Tech / General EngineIs your car making a strange sound or won't start? Thinking of adding power with a new combination? Need other technical information or engine specific advice? Don't see another board for your problem? Post it here!
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I'm deciding on a cam for my 92 camaros 383. I want a hydraulic roller and about 230/236 dur @.050. I found a comp cam p/n 08-432-8 but it has a 110degree LSA. Can I put a nitrous cam with smilar specs but a 113degree LSA and get better gas milage? What else does LSA do?
Overlap is one thing that affects fuel economy. Spreading out the LSA decreases overlap and there's less unburnt air and fuel that could blow straight out the exhaust. But really, if you're talking about mileage, a smaller cam is what you want. Spreading out the LSA generally gives you a wider, less "peaky" powerband, but overall a lower one. It also smooths out the idle. It opens the exhaust sooner, possibly letting the cylinder "blow down" before it's really done giving all of it's energy to the crank. And lastly, it closes the intake valve later, which lowers your dynamic compression (cylinder pressure) and might lower combustion efficiency at low RPMs. But you're changing the basic breathing characteristics of your motor- it's not a change to consider lightly. And frankly, with all the puts and takes, you're talking about a small difference in economy.
If you want to get better bang for the buck, drop your durations by 10* across the board, leaving everything else the same, and you'll probably be a lot happier with the end result.
Overlap is one thing that affects fuel economy. Spreading out the LSA decreases overlap and there's less unburnt air and fuel that could blow straight out the exhaust. But really, if you're talking about mileage, a smaller cam is what you want. Spreading out the LSA generally gives you a wider, less "peaky" powerband, but overall a lower one. It also smooths out the idle. It opens the exhaust sooner, possibly letting the cylinder "blow down" before it's really done giving all of it's energy to the crank. And lastly, it closes the intake valve later, which lowers your dynamic compression (cylinder pressure) and might lower combustion efficiency at low RPMs. But you're changing the basic breathing characteristics of your motor- it's not a change to consider lightly. And frankly, with all the puts and takes, you're talking about a small difference in economy.
If you want to get better bang for the buck, drop your durations by 10* across the board, leaving everything else the same, and you'll probably be a lot happier with the end result.
will it be streetable enough?
driving 10-15 miles to work everyday.
I got afr 195cc street heads
demon 750, eagle stroker forged rotating assembly
edel rpm air-gap intake
It'll be a little grumpy but nothing you can't put up with on a short commute. Mostly you're going to not like it when it's cold. Carbs, fairly large cams and a heat-isolated intake don't make for sparkling drivability on a cold engine. It'll be running super about the time you roll in the parking lot at your job.
If you're running an automatic trans you'll want a higher stall converter than stock, for sure (about 2500 at least, give or take). Not just to let the motor get into it's powerband when you're launching hard off the line but also becuase it takes a lot of the load off the motor at idle in-gear. Otherwise you'll be 2-footing it at every stoplight. A manual trans car wouldn't have to worry about this, obviously, but you'll still find you need to get some RPMs going before you let the clutch out to pull away from a stop.
