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Author Topic: Block for V8 conversion  (Read 755 times)

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Block for V8 conversion
« on: May 10, 2020, 12:58:08 PM »
What are the pros and cons of a Chevy 350 small block vs a Ford 351 small block conversion?
John Thomas


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Re: Block for V8 conversion
« Reply #1 on: May 10, 2020, 01:29:06 PM »
The original V8 optioned cars used an improved GM 215. I would stick with GM.

Frankly, I think going with either of the two is ridiculous because the chassis simply isn't heavy enough to put all that power to the ground, all it would do is burn up tires. A 200hp MGB would outperform a 500hp one, handle better, etc. unless you're doing a build that uses nothign but the cosmetics of the car

When the MGB was built, it was with the aim of producing a well-balanced, great handling sports car that was competitive with the sports cars of its time, and wasn't too expensive. It wasn't the fastest, nor the most powerful, but it was a decent competitor, and people have raced them with the factory components for many years. Fast forward to today, and we see the Mustangs, Camaros, Challengers, Chargers, WRX's, and a host of other cars with over 300 hp. However, these cars are physically larger, have the capability to put the power to the road with larger tires, and have more modern, maybe more appropriate suspensions and brakes. The MGB chassis, suspension, and braking systems will be overwhelmed with 300+ HP, and will be hard to control on the road or track with that kind of HP. If you just want smoke, go for it, because that's what will become of the rear tires. However, if you want a serious car, go with a Stage 2 or Stage 3 MGB engine, or a more modern 4-cylinder or 6-cylinder engine tuned to around 200HP or less.

It will improve the acceleration of the MGB to the point of exhilaration, but will be much safer, especially around the twisty's.

Scott Stuchell

American MGB Association
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North America's oldest and largest club for all MGBs, MGB-GTs & Midgets.  A nonprofit organization founded in 1975 and offers color magazines, emagazines, technical advice, member recommendations on service shops, registration of your MG, a tradition of service & FREE member classified ads that appear in the magazine & on the website.


  • chfwrench
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Re: Block for V8 conversion
« Reply #2 on: May 22, 2020, 12:52:27 PM »
I agree with Scott.  Forget about the horsepower, the 350 Chevy or 351 Ford are all iron and way too heavy for the suspension or any kind of decent handling. 

The real beauty of the original Costello/Factory MGB V8 swap was that the GM 215 CID or the Rover 3.5L (essentially the same engine) were aluminium blocks and heads, so were about the same weight as the cast iron 1.8L I-4 they replaced.  Only suspension change was to use steel-sleeved bushings on the inner control arms of the front end (still available from Moss or Victoria British catalogs).  They also tended to run cooler for the same reason.  Note that the Rover 3.5 is 'based' on the original GM engine that was used in the Buick Skylark, Oldsmobile F-85 and even the Pontiac Tempest for their first few years of production.  As a unit the GM and Rover engines are interchangeable.  They are also plentiful.  GM built nearly 3 million of them over 3 years in the early 60's and BMC used the 3.5L and a later 4.0L variant up through about 1990 in various models, including the MGR V8.

I helped a friend in Costa Rica with older Range Rovers equipped with the 3.5L V8 back in the mid 80's that were having both reliability and altitude problems.  We ditched the SU carbs, Lucas ignition, distributors and alternators for Holley or Carter 4bbls on Edelbrock or Weiand manifolds and either Crane aftermarket or stock GM HEI distributors along with Delco alternators. All bolted right in and performed really well and reliably.

Finding a Rover (or GM) and equipping it with aftermarket performance gear (all still available from performance catalogs like JEGS) can make a pretty formidable performer in an MGB.  And you lose nothing on handling due to excessive weight, like the CI V8s you're considering.  Conversion kits are available from Andy's Motorsports ( and others.  Consider using the Mustang 5 speed box conversion as well.

Safety Fast!

Art Isaacs
AMGBA Tech Staff


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