I have a 2004 Chevy Blazer, 4.3l vortec engine. Lately I get what sounds like a loud engine roar on hard acceleration. It doesn't affect the way the car runs, it sounds like I have no exhuast muffler for the time it;s roaring. Any ideas?

 

Might just be the engine fan kicking in, but the 4.3 is pretty noisy at full throttle anyway.

 

rriddle3 has hit the nail on the head, I think. Mine especially on a day when its hot (for example if I come home and leave within lets say 30-45 min and the engine is still hot when I first take off the fan clutch will engauge and it will roar for 1-2 blocks, then every stop sign I stop at for few blocks after that when I accelerate it will roar till it hit about half way through 2 gear then after its cooled for a bit it will slowly go away its normal. It really depends on your driving style, how many starts and stops you do and last the temp. Where I live we get extreme humidity in the summer so mine tends to do it more than what I have found out others do.

BTW: from what I have been told these motors were based off of the 350 just minus 2 cylinders. They are very torquey motors that live mostly in the lower rpms. To get mine about 3-3,500 rpms I really have to mash my loud pedal. I drive alot and have never had to push the motor passed 3,000 rpm during normal every day driving. Even offroading I've never needed to hang out the rpms ( I can only count like5-6 times spinning in mud or snow I've need to rev more than 3,500 Rpms. These motors are naturally noisy and even louder with an aftermarket exhaust.

 

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