FAQ: Down Pipe Questions (Series I SC)

just got mine, and after looking around for awhile i found a shop that will be willing to take the cat off for me which i will be taking in tommorow.

The 3in shorty will not hook up to the 95's where you bolt it up to is too wide no im stuck with the cat off and only the stock downpipe not even hooked up the the rest of the pipes which i need to get. i treid driving around and it wasnt a good experince lets just say your going to need earplugs. i think im just going to have my friend drive me in his car to get the pipes.

hey im new here done alot of lookin around and learned alot of stuff. must say this forum is a great place. i use to have a riviera but my brother totalled it, before i got to see its potential. ended up getting a 95 park ave ultra from my grandfather and looking forward to modding it. i have already made a fwi. next step is 2.5 pulley with 104's. i will be getting a downpipe i just dont want to spend tons of money.
would one of these fit a series 1 in the park ave ultra? or would i be better off getting a custom one made? if custom what do yall think the price range would be?

http://www.wbodystore.com/grandprix/3-downpipes-3800-v6-new-options-p-239.html

or the zzp 3" shorty?

I'm afraid I can't help with the downpipe, as I don;t know. However you might want to consiter this article before just dropping your pulley to 2.5"
http://www.pontiacbonnevilleclub.com/forum/viewtopic.php?f=44&t=1660

what scan tool do yall use. all i see is one on seriesoneperformance.com or whatever but the link is dead. i have the obd1.5 case so i need one that will work. im looking into sinister performance's tune. not sure if anyone has any opinion or feed back on there tunes. it would help. thanks again

I have a 96' riviera. I want to get a 3" DP, what would be the best thing to do?

texasfan010 wrote:

I have a 96' riviera. I want to get a 3" DP, what would be the best thing to do?

ZZP 3" Shorty.

L67 wrote:

texasfan010 wrote:

I have a 96' riviera. I want to get a 3" DP, what would be the best thing to do?

ZZP 3" Shorty.

and have a local shop weld it in.

which one do i buy, the bonniville one?

So i have a question..how do you gain flow by going to a 3 inch down pipe when the opening at the mani is still the same? When it warms up outside i want to redo my whole system, so im trying to all the info and parts now..i dont mind welding and cutting..

i think the system,once warmed up,the exhaust velocity speeds up.i could be wrong though. imo,its probably smarter to replace the entire length of pipe to 2.5 or 3". the 95 headers are really restrictive and we cant buy a quality header system for our year to benifit more from complete exhaust mods. with the 95 you have to customize everything....hows that grab ya?

Well i guess ill start with the 3" dp and go custom from there. thanks for the help.

95rivy wrote:

Well i guess ill start with the 3" dp and go custom from there. thanks for the help.

i didnt know they made one to fit the 95?

I just thought someone here made one fit from zzp..from the bonneville i think..but any way since we cant do headers on our year, is it worth doing a bigger down pipe?

How could you attach a 3 inch downpipe to the manifold if it is set up to hook up to a 2.5 inch down pipe? does that flange taper off to a 2.5 diameter?

I was under the impression that the series 1 rivs and the series 2 had the same downpipe, and that the zzp downpipes would fit the series 1, is this the case?

95rivy wrote:

So i have a question..how do you gain flow by going to a 3 inch down pipe when the opening at the mani is still the same? When it warms up outside i want to redo my whole system, so im trying to all the info and parts now..i dont mind welding and cutting..

You will see a gain because having 18" or so of free-flowing 3" downpipe is better than the 2" version installed at the factory. Doesn't matter if it's choked in upstream. Every inch of restriction adds up; every inch of free-flowing exhaust (especially upstream) increases horsepower.

So did we ever come to a conclusion on what d/p will fit a 95 s/c riv?

I am confused. does the 3 inch shorty fit on the 95 riviera? I was hoping it would bold up to my rear manifold and then i could have the other end welded without a cat

it will not "bolt up" but it should fit. The same thing with the 96's. The flange was changed on the 97+ cars. You will need to take it to an exhaust shop to have them install it but it can be made to work with little effort.
My shop had to either remove the cat or move it down. I chose to have it removed because FL doesnt do emission checks.

how does the exhaust shop get the flanges to line up? do they weld a different flange on to the shorty?

it lines up well enough to bolt at the top. There is a difference in doughnut gaskets used and i really dont remember all the details (it was 4 years ago for me) any exhaust shop can install it for you or if you know how to weld then you can do it yourself. Just dont order it expecting it to be a bolt-in application.

I wouldn't use the flanges. If you're going to be cutting and welding pipe, just weld in a venturi reducer like this one:

i was referring to the upper flange (only one on the 96's). I think the 97+ rivs had a rear flange like the w-bodys.
regardless, that reducer is a good way to join the rest of the exhaust system to the DP.

Awsome! i was thinking i would need to buy a reducer. How much would you expect to pay to have the downpipe attached to the manifold and the reducer to be welded in at a muffler shop?