CLASS RACER FORUM - View Single Post - Spark Plug Heat ranges, what gains have you made?

Stan Weiss · 08-27-2021, 03:59 PM

A wrist pin offset normally is 0.060" to 0.080". When people reverse the wrist pin offset (do people still do this in stock?) this moves the pin center line 0.120" to 0.160" they may see a very small difference. Lets look at a 0.060" reverse and we a talking a little under 1 degree change in Piston TDC to crank journal TDC

Bore = 4.0 Stroke = 3.25 Rod Length = 5.7
Actual Piston Stroke 3.25019600382
Cylinder Volume 40.843168 CI 669.299602 cc
Engine Size 326.745340 CI 5354.396814 cc

Wrist Pin Offset = 0.06
Crank Angle Piston TDC -0.46932221356 Piston BDC 179.15635067565

Wrist Pin Offset = -0.06
Crank Angle Piston TDC 0.46932221356 Piston BDC 180.84364932435

Where you can really see a difference is with an inline motorcycle engine where the crank line has been moved 10 mm.

Stan

08-27-2021, 03:59 PM	#8
Stan Weiss Senior Member Join Date: Apr 2020 Location: Phila, PA Posts: 793 Likes: 0 Liked 733 Times in 384 Posts	Re: Spark Plug Heat ranges, what gains have you made? A wrist pin offset normally is 0.060" to 0.080". When people reverse the wrist pin offset (do people still do this in stock?) this moves the pin center line 0.120" to 0.160" they may see a very small difference. Lets look at a 0.060" reverse and we a talking a little under 1 degree change in Piston TDC to crank journal TDC Bore = 4.0 Stroke = 3.25 Rod Length = 5.7 Actual Piston Stroke 3.25019600382 Cylinder Volume 40.843168 CI 669.299602 cc Engine Size 326.745340 CI 5354.396814 cc Wrist Pin Offset = 0.06 Crank Angle Piston TDC -0.46932221356 Piston BDC 179.15635067565 Wrist Pin Offset = -0.06 Crank Angle Piston TDC 0.46932221356 Piston BDC 180.84364932435 Where you can really see a difference is with an inline motorcycle engine where the crank line has been moved 10 mm. Stan