MGA Forum
1500cc engine to 1800cc
Posted by GeordieMga
GeordieMga
Philip Reed
Tonbridge, Kent, UK
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Aug 30, 2016 02:28 PM
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I think you will find that the original MGA engine probably has a different stroke and cylinder diameter than an MGB.
A rebuilt MGB engine, even if it needs a rebore to the next oversize may be a better choice.
Read this url:
http://www.mg-cars.net/mgb-technical-bbs/what-is-the-max-over-bore-size-without-sleaving-2007103016294822997.htm
Roger N. Tanner
Professional Engineer, Retired
A rebuilt MGB engine, even if it needs a rebore to the next oversize may be a better choice.
Read this url:
http://www.mg-cars.net/mgb-technical-bbs/what-is-the-max-over-bore-size-without-sleaving-2007103016294822997.htm
Roger N. Tanner
Professional Engineer, Retired
Judge Jeffs
Bill Jeffries
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Aug 30, 2016 02:49 PM
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The 1500 will can only be overbored by +60 thou, so effectively making a 1560cc.
Beyond that the cylinder liners would be too thin and fail.
Actually, despite the lower power output, there is nothing like a well sorted original spec 1500 for sweetness and pleasure of driving, if in road use. Even the original standard camshaft was well profiled to give fine all round performance.
Fit an 1800 B engine and you'll have much better performance, but it will be much harsher experience. Bill.
Beyond that the cylinder liners would be too thin and fail.
Actually, despite the lower power output, there is nothing like a well sorted original spec 1500 for sweetness and pleasure of driving, if in road use. Even the original standard camshaft was well profiled to give fine all round performance.
Fit an 1800 B engine and you'll have much better performance, but it will be much harsher experience. Bill.
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GeordieMga
Philip Reed
Tonbridge, Kent, UK
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GeordieMga
Philip Reed
Tonbridge, Kent, UK
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dipstick
Kenny Snyder (RIP)
La Center, WA, USA
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1941 Ford N-Series
1958 MG MGA 1500 Coupe "Rosie" 1970 MG MGB GT "Pat's GT" 1971 MG MGB "Gifted To Me" & more |
Aug 30, 2016 02:58 PM
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Blueosprey90
Jeff Sienkiewicz
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Aug 30, 2016 03:20 PM
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I don't think these guys are in business any more, but they had specs to take it up to 1698 cc. You can see the other options.
http://mgbmga.com/tech/mga3.htm
I have a 1500 block in my basement that is bored out to a 1620 cc spec, but I think the block was shaved too much and I haven't had the time, inclination or experience to figure out how to overcome that fact.
http://mgbmga.com/tech/mga3.htm
I have a 1500 block in my basement that is bored out to a 1620 cc spec, but I think the block was shaved too much and I haven't had the time, inclination or experience to figure out how to overcome that fact.
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Judge Jeffs
Bill Jeffries
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Aug 30, 2016 04:35 PM
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Jeff. Need a set of new cylinder liners to take it back to 1500, which cost around £120.00 for 4. Don't know the cost of fitting, but it's a specialist shop job, so probably big bucks. Also a new set of standard pistons, would be required at a further £200. It now becomes questionable if it's worth it.
Bill.
Bill.
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dipstick
Kenny Snyder (RIP)
La Center, WA, USA
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1941 Ford N-Series
1958 MG MGA 1500 Coupe "Rosie" 1970 MG MGB GT "Pat's GT" 1971 MG MGB "Gifted To Me" & more |
Aug 30, 2016 04:47 PM
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GeordieMga thanked 59mgaguy for this post
Blueosprey90
Jeff Sienkiewicz
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Aug 30, 2016 09:44 PM
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In reply to a post by Jeff. Need a set of new cylinder liners to take it back to 1500, which cost around £120.00 for 4. Don't know the cost of fitting, but it's a specialist shop job, so probably big bucks. Also a new set of standard pistons, would be required at a further £200. It now becomes questionable if it's worth it. Bill.
Thanks Bill, no. The block was decked so that the pistons ride up above the top of the engine block. I think 0.30" if memory serves me correct. Apparently all in the interests of higher compression. Builder should have found flat topped pistons instead. I think I can get it to work with an 1800 head.
dipstick
Kenny Snyder (RIP)
La Center, WA, USA
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1941 Ford N-Series
1958 MG MGA 1500 Coupe "Rosie" 1970 MG MGB GT "Pat's GT" 1971 MG MGB "Gifted To Me" & more |
Aug 31, 2016 02:37 AM
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"The block was decked so that the pistons ride up above the top of the engine block."
Sometimes the tops of the pistons can be milled down. The piston tops pictured were milled down .035”.
Be safe out there.
Kenny
Sometimes the tops of the pistons can be milled down. The piston tops pictured were milled down .035”.
Be safe out there.
Kenny
Judge Jeffs
Bill Jeffries
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Aug 31, 2016 04:18 AM
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Phil. I imagine you're facing all the usual thoughts of whether to keep 'original' or not. If you have a completely original gem that is a show car, then greater consideration might be made to keeping the original 1500 engine.
There's much you can do to raise the power output from the humble 71bhp without spending a fortune and having a briskly performing car - increase capacity, increase compression ratio (skim head) rework head combustion chambers and improve inlet/exhaust ports. Add a mild road camshaft, increase carb jetting and you'll have a handy 80/85 bhp.
To go beyond this, is limited by the weak crankshaft, which was improved in the later 1600 engine.
If originality is not an issue, go the early three bearing crank MGB unit which in original form had 95 bhp and fits without trouble, although, these are getting scarcer and therefore more expensive.
Or, alternatively, find a 1622 unit, which can be tuned easily and still quite a few available as in different levels of tune were fitted in many BMC products.
All good fun!
There's much you can do to raise the power output from the humble 71bhp without spending a fortune and having a briskly performing car - increase capacity, increase compression ratio (skim head) rework head combustion chambers and improve inlet/exhaust ports. Add a mild road camshaft, increase carb jetting and you'll have a handy 80/85 bhp.
To go beyond this, is limited by the weak crankshaft, which was improved in the later 1600 engine.
If originality is not an issue, go the early three bearing crank MGB unit which in original form had 95 bhp and fits without trouble, although, these are getting scarcer and therefore more expensive.
Or, alternatively, find a 1622 unit, which can be tuned easily and still quite a few available as in different levels of tune were fitted in many BMC products.
All good fun!
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GeordieMga
Philip Reed
Tonbridge, Kent, UK
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GeordieMga
Philip Reed
Tonbridge, Kent, UK
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