Jamie Johnson Asks…Do Similar Duration Cams All Perform About the Same, or Differently?

QUESTION My favorite article is “Affordable Horsepower: Building a Low-Buck Small- Block” at HotRod.com. I like it because it shows how to get cheap, usable horsepower with lots of beautiful torque.

- Marlan Davis

I have a 355 in a 1979 Z28. From what I’m told, it has Speed Pro [pistons]; a 222/230-degree, 0.480/0.480-inch-lift cam; 305 heads with streetable porting; headers; intake; and a 650-cfm Edelbrock carb. I would like to copy your engine setup from the article, but I have a cam question for you. The Summit K1105 cam choice is where I’m lost. It has a range of 2,400–6,000 rpm, yet it gave great numbers in such a usable range. How can this be?

There is a different cam (Comp PN 12-321-4) with similar specs but a 1,500–6,500 rpm range; will this be better, worse, or the same? Is it worth using this different cam?

ANSWER To get our readers up to speed, for a $1,073 outlay (in 2010 dollars) reader Johnson’s referenced top-end conversion used a stock 350 pulled in the boneyard for $150 (including core charge) that, in its ultimate form, made 418 hp at 5,500 rpm and 444 lb-ft of torque at 3,800 rpm. Torque production exceeded 400 lb-ft from 2,800 rpm all the way to 5,500 rpm. Key parts included Summit’s K1105 flat-tappet hydraulic cam and lifter kit, and Procomp aluminum cylinder heads, rocker arms, dual-plane intake, and gaskets.

I’m going to take you at your word that you want to duplicate as closely as possible the article’s build, including the heads, intake, and the carb; and not reuse your existing top-end parts. Procomp heads have been rebranded Speedmaster, and remain quite affordable. Still close analogs to the 2010 castings, they’re currently offered with 59 or 64cc chambers (instead of the 70cc volume in the original article). That raises static compression ratios about ½ to 1 point, always a good plan with cooler-running aluminum heads and larger cams.