At the bottom of this post, is a drawing of what I plan to do to the OEM N/A Header pipe & a pic of what the difference in length is between(both n/a) a Volvo OEM 1982 B21F header pipe and a 1991 OEM Volvo OEM B230F header pipes in the length of the secondary pipes & the difference in length of the collectors.
I have a new Starla 1991 style header pipe that I am going to have modified to the specs of a 1982 B21F header pipe, and make the collector 2.50 inch diameter.
Then use a new 2.50" in/out MagnaFlow cat(part number 53006) behind the collector. This is still a OEM sized body on this cat, so it'll fit in the recess of the car's floor like OEM one does, for added ground clearance. Because this 240 will be lowered on IPD Sport Springs.
The 1991 cat had the OS bung made into the upper, driver's side right behind the cat inlet at about 30 degrees from top center of cat. I'll have to have an OS bung welded into the 2.5" collector in about the same location. So that the OS wires will reach the OS, but still pop into the OEM plastic OS wire "holder.
Also, if the only mandrel bends muffler shop I will be dealing with can make my collector like the KGTrimning's B230 header collector at not too much more expense, I'd like to have it made like in the small pic in left lower corner of my header pipe mods drawing. Again, for added ground clearance on a lowered 240 sedan.
Now.... here's where I'm not positive of what/which, I should do next....maybe someone can tell me which would be best.
I'm leaning toward the 2.25" pipe, from cat back to 2.50" MF muffler, and a 2.50" tailpipe.
I'm figuring the worst restriction was the OEM 2" collector, which will now be a 2.50" diameter collector.
And the 2.25 pipe from the cat back to the 2.50" muffler will give me some needed "back pressure" to help bottom end torque even more.
Flowmaster specs say 2.25" pipe will support 150 HP. But how true this is I dunno.
I figure even with a higher lift cam, I'd be lucky to be making 145 actual HP. OEM 1991 B230F is rated at 115 HP IIRCC.. So a cam change will net me maybe 20hp?
From the cat on back , I'll can go with 2.25" diameter pipe to where the IPD Sport Exhaust starts (where the OEM resonator was), and use the IPD Spt. Ex. under axle pipe, and let it feed into a Magna Flow 6" round X 18" long, 2,50" inlet/outlets.
I'll have to have a 2.25" to 2.50" "step up" adapter to mate the IPD Sprt Ex. to the 2.50" in/out MagnaFlow muffler. The have him make me a 2.50" L shaped tailpipe, and weld on my 2.50" to 3" MagnaFlow SS exhaust tip.
OR GO THIS ROUTE............................................
I can have the shop make me up a 2.50" pipe from the cat, back to the 2.50" in/out MF muffler, in which case, I'll probably go with an over the axle pipe design. And still have th 2.50" L shaped tailpipe out the rear of car.
There are a couple of other MagnaFlow mufflers I am considering on using. One is a 22" long offset oval, but it may be too tight a fit. So I may end up having to also use a small MagnaFlow oval mounted in the OEM resonator location.
Depends on how loud the 18" long ,6" round MagnFlow muffler is. With 2.50 cat back system, I'm told 2 mufflers will most likely be needed.
Now.......... my B230F is LH 3.1 . And a little better street type camshaft install & maybe/possibly installing greentop injectors, if needed, are the only & all the mods I plan to ever do to the engine itself.
And I am after good torque & HP from 1500 rpm to 5500 rpm. With 5200 most likely the rpm limit most times.
I am not after peak HP only. I want good torque & HP all through the rpm range. After all, It's a street only 240 I'm not wanting a "race cam". I want a good running street cam.
With my planned header pipe & collector mods, and my current stock B230F engine with M cam(I know), and a future planned V,VX or RSI n/a cam very likely, would I be better to stay with the 2.25" cat back pipe to the IPD under axle pipe system, then to the MagnaFlow 2.50" muffler & tailpipe??
Or would I be better to go with 2.50" from the cat back, all the way to rear of car?
Remember now... It's LH 3.1 & a little better street type camshaft install & maybe/possibly installing greentop injectors, if needed, are the only & all the mods I plan to ever do to the engine itself.
PICS BELOW....................................