FAQ: The Exhaust Thread

So has anyone ever thought about welding up a custom 3 in down pipe for a series 1? I was thinking that you could weld 2 elbows( I think probably 2 45 degree elbows) together with one of those flex couplers in the middle. You could then weld the correct flange for the 95 rear manifold, and weld the other end to the catback. Just an idea, something i may possibly work on with a friend this summer.

Something like these s pipes may also be helpful
http://www.jegs.com/i/Flowmaster/389/15927/10002/-1?parentProductId=810783

An even greater flow gain would be to put your talents to fabing up a set of headers.If you have a welder and a box of exhaust parts you can make 'em.
The series 1 headers or exhaust manifolds,are ultra restrictive.

I also considered this option, but what type of metal needs to be used for the headers, and do you know who sells reasonable parts to make headers?

I've always though the most cost effective option for series one headers would be to take series 2 headers, cut the flanges, and weld on series one flanges. One primary would need to be shorteded, and one lengthened to make the siamesed ports, IIRC. Then you know that they will physically fit since its not really new putting series 2 headers on a riv, and no re-inventing the wheel.

That's a good point Karma, that kind of crossed my mind as well, but really i was considering creating a down pipe over headers, because of the cost. I just really don't have the funds to spend over 700 on anything right now. I was hoping that a 3 inch down pipe would help to open up some more power for the series 1, and possibly lower kr enough to run a 2.6 in pulley.

I've looked over the whole system.Its not the front manifold that ReaLLY needs modification or the down pipe.Its the rear header that strangles the system.
I ported both the front and the back and that helped some.The easiest option would be to fab a "Fuel log" at least thats what ZZperformance calls em

http://shop.zzperformance.com/store/p/92-304-Stainless-Power-Log.aspx

They go on and on about the front manifold being the main culprit in the strangling but they dont make a rear log. making a rear manifold is doable. they dont do it because theres very little space.But it can be done.it will be a shorty for sure but it can be done.

here's they're offering for the rear.with a core charge.At least they are doing something but still,they only offer the log for the series 2. you might be able to talk them into porting a series 1 but its stupid easy to do and only takes a couple hours and about $10 bucks in sanding rolls.

That would be an interesting idea as well, i am pretty set on making a 3 in down pipe, but i think one of those rear manifolds may be a possibility as well. It is strange, i keep hearing conflicting information about series one exhaust manifolds.I have heard some people on the bonneville forum say that they flow a lot better than the series 2s and i also read the same on this forum http://www.a-body.net/forums/showthread.php?1091-Series-I-3800-headers-do-they-exist

In a nutshell, stock s1 is better than stock s2.
A ZZP p-log is better than the series 2 front manifold, but barely better than the stock series one front manifold.

The closest headers that fit are for the GN, but the engine is the wrong way around, and the bolts are very slightly different than the 3800 series one.

To make a front/rear manifold set you would have to make a jig to work from.In otherwords you would make and actual attachment jig that the stock mani would bolt up to on a bench.Once you have all your bolt locations lined up you could start piecing together from raw tubing the manifold. Sounds easy but it aint.lotsa work.

I think a more doable idea would be to have the rear manifold exit out the bottom and run into a 2 into 1 pipe to meet the front manifold instead of ramming into the crossover pipe @90deg.thats collision right there

I also think this would be a good way to go. A hand formed sheet steel manifold. lotsa work too but nice

http://www.dragtimes.com/parts/FERRARI-F430-430-LEFT-SIDE-EXHAUST-MANIFOLD-HEADER-OEM-FACTORY-NO-RESERVE_160708349288.html

Gee..do ya think the Ferrari manifold would fit our car??

So it sounds like i should work on fabbing up something for the rear manifold and down pipe. I just don't see how i would make a power log for the rear, because each of the pipes in the rear shoot straight back instead of to the side like in the front. Any ideas? I would like to attempt this. I really don't feel comfortable dropping pulley sizes without some sort of a kr reducing mod. That is a good idea robo, to modify the crossover and the rear manifold to exit into a 2 to 1 pipe.

You should be able to drop SC pulley a bit without doing headers. Downpipe is the biggest restriction, imo. That shouldn't be do difficult to fab up.

If you pick a manifold to replace, I'd do the front side. The rear (at least on Series II) is pretty much like a header in stock form. This is why they created the Power Log. Others have bolted on a front only header and connected to the crossover - in your case you'd need to make the front side header, but that's easier than a full set.

Our point AA is,The S1 front mani is A-ok. not that big of a deal regarding flow.Its the REAR that keeps us up at night.

The SI front mani looks like this:



I can't find a picture of the rear, but how is it any worse? I also don't see how the front would be "A-ok" with such unequal tube-lengths and those near right angle bends.

It is ultra restrictive. This is not it exactly but the closest I can find

http://www.ebay.com/itm/GM-BUICK-3-8-S-C-SUPERCHARGED-EXHAUST-MANIFOLD-RH-RIGHT-SIDE-/221019117620?pt=Motors_Car_Truck_Parts_Accessories&vxp=mtr&hash=item3375c41834

Yeah, the series one front manifold has easily twice the flow of the stock series 2 one. (I did a P-log on the wife's 98.) Improvements would be the rear and downpipe, which is why for the fabrication required anyway, IMO why not modify series 2 headers for the job. You can mess around with porting, or custom fabricating something, or find a used set of series 2 headers. For the price of series 2 headers, you would be hard pressed to buy the material, let alone make something out of it. If you are going to DIY, every joint you put in would be a flow disruption. Whereas with modifying series 2 headers you can keep the majority of the mandral bent shapes, just adding in the changes. 300 bucks can get you a new set of s2 headers, nevermind about a used set. That does most of your fitment research, and comes with a downpipe anyway. IMO that would make the most out of money spent.

Edit: AA the bigest issue with the s2 front manifold is where it folds down right off the heads. The cross-sectional area halves. The s1 front manifold has better transitions and is closely related to the ZZP p-log. And the rear is really not too bad, but if someone was looking for room to improve that would be where. .. though to repeat myself, money, effort, and time spent I'd adapt s2 headers.

Okay, so the front mani is ok, but the rear mani robo posted doesn't appear bad at all. Looks very similar to the SII rear - more like a true header because the primaries are equal length and dump into the collector at the same point. This should flow pretty well.

If the front isn't so bad, and the rear is what it appears to be (basically a header), I wouldn't rule out the possibility of the SI stock manifolds being not too restrictive as-is. Imo, focus on improvements elsewhere first, unless you just like the idea of having headers, and a bit more noise and heat under the hood.

(It was acutally a s2 rear he posted. you can tell from the EGR port that doesn't exist there on the s1.)

But IMO the rears are not too bad either. The early LN3 rears were *terrible* though. Just a hole blasted into the pipe with a plasma torch, and the pipe welded against it.

Hey Karma youre idea sounds great. I'll look into finding a set an dope it out...

Ahh, okay. On the SII, some folks would keep the rears (ported) and replace the front with a header. If your front is better flowing, it would seem the SI system as a whole outflows S2 possibly?

Assuming they perform okay. I'd keep'em on unless there are no other mods left to do. Has anyone replaced the downpipe to see what gains are had?

Ideally it will take some messing around with an engine on a stand, cause the deck height difference on the series 1. That will change how far apart the front and back banks are, and what angle the primaries leave at. I was hoping to have a go at it this summer but if someone gets to it before me all the better. My guess I'll be doing it this fall/winter.

Edit: the stock s1 downpipe is 2.5" fyi...

Edit edit: now here's some manifolds(LG3)


and s1 headers for a different car:

In the first pic (LG3), I can see how the fronts would flow better than the rear. Rockauto's picture for 95RivSC is different. Are the rears any better on the 95 Riv compared to your LG3 pic?

2nd pic is how it's done!

MMMM lovin those headers.

what kind of car does that last engine pic come out of?