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My Brother In Law is putting together a 56 chevy truck with a 355 C I small block. It is running 7 to 1 compression and a B&M 162 blower with the super street B&M cam. it has a holley 750 cfm carb and MSD ignition. it has the 5/8 inch plugs but I don't think the heat range is correct. Anybody run something similar and do you have ideas on what spark plugs should work with this combo? Any educated guesses would be greatly appreciated.
 

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My Brother In Law is putting together a 56 chevy truck with a 355 C I small block. It is running 7 to 1 compression and a B&M 162 blower with the super street B&M cam. it has a holley 750 cfm carb and MSD ignition. it has the 5/8 inch plugs but I don't think the heat range is correct. Anybody run something similar and do you have ideas on what spark plugs should work with this combo? Any educated guesses would be greatly appreciated.
I'm presently running a 671 BDS blower with 2 600 Edelbrocks. Its on a 406 sbc with 8-1 compression. Its been 5 yrs. since I put it together and I don't recall the type plug or heat range. I do recall researching blowers in general by reading several books at Barnes and Noble on this subject matter. The one book I read-Supercharging and Turbocharging-greenish cover-went over everything including which spark plug to use. It was a wealth of information.
Also, as a suggestion, some of your bigger manufacturers of blowers also have web sites with alot of good info for the viewing. Might be worth giving them a look. Hope this was a little helpful, Carmine.
 

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Link to a good visual reference of making your determination. Generally 8:1 to 9:1 compression, I would start with the stock plug then one step colder in heat range for each 1 over (10:1 add one heat range 10.5:1 add two etc) and one step colder in range for each 4 degrees of cam duration above stock. Never base lined a blown or charged engine but I would think the same applies in a percentage increase of VE. (step warmer than stock for the lower comp ration then step colder 1 step per 10 percent boost - given that in a SBC 8degrees of added duration gives you about a 10% increase in VE at WOT).

I guess the easiest way (aside from dyno) would be to start stock and do a part thrott run and see where its at based on the ground strap then adjust accordingly until you look good at WOT. Just keep your timing close in (like 32 max) and your jetting slightly fat (11.5-12:1 AFR) until you get the heat range right.
 
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