The junk exhaust on my '68 seems to me like 2". Obviously not going to be enough for my engine. The engine is a BBC 454, hopefully will be ~500HP, with 1 7/8" Hooker Super Comps. I'm trying to figure out what I should run for exhaust, 2.5" or 3". I've read that 3" is a hassle to run as it wont fit through the trans crossmember, but I know norval and gkull have gotten around this.

Thoughts? Thanks. :flag

 

I'm running 2.5" and an X pipe with 540hp...


[Modified by StingrayRacing, 4:39 PM 9/18/2001]

 

What if I have a 4-spd man?

 

I'm not sure what it would take w/ a 4 speed, so I can't help you there. As for size, just understand that 3" pipes will be noticably louder than 2 1/2" pipes. It depends on how you want to use the car as to whether the extra noise is a factor to you. Another option would be using 2 1/2" mandrel bent pipes- they flow alot better than regular 2 1/2" from what I've read & may offer the best of both worlds.

 

A good 2.5" should be fine for your car. I just replaced the 2.5" with some 3" on my 700+ HP 540" motor in my '67 and really couldn't tell a huge difference. I used the same 2 chamber flowmasters. I was running 11.20's at 123 mph with the old 427 in this car through the 2.5" pipes.

The 3" will fit if you find a good muffler guy. He will cuss some but it can be done. The biggest headache is usually what to do with the connections at the rear by the spare tire carrier. I don't carry it so it's pretty easy to do and the pipes look killer from the rear. Ground clearance hasn't been an issue, in fact this guy did better than the guy did on the 2.5 system.

They will go through the crossmember, it's just tight. If you have good hangers it won't rattle.

I suggest leaving the whole system in sections so that it can be removed later if needed. If you weld it all solid your stuck with cutting it apart later. I used band clamps to join the sections together and they work great, They are a flat piece of strap metal made to wrap around the pipe and then tighten together with the two 3/8" bolts on them. You can get them at truck supply houses for about $6-7 each. This also allows you to remove the forward section and uncap it if wanted at the track.

I didn't notice much noise change... in fact it sounds "smoother" if anything with the 3" pipes.

Jim

 

427Hotrod, thanks for the great info. I guess I'll see what the exhaust shops around here can do for me for prices. All the spare tire stuff on my car is missing, and I'm not gonna replace it, so I wont have that either. Sounds like a 2.5" Mandrel bent or a 3" are about the same, seems like it just comes down to what you want to spend.

Thanks!

 

I have 2-1/2 mandral bent pipe on my '64 with Dynomax stainless ultraflow mufflers and a 2" crossover and love it. I also have 2-1/2 angle-cut tips! (Even the stock 2-1/2" pipes had 2" tips.) The 2-1/2" tips look NASTY (but require more careful centering) and why invest in a larger system only to have it corked up at the end?

 

I easily modified the stock crossmember and ran 3 inch straight back. I agree with the extra noise but I wanted the full 3 inch.
Norval

 

For your combination I'd use the 2.5". Mandrel bent. It should flow plenty and make more torque throughout the powerband. Remember, bigger is not always better. My car is in the low 12's running through a single 3" pipe.
Of course if you plan on upping power in the future even more you should probably go bigger and be ready.
Good Luck!
:cheers:

 

DDN. DID YOU EVER THINK ABOUT SIDEPIPES. UNLESS YOU HAVE TO HAVE UNDER THE CAR PIPES, ITS A GREAT WAY TO GO. JUST A THOUGHT !! JCL :cool: :chevy

 

How well does 3" sidepipes work (performance wise)?

 

BIFKIN. THE ONLY 3" SIDEPIPES I KNOW OF ARE THE THRUSH STYLE. SAW A C2 AT CARLISLE WITH THEM ON. LOOKED PRETTY GOOD. WOULD HAVE LOOKED "BETTER" (MY OPINION) WITH 4" PIPES !! IF YOUR LOOKING FOR MORE PERFORMANCE I BELIEVE 4" WILL BE BETTER. THERES A POST ON THE C3 SECTION CALLED "LET ME SEE YOUR PIPES". GOOD PLACE TO LOOK AT DIFFERENT COMBINATIONS. JCL :cool: :chevy

 

I studied this question a bit a month or two ago... asked a lot of questions, read a lot of articles. My conclusion was basically going on Flowmasters recommendations:

They say:

dual 2 1/4" pipe up to 320 flywheel HP
dual 2 1/2" pipe up to 400 flywheel HP
dual 3.0" pipe up to 600 flywheel HP

They were not saying that a 500 HP motor would run bad with 2.5" pipe, they were simply saying it would run a bit better with 3" pipe, or in otherwords 510-520 with 3.0" pipe vs 500 with 2.5" pipe.

I personally do not know how accurate this is, I'm sure Flowmaster in theory knows what they're talking about, or at least moreso than me... but I'd guess different motor combinations would react different to the larger pipe regardless of the HP. With a big cube motor like yours, I'd guess you'd run good with 2.5" pipe, but if you're a dedicated racer looking for every last tenth out of your set-up, sounds like 3" pipe might give a few extra ponies.... but dunno for sure.

good luck
Beach

 

JCL,
I haven't bought my headers yet. What sould a Hooker sidepipe setup cost me? Before I thought I could keep my undercar exhaust. Now that I realize it has to get replaced too, I am seriously thinking about going with the bad butt sidepipes I always wanted.

Straight back, big pipe, no cover...what's it cost?

 

ddn I just went through this myself. I have a 69 with a 502 and wanted undercar exhaust so I bought the hooker supercomps with the 2 1/8 inch primaries and was going to run 3 inch exhaust under the car. Well I got the headers on and found I had about 2 inches of ground clearance and they would bang the floorboard with every bump. So I licked my wounds and bought the Hooker sidepipe headers from summit for $535 for just the headers and bought the sidetubes and baffles (mufflers) from JCL. I gotta tell you I love this system. There is less heat in the cockpit with the side exhaust and I won't have to drop the exhaust to work on the car and no ground clearance problems. The sound is awesome and they do seem to flow very well. The price for the headers was for black and maybe this winter I will send them off and have them ceramic coated. I am really starting to like the mean look of the sidepipes too. Hope this helps.

 

Hey 69ttop502.....

Wanna make a deal on your old 2 1/8" hookers?

JIm

 

Sure Jim e-mail me at kvanorma@aol.com. I have them listed on the c3 parts for sale forum. We can make a deal.