Displacement?

[MV8]

18 minutes ago, Timothy Keith-Lucas said:

I was hoping to resolve the issue without taking the head off to measure the bore and stroke. The car was factory assembled, and I think we've established that it started life with a 948cc engine, but the term "race prepared BMC "A"" could hide all sorts of mischief. 

What issue?

[wdb]

I'm not having any luck finding the 1962 SCCA class specifications, but from what I have been able to see a 948cc engine would put the car in F, G or H Production classes. Given the tendency of governing bodies to put the 7 in classes above its engine displacement it would probably be best to look for the car, rather than the engine size, to determine where it may have been classed. For example a Lotus 7 won the C Production national championship in 1962, which I believe had engine sizes above 2 liters.

[Timothy Keith-Lucas]

That may be as close to certainty as I can get until I experience a "Catastrophic failure," leave broken parts and oil all over the road, and then have other reasons to pull the head. Thanks for your wisdom.

[Timothy Keith-Lucas]

She raced in "FP"

[panamericano]

Forget the displacement.  It was a racer.  It was easy to change classes by changing little things, like an engine.  With the info you have, you might contact International Motor Racing Research Center.  They maintain the SCCA archives.  More history on a car makes it more valuable and interesting than a 100CC.s

[wdb]

Regarding what might have been done to the engine, here are some links to 948 engine mod discussions. It is important to determine exactly when any race prep took place because some of the stuff discussed is from later engines, which may or may not have existed when your engine was prepped.

 

https://board.mmoc.org.uk/viewtopic.php?t=71367

 

https://www.ahexp.com/forum/the-sprite-forum.6/mild-tuning-for-948cc-engine.197511/

 

https://www.mgexp.com/forum/mg-midget-forum.3/a-series-rebore.1232128/

[7Westfield]

On 12/23/2025 at 9:13 AM, Timothy Keith-Lucas said:

She raced in "FP"

As I (dimly) recall, the old SCCA classes for Spridgets were FP GP HP, based mostly on engine choice  Run a bugeye with a 948 in HP or throw in a 1275 and run FP

So, a 948 7 in F makes sense    Smaller, lighter chassis means a higher class

[Timothy Keith-Lucas]

Ok.  I'm going to be comfortable with calling her a 948. At the minimum I won't be overstating her displacement, and it seems by far the most likely bet. If I ever take her head off, I'll be sure to measure it. Thank you all for both sharing your wisdom with me and engaging in a really interesting discussion. I've learned a lot more than just her likely displacement. God rest ye merry gentlemen. --Tim.

[EdWills]

On 12/25/2025 at 7:42 AM, Timothy Keith-Lucas said:

Ok.  I'm going to be comfortable with calling her a 948. At the minimum I won't be overstating her displacement, and it seems by far the most likely bet. If I ever take her head off, I'll be sure to measure it. Thank you all for both sharing your wisdom with me and engaging in a really interesting discussion. I've learned a lot more than just her likely displacement. God rest ye merry gentlemen. --Tim.

Hi Tim.

I found these pages in my notes from when I purchased my car.  The second owner had raced the car in Canada.  The first 2 pages were from a 'black book' but not sure if it was SCCA or CASC (Canadian Automobile Sports Clubs 1958 - 1988).  I have also included a page from the CASC dated 1978, which specifically details the Series 3, however you may note the error of the person/body/organizer who typed in the note that the front brakes specified for the 'Lotus Super Seven Series 3' were  '8" drum' with a disc brake conversion as an option..  As front drums had not been used on a Lotus Seven for quite a number of years (and never were used on the Series 3), one can only conclude that they took the info from a very old spec. regarding the Series 1 or early Series 2 cars?  Also, not sure if they 'borrowed' the specs from the SCCA?  Forum members who race(d) in the older SCCA series may know if the smaller pages are in fact SCCA or possibly CASC specifications? Will.

 

And a P.S. Tim.  I hope you won't require a magnifying glass to read the specifications? They are from a very old photocopy from the early 1970s.

Edited December 27, 2025 by EdWills