I have a 40 Ford 2dr sedan and I am getting exhaust fumes inside of car there are no leaks in the system I am wondering if I should lengthen the pipes or shorten them currently they are 6" past the body

 

Nice toy !

What about the inside of the rear of the vehicle ? Could the fumes be coming in through the separators between trunk and passenger compartment ?

 

I don't think so I have replaced all rubbers on the car I did the trunk first thinking that was the problem it helped some but not enough

 

How did you check for leaks?

 

The system is all welded I was also under the car while it was running did not feel or hear any leaks

 

A couple of things,

What if you took off the chrome tail extension (s) with the curled edges,
Had someone hold a piece of wood or metal to partially block the exhaust while you checked for any leaks
Hold the engine RPM up so exhaust pressure would increase and then get under to check for leaks
As you know , welds can look good and still have pinhole leaks
If there is a "Y" pipe, is the size to single exhaust to muffler cramming pipe pressure into one small pipe out ?

Is the original engine still in the vehicle?

 

I'll give that a try no Y pipe I'm running a 5.0 HO Mustang motor so They're are headers