe "Y" into the catalytic converter, from the catalytic converter back is 2.25" through
a single glasspack muffler. (It sounds pretty mellow until the engine opens up).
|Drivetrain:||The MG transmission crossmember was modified and used with the RPO M49 (T5) 5-speed.
Two of the original mounting bolts were able to be utilized. The GM hydraulic clutch
line was adapted to the MG master cylinder. This retains the MG master cylinder and the
GM quick disconnect at the bellhousing. (The slave cylinder is inside the bellhousing).
A new 2" heavy wall driveshaft was built to mate with the MG rearend. With the 3.909:1
rear axle gear ratio, first gear is useless. I'm looking possibly at an 8" Ford.
|Steering:||An additional "U" joint just above the frame. The original "U" Joint was replaced with
a smaller unit from Borgeson.
|Body:||Firewall modifications are very similar to a Buick 215cid V8 conversion. The engine and
transmission are approximately the same length as the original MGB. A small bulge on the
passenger side of the tunnel was all that was required for transmission clearance. The
gearshift lever was modified (offset forward about 3" and to the right about 1") to bring
the lever into the correct location.
|Electrical:||12 fuses now replace the 2 MG fuses. Original Oil and Temp gauges were used, while VDO
Series 1 tachometer and speedometer were mounted inside the MG housings.
|Performance:||With the headers and less restricted K&N air filter, it produces approximately
210 horsepower and 240 foot-pounds of torque - so hang on!