so here's the kick in the butte i go and rebuild the top end on my 305 you know the cam and the fun stuff in life and i am running this old 77 chevy silverado on propane and now tuning the thing has been the biggest pain the rear axle... the ??? is what am i to different when tuning propane instead of gas i cant seem to get the timing to set just right like i had it set before the top end was rebuilt. the truck has been on propane since i bought it for $400.00 cheap little turn key operation that it was hehehe