Author	[Modern View]
6 cylinder puller 09-10-2012 17:31:40 71.31.183.158 Report to Moderator	was wondering what my compression ratio would be if I have 6.5 to 1 compression now and I overbored the cylinders .100ths [Reply]   [No Email]
Indiana Ken 09-12-2012 18:38:01 66.249.234.244 Report to Moderator	Re: Overbore affect on compression ratio ? in reply to 6 cylinder puller, 09-10-2012 17:31:40   Quoting Removed, click Modern View to see 1) Since you know the compression ratio, the chamber volume can be calculated given the bore and stroke of the engine. 2) The compression ratio resulting from the 0.100" over bore can then be calculated, using the chamber volume calculated in step 1). You stated the engine bore is currently 4.5" can you provide the stroke dimension? [Reply]  [No Email]
mlpankey 09-12-2012 14:45:21 152.85.8.33 Report to Moderator	Re: Overbore affect on compression ratio ? in reply to 6 cylinder puller, 09-10-2012 17:31:40   I get 6.8 .1 Never give up cubic inches for anything . I know some will say bore causes detonation rod stroke ratio head flow the list goes on should limit cubic inches . the areodynamics of a buble bee technically says it cant fly but it does every summer day. [Reply]  [No Email]
Dodgeit 09-12-2012 13:19:22 65.199.61.227 Report to Moderator	Re: Overbore affect on compression ratio ? in reply to Dieselbear, 09-10-2012 17:31:40   Just giving an example the numbers are not actual. Lets just say that a 4.5" bore has 1948.4cc and a 4.6" bore has 2020.5 cc and the combustion chamber is 300 cc you would have the following compression ratios. I used a 5" stroke for my calculations. Flat top pistons with no valve reliefs just to keep it simple. Valve reliefs, head gasket height, piston down the hole @TDC, piston dome + or - and other things determine your heads compression chamber size. 4.5" bore = 6.49-1 this engine has 476 C.I. in 4cyl. 4.6" bore = 6.73-1 this engine has 493 C.I. in 4cyl. Now if you add a decked head down to 250ccs you have 8.00-1 compression with a 4.6" bore and a 5" stroke, and 10.1-1 with a 200cc chamber and 4.6" bore 5" stroke vs. 9.75-1 with the same 200 cc chamber size and a 4.5" bore and 5" stroke. [Reply]  [No Email]
Popinjohn 09-10-2012 20:19:45 24.168.43.43 Report to Moderator	Re: Overbore affect on compression ratio ? in reply to 6 cylinder puller, 09-10-2012 17:31:40   With all other items left the same; head gasket; cylinder head; piston dome; etc. there would be a slight change in compression ratio. This can be calculated by comparing the cubic inches before to the cubic inches after with the chamber volume of the combustion area. Compression ratio is the volume of the cylinder with the piston at the bottom of its stroke compared to the volume when the piston is a top dead center. [Reply]  [No Email]
Dick W. 09-10-2012 18:56:12 69.40.243.176 Report to Moderator	Re: Overbore affect on compression ratio ? in reply to 6 cylinder puller, 09-10-2012 17:31:40   That depends a lot on the size of the combustion chamber and the stroke of the crankshaft. [Reply]  [No Email]
Dick W. 09-10-2012 18:57:20 69.40.243.176 Report to Moderator	Re: Overbore affect on compression ratio ? in reply to Dick W., 09-10-2012 18:56:12   And the size of the original bore. [Reply]  [No Email]
6 cylinder puller 09-11-2012 15:12:54 24.101.25.254 Report to Moderator	Re: Overbore affect on compression ratio ? in reply to Dick W., 09-10-2012 18:57:20   bore before was 4.5 to 4.600 now [Reply]  [No Email]
wHOcARES 09-10-2012 18:11:35 38.123.14.49 Report to Moderator	Re: Overbore affect on compression ratio ? in reply to 6 cylinder puller, 09-10-2012 17:31:40   6.51:1 [Reply]  [No Email]