I had ordered a ZZP downpipe for the 2006 Grand Prix GXP a while back. Finally got around to install it yesterday, but discovered it won't fit. The rear flange appears to be wrong. The bolt holes don't line up. Looks like about a 1/8" off (bolt hole centerline needs to be a little wider). Anyone else have this problem? Trying to decide if I should just elongate the holes myself or send it back. Not sure if a dremel would work since the flange is fairly thick.

 

This is true, I just ran into the same issue. The bolts on the stock flange do not match up with the ZZP one. The stock studs are wider. My fix would be to remove the studs and modify the stock piece.

If you are going to hook up to an aftermarket exhaust, the ZZP one fits fine. It fit perfectly with the Magnaflow cat back. Luckily, I had the MF cat-back already and just put it on instead of the stock. Not to mention it sounds bad *** with the MF

 

I found another post about needing to gind out the bolt holes on the rear flange.

I didn't think about removing the studs since that required more work under the car. Will the studs punch out easily or do you need to grind them off and drill them out? I'd rather mod the new downpipe flange so I can put the stock downpipe back on in the future if I want to demod.

My wife wants a Magnaflow catback. If the ZZP downpipe fits the Magnaflow catback, then I know what she will want to do. Means I'll be spending more of my hard earned cash.

 

I had to grind out my studs on my stock catback for my ZZP Downpipe. Just repalced with some Grade 8 bolts. I will say, the gasket they give you, leaks. At least mine does.

 

Are the middle flange studs pressed in or tack welded on? From the pic, it looks like you ground the stud head off. Then you just punched it out?

I'm still leaning towards elongating the bolt holes on the new downpipe. That way I can easily work on the new downpipe on the bench and have it all ready for minimal down time when I pull the old one off (I reinstalled the stock pipe for now). I'm gittin' too old to do a lot of work under the car with it up on jack stands. Wish I had access to a lift.

 

I don't understand you people.

Send that **** back! Tell them to fix their shoddy work. Nothing sends a better message than that.

If I buy a part that's supposed to fit my application, I actually expect it to fit without issue.

 

Mine were rusted, fused and broken. I had no choice but to grind it off. But yes, grind and punch out. It also made install easier that trying to work around the studs. My Grinder made sort work of them, had them out in like 10 minutes.

 

I ground and punched as well, just seemed easier. Meh, I'll notify them of it not fitting 100% to stock but I wouldn't send it back when the means to make it fit were right in front of me.

 

Ran into this also.. I just ground out the holes a little. problem solved..

 

I did attempt to post a review on this, noting the stock fitment. It has yet to be approved hehe. Gave it 4 stars since it does work as it should, just the fitment is slightly off.

 

I got it on finally. I used a Dremel and grinding stone to elongate the bolt holes/slots. It took a while since the stainless steel flange is pretty tough stuff. I'm a little irritated to pay good money for a part and then have to mod it to fit. But, I did not want to hassle with sending it back. Oh well, it's installed now. Time to get this beast tuned now.

 

Same here when putting the zzp downpipe on my Lacrosse Super. Bolt holes are off and would not line up to mate to stock exhaust. I did not want to elongate the holes as it looked that there would not be enough material. So I had the exhaust shop weld a new flange on stock exhaust to mate up properly. I am sending zzp the bill. I agree that this should not be an issue. Let alone that all of us had problem....its obviously never been addressed and they must know. I had a Hogan down pipe at one time and no issue, bolted right in. Anyone elses down pipe sound like it has an exhaust leak? I can't seem to find it and just wonder if it is just resonance due to no cat.

 

i grinded holes on flange plenty of meat there

 

Probably the flex section. If its not a double walled flex you'll have that sound.

Hope you're getting a tune too. Your car will sound like *** until the cat codes get turned off.

 

Not sure if I missed this but I'll add that the downpipe fits the magnaflow cat back just fine. Just not the stock pipes.

 

Update...ZZP refunded the cost that I incurred to have an exhaust shop correct the flange issue ($31.80). ZZP advised that they are addressing the issue with the downpipe flange when mating up to stock exhaust.

 

Any exhaust leak before the o2 can cause a false lean condition and cause your car to run rich fyi

 

Had great luck with mine on 06 impala the noise isn't noticeable if did is turned off below 45 I already had MagnaFlow cat back installed but had to re straighten the whole rest of the system as the zzp downpipe directed the rest of the exhaust to the passenger side...actually melted my rear bumper cover the 20 miles it took to get home but got rear ended 3 days later, the only good luck I have had in a long time. There is an alternative to having a tune done to keep cel light off if you order it with rear o2 censor bung it's A little piece that has the heavy metals in it so any gasses making it to the o2 sensor are catalyzed can't find the link now but let me know if you need it I am sure I can find it it only costs about 30 dollars.. definitely a really low end and very top end improvement to eliminate the cat