replacing my 3900 exhaust, need advise

[chuck]

I'm pulling my engine to replace the camshaft with a non-vvt piece. I'm fairly disappointed with the performance of this engine which is why I'm doing the cam. I figure while it's out I'll replace my unequal length headers with some equal length headers. Current headers are 1.75''. I have 1 5/8'' tubes to replace them with. I'm thinking of going with a dual exhaust setup so I won't have a crossover. I think I can squeeze a 18'' magnaflow under the trunk, after I cut it, with 2 1/4'' pipes. I also have corvette tips. I'm still concerned that it's going to be too loud. I haven't bought mufflers, cats or exhaust tubing yet. Just wondering if anyone has advise on quieting it down or if you think it'll be good enough?

[Emc209i]

I hear that turbo's are great for noise suppressant purposes.

[chuck]

I've thought about it but the time has come where I have to say enough is enough. I'm doing the cam swap, headers, maybe deck the heads but I doubt it, Then it's tune and drive time.

[Emc209i]

You're building headers and tuning. Throw in a WBO2 and tune for boost.

[Shaun41178(2)]

what makes you dissapointed with the 3900? It came with around 240 hp pending on the year. That should be around 190-200 pending on tune and tranny.should be good for high 13's to low 14's.

Have you dynoed it to see if its running up to snuff? You don't need a turbo but a cam and headers should give it about another 20-30 hp or so.

[chuck]

I've had it tuned. I've also exchanged a couple emails with sinister to get the tune fixed up after the cam swap. It did put down 206hp I think but I don't believe it. It's just a turd. I tried retarding the cam but it won't even run fully retarded. Now it's advanced but can't rev it past 5,000rpm. Well, I could but it's pointless. Sappy is saying 310hp for my new cam, that's why I'm fixing my headers to try and squeeze a little more out of it. Also, low end is fairly miserable. Can't pull hills in 4th. Need to run 3rd gear pretty much all the time, I have a 4t65e-hd. Does anyone think 18'' magnaflows and corvette tips will be enough to quiet this turd? I could try an add Cats if it'll help but I'm not sure where I would put them.

[Gooch]

I am pretty surprised to hear this. I felt like the 3500 and 3900 were going to be the "new" Fiero swap.

[The Dark Side of Will]

Obviously it still has serious problems. The fact that it won't do anything in 4th makes this pretty clear.

Not sure what you mean by "206 HP" when you later say that it won't run with the cam fully retarded and won't rev above 5K with it advanced.

When running correctly, it should be just fine and run well into the 13's... after all a stock 3.4 TDC can push a Fiero into the 13's and a 3900 ought to be 40 HP up on that engine.

However, remember that Jon Lagler got a NA 4.9 Fiero into the 13's, but everyone else's run 15's... I never would have thought the thing that hard to get running right but maybe it is.

[fieromadman]

How about a part number for the muffler josh?

[chuck]

http://www.jegs.com/i/Magnaflow/642/104 ... tId=751042 This is what I'm thinking about. I think it'll be pushing the limits length wise but i'm tired of the noise. As far as Will's comments, I think I described it accurately. I tried doing the swap initially with the cam locked into full retard. It wouldn't even fire. I put the phaser back to stock and bought the wiring harness for it to get it working. It fired right up in the fully advanced position and stalls when engaging the phaser. It's obvious GM left some extra room for timing chain stretch or something. Without the factory PCM it just isn't worth it. The engine works too hard in 4th at 60mph. 3rd gear is actually quieter. I am confident that the 3400 cam swap will give this thing performance I can be proud of, I just want it to be a little quieter with a good exhaust.

[Emc209i]

Out of curiosity, which year cradle are you working with? Having tie rod links will make things difficult for you in fitting everything at the trunk wall.

[chuck]

It's an 88. I managed to keep the trunk stock with the first exhaust but I've decided to cut the bottom in order to make a longer and hopefully quieter exhaust. Still no opinion on magnaflows and corvette tips?

[Series8217]

Those magnaflows will be loud, they're just glasspacks.

[Atilla the Fun]

I'm not convinced that even a stock 3.9 could pull the tallest possible gearing in the 4T65E, so I'm curious which gearing are you running, and which sprockets for the chain? And if you are building for high rpm HP, I'd definitely be trying for the 3.69:1 final ratio. That should put you between 2200-2300 rpm at 65 mph, so you should still get mpg in the high 20s.

[chuck]

http://modernmusclecars.net/forums/show ... hp?t=10353 I was going off of this list. It seems the magnaflows are quieter than the spintec I am currently using. I'm really not sure what else to look at. Do I just need to add a couple catalytic converters? If I avoid a crossover like I want fitting two cats will be difficult. It is stock hd gears. 2.93 I think. I had planned on changing gears but the tab is getting high so that'll have to wait.

[Atilla the Fun]

I do understand about running out of budget, but be aware that a bigger cam is gonna virtually guarantee you can't use OD until you do change the ratio.

[Series8217]

http://modernmusclecars.net/forums/show ... hp?t=10353 I was going off of this list. It seems the magnaflows are quieter than the spintec I am currently using. I'm really not sure what else to look at. Do I just need to add a couple catalytic converters? If I avoid a crossover like I want fitting two cats will be difficult. It is stock hd gears. 2.93 I think. I had planned on changing gears but the tab is getting high so that'll have to wait.

That muffler shootout doesn't give enough information on what they're comparing.. all of those manufacturers make a lot of different systems.

I think the best way to go quiet would be to run the exhaust around the front of the motor like with the factory Fiero system, and to run a single inlet, single outlet muffler that takes up as much space as possible between the trunk and the engine.

[chuck]

The nicest headers I've seen with the stock routing are the FOCOA ones. Following that design I don't think would allow for a decent length primary. I suppose any sort of equal length would be better than what I have. I definately can't live with a single exhaust though. I suppose a cost effective way would be to run stock fiero routing with a high flow cat and use the spintec that I have now with the corvette tips. Not perfect but could be worse.

[Series8217]

Do you not want single exhaust just because of the looks?

You could either put a fake tip on the right side, or run no tips at all, a la Chris West's car. He has some sweet louvered covers that fill in the exhaust tip cutouts on the bumper. He has a single side exhaust instead.

[fieromadman]

I think you should go with the single in dual out crossflow Magnaflow muffler and vette tips. Magnaflows are generally quieter than others. I am going to be switching to one this summer even if it means making the skinnier part of the trunk skinnier. My flowmaster is shit anyhow.