3100 Downpipe/manifold questions.

[IsaacHayes]

Ok, I've heard there is a 1.5" restricter in the downpipe of the 3100. Is that in the down pipe or cast in the manifold?

2nd question, if one were to unbolt the downpipe from the manifold, and re-bolt up, what gaskets would I need to replace?

3rd, if one were to make a new DP, what do you use to bolt to the manifold? Is there a universal flange you get? Or would it be best to hack up the stocker and remove the restricter, and weld that to your new larger exhaust pipe?

[Guest]

I made my own down pipe using a flared 2 1/2 piece and a flange to hold it to the manifold, you could use the stock flange but you'll still be restriced to about 2" or so... But yes the downpipe is the one with the 1 7/8 internal pipe, that is supposed to quiet down the exhaust system.

Here's pics of mine.



This is a custom downpipe 2 1/2" also with the 3400 tubular rear manifold.

[IsaacHayes]

Nice! where did you get the flange? And did you loose any space around anything with the 3400 rear?

What did you use for gaskets. I see the spring things arent there anymore. No flexpipe needed?

[Guest]

The flange I just got from my uncles shop, it was a 2 1/2 flange that had a slight flared end to it, so putting in a flared pipe worked perfect, I just used the similar gasket that comes on the beretta manifold but I found looking around in the gasket area, one that was a flat back that had a cone style end to fit a flare, but was made from like heavy tinfoil... stronger than the other graphite or whatever it was one.

Didn't lose much space with the 3400 rear, but i did tack a plate to the top of the flange that covers the first bend to protect the rack from unnecessary heat.  I have since replaced the short original manifold studs with the stock beretta ones with a spring but yes I was using a flex pipe and still am... but it makes my exhaust scrape in some places so it needs to go badly.





Blurry but you can see the flex.  It was one of those braided over flex pipes...

[IsaacHayes]

Great thanks for the info. I wonder where a cheap place is to locate a flange like that. (getting ideas for future projects)

Do you think a flex pipe is needed? There isn't one on the stock exhaust, but do those spring bolts allow any movement or is it just to keep them from walking out??

Oh and what have you ran w/o the spray in the 1/4? Wonder what you could do NA with your trans now..hmmm

[Guest]

Never got a good time N/A I don't know why...  The best I got before was a 15.7... so Now I need to break a 15.3 too look good because thats what other 3400's are getting.. with autos too... so we'll see.  Just check an auto parts store for the flange, it shouldn't be that hard to find.  There was a need for the flex before because it was so solid mounted to the manifold, now with the spring bolts it can flex if needed, so I can actually take away the flex part.

[IsaacHayes]

Surely you can do better than a 15.7. I did a 16.01 in august heat with full street trim then some. I know it runs faster in cool temps (boy do I know, fun! lol) So I bet it's possible I could run a 15.7 stock (other than muffler).

After I get my intake manifolds on and wheel air intake, who knows what I could do on this old motor. Unforntunatly, the drag strip closest to me is gone now. I've seen others not run very good after a 3400. I'm guessing its ECM issues not tuned exactly right for it.

BTW how is that trans doing now? I bet it's a blast with those gears now. From a dig is traction a bigger problem now?

No sure how the spring bolts help it move on a solid flange (and not leak) but I guess thats how stock works. What would you ask at the store? They always ask for what vechicle/year.

[Guest]

I just said i need a two bolt 2 1/2 flange, that will fit a flared pipe... remember this gasket has a cone head to it that fits in the flared pipe so it can move up and down and still seal.  As far as the trans, I love the 3.33, I gave a Sentra SE-R something to think about on the highway, and that’s like a first for me.  Traction is not so much a problem thanks to the LSD but still a little... I need to break in the LSD more before it grips really good... Its slipping more now and I think its due to the synthetic I used, so break in may take longer, swapped out the fluid for type f though so it should be diluted enough to start working soon.

[IsaacHayes]

Man, I want your trans. That or a 5spd. You can keep the LSD, as longs as I get the 3.33!!! Highway is usually where my car does best against others. Off the line it's not so hot if the car is geared low and has close to the same power as mine. Didn't think about it but yeah 3.33 would help everywhere! So does the car feel like it has more throttle response/touchy when pulling out onto the road? And also when you let off of it, it feels more connected, because it doesn't coast b/c of the high gear, it slows a little.. Know what I mean? Should feel like the car is always ready to go instead of slowly move, let off, float, press a little on the gas feels mushy... What's the RPM at 70mph? Should help it not kick in/out of OD as much on hills...

Oh & thanks for the info! I guess one would need to measure the spacing for the bolt holes on the flange, unless it doesn't come with holes..

[Guest]

yeah measure that spacing, and you still may need to slot the holes... I had to for the spring bolts to fit through... and i ripped open my pinkie in the process.

As far as the trans yes it feels way more connected, also going in and out of OD is no big deal because at that gearing you want it, and it will also come out in a hurry if slammed.  Around 2200 to 2300 at 70mph.. Not too shabby.  All and all it helped the car wake up alot and was well worth it.  I actually got better gas mileage this last tank and I think it was because before my torque lock wasn't working for a while and now it does, so that helped.  Its well worth the time and money if you know what you’re doing.

[number93beretta]

I've got a 3100 Grand Am SE that I'm building for a stock car in the FWD class.  On my car, I used a hoe saw and a drill press to core out the factory flange from the pathetic factory opening....the flange has been opened up to 2.5" and has a straight exhaust and 2.5" tubing all the way back to where I turned it 90degrees to come out in front of the rear passenger wheel.

It cost me $25 for tubing, $15 for 2 bends and couplings (45&90 degree), $12 for clamps and hanger brackets and $5 for the turn-down at the outlet.  It took 5 hours of my time and lots and lots of cutting and fitting and cutting again untill it was all perfect....no muffler or cat convertor...this car is oval track only.  You could add a glass pack to this same setup so easily and be streetable then.

Once everything was fitting properly, it got tack welded with a wire-welder....removed it from the car and welded it all up.  It sounds wicked, but I haven't had it on the track yet.

I don't have any pics to prove it, but it's on the car now.

OR JUST GO BUY A FART CAN AND GAIN AT LEAST 30 HORSEPOWER!!!!!  Just kidding....RICER MUFFLERS SUCK ***.