Quote:
Originally Posted by MrPbody
Nice find! '72s are getting rare.
A 350 is a small block. No need to repeat.
Adding a 4-bbl. will not help unless you also change the camshaft to take advantage of the increase in fuel/air. We've done this for people in the past, only to have the car perform "worse". The '72 engine is "low" compression, so a Comp XE grind is ideal. For a stock converter, XE256H or XE262H are called for, the latter being a bit more "rowdy" (not too much, though). For anything over 228 degrees @ .050" lift, a "stall converter" is called for.
If not doing extensive modifications to the engine, the 1 1/2" headers are the better choice. They will enhance low-speed and mid-range power. No need for "expensive" headers at this point. Edelbrock "Performer" is the perfect compliment to them. NOT "RPM". "Air Gap" is okay, but a waste at this level. A small Edelbrock or Rochester carb (650 CFM) is also the best choice here.
Always remember: "Just as good only cheaper" and "get away with" are two terms to be purged from your vocabulary regarding the old car and engine modifications. The first is VERY seldom true, and the second is dangerous.
Jim
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Jim, I disagree with your advice here. 1 1/2" headers might do well on a 262, 265, 283, 305 or 307, but they are too small for a 350. Check on ebay, there are some stainless headers that are very affordable and easy to fit.
The Edelbrock Performer is a "grandma goes to Bingo" kind of manifold that will not show any improvement over a cast iron stocker. Its only saving grace is that it will remove weight from the front end of the car. Any car that even hints of performance will make power as low as 1500 rpm's, the beginning of the range of 1500 to 6500 of the Performer RPM. It takes longer and bigger runners to make good power in a street performance motor and the RPM fits the bill perfectly. Now, on the other hand, I cannot recommend the Performer RPM Air Gap for anything but a race motor. I have had complaints from fellows who have experienced bucking and misfiring from their motors in cool or cold weather using these manifolds. They'll work great on a race motor that goes from idle to wide open and stays there, but they won't work so great on a street motor that must be modulated from idle, through mid-throttle to full throttle and back again, red light after red light. Such a street motor needs the heat provided by the manifold to help atomize the fuel/air mixture so that it will burn properly.
Furthermore, I cannot in good conscience recommend the Comp Extreme Energy camshafts for a street motor. They work the lifters too hard, wearing out the whole mess in a shorter time than a milder ramp profile and are noisy on the street. This is another case of, like the Air Gap intake manifold, a product that works great at the drag strip where you will be disassembling the motor a couple of times a year for maintenance, but ain't worth a hoot in a street motor where reliability and quiet performance must be given importance. The work that a cam lobe does can be measured by a term called "Hydraulic Intensity". This term was coined by famed cam grinder Harvey Crane, and explains the work that a lobe does to get the lifter from the heel of the lobe to the nose of the lobe. Harvey used to grind all his cams on a H.I. of 62, after determining that 62 was a good, all-around profile to get the valve open and closed. The way you use this information is to find the advertised intake duration and the 0.050" intake duration, subtract the smaller from the larger and you have H.I. For instance, if you have a cam with an advertised duration of 280 degrees and a 0.050" duration of 218, after subtracting one from the other, you are left with an H.I. of 62, exactly where Harvey ground all his cams. As cams go higher and higher numerically, they are easier and easier on the valvetrain, coming into the scope of a stock cam that was meant to last a long time, while offering good performance in a stock type motor. Your general, run of the mill engine rebuild garage will use one of these high H.I. cams in the motors that they build for the general public, because they are easy on the valvetrain and will result in fewer unhappy customers and comebacks. A couple of decades ago, cam grinders such as CompCams began to tighten up the ramps on some of their cams, making the lobes work harder, making them noisy and shorter lasting than cams with a larger H.I. Current Extreme Energy hydraulic roller cams are ground on an H.I. of 52 and if you are not concerned about a noisy valvetrain or reduced life of the cam, go for it. I would use one myself if I were building a competition motor where I wanted to get ahead of the other guy in my class by a headlight rim, but I would not use one in a street motor build where I wanted quiet operation with long life. If I wanted to keep the valves open longer, I would simply go to the next larger cam grind.
Please understand that you have to match the cam profile with the static compression ratio of the motor. You cannot just reach out into the air and grab any cam that appeals to you without matching it to the motor. Low static compression ratio requires a mild cam profile, high static compression ratio requires a rowdy cam profile. I am also a member on Hotrodders.com under the screen name of techinspector1. Several years ago, I wrote this tutorial which will help you to understand that a cam must be matched up.....
https://www.crankshaftcoalition.com/..._compatibility
I'm 78 years old and have been around the bush a couple of times. I have a lot of information stored in my brain and would welcome questions or comments. Thank you for reading.
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