im re doing the exhuast on my 83 6.2l non turbo and i was going to put in a 4in straight pipe that drops right after the axle and i was wondering well the 4in pipe effect my power because i was hearing on gassers the have to have compression in the exhuast for power and do i have to have that compression in the exhuast with a diesel?

There is a lot of reading via google on 'diesel exhaust back pressure'

I have a feeling that without a turbo or turned up IP that new 4" pipe wont give you much extra power. But I don't have any personal experience with that.

Are you replacing your dual 2.5" exhausts with dual 4"?

well the IP is turned up and blows black clouds, and sooner or laater im getting a turbo, intake,manifold for $450 and yea im replacing the old dual 2.5s

The 4 inch may not give you much of a performance upgrade, but it won't hurt either, and it will sound alot cooler! Gassers mostly need backpressure in the exhaust to scavenge out the exhaust fumes, but a diesel is so much higher compression that backpressure isn't as important.

Thats not entirely accurate. Naturally aspirated engines are subject to performance gains/losses based on exhaust tuning. A single 4" exhaust on an N/A 6.2/6.5 will kill torque in the lower RPM range. Turbocharged engines are not nearly as affected by the exhaust system so long as its big enough. general rule of thumb-the best exhaust for a turbocharged engine is no exhaust.

If you are blowing black clouds you have too much fuel or not enough air. Black smoke is unburnt fuel. This also raises exhaust temps to the piston melting range. Dual 4" won't increase your performance. Mandrel bent 2 1/2-3" works best. The outlet on the manifolds is less than 2 1/2 so that is the limiting factor.

ok so wat im gettin is tat dual 4 in is to much flow for my 6.2l but a single 4in will be fine and my truck has ovr 400k on it and has one piston ring melted aready and aint changing the performance, and i was think bout re doing the exhaust pipe from the manifold to the transfercase and combinding the to into a 4in

ok so wat im gettin is tat dual 4 in is to much flow for my 6.2l but a single 4in will be fine and my truck has ovr 400k on it and has one piston ring melted aready and aint changing the performance, and i was think bout re doing the exhaust pipe from the manifold to the transfercase and combinding the to into a 4in

A single 4" is still too big for an N/A engine IMO. I run a 4" system on my 6.6 'max. Now if you put that turbo on there it will be a whole different story...go ahead and do the 4" single if you are really serious about installing the turbo later on, it will save you the work of re-doing the whole thing. And it won't hurt much in the meantime, mostly just not cost-efective.

you can use the 4inch pipe but till you get the turbo use a glasspack muffler and when you get the the turbo take it off the make good back pressure and and still loud .one point is make shure you run the pipe down the right side most single head pipes run down the left