ojm3

Hey guys I'm looking to do a custom exhaust using the stock manifold. From the research I've done the stock manifold is pretty decent if you open it up after the couple. Im wanting to know who out there has done this. And how did you do it? I'm thinking about getting a muffler shop to match up two 1 5/8 pipes to the coupler at t the stock manifold, then extend those pipes as far as the stock 1 incher reached. Then have them couple to a 2 1/4 inch coupler. Run 2 1/4 through the muffler, no cat.

babyfood1217

On my last truck, I got a high flow cat and a 2 1/4" muffler, and using 2-1/4" tubing and some adapters, welded up a system from the manifold back. I ended up getting my hands on 22re downtube that been cut off downstream of the O2 sensor, and with measuring and tacking, ended up grafting the 2-1/4" tube right onto the 2-1 merge. Cutting off excess, removing/reattaching the O2 bung, solidly overwelding and adding mounting points (homemade), I essentially recreated the stock routing/angles, but with oversize pipe and fixtures (cat, O2, muffler.)

I was using oxy/acet on galv'd piping (yes it was ventilated), and while it was a little messing, it worked great.

If you can weld (and have access to a ventilated station or an organic-fume respirator), it was pretty fun. Having a muffler shop would be much easier and would likely be pretty reasonable cost wise.

Why not keep the cat though? There are high flow's out there that you would never even notice...

-babyfood1217

ojm3

Idk why but i dont favor cats lol. most vehicles ive had the most restrictive thig that robbed hp, and gas mileage was the cat. granted all my vehicles have been used and it could have been due to just being clogged. But on my last 2 trucks, and 1 car ive eliminated the cat only get have an increase in hp and mileage. Florida has no emission THANK GOD! Ive always wondered if im hurting anything due to decreased back pressure. But then again most performance builds are free flow straight through exhaust with no cat. Im not opposed to installing a new, clean cat. what type are you running?

highonpottery

iTrader: (1)

I just did basically what you're asking for after my CAT got stolen last month. I, too, read that a great setup besides going with an aftermarket tri-y header (like Doug Thorley) is to keep the stock manifold/y-pipe setup (which is also tri-y/4-2-1) because you need the backpressure for good power at lower rpms, and then open it up as far forward on the downpipe/y-pipe as possible to 2" then to 2.25" after the CAT. These days there really isn't any excuse not to run a CAT since the aftermarket free-flow versions are straight-through design whereas the stock are diverted - so do your part and stay somewhat Eco-friendly.

I spoke to the exhaust guy about remaking the stock down pipe (1 3/4") to 2" up by the y-connector, but he talked me out of it because of the differences in quality of steel used on the old pipe vs the new stuff. Ended up jumping up to 2" about where your feet are, so tranny area or maybe 12-18" before the stock CAT flange. My CAT is a Magnaflow 2" that you can see straight through. CAT back is 2.25" with tucked up routing exiting in stock location. Muffler choice was a Magnaflow turbo-style because its a straight through design that isn't obnoxiously loud or tinney like a flowmaster sounds. Flowmaster is a diverted design, so the turbo muffler is actually freer flowing.

Out the door my exhaust was $500 because he had to do extra work on installing 2 o2-sensor bungs (wow!) but I am very happy with the price paid because it was still cheaper than 5 other shops. Sound is quiet like I wanted but noticeably deeper over stock. Power is definitely increased over stock and can be felt on the "butt dyno", especially 2nd gear from a stop. Hwy cruising power is also noticeably increased and I'm hoping for maybe 1mpg gain due to the free flow. Overall I am VERY happy even though I was forced to upgrade and its too bad I didn't do this earlier.

Good luck!

ojm3

I think im going to do a bit of what both of you are saying. im going to get some tubing and extend coming right off of the two outlets on the stock manifold. The outlets have a 1/8 inch shelf inside of them where the gaskets sat. The actual size of the two exhaust openings on the manifold are really only 1 1/4 inches in diameter. So ill get some 1 1/2 inch tubing to weld into that, extending down at an angle till just below the cab, just as most aftermarket headers. Ill find a muffler shop to weld on a 2.5 inch collector at the end of the 1 1/2 inch tubing. Ill then put on a 2.5- 2 1/4 inch collector reducer into a magnaflow cat, to a cherry bomb exhaust out the back.