How to build a 13 second 340 Duster
Idaho said
Not sure about "better machining". Not sure how pistons are "set to 0 deck".
I presume the 10.5 comp 340 could breathe a little harder and make use of the slightly larger valves so it makes sense to me if I raise the compression and the heads are being rebuilt anyway to enlarge the valve. I wonder though if this would only help at high rpm (good for track time) and hurt low rpm performance (not so good on the street).
I'm guessing 10:1 is around the upper limit for todays's pump gas? Chamber size would be per factory J head.
What he means is, a shop can do a real performance enhancing rebuild, or they can do a basic rebuild. Things like boring, honing, and turning a crank and valve job are basic rebuilding things. Things like square decking, using top of the line equipment, align honing, cylinder honing using a torque plate, degreeing the camshaft, 5 angle cutter type valve jobs, ccing the heads and correcting valve train geometry..Those are the areas that a performance shop build up will get you. It costs more, but results in smoother, more powerful, and longer lasting engines. Square decking and setting the block's cylinder head surface exactly where the factory blueprint puts it, results in 0 deck with the right piston. The process also allows for any piston (or almost any...lol) to be set that way. As far as cylinder head theory, there are as many ideas as there are guys doing the work. Personally, I use the largest intake valve I can. Because at low lifts, the more curtain area you have, the better. But, I dont make huge ports, because that does seriously hurt low end power with short stock strokes. I like static ratios in the 10:1 area with iron heads and pump gas. With careful cam choice, you can go higher, but it's not really worth the hassle. The biggest thing is, by skimping what I consider the mandatory machining, You sacrifice a lot in the resulting power. So bigger cams, bigger heads, etc are all employed, when in reality, better quality work and more mild parts would have performed more than adequately had things been "right".