I have a set of shortie headers I bought off Ebay a few years back and have them on my engine in my car now. They had wrap on them and I never took it off to check for a brand name on it. They have 3" collectors where the pipes come together with a 3 bolt triangular flange. What I want to know is will the Heddman (or maybe it's Hooker) Y-pipe bolt up to my headers. They look almost identical to the Hedman Hedder Headers, and they have big primaries (although I never measured). Or if anyone can ID them for me thru pics and such. So if anyone can lend a hand and point me in the right direction I would appreciate it, and so would my ears, hard to tune an engine you can't hear!!

 

You will have to ID the headers to find a y-pipe that will fit. Alot of companies have specific y-pipes that won't fit on another set of headers. If you can't id them, get a custom y-pipe done at a local shop.

 

Nevermind, I looked and found the Hooker y-pipe....it was a matter of wording it differently

 

SO what is a good cat-back system?? I know you dont seem to like Flowmaster, Urban, but besides big dollar things like SLP, what else is good?? Mind you I won't be using a catalytic converter

 

As far as catbacks go, I'd probably get a custom job with a bullet muffler done if I had your car. Best flow you'll get, and it'll have some great sound under load and at idle you'll hear the cam. $37 at summit. Click here to hear my old car (bolt on LT1, no cat, 17" dynomax bullet).

If you're looking for a mufflered system, you're right, I don't like Flowmaster at all. They're over-rated, over-used and don't perform up to par. I went with a Magnaflow on my car, and love it. It's deep and bassy while cruising, and that turns to a scream up top - I've never even heard another car with it besides my buddies built L98 (he didn't like it so he gave it to me. Didn't sound good with his TPI motor - WAYYY better on the LT1). It will hide your idle however, if that's a big deal to you. Personally I like to hear a cam lope. If that's a problem, I'd recommend the Hooker Aerochamber (heard one on a built 350 a few days ago, it was very sweet). You can hear the idle very clear. Also there are Spintechs (nice clean sound, screams up top, doesn't sound all that spectacular down low) that you might be interested in.

You can also go expensive. GMMG makes an excellent piece, so does Borla and Corsa. However be prepared to pay out the nose for any of those. GMMG has (arguably) the best sound on an SBC - or at least many people think so. I personally really really like it.

All in all it comes down to personal taste. There are several other brands as well (Dr. Gas, Bassini, Ravin, Pacesetter, Dynomax, TSP, Edelbrock and on and on) and it's up to you. You can also custom one off stuff, like with a Dynomax Bullet Muffler, Glasspacks, chambered sticks, and so on. I just advise to get 3" at least, and stay the heck away from Flowmaster.

 

So would you reccomend 3" all the way back?? Cause the Hooker y-pipe goes from 3" into a 2.5 and out, but it says that has an outlet attachment, so would that be where it turns into 2.5" or would it be right at the Y?? I plan on putting a manual cutout in after the y-pipe anyway, but should I still go 3" all the way back?? Thanks again urban!!

BTW I did a little research a while back on exhaust tubing size, and what I found and read was that as long as you have a big enough chamber off the header/manifold collectors, behind that has little effect because the exhaust will be off the valve and no longer affecting the flow, curious to have your input on whether this makes sense. So going from a 3" to 2.5" should, by this theory, have no affect on the engines performance.

 

That theory is dead wrong. The exhaust is never "out of the way" until it's out the back of your car and into the atmosphere. And even at the end of the pipe, remember that it's still sending a reflecting wave back up the exhaust (think of water bouncing off a wall - when a moving object hits another object, there is a transfer of energy). When that reflected wave reaches the exhaust port, it's at a lower pressure than the exhaust exiting. As the exhaust exits the port, it's sort of 'sucked' out by the lower pressure. Now the length and size of the exhaust changes this reflected pulse, tuning it for one RPM band. When it's out of this band, the reflected pulse will be returned at a higher pressure. Generally, the shorter the pipe, the higher in the RPM band your power is going to be made, and the more potential it has. By going 2.5" you're shoving that RPM band down to where it won't make much after 4500 RPM, and it's overall potential is extremely limited. If you're curious about all of this, check out my backpressure FAQ. It's in the stickys on this forum.

A 2.5" pipe will choke even a stock 305. Going 3" all the way back (mandrel bent, no crimps in the tubing!) is the ONLY way to go for a performance application. Open that exhaust up, and the powerband will be much better, and you'll make much more power. I'd recommend a y-pipe that takes the headers into a 3" merge, then 3" all the way back into a 3" muffler. dual 2.5" exits out of the muffler are fine.

If you have a cutout directly on the y-pipe after the merge, you'll be okay. As long as the pipe feeding into the 3" cutout, is a 3" pipe. When you open it, your motor will be tuned for a higher RPM band, and make more overall power. Don't restrict it by going 2.5", you will be severely limiting your motor's potential. And by the looks of your sig it'll make in the neighborhood of 300+ horsepower (difficult to tell without cam specs), which DEFINETLY needs a 3" pipe. I'd recommend a total 3" system for normal street driving, along with a cutout for when you want to go racing. That system is very effective for these cars, making power in your range.

Here's a diagram I stole from my FAQ thread, the graph on the right shows an open cutout. The graph on the left is a closed and mufflered system. You can easily see how tuning the length/size of the pipe effects your exhaust.

 

Thanks, I read your sticky but it was a bit much to absorb all in one sitting. My cam specs are below. So my best bet is to go 3" all the way back, because otherwise it will shove the power band way down and ruin top end power right? And the shorter the length of pipe is before it reaches the outside air the more power it makes at higher rpm's right?? Trying to get this all correct so I don't waste my money, thanks urban!!

Grind Number: 302 H06
Operating Range: 3500-6500 RPM
Duration Advertised: 302° Intake / 302° Exhaust
Duration @ .050'' Lift: 246° Intake / 246° Exhaust
Valve Lift w/1.5 Rockers: .500'' Intake / .500'' Exhaust
Lobe Separation Angle: 106°
Max Lift Angle: 102° ATDC Intake / 110° BTDC Exhaust
Open/Close @.050'' Cam Lift: Intake - 21° BTDC (opens) / 45° ABDC (closes)
Exhaust - 53° BBDC (opens) / 13° ATDC (closes)

 

That's the gist of it haha. Remember when dealing with these V8 motors, backpressure = bad. That's all there is to it. Any restriction in the pipe, including the pipe itself being too small, is bad. So yes, 3", all the way back, mandrel bent, no crimps or other intrusions. I'd recommend putting the cutout directly after the Y-pipe, if you're running a cutout.

That's a top end cam. Your low end is going to feel kind of soggy no matter what exhaust you put on. Once your RPMs get up a little bit though, it's going to pull like a bat out of hell. What gears do you have? How come you're going with the RPM Performer and not a single plane? Is it going to see mostly track time or some street as well?

 

Thats my plan with the exhaust, and with the stall in the car (which will be a 3k stall) I figure atleast a 4.11 gear, altho if needs be I will put in a 4.56, once I get the trans built I will make up my mind after testing it out with the stock gear, a buddy of mine does rear ends and say he will help me get the right gear. The intake I have doesn't have the split all the way at the base of the carb, for the most part it have an "edge" about 1" down in before the first base level for the passenger side runners start. Its a little different from the Performer series, it is a high rise intake because the runners sit off the base of the intake.

As for the pulling part, I drop it home from school (going to school to work on cars and having a whole shop environment to your disposal ROCKS!!) but when I got on my street I got on it, lit up the rear tire from a roll and the car squatted real nice and pulled really strongly for being a stock car aside from the engine, surprised me for the most part, didn't expect it to pull like that, can't wait till I rebuild the trans and go to the track!!

Do you have any other suggestions/ideas that make help me get the best out of my car?? I am picking up the y-pipe next saturday (hopefully) and will have the full exhaust shortly after that. But thanks for the help thus far, it is greatly appreciated!!

 

You might have to play with your gear and tire size combos. You want whatever is going to make you cross the traps at your hp peak (probably near 6k). I'd venture 4.10s would probably be okay.

You can pm me if you have any questions, and I'm sure most of the other members here would be happy to help as well.

And remember, at the drag strip you don't want the car to 'squat' persay. You want it to just LIFT those front tires, while maintaining the gap in the rear Like the ones in this thread:

https://www.thirdgen.org/forums/organized-drag-racing-autocross/312065-wheels-up.html

Some very sick pics in there

Good luck with your hot rod!