[DeTomaso] Compression ratio

[Garth Rodericks]

<<< Is there a way to determine compression ratio based on compression or something else. I didn't measure it when the engine was apart and would like to determined it now. Any suggestions? >>>

Just tell everyone it's 10.0:1 and they'll be suitably impressed! :)

Seriously, it's not worth measuring by all the fancy means others have reported - it has no value and won't change how the engine runs.  But if you gotta know, calculate it.  As Janne already pointed out, the best estimate would be based on what you know about the parts that went into your engine (bore, stroke, pistons-valve relief cc,  piston to deck clearance, head gasket compressed  thickness, head cc).  It will get you in the ballpark...


Calculation:

  CR = (VS+VC) / VC
  Compression Ratio (CR) = [ Sept Volume (VS) + Clearance Volume (VC) ] / Clearance Volume (VC)

Compression Ratio Calculator:
  http://www.csgnetwork.com/compcalc.html

Example: (with my engine)
  Stroke = 3.75
  Bore = 4.02
  Deck Clearance = -.013
  Head = 60 CCs
  Gasket = .036
  Piston = Dished (16cc)
  Rod Length = 6.126
  Final CR = 10.65:1


References: 

  http://www.fordracingparts.com/download/tipsPDF/EngineBuildingTipsSpecs.pdf
  http://pantera.infopop.cc/eve/forums/a/ga/ul/1350091684/351C_compression_ratio.doc

Cheers!
Garth
#4033