The_Dude

Stock is 9:1. That really isn't very high.

mjr46

all right guys, lets put an end to all the misinfo.......if it is a stock 5.0 and timing is set to factory spec still, it was designed to run on 87!! nuff said

oldfordisbetter

so should i be getting higher grade fuel since i got a built motor? ive been just doing 89 fuel... its 89 here not 87.... should i go higher? will it run better?

majohns

how is the motor built? what has been done to it? if its a mild build, then yes low grade is fine. if its a borderline race engine then i would suggest higher grade maybe even a mixture of 111, 114, or 118. if its a full race engine i would would say race fuel or carb it and jet it for alcohol. that answer your question?

Five0hFox

I'm confused, since your sig says you do "high performance tuning", shouldn't you know what octane to use in a car?

oldfordisbetter

see my sig....

majohns

basically its a carbed 306 with H/C/I. i would say it would be ok to run a low grade gas. prally no real advantage to running higher grade. like i said you want want it to run better mix you some C16 with it!

primetime5.0

I ran my 348 on 87 octane with 34 degrees of timing.. I do live at a high elevation though