Non mandrel bent exhaust?

-
Q

qwk dust

Well-Known Member
Joined
Feb 7, 2008
Messages
124
Reaction score
1
We are in the process of building our 318 fun motor. The set up will be a .030 over bore with KB 167s, 302 casting heads with 1.88 1.60 valves, cleaned up and gasket matched to Hooker comp headers and an Edelbrock RPM Air Gap with a Holley Street Avenger 670. We are strongly considering the Comp XE274 cam but have not fully decided yet. The rear end is an 8 1/4 with 3.90s and the trans is a 904 which will be rebuilt and a transgo kit installed. We are waiting on the torque converter selection until after the motor is finished and the cam selected.
I like the sound of the Spintech mufflers that I have heard and am considering them. My question is....Instead of running a 2 1/2" mandrel exhaust can I run a 3" non mandrel bent exhaust and get close to the same backpressure. I don't want to lose the last little bit of a bottom end the little teen might have by using too big of an exhaust but I do want her to flow well and I do want the sound... What do you guys think? 3" non mandrel is much cheaper and more readily available. Does the non mandrel neck it down enough to keep it close to a mandrel 2 1/2? Thanks
 
Nobody knows the flow difference in mandrel v regular bends for exhausts?
 
Ok....For a Naturally Aspirated 318, 2.5" Crush Bent will be overkill.

2.5 Straight Pipe has the flow capability to handle 350hp through (1) Stick of 2.5" Pipe.

x2 would be sufficient for 700hp before it becomes a restriction.

How would I know?

I have stuffed 350hp through a single stalk of 2.5" Pipe...thats how...13.31 @ 106 through (1) 15' stick of 2.5 Aluminized Pipe.

I then upgraded turbochargers and blew 380hp through a single 3" pipe to go 12.77 @ 113 on pump gas.

So, My recommendation for your setup includes Dual 2.5" pipes with a "X" Scavenging Cross Over....It will fit and go over the axles better and fit INSIDE the leaf springs to the bumper if you so desire.

Good Luck.
 
Prine, thanks for the response. Our motor should make close to 400hp off the spray and then we are planning a 100 shot. We should be very close to 500hp on the bottle. I know we want/need 2 1/2 mandrel bent at a minimum. My question is what is the flow difference between 2 1/2" mandrel and a 3" regular bend?
 
The problem here is the answer isn't exactly in stone due to the pipe bends. Where they are, how crushed they are. The big tube is a problem no matter what and/or where the bends narrows. It's still a 3 inch sewer pipe.

A simple semi temp soultion is a Jegs or Summit exhaust. Very cheap, but a true dual. I have a Jegs system on my Dusters teen. You can add an X in it later on. The true dual isn't as powerful as a X system, but will allow for lots-o-power.

Click here, it's in there somewhere; http://www.forabodiesonly.com/mopar/showthread.php?t=10508&page=1&pp=20
 
i've heard that mandrel bends are worth 10-12% better flow than traditional bending. A good exhaust guy shouldn't "over"crush regular pipe, soo my .02
 
manrel bent is the wany to go hands down for me...each ripple can restrict flow...it starts adding up...if you dont care to pull every ounce of performance from your car...it might not be worth getting mandrel bent done...
 
I imagine the amount of restiction could be calculated if the degree and
number of bends where known.
Is there a reason you have to go with a kinked pipe instead of a mandrel bent pipe?
I think the turbulence in the gas flow is more a problem than the restriction
of the pipe.
I have to vote with rumble and Prine, I'd do the 2.5 jegs pipes.
That is what I have for mine, if you need a pic of the system mines
still in the box and I could get you some.
 
There is really no reason that I would have to go with a non mandrel bent set up other than it can be done locally by a regular shop and a little cheaper since I don't want to get the mufflers with the pre made kits. I just wondered if 3" crush pipes flowed close to 2 1/2" mandrel. It sounds like the strong concensus is just to go 2 1/2 mandrel from Summit etc.
 
Call Jegs/Summit and ask for a sub. on the mufflers. I do think the Summit kit can be had without mufflers for just this purpose.
 
You must log in or register to reply here.
-

Back
Top