Possible restrictive rear muffler

[ace124]

I have a 4-2-1 mild steel header, a 2" OD system, with one 2" straight thru middle muffler, terminating on the original Fiat 124 1,3/4" rear muffler.
The engine is a Fast road 1800, 10.2:1, stock 131 sport cams with 45 DCOE's.
The question is, how restrictive is the original rear muffler given its ID is smaller than the 2" of the rest of the system? It is of straight thru design.
I figured by the time the gases reached the rear they would have expanded and have less intensity, so didnt worry about upgrading the rear. Besides i like the original look.
The car pulls past 7000 RPM but power drops off after about 6000, so im suspecting there may infact be a restriction in running the smaller diameter rear muffler. Granted i also put the top end down to the mild original cams. The engine is very torquey between 2-5500 rpm on part throttle however.

[Guy Croft]

Never trade performance for appearance with silencers. Get rid of the standard thing and buy an AX891 from me.

There are several possible causes for the power dropping one of which is ignition timing, what is yours set at?

GC

[ace124]

Timing is set at 36* @ 4000 rpm.
Is the AX891 usable as a rear muffler?

[Guy Croft]

I am sure you can figure out a way of fitting a 2" OD pipe into a 2.25" ID muffler?

G