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Post by Mabel on Jan 21, 2019 19:32:54 GMT
I should get Mabel back this week after a rebore has taken place and amongst other items new oversize pistons and rings etc have been fitted.
Given the original engine was 1489 cc, how do I calculate or even guess what the new cc will/might be. I’ll know more soon about the size of the rebore.
Oh, and by the way, the block has been skimmed owing to it being warped.
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Post by noddy on Jan 22, 2019 18:20:52 GMT
Hi Graham, I worked out all the figures for the engine capacity with each rebore size, when rebuilding my replica engine. Here they are ... Standard 1489.34cc
0.010" 1499.72
0.020" 1510.14
0.030" 1520.59
0.040" 1531.07
0.050" 1541.60
0.060" 1552.16
I hope this is of some help? By the way - for period FIA racing spec you are only allowed to go 40 thou over! But I don't know anyone who has stuck to this (including us  )!
With the block being skimmed you might find that the compression ratio will have increased slightly.
Great to hear that Mabel is on the mend,
Roger |
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Post by canuck on Jan 23, 2019 19:41:32 GMT
I should get Mabel back this week after a rebore has taken place and amongst other items new oversize pistons and rings etc have been fitted. Given the original engine was 1489 cc, how do I calculate or even guess what the new cc will/might be. I’ll know more soon about the size of the rebore. Oh, and by the way, the block has been skimmed owing to it being warped. Colour me envious! Bravo to Mabel. 
so displacement is figured out by our high school geometry and we need (pi) remember that funky number?
But easier now in the decimal age, we simply use 0.7854 multiply it by the bore squared and then multiply by the stroke. (this is in the factory manual) After doing all this and your head has stopped hurting multiply this by 4 (or 4 cylinders) 
The block deck being skimmed will not affect the capacity as there is always a space between the top of the bore and the cylinder head. BUT the skimming of the block will affect the compression ratio, this is a good thing.
We can figure the compression ratio as well. Simple mathematics again.
B
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Post by noddy on Jan 23, 2019 20:12:10 GMT
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Post by canuck on Jan 27, 2019 18:56:05 GMT
I am a dinosaur I guess, now let me put my slide rule down for a minute!  of course you are right the www can and does answer pretty much all we ask. Seriously this is a great opportunity for Mabel. Although the increase in cc will probably not be felt, (1 -2%) the increase in compression ratio is s definite plus, and can be felt. Remember the first step to a stage tuning engine is compression ratio increase. Mabel is on the right road, and If Graham provided us with some numbers we can figure out the compression ratio, probably using an online calculator.  FWIW with George I increased the CR after a failed head gasket. Throw in some porting and the little guy really woke up. No down side what so ever with overall better running. I have done the same with the 18G engine I am building, in fact my cylinder head is at PB right now getting the magical finishing touches. Should be back to me by mid April. Carry on Graham, Mabel will thank you. B |
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Post by Mabel on Feb 21, 2019 19:05:29 GMT
Progress at last. The engine is back from the machine shop. Block has been bored out to 30 thou oversize. So, it's bye bye 1489 cc and hello 1520.59 cc. New flywheel gear also installed as there was a strip of about five inches where there were no teeth. How it managed to ever turn over, which it did with perfect regularity, I'll never know. Having problems uploading photos. Don't know why as I've never had problems before. Is there an idiots guide for this? ![]() ![]() ![]() |
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Post by Mabel on Feb 21, 2019 19:40:55 GMT
Progress at last. The engine block is back from the machine shop. It's been bored out to 30 thou oversize so it's bye bye 1489 cc and hello 1520.59 cc. Not sure how much the block has been skimmed by but with all the work that's gone on I hope I notice a difference with increased cc and compression.
The flywheel gear has also been replaced as it had a five inch strip with no teeth. How it ever turned over without fail is beyond me.
I'm really struggling to upload photos which is unusual as I've done so many times before. They keep coming out as landscape when they should be portrait and vice versa. Is there an idiots guide on how to do this?
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Post by canuck on Mar 1, 2019 14:30:38 GMT
Great news Graham, I think you will notice an improvement if not by the increased displacement and compression ration rather a well balanced and tight engine. Couple this withe the redone cylinder head and you will have a 'runner'. FWIW I will be installing one of these on George boot lid this summer.  B |
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of course you are right the www can and does answer pretty much all we ask. 
