Question about timing

[Ho Hum 74]

Wayne or others,

I have completed my recent rebuild. Thanks for the great book and all the advice on this forum. Thanks to Chris Streit and Souk for advice and the short block help. I have a few gremlins but otherwise the engine runs strong.

I do have a question regarding timing. My engine is a 2.7 MFI with Elgin Mod-S cams, 9.8:1 JE Pistons. So it is similar to RS spec. The timing spec for RS MFI in the book is 0* or TDC. I set it with a timing light to be at Z1 for cylinder #1. Engine felt fine (actually quite good ). In speaking with some folks they thought I should be at 5* ATDC. I reset the engine like this but now it's backfiring when letting off the gas and coasting. I must say that my shut off solenoid is NOT connected (it shuts the entire engine down - another story) and this could be the source of the backfiring.

However I still want to know what timing I should use for this engine and how does advancing or retarding the timing effect the engine?

Thanks all
Tristan