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Larry Barnes
Colorado Springs
(177 posts)

06/11/2009 02:12PM

Main British Car:
1980 MGB GM LA1 3400 V6

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Larry Barnes' 1980 MGB-LE with GM 3400 LA1 V6
Posted by: lars49
Date: September 02, 2012 02:50PM

Owner: Larry Barnes
City: Colorado Springs, CO
Car Model: 1980 MGB-LE
Engine: GM LA1 3400 (FWD) V6 w/EFI


Oct 5, 2012

Just added to my collection of parts. Scored a set of '95 Miata power mirrors with the switch on Ebay for $100. They are red so I will need to paint them black when I finally get the car painted.

Sept 2, 2012

This is a work in progress. Most of my time has been taken-up researching and purchasing parts. I would say that 95% of the parts have been purchased and I am in the process of putting the engine back together.

Engine: The engine is a GM Gen III LA1 3400 V6 from a 2003 Olds Alero. The engine has been stripped down and completely rebuilt with new bearings, pistons, camshaft, pistons, valves, valve springs, and spring seats..

The pistons have been replaced with Federal-Mogul hypereutectic. The crankshaft, rods, pistons, and flywheel have been statically and dynamically balanced to 6500 RPM by Lanier’s Speed Shop.

The Comp Cam camshaft was supplied by WOT-Tech and has a 262° duration/.480” lift with 1.6:1 roller rockers and a 112° LSA.

This cam requires stronger springs than were stock. I chose to use the springs from the Corvette LS6 engine since The LS6 springs are narrower at the seat than the stock LA1 spring seat as seen here.
So the LS6 spring seats are also needed. If my engine were built prion to 2000 this wouldn't be a problem as the seats fit nicely over the valve guide. However, in 2000 the LA! valve guide boss OD increased requiring the spring seats be opened up. I am planning on building a jig and doing this on my lathe rather than using a Dremel and grinding them out as suggested by other folks who have done this.

Since the stock LA1 seals attaches to the seat, using the LS6 seat precludes using stock seals. A larger seal is needed. Seals from the Dodge Ram 5.2 engine will be used instead. These fit the valve stem and seat.

The lower intake manifold is stock. The upper intake manifold is from 2005 Chevy Malibu 3500 V6 since the 3500 UIM has better flow characteristics than the 3400 UIM. In this picture you can see the throttle opening differences between the 3400 and 3500 UIMs.

Here' as look inside a 3500 UIM that has been split in two to do some interior work. I chose not to do that but you can see how short and open the runner is.

The upper and lower manifolds were blended and gasket matched by WOT-Tech. Here is the work that Ben did on the LIM
3400-Lower-A1.jpg .


The LIM gaskets which have had a recorded propensity for leaking have been replaced with Federal-Mogul Problem Solver gaskets.

I did a preliminary simulation using what data I have been able to glean about the LA1 construction and the cam specs. The following are the results at the flywheel.

The intake manifolds have been rotated 180 to place the intake at the front. The timing cover and waster pump have been replaced with one from a 1996 Camaro to eliminate the interference with the intake manifold. The throttle body has been replaced with a TCE- Motorsports 65 mm billet throttle body.

The OBD-II PCM has been replaced with one from a 1998 Chevy Venture van to eliminate the requirement to also have the Alero BCM installed for the stock PCM to work correctly. The PCM has been tuned by Sinister Performance.

I chose to use Todd Budde’s aluminum fuel tank instead of retrofitting the tank with a high pressure pump. The fuel and return lines will be 3/8” aluminum with an Aeromotive 13301 pressure regulator.
The engine mounts are from Custom Conversion Engineering and will be modified to fit the 3400 block.

Cooling: The stock radiator has been modified to eliminate the thermal switch and add drain and purge fittings. The dual pusher fans will be replaced with a single puller fan from a Chevy Corvette.

Exhaust: Headers built with parts from various vendors. 1-5/8” primaries to 2” cross pipes to 2-1/4” exhaust. High flow catalytic converter, Magnaflow muffler, Pace Setter tip.

Transmission: Borg-Warner T-5 from a 2002 Camaro. This bell housing has the starter pocket on the driver’s side which matches the engine. Howe throw out bearing.
2002 Camaro Bell Front.jpg

Rear Axle: A shortened Chevy 7.5” axle from D & D Fabrication with a 3.09 Auburn LSD.

Front Susp.: Contemplating drop spindles from MGB Racing. Polyurethane bushings

Rear Susp.: Lowered 1” Polyurethane bushings

(master) stock
(front) stock with slotted disks and chrome plated pistons, all from British NorthWest
(rear) Chevy S10 drum brakes. Handbrake with fly-off pawl from Jeff Schlemmer

Wheels/Tires: Standard LE aluminum wheels with 185/65HR14 Falken ZE-912 tires

Body Mods: Replacing LE air dam with modified Special Tuning air dam. Gray engine compartment instead of black. 2 stage paint with LE stripes pained on instead of appliqué

Interior: Fiero seats,

Electrical: Replacing entire harness and fitting with GM metri-pack connectors, daytime running lights, VDO gauges, Alpine stereo, European tail lenses, driving lights, cruise control, alternator from '97 Blazer

Edited 8 time(s). Last edit at 10/05/2012 12:20PM by lars49.

Curtis Jacobson
Portland Oregon
(4577 posts)

10/12/2007 02:16AM

Main British Car:
71 MGBGT, Buick 215

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Re: Larry Barnes' 1980 MGB-LE with GM 3400 LA1 V6
Posted by: Moderator
Date: March 04, 2013 05:38PM


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