MG Sports Cars

engine swaps and other performance upgrades, plus "factory" and Costello V8s

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Bv8nc
Mike Peacock
Wilmington, NC
(10 posts)

Registered:
02/23/2015 04:48PM

Main British Car:
1977 MGB Roadster Rover 3.9

3.9l to 4.6l
Posted by: Bv8nc
Date: April 28, 2015 09:08PM

I bought a MGB V8 project car with a 3.9L Rover engine installed. It loses oil pressure once it warms up due to worn main bearings. (My mechanic has confirmed that both the oil pump and pressure relief valve are OK.) As long as the engine has to come out I'd like to fit a 4.6L engine, but my reading seems to indicate there will be clearance issues with the 4.6 front cover and crank pulley. Can I fit my 3.9 (early style) cover and pulley to the 4.6? If so, will any modifications be required? Are there better alternatives available? Same basic question regarding the oil pan and oil pickup: clearance issues, interchangeability?

Thanks,
Mike


mstemp
Mike Stemp
Calgary, Canada
(200 posts)

Registered:
11/25/2009 07:18AM

Main British Car:
1980 MGB Rover 4.6L

Re: 3.9l to 4.6l
Posted by: mstemp
Date: April 29, 2015 01:21PM

Mike P,

You would need a different oil pan, pick up tube, timing cover etc to use the 4.6L. At least that was what I did 12 years ago. Since that time others have been able to fit the lower the motor and move it further back I believe to get it into position without steering rack interference.
Look at

[www.britishv8.org]

for an example.


Bv8nc
Mike Peacock
Wilmington, NC
(10 posts)

Registered:
02/23/2015 04:48PM

Main British Car:
1977 MGB Roadster Rover 3.9

Re: 3.9l to 4.6l
Posted by: Bv8nc
Date: April 29, 2015 06:21PM

Thanks Mike,

What I'm mainly wondering is if those pieces from my existing 3.9L engine will fit the 4.6L engine.

Mike


mstemp
Mike Stemp
Calgary, Canada
(200 posts)

Registered:
11/25/2009 07:18AM

Main British Car:
1980 MGB Rover 4.6L

Re: 3.9l to 4.6l
Posted by: mstemp
Date: April 30, 2015 07:24AM

Yes they can be used. You will need a spacer ring for the crank damper. Available from D&D and the wedge shop for $20.


Bv8nc
Mike Peacock
Wilmington, NC
(10 posts)

Registered:
02/23/2015 04:48PM

Main British Car:
1977 MGB Roadster Rover 3.9

Re: 3.9l to 4.6l
Posted by: Bv8nc
Date: April 30, 2015 01:48PM

Thanks very much Mike. That's what I thought I was reading, but some of the info was pretty vague.
Also good to know the sources for the spacer.

Mike


Moderator
Curtis Jacobson
Portland Oregon
(4411 posts)

Registered:
10/12/2007 02:16AM

Main British Car:
71 MGBGT, Buick 215

authors avatar
Re: 3.9l to 4.6l
Posted by: Moderator
Date: April 30, 2015 09:18PM

Other than oil pressure, how do you like the 3.9? I don't think I'm the only one around here that would rather have a really well built/tuned/sorted 3.9 than an average 4.6. Have you considered optimizing the engine you've got?


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