340 cam in a 318
I have a question about putting a 340 cam in a 318. From what I've found out, the 340 cam has a ivc point of 69* and this brings down the dcr to like 6.63:1 ( 18 psi lower cylinder pressure than a stock 318 cam ). Wouldn't this hurt performance rather than help? I based this on a 1973 318 with a 8.6:1 cr. Did I figure something wrong or have the wrong information?
A lot of things to consider.
When emissions BS came about, the big 3 began using different cam profiles in their bread and butter "economy" engines. I forget the Mopar specs, but they all reduced intake lift and increased the duration. The lift at the valve was about 0.050" less. That impeded intake flow past the valve, vaccum developed in the cylinder was not seen in the intake manifold and economy was terrible. '73 and '74 were bad as the small displacement engines had to meet more stringent emissions. The screwed in the hoop solution was to jet the carburretors rich, and all the fuel could not burn in the cylinders as it ran out of O2. An air injection system was installed to introduce fressh air to the exhaust ports. Of course real hot exhaust would then burn the rest of the fuel in the exhaust manifolds. Those suckers got hot.
I bought a 1982 Blazer with the 305 4 barrel and first year 700R4. Drivability sucked **** through a tube. On the hwy it shift cycled into and out of OD unless you had a strong tail wind or were going down hill. Now we need not be talking a steep grade, only that if you had a pee, it would run down the way you came from. I got looking in the TRW cam catalogue and found out about the reduced lift. Chevy for the 305HO installed the same cam the 350 used. They also used heads with larger intake valves and smaller head chamber volumes. World of difference. I also noted that Ford and Mopar did the same. When Ford came out with the 5.0L HO, it used the 351 cam and firing order. By then the 302 and 351 were using the same heads. I purchased a cam labled as a RV cam that the guy said was too much for a 305. Worked fabulously. Still had some shift cycling but greatly reduced. Fuel economy went from 15MPG IMP to 19MPG IMP.
So IMHO, install the 340 cam with new lifters. If the 318 has a 2 barrel carb and money is a bit tight, run it that way until you can afford a 4 barrel.manifold and carb.
In automotives class in high school, one of the guys had a 58 Vette he inherited from his brother who died in Vietnam. He had obtained a pair of ported fuellie heads that they drilled and rollpinned to prevent the studs pulling. Long time before commonly available screwin studs. Bored the 283 for 327 pistons. This was commonly referred to as a 301, but bore and stroke were the same as the then just out Z28 302. He got a fairly aggressive cam, and for breakin put a 2 barrel intake on it. Restricted intake flow a bit to prevent getting too sporty during breakin. The pistons were 11:1, so still fairly quick. After breakin and all the parts liked eachother, he installed a tri-power intake.
