70Vette Big Block firing order
10-15-2009, 02:42 PM
#2
Melting Slicks
Yes. Although the BBC and SBC are 18436572, the 4-7 swap cams have 18736542. The firing order does go with the cam.
10-15-2009, 03:52 PM
#4
Drifting
Member Since: Apr 2007
Location: Springfield Illinois
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Any cam manufacturer could have custom ground that cam.. my question is does the engine run right? No misses or anything? The 4-7 firing order swap only smoothes out the idle a little bit, there is little to no proof of it being a performance gain. I cant see why anyone would have gone with the firing order that you mentioned unless it is not a BBC..
10-18-2009, 04:50 PM
#6
Melting Slicks
That firing order is impossible if you do the visualization and graphing. The first crankshaft journal must hold the #2 and #1 rods; the last journal must hold #8 and #7 rods and must be 180 degrees opposite from the first journal. Similarly, the second journal holds the 4 and 3 rods; the third journal holds the 6 and 5 rods.
If you make a diagram looking at the front of the engine with four circles in an "x" arrangement representing the 4 journals, and then step it through the firing order, it can't work. Do the same thing with a "flat" crank and it can't work either. Either it's a misprint or someone is fooling with you.
My advise to you is to remove the valve covers and turn the engine in 90 degree steps. Record the cylinder which has its intake valve partially open but closing. When you do this for all eight cylinders (two full revolutions) you will have the firing order of your cam.
If the cam is out of the engine, you can do the same thing, but the visualization is more difficult from the intake lobes on the cam.
