I have a Chevy Nova wagon with a 4 speed and a 194 6 cylinder. I have added headers and dual exhaust. I will be adding a 2bbl soon. Rear gears are 3:36 tires are 14/70s. The car gets driven daily and I want more grunt out of it.
The two cams I'm looking at are Comp Cams's 252H and 260H.
The manufacturer suggests I go with the 260H. My only concern is a large drop in gas mileage. The cam I have now is stock. Granted the valves will be held open for higher and longer times, but for the times I'm driving "normal" will this be an issue? Thanks.
2007-04-03 05:16:29 · 5 answers · asked by m k 5 in Cars & Transportation ➔ Car Makes ➔ Chevrolet
I also drive the car for events in other states.
2007-04-03 05:41:50 · update #1
An engine is basically an air pump. The more it breathes the more power it makes because at the stochiometric ratio of approximately 14.7:1, for every additional 14.7 parts of air you take in you are taking in 1 additional part of fuel. The more air and fuel you can get into the combustion chamber prior to closing the intake valve and lighting it off, the more power you're going to get. The increase in volume is something that I'm sure someone can measure and use that to calculate the thousandth of a cc of additional fuel per cycle etc. and it will show you will get reduced fuel economy. Sure, you're going to be bringing more air and fuel to the party, but with a mild upgrade to either the 252 or the 260 cam, you're not going to be watching the gas needle go down as the vehicle speed goes up. I'd go for either without any conerns. You'll still have a good quality idle and good fuel economy with either.
Adding the 2bbl wil also decrease fuel economy but aid in driveability. I wouldn't hesitate (no pun intended) on changing the carb as well.
hope that helps
2007-04-03 11:21:53 · answer #1 · answered by honda guy 7 · 1⤊ 1⤋
A bigger lift cam will also have more duration and overlap which will make you gas mileage worse. Just because you have more power doesn't mean you get better gas mileage. There is a small range of efficiency for a vehicle depending on weight and aerodynamics . Being under powered will hurt as well as being overpowered . The 252H will give you enough grunt to be a nice daily driver and still have pep.
2007-04-03 15:38:52 · answer #2 · answered by 1diputs 4 · 0⤊ 0⤋
Either cam is a good choice. If in doubt go with the smaller one. Replacing the stock worn out cam would even help alot! Offenhauser also makes a killer 4 bbl intake for your engine. Go with a very small 4 bbl (390 Holley i think).You can get better mileage if you keep your foot out of the gas pedal.
Ebay also has a great assortment of new and used HEI distributors to keep everything firing just right.
2007-04-05 10:44:08 · answer #3 · answered by gittit 3 · 0⤊ 0⤋
look if your cam increases horsepower it can ony be from increasing efficiency. unless your overfueling it, the thing should actually get better mileage. the fact is it takes X amount of fuel to move X amount of weight X distance. the factors that increase fuel comsumption are acceleration rate, and top speed. If your engine produces a lot more power, it is from either overfueling it, or it has become more efficient. Most people get bad mileage after a modification because they horse on them
2007-04-03 12:24:25 · answer #4 · answered by Gary M 3 · 0⤊ 1⤋
Change your question to which cam is better and ask who likes which one best.
2007-04-03 12:23:29 · answer #5 · answered by kellbell 2 · 0⤊ 3⤋