Cubes & Diff

[moetstockie]

Evening all, I have a FB 138 grey which has a 60 thou rebore. Can any one tell me what Capacity in Cubic inches this is now ? Also I've read a little on diffs etc. I have a standard FE diff in my wagon with 175/80/13 tyres on std rims. Any comments on diffs of choice. At the moment I'm doing more highway than town but that may change. Seems to rev a little  on the highway but this my first experience driving a grey. I am wary of changing unless there's a very good reason.  Any comments  ...Moe`t

[colt]

You now have a 3 1/8" bore. 138 is 3 1/16" standard, 60 thou is 1/16 of an inch. Someone else can work out the math, but you are halfway to a 149, which is 3 1/4". So it makes it around 143 or 144 c.i.

With your diff, I would put in a 3.55. Make cruising a bit better without knocking off too much performance.

Colin.

[EffCee]

An explanation on the math.....

The measurements you need to work this out are the bore and stroke dimensions. Take half of the bores' dimension and multiply it by itself, then multiply by Pi (3.14). Next, take the stroke dimension and multiply this by the previous figure you calculated, then multiply this number by the number of cylinders in the engine and there you have it.

This was a 138 bored 60 thou. So we take the 3.0625 bore of the 138 and add the 60 thou overbore which gives us 3.3.125 and divide it by 2, which gives us 1.57. We then multiply this figure of 1.57 by itself, and then by Pi which is 3.14 which then gives us 7.739786. We now take this figure and multiply this by the 138 cranks' stroke which is 3.125, 7.739786 multiplied by 3.125 gives 24.19. Now we then multiply this by the number of cylinders which is 6, so 24.19 multiplied by 6 is 145.14.  At last this gives us the final engine capacity of around 145 cubic inches.

Now if you want to know how many cubic centimetres your engine displaces you multiply the cubic inches by 16.43. So our 145 multiplied by 16.43 gives us 2384, which is how many cc's the engine now displaces.

You can use the method described for determining capacity with the bore and stroke dimensions in centimetres or millimetres to give you cc in the first place if you are more metric minded. But remember if you use millimetres you will have to move the decimal place three places to the left when you get your final figure for it to be in cubic centimetres.

Keith

[DN2168]

My head hurts.... :P

[Dave Lakin (Davo Lako)]

Yeah ... Aspro !!!! LOL ...but well done Keith ...

[RET]

Mmmmm.. pi...

[colt]

Geez Keith, when I said someone else can do the math..............

When I looked up pi in my book it says it has a lemon filling and a meringue top.

Well done.

Colin.

[Spinner]

Here's a spreadsheet that you can use to work out your engine capacity.

Engine Capacity Calculator (Excel)


Thanks to Ret for putting it within reach.

[moetstockie]

Thanks Guys ....and keith in particular. Pi, peas, sauce yum!   Is there such a thing as a standard diff in my FE though ?? I'm sure it hasn't been changed. Incidentally now I'm used to the noises etc I find my li'l rocket cruises at 60-65MPH.  Cheers Moe`t