Old crapy exhaust 6k easy, new exhaust bogs at 4k

So I had a very loud car. Sounded like it had blown header gaskets.
But it turned out to be the exhaust system.

It was pretty much rusty from the “cat” back. [Cat is gone.]
Lots of holes and blow through along the whole pipe. Especially at the bends in the back over the axel.

I don't have very much money so I removed everything bad.
And ran a new pipe from the cat position to just before the axel.
I stuck a $20 AZ muffler.

All the pipe is smooth and straight. And the system is about 3 feet shorter and it has to flow better. But it would easily rev out to 6k before like no problem. It didn’t stop till you lifted. Just hold the pedal down. Now when I give it the gas it will hit a flat spot at 4k and I need to lift and float the pedal some or shift. Like the pedal input is too much.

The stock muffler was a rust piece of crap full of rust too.
I can't see it being a backpressure issue but maybe?

Other idea. I run RP 20/50 oil and it never had a problem with it and good PSI.
Maybe now that it does free flow, the oil is making a difference?

The car is a 2.8 stick shift. It was rebuilt and bored once. But not sure on the spec’s.
But the change happened during the exhaust work. But it seams strange that a shorter all new system would do that.

 

Cheap muffler meaning very restrictive maybe? What size piping?

 

Muffler restricting it.

 

unless you are burning 10/30 like heck, or you are running over 200* oil temp, you don't need 20/50, and infact it may be what is killing the engine. that stuff is way way too thick for a stock engine. i am surprised that your oil pump hasn't went out or broke yet from trying to pump that thick stuff. back down to 10/40 atleast and go with a k&n oil filter. if i put that thick of oil in my car, i would sieze the thing up before it hit the driveway.

you are not revving due to the fact that you are getting great oil pressure, but not enough flow, so the engine is starving itself of lube that it needs, bearrings are getting hot, and are slowing down the moving parts.

friction is a pain in the butt. and with that oil you may be trying to reduce friction, but you only reducing it a little more than running no oil at all. my car calls for 5/30 from the factory, it burns that stuff up so i use 10/40 and that does just fine. no need to try anything more cause with that it don't burn oil at all.

 

even 15/40 oil would be better but thats not the main problem. he said he cut the cat straight pipe to an el cheepo muffler and dump before the axle.......nowhere near enough pressure for basicly a stock motor.

 

I thought the muffler also but it doesn't seam right in a way.
Car allways had RP 20/50 in it. The only changes were exhaust.

I only mention the oil as maybe now it does flow better and is trying to rev faster then before. So now the thicker oil is a problem.

An oil pump wouldn't wear out or break from thicker oil I think.
Its just two gears in mesh with a cover plate. Dirt and junk would be the only thing to wear it out.

 

It never had a cat. It was just rusted from there back. There was just a butt joint clamp.

I used the same size pipe as was what one it. looked like an old Midas jobber basic install. I just bought a piece of straight pipe and a muffler. Didn't have fund for a axel over pipe to install it in stock location.

 

right but you still only have half the old ehaust

 

It was the muffler. I yanked it off and it rattled big time.
Something inside must of came lose or wasn't installed right.

AZ gladly gave me a new one for my trouble and problem fixed.