The 1947 - Present Chevrolet & GMC Truck Message Board Network - View Single Post

**Bob B.** · 03-26-2017, 05:39 PM

I have heard the same comment from others who have driven 637's, you had to spin them up to get the power out of them. Not sure if that characteristic had anything to do with the head design, it could also have been due to the cam profile.

03-26-2017, 05:39 PM	#7
Bob B. Senior Member Join Date: Aug 2005 Location: Los Angeles Posts: 1,309	Re: GMC JE 9500's with a 637 Gas I have heard the same comment from others who have driven 637's, you had to spin them up to get the power out of them. Not sure if that characteristic had anything to do with the head design, it could also have been due to the cam profile. __________________ 1967 GMC CM-2500 Camper Cruiser, 351E V-6, NP 435 4 speed, Dana 60, and factory A/C. 2012 GMC K-3500 WT regular cab, 6.0L Vortec, 6L90.