Hi everyone. I know I've kinda posted a lot, but you guys are great for information. Anyways, I have a 87 Camaro 305. I'm thinking of putting dual 2.5" (or 2.25"?) with a H-pipe, with two Bullet mufflers (or the Moroso Spirals, or no mufflers?). I'm undecided about replacing my manifolds with headers though. Any advice? Anyways, that's my thoughts so far. How does that sounds? How would it sound on my 305, and could I gain any power? Thank you!

 

what makes exhaust sound good and be loud is the amount of flow and power you have....with stock manifolds you are not gonna address any of that...your exhaust is oinly going to flow as good as your weakest link...i'm also wanting to run dual 2.5's through dual bullets, but i'm not sure if i'm going to like the sound of the bullets or not, so i might end up putting a couple mufflers in the mix...but i would say, if you like the real loud exhausts, upgrade your manifolds to headers, and run your duals and you should be good to go....

 

Would you rather go with 2.5" or 2.25"?

 

Dual 3".

I've heard dual 2.5" pipes will flow less than a single 3". I don't know how true that is... but it may be something to think about.

 

You need to calculate flow area to determine which has the potnetial to flow more.

For dual 2.5", pi*r^2 = (3.14)(1.25^2) = 4.9in^2 or area per pipe. Dual 2.5's will double that to 9.8in^2.

For a single 3" (3.14)(1.5^2) = 7.06in^2.

The sizes are acutally smaller minus material thickenss since exhaust piping is measure by its OD and not ID. Also, the dual 2.5" will have more wall friction due to the increase in internal surface area.

A single 3" is all you need for your stock 305. If you want true duals go for it. To me it is not worth the hassle and cost of fabing it up on a motor that only makes 170hp. Headers will make a big difference on your car. The entire stock exhaust system is too small and riddled with factory kinks. I would just buy a complete TPI single 3" system for your car and call it a day. A single 3" comfortable supports cars that make 150rwh to cars that make 400rwhp.

 

For headers, will getting headers with 1 1/2" primaries be good enough for my 305? *waits to be slapped for ignorance...*

 

No slapping required. You are learning. No one just wakes up with this info.

1 1/2" primaries are fine if you intend on keeping your motor near stock. There is only one problem though. There are 3 kits for our cars that offer 1 1/2 primaries and they are all basically the same header. They suck in all aspects. They are just pure garbage with an eqauly worthless y-pipe. I am plagued with a set right now and new SLP's are about to be ordered. So, due to their lack of quality I reccomend a set of 1 5/8" primaries with a 3" y-pipe. There are three sets that are all on par with each other and have great y-pipes. The mac's, hooker 2055's or SLP's are what you want. Take some time to search the boards (and stickies) to read up on which ones sound right for you.

 

well i'm for sure doing the dual exhaust, and now that you brought up all those forumula's, does dual 2.5's outflow a single 3 or 3.5 pipe? because i was originally going to go with dual 3's, but they said dual 2.5's is enough..my motor will be about 400 hp...i get my mind set on one thing becuase i think its good, then somebody brings up a point and makes my idea sound not so good!!!

 

Just run the math to see which set-up has the larger area.
(the acutal values are smaller but I am using the OD instead of the ID as an example)

Single 4" = 12.56 in^2
Single 3.5" = 9.62 in^2
Dual 2.5" = 9.8 in^2
Single 3" = 7.06 in^2
Dual 2.25" = 7.95 in^2

If your motor is going to make 400 hp at the crank a single 3" will suffice. Duals are only needed when you need a large amount of exhaust volume. You need a lot of space to run them of which 3rd gens lack. You will sacrifice ground clearance. A dual 3" system is HUGE and would only be needed on a full drag car making in excess of 600+ HP. You would have a touch time driving over bumps in the road with a set-up like that.

 

The best setup I have used (every year it seems I have a new setup) is the shortie headers with dual 2.5 inch pipes with CHERRY BOMBS...... No it doesn't sound like a truck...

I have the exhaust mounted so it sweeps out to the rocker panels of the car before the trans x member.... it is mounted where you would put your sub frame connectors....

I still have a lot of room for SFC's also.... NEVER scrapes ....

Very easy to fab up...

 

4th page on cardomain site, link in sig...

 

alright dual 2 1/2's outflows a single 3", so i'll stick with my plan, i'm also dumping it right before the rear axles through, I believe, aerochamber mufflers....then if thats not loud enough i'll get dual electric cutouts...

 

If you even plan on lowering your care I would really re-think the dual option. I would spend some time searching and looking at pics of peoples dual set-ups. You should get some great ideas how to run your set-up if you choose to go that route. Also, just because one set-up flows more than another, it doesn't mean you need it. You can go too big and decrease exhaust scavaging which will hurt the repsonse and power of your motor. Bigger is anot always better. Provided your new motor makes 400hp you should be okay.

 

I ran dual flowmasters. Getting the pipes under the crossmember is a pain... I mean I could not do a lot of things with my "street cruiser"...couldnt cruise!!... But it you must....

Use shorties and run them in the stock location with a X over pipe where the cat would sit...........

Hammer your rear floor pans.. and stick the muffs there....

I actually welded a bolt to the top of the muffler.. used some washers as a spacer ....and mounted the muffler through the seat pan..... with a fender washer.....

MAKE SURE YOUR REAR SPRINGS are up to the task.... I bent the crap out of my exhaust going about 55 and having the car bottom out.....

I would not recommend this setup........... also... if your running them in the stock location..... LOTS OF BENDS.... not good for flow.......

Just my experience...

I really would suggest a single 3 inch catback and universal "gutted" cat from JC WHITNEY. The exhaust is 3"...

I loved my 80 series.... so did everyone else....

edelbrock TES
Pacesetter 3" catback
Catco universal 3" cat
80 Series Crossflow muffler

Awsome setup...

edelbrocks will be good for around 400 horse...

Go 3" and be done with it.

 

my car is lowered with sportline springs, 1.6" drop I believe...i realize bigger is not always better, thats why i said dual 2.5's instead of dual 3's...also i heard an 80 series, and i hate the way it sounded, and also crossflows are more restrictive than tradition mufflers, so if i ran a single pipe it would be a single 3 1/2 because that is what I feel would be sufficient...do any companies besides mufflex make a single 3 1/2? mufflex is kind of expenisive...if i ran a single 3.5", i would run a spintech crossflow muffler too....also, i already have the hedman long tube headers, so theres no switchin to shorties now....i think my plan would work out good, i looked at a lot of dual setups, and i figure if i run them real close to the driveshaft tunnel i should be good...then put the mufflers right under the rear seat pans...alot of people have said they had a very good amount of ground clearance...they said the long tubes will scrape before the rest of the exhaust...but don't get me wrong, i would love to run it in factory location, and buy a prefabbed cat back kit, because that would definately be the easiest and most cost effective, but i'm afraid a single 3" through a crossflow isn't enough flow for what i'm doing...the way i see it, is if i'm spending this much money on an exhaust, i want it to be good for a while even if i build my motor up a little more, i want to have the extra flow there, and not having my exhaust holding me back again...i've been thinking about what to run for 4 months now, and still haven't settled on something...

 

Well then, Go get yourself some S- extensions and some straight pipe..... and put on your mufflers. Should not take long.

Make sure it gets welded. So that when you scrape the ground they won't come off easy.

I'm sure you've already made up your mind.

Just do it!

 

What are your goals? A single 3" will support over 400 at the wheels before it starts to become a restriction. Cat-backs are cheap in the grand sceme of things. I would rather spend another 350 bucks on a larger cat-back down the road when I need it then have one that is too big and hurts the performance of my current motor.

 

well i didnt' make up my mind quite yet, but I thought I did....I am open to other possibilities...i guess i'm just iffy about having a single 3" support 400 HP...then another thing, I dont' really like the catback systems that are out, for example...i like the sound of the aerochamber, but i don't like the 1 into 2 Y tips on there.....then you got the american thunder, the tips look good, but i hate the sound of the 80 series muffler...then the dynomax, my buddy has this, its not even close to being loud enough...anybody know of any other choices? if i drag my exhaust up over the axle, i want dual outlets, not just one pipe on the side...but like i said, i'm open to suggestions, but time is really ticking down now, the car is going back together and exhaust is going to start to creeping up on me....

 

if you really make 400 at the wheels it won't matter what cat-back you have. You are picky now because each system sill expose the weaknesses of a 200hp motor. Any 500hp motor at the crank will sound like pure domination behind any cat-back.

 

well i'm not going to be putting 400 at the wheels more like 400 at the crank, probably just under 350 to the wheels then...i have no cat either, so that will free up some more flow, and i guess i could go with a 3" catback, because i'll probably be getting a cutout also....but now the question is, if i go this way, which system do i get? is there a company that just makes the intermediate pipe, then i can run a spintech muffler or something?? i can make my own slash tips, i've already made some and they turned out great....polish them up on a lathe and whatnot....thats why i think it would be better to buy piece by piece...don't you??

 

For the power you are going to be making any 3" system will feed it fine. The flowmaster kits tend to be the most restrictive where as the magnaflow, hooker, and random tech kits seem to make the most power. However, you can buy any of these kits and put a spintech muffler in place. None of the supplied muffers will cause any power loss though, especially if you have a cut-out. Your power goals are impressive but aren't high enough where you need larger than a 3" cat-back. There are LS1 and LT1 cars making 400+ at the wheels and running high 11's on a single 3" exhaust. I just would hate to see you lose all that low RPM scavaging by going too big.

 

Someone told me that duals will sound better than a single exhaust, and that's kinda what I'm looking for. Will dual 2.25 (or 2.5?) do more harm than good to my 305?

 

Don't even think about dual 2.25 inch exhaust.... use dual 2.5 inch if you must. And your going to be restricting the dual exhaust trying to get it up and over the axles..... and out the back...

You must make sure both pipes are the SAME. length...throughout the whole exhaust system.. or one side will be louder than the other - annoying...

You can't just use autozone piping. You must buy mandrel bent tubing........no crinkle bends.......


I went throught this exhaust stuff for months..... ....

Rob....

 

2.25 is just too small then?

 

yea dual 2.25's is a waste of time.....if i go the dual exhaust route i'm going to dump it before the rear axles, so i wouldn't have a problem with unequal lengths or kinks over the rear axle, however if you are going over, that is something to watch out for...

 

If I use an H-pipe, will unequal pipe lenghts still be bad?

 

probably...just try and get it as close as you can...

 

One more question I guess. Which will sound the best - 2.5 duals dumping before the axel, 2.5 duals dumping in the back, or a single 3? And will I get the better sound with headers or manifolds?

 

you'll get better sound with the headers, more airflow....i don't think any of us can give you an answer on which setup would give you better results..because its all about tastes and preferences....if you dump it in front of the rear axle, it would probably be the loudest because its shorter pipe, less bends, and its almost right under your seat...the 3" might give you a bit deeper sound because its a single bigger pipe, but i think all 3 of the systems are going to sound pretty close to the same...theres not gonna be a dramatic difference between them, that is if your using the same muffler...

 

i got another question, does anybody like dynomax or something make like a 3" or 3.5" interemidate pipe, just from the cat to the muffler? How hard is this to fab up? I'm debating if maybe I should just have a shop do it or if i should do it myself...i think i'm capable tho...i'm in an advanced auto mechanics shop at school and i have access to a hoist and welder and antyhign else i need....i was thinking of just leaving my car in there for a week, get some J or U bends bent up by a shop, and just cut out the angles I need...the only part that scares me is the axle hoop...should i try this or just have a shop do this? anybody know how much that would cost?

 

Pacesetter 3" exhaust from J.C whitney.... and substitute your muffler... too me 30 - 40 mins to install.... and that was with a lot of wasted time......

 

A good speed shop should be able to order just a dynomax intermediate pipe.

 

Has anyone ever heard an American Thunder system on a 305 with stock manifolds?

 

buddy of mine has it on his 86 ta, it sounds really nice actually.