Author	[Modern View]
Mr. T. Minnesota 12-13-2012 11:27:47 68.170.114.158 Report to Moderator	Forum Members, Curious if it is possible to increase the compression ratio when rebuilding an 8N engine to higher than 6:1? Any thoughts are appreciated! Mr. T. Minnesota [Reply]   [No Email]
Ken(Ark) 12-14-2012 21:13:22 173.187.227.94 Report to Moderator	Re: higher compression ratio? in reply to Mr. T. Minnesota, 12-13-2012 11:27:47   Quoting Removed, click Modern View to see Angle mill an 8n head and or Mill the block . New Valves and seats . ( Thicker for Static Compression , Larger w/ swirl polished stems for Dynamic Compression ) Oversized pistons . Offset weld the crankshaft Dual Exhaust manifold & port work ( Dynamic Compression ) I think a custom tube header would be the cats meow . A custom ground Cam from ??? could knock the heck out of the Dynamic Compression as would a forced induction system . Low impedance air filter , gas cool can , electric fan , genny cut off switch (H.P.) Let's not forget NO2 Run the 9/16 pump with light weight full synthetic oil . Polish connecting rods and balance the rotating assemble . Or go buy a 226 flat six , get crazy and rip all the guts out of the drive train . A properly built N motor has the best high ratio of power at the lowest risk of drive train damage . [Reply]  [No Email]
Hobo,NC 12-13-2012 19:10:19 75.89.255.106 Report to Moderator	Re: higher compression ratio? in reply to TheOldHokie, 12-13-2012 11:27:47   Mr. T. Minnesota said: (quoted from post at 03:31:36 12/14/12) Forum Members, Thanks for the info. Reason for the question is the 8N I purchased this summer had been newly overhauled. The seller said he had added special pistons, shaved the head and decked the block. He said the compression "may be an 8:1 ratio" ?? Even as a novice to mechanics the math just did not seem to work out. There is only so much space to work with. With that being said, the 8N seems to be a lot more powerful than my not so worn out 2N. Had to change the 33 to a 243 carb to make it run right which may also add to the power. Again, any other thoughts are appreciated. In retirement my goal is to learn something every day. Mr. T. Minnesota My guess if you save the head and deck the block its possible to gain a pony are 2.... No guess the difference in a 2N and a 8N engine is the head that's it,,, the difference is in the valve pockets... Put a 2N head on a Very good running 8N and the power lose very noticeable.. A 8N head is very close to the Hot Rod aluminum head that was offered for a N... You can shave a N head all you want to the valves will never hit ( write that down )... The piston is a different story but can be over come... A """"NEW"""" reproduction head has the same valve pockets as a 2N head and will cost you a pony are 2 so don't go their..... If you are power hungry bump the RPM up if you can hang on Theirs 40 of'em their waiting to be turned loose :lol: This post was edited by Hobo,NC at 19:12:29 12/13/12. [Reply]  [No Email]
Mr. T. Minnesota 12-13-2012 15:31:36 68.170.114.158 Report to Moderator	Re: higher compression ratio? in reply to Mr. T. Minnesota, 12-13-2012 11:27:47   Forum Members, Thanks for the info. Reason for the question is the 8N I purchased this summer had been newly overhauled. The seller said he had added special pistons, shaved the head and decked the block. He said the compression "may be an 8:1 ratio" ?? Even as a novice to mechanics the math just did not seem to work out. There is only so much space to work with. With that being said, the 8N seems to be a lot more powerful than my not so worn out 2N. Had to change the 33 to a 243 carb to make it run right which may also add to the power. Again, any other thoughts are appreciated. In retirement my goal is to learn something every day. Mr. T. Minnesota [Reply]  [No Email]
HCooke 12-13-2012 17:25:43 70.195.70.93 Report to Moderator	Re: higher compression ratio? in reply to Mr. T. Minnesota, 12-13-2012 15:31:36   8:1 seems like an exaggeration, but my '51 8N does seem stronger than any of my 5 9Ns. [Reply]  [No Email]
HCooke 12-13-2012 17:25:42 70.195.70.93 Report to Moderator	Re: higher compression ratio? in reply to Mr. T. Minnesota, 12-13-2012 15:31:36   8:1 seems like an exaggeration, but my '51 8N does seem stronger than any of my 5 9Ns. [Reply]  [No Email]
Dean 12-13-2012 18:39:25 152.216.3.5 Report to Moderator	Re: higher compression ratio? in reply to HCooke, 12-13-2012 17:25:42   It will be if everything is as manufactured. Late 8Ns do have higher CR and more HP than 9/2 Ns. Dean [Reply]  [No Email]
Dean 12-13-2012 17:12:50 152.216.3.5 Report to Moderator	Re: higher compression ratio? in reply to Mr. T. Minnesota, 12-13-2012 15:31:36   It's not 8:1. Probably closer to 6.5:1. Your 2N most likely has flat-topped pistons in it while the 8N almost certainly has late 8N domed pistons, which are good for a noticeable increase in torque and power vis-a-vis the flat-topped pistons. Dean [Reply]  [No Email]
soundguy 12-13-2012 15:13:02 173.107.60.133 Report to Moderator	Re: higher compression ratio? in reply to Mr. T. Minnesota, 12-13-2012 11:27:47   shave an 8n head a lil.. then check valve clearance with putty and no head gasket.. then relieve as needed and bolt on.. that's about it.. as dean and the others said. other goodies not so available. and the merc pistons in the parent bore.. well.. it works.. bat can cause issues later and requires overbore to correct. also don't give you much more hP. if you have an 8n and want more hp.. get a naa or 6xx ( or 8xx and have near 2x hp ) [Reply]  [No Email]
Bob Harvey 12-13-2012 15:39:47 209.121.225.210 Report to Moderator	Re: higher compression ratio? in reply to soundguy, 12-13-2012 15:13:02   Or go the Baumann way and install a turbine/V-8/Valkirie !! [Reply]  [No Email]
soundguy 12-13-2012 16:06:35 173.107.60.133 Report to Moderator	Re: higher compression ratio? in reply to Bob Harvey, 12-13-2012 15:39:47   yep.. jet engine HP :) [Reply]  [No Email]
Dell (WA) 12-13-2012 13:27:17 71.217.17.40 Report to Moderator	Re: higher compression ratio? in reply to Mr. T. Minnesota, 12-13-2012 11:27:47   Mr T..........take yer sleeves OUT and run bigger pistons. By definition, you have increased yer compression ration. (ratio of swept volume to combustion chamber volume) As the flathead V-8 guys have found out, It is really difficult to increase compression. Since ALL cylinder heads are interchangeable, Buy a NEW 8N cylinder head and gitt 6.5:1 compression. Howsomevers: you want more power? Gitta 454 Chevy smog pump and NAA carb and SUPERCHARGED yer engine. You doubt? Google "Dirt cheap supercharger by Steven Richmond" ........Dell [Reply]  [No Email]
Dean 12-13-2012 12:20:31 152.216.3.5 Report to Moderator	Re: higher compression ratio? in reply to Mr. T. Minnesota, 12-13-2012 11:27:47   Only slightly without the NLA pop-up pistons. The late 8N engine CR is nearly maximized. Dean [Reply]  [No Email]
HCooke 12-13-2012 12:03:22 70.195.66.84 Report to Moderator	Re: higher compression ratio? in reply to Mr. T. Minnesota, 12-13-2012 11:27:47   Sherman made a 'high' compression head - it was made out of aluminum. 8Ns have a compression ratio of 6.5:1. Many times these heads get trimed (decked) to correct a warp. Caution there is not much room before the piston begin to contact the head. [Reply]  [No Email]
kylemorley 12-13-2012 14:27:28 69.130.58.44 Report to Moderator	Re: higher compression ratio? in reply to HCooke, 12-13-2012 12:03:22   6.5 to 1 is pretty much the limit because above that everything is too crowded to let the valves and heads breath effectively - you can't run a piston right up to the valves like an OHV can do, when they are off to the side. Harley Davidson put huge amounts of effort into developing the flathead long after it was obsolete, well into the '60s, due to a loophole in the US racing rules that let HD run 45 c.i. sidevalves against 30 c.i. OHVs. While stock sidevalve Harleys ran compression ratios similar to the 8ns, the fastest racers usually had even LOWER compression ratios, 5.5 or so, since there was no way to port them without lowering the ratio, and good breathing was found to be more important than compression ratio. It's likely some 8ns are now nibbling at the upper limits of compression without benefit of trick heads due to the heads and/or blocks having been resurfaced. [Reply]  [No Email]