MGA Forum

Hi

I have a mga,Would it be possible to rebuild a 1500cc to a 1800cc or am I best off with a Mgb engine.

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.

Thank you Roger

Thank you Bill

"I think you will find that the original MGA engine probably has a different stroke ...."

All MGA and MGB engines have the same stroke - 3.5".

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Be safe out there.
Kenny

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.

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.

I would go to a 3-main MGB bored .060" over (1868cc).

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Be safe out there.
Kenny

You do know we want to see pictures of your car. Is the 1500 need of rebuilding or are you trying for more power to keep up with you M roads?

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.

"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”.

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Be safe out there.
Kenny

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!

I think I'll go with 1800cc Mgb engine and a 5 speed Sierra gear box.
It will go in my 1956 mga, that I bought last year in the states. It now is RHD, although it LHD doesn't really bother me that much.

It's in good condition,just had a respray and looking for a little bit more comfort, in regards to cruise speed.