View Full Version : on center block vs off center

04-02-2005, 10:50 AM
Hey, another stupid question. Is a stock GN 109 block off or on center? what is that in reference to? what does that mean? what is off or on center? I had to send a cam back to comp. The machinist ordered me the wrong cam and had a lobe seperation of 110.0 does any one know what it should be? I looked for any thing on this site to tell me what center the block is so I can tell comp cams.

04-02-2005, 01:32 PM
The stock blocks are 'off center'.

'On center' blocks have "the cylinder bores on-center at the crankshaft, requiring different connecting rod journals and intake manifold". Also requires a reworked front cover. That quoted phrase is taken straight from Buick Stage II sales literature. See http://www.gnttype.org/techarea/pictureguides/blocks/blockguide.html for the more block info and pix.

Stock cam lobe separation is 107. See http://www.gnttype.org/maint/quickref.html Wider lobe separation will increase NOx on emissions, if that is a concern. For an explanation of what it means, see http://www.chevyhiperformance.com/techarticles/95298/

04-03-2005, 09:40 AM
Thanx, so much. I live in cook co., Illinois, and we have emissions testing I believe once every or every other year. I did find the stock spec on the cam on the site after more research. Cheers :cheers: