The Ford Barn

30ratrodder · 12-31-2011, 06:06 PM

I think that i might have to play around with gear ratios in my tranny and rearend. I have a 4" crank in my flathead. What is the maximum rpm that i can run safely while cruising and not blowing the sucker up?
Thanks

Ol' Ron · 12-31-2011, 07:35 PM

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Cruising RPN is based on the cam, or the middle of the torque curve. Get a copy of jWL's book and you'll see what the torque curves look like. The stock cam runs best from 1600 to 2200 after that it begins to fall off. Running the engine at a higher RPM probably wont hurt it too much, but it won't be very economical.

12-31-2011, 06:06 PM	#1
30ratrodder Junior Member Join Date: May 2010 Posts: 11	Cruising rpm I think that i might have to play around with gear ratios in my tranny and rearend. I have a 4" crank in my flathead. What is the maximum rpm that i can run safely while cruising and not blowing the sucker up? Thanks

12-31-2011, 07:35 PM	#2
Ol' Ron Senior Member Join Date: May 2010 Location: Chester Vt Posts: 8,860	Re: Cruising rpm Sponsored Links (Register now to hide all advertisements) Cruising RPN is based on the cam, or the middle of the torque curve. Get a copy of jWL's book and you'll see what the torque curves look like. The stock cam runs best from 1600 to 2200 after that it begins to fall off. Running the engine at a higher RPM probably wont hurt it too much, but it won't be very economical.