Redslaya Posted November 3, 2014 Share Posted November 3, 2014 SO i have a full 3" exhaust system coming in a few days, and as far as I can tell it only has gaskets to attach the mufflers and the y pipe to the mid pipe. I still have the stock DP, which is 2.5". I was wondering what kind of gasket i would need in order to do the install from the 2.5" dp to the 3"mp properly and not have a nasty exhaust leak. As it appears my bolts that are on the stock system are so far rusted ill need to cut/break them off, so what replacement bolts do you guys recommend, just some more OEM ones or is there a better 3rd party alternative. thanks! Link to comment Share on other sites More sharing options...
Max Capacity Posted November 3, 2014 Share Posted November 3, 2014 Grimmspeed makes a 2X thick 3" gasket that I use for my 3" dp to stock mid pipe. PM "underdog" and have him get you one. He may have some thought's too. Just get any 8mm or 3/8" bolt nuts and washers that will fit. It really isn't that important. If your new to this, get some PB Blaster and anti-seize compound too. 305,600miles 5/2012 ej257 short block, 8/2011 installed VF52 turbo, @20.8psi, 280whp, 300ftlbs. (SOLD). CHECK your oil, these cars use it. Engine Build - Click Here Link to comment Share on other sites More sharing options...
Redslaya Posted November 3, 2014 Author Share Posted November 3, 2014 Grimmspeed makes a 2X thick 3" gasket that I use for my 3" dp to stock mid pipe. PM "underdog" and have him get you one. He may have some thought's too. Just get any 8mm or 3/8" bolt nuts and washers that will fit. It really isn't that important. If your new to this, get some PB Blaster and anti-seize compound too. so for the double thick gasket can i just turn it around for the stock DP to 3" mid? and thanks for the quick reply Link to comment Share on other sites More sharing options...
iNVAR Posted November 3, 2014 Share Posted November 3, 2014 No, a 2.5" round fitment (donut) may not mate up properly with the 3" flat flange. They have an adapter that is for 3" DP to stock catback (round) but you have the reverse of that. I don't know if the adapter can be flipped around and used the other way or if it'll create nasty turbulence. http://www.fredbeansparts.com/3-inch-downpipe-to-2-5-inch-cat-back-exhaust-adaptor-738.html Link to comment Share on other sites More sharing options...
Redslaya Posted November 3, 2014 Author Share Posted November 3, 2014 If anyone who has done stock dp to 3" catback could chime in that would be great Link to comment Share on other sites More sharing options...
magnusonsubie Posted November 3, 2014 Share Posted November 3, 2014 I ran it for a little while before I got my 3" downpipe on and I was able to just mate the flange of the catback up to the donut gasket of the stock downpipe no problem. I had to get new bolts though since the stock ones were too large to go through the wholes on the flange of the catback. 2005 Vader Wagon Material Tests on Ringland Failure Piston I should have held off and purchased a wagon instead of the spec.B Link to comment Share on other sites More sharing options...
Underdog Posted November 3, 2014 Share Posted November 3, 2014 PMed but I'll post it here too for reference. To mate an OEM-style DP (Cobb also uses donut gasket interface) to a 3" aftermarket CBE you need Grimmspeed adapter #077046 and a new Subaru donut gasket. The adapter comes with hardware and a 3" gasket, so this is all you need to get the DP and CBE to mate up. The other adapter (#077044) is for a 3" DP to an OEM-style CBE and it can't be used in reverse. With this adapter you also need to purchase both gaskets as they are not included. Last thing worth mentioning is that the GS adapters come with rigid hardware so you will not get the benefit of system compliance at the donut gasket that the spring-loaded bolts provide. For this reason I only recommend using these adapters if you also have a flex section on the tail end of the DP or at the front end of the midpipe on he CBE. The Crimson Dynamo Link to comment Share on other sites More sharing options...
BHanz34 Posted November 6, 2014 Share Posted November 6, 2014 Get a grimmspeed Stock 2.5" DP to 3" catback exhaust adapter. I did it. Ran it for awhile till I got a 3" DP too. Its like $40 Link to comment Share on other sites More sharing options...
chrish8r Posted November 7, 2014 Share Posted November 7, 2014 I just installed one of the Grimmspeed stock dp to 3" catback and it works very well. It comes with a 2 bolt gasket. If your donut gasket is bad, you will need to order a new one to use with this kit. Installed on my Megan Racing exhaust. Link to comment Share on other sites More sharing options...
chato Posted November 8, 2014 Share Posted November 8, 2014 i was never able to get the grimmspeed adapter to seal up correctly on the flat gasket side, even with high temp RTV. ended up just turning the donut gasket around and it sealed at least as good as the adapter. Link to comment Share on other sites More sharing options...
chato Posted November 8, 2014 Share Posted November 8, 2014 speaking of which, I have an adapter and fresh flat gasket that I'd sell you Link to comment Share on other sites More sharing options...
Redslaya Posted November 8, 2014 Author Share Posted November 8, 2014 I got all the parts in and am trying to remove the stock catback (which has 113k miles of north eastern rust on it) and i cant seem to find the right socket size. ive tried 14mm which appears to be just a little too big and 13mm is a little too small, does anyone know what the right size is? even then ill probably have to use an angle grinder to get them off, they are basically fused to the flanges Link to comment Share on other sites More sharing options...
magnusonsubie Posted November 8, 2014 Share Posted November 8, 2014 One side is a 14mm and the other is a 12mm on the spring bolts. At least that's how mine was when I did it 2005 Vader Wagon Material Tests on Ringland Failure Piston I should have held off and purchased a wagon instead of the spec.B Link to comment Share on other sites More sharing options...
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