wolfman98

So I am changing over from single to duel exhaust. I ordered the manifolds (left and right) from Thorntons and will be getting mufflers either from Flowmaster or Megaflow( toss up right now ). The question on the exhaust is does it run straight back from both manifolds to exit the rear? I have seen some exhaust job pics on different threads but always on Cutlass' or 442's etc and they always run from manifolds to X crossover then to mufflers.But the full size 98 may be different? I want to improve the performance of the car by adding the duel exhaust , I just put an aftermarket air cleaner on the rebuilt carb and took it out for a run and it works better. On the highway once in high gear she was really pulling strong til I hit around 100mph then the speedometer needle started going haywire bouncing back and forth from 0 - 120 four or five times and the needle broke off
I guess problem 2 is going to be getting a new speedo cable and fixing the needle. I have no idea about how to fix the needle part of this problem but I did read on a thread about a company here in Canada that makes speedo cables. Anyone know who that is? And anyone know what I need to fix the needle?

Olds64

I put dual exhaust on my 71 98 recently and had an X pipe installed right behind the transmission. If you want to pay extra to have an X pipe installed then do it. It won't hurt anything, then again, it probably only gives an insignificant add to HP (at least for big cars like ours).

You mentioned your speedo broke... does it work at all now? If it doesn't work at all then you will probably have to trace the speedometer cable from the front wheel hub to the insturment cluster. I think you can buy replacements from Fusicks. If the needle actually broke off of the insturment cluster then you will probably have to get the insturment cluster reubilt.

Oldsmaniac

Near rear bumper there may be a horizontal frame brace that is notched and that would be where the tailpipes should be located at rear. Most factory exhaust tailpipe ends angled down at about 45 deg angle. From the manifolds the pipes usually angled in toward the driveshaft some. I believe too the full size cars used resonators after the over axle pipes. Without them the exhaust will be kinda throaty.

Olds64

Oldsmaniac is correct. I can see the horizontal frame brace near the rear bumper on my car. The exhaust shop I had do my pipes put the tailpipes in the notches of the horizontal frame brace; however, I wanted tailpipes that came straight out as opposed to out at a 45* angle.

I also didn't use resonators. I have 2 45" Thrush glasspacks that are 2.5" ID. The exhaust is definitely "throaty."

I wish I had remembered to take a pic of the exhaust with the car on the lift. Sorry...