reidry

Ok so I'm converting my 1969 Corvette to an LS1 with sidepipes.

I'm concerned that if I go with a header setup I'll end up with tighter bends and maybe going backwards to get to the ideal area to pass under the frame rail. With the LS1 I can't use standard hooker or headman sidepipe headers unless I have them cut apart, a new flange made and remanufacture the tubes to match the LS1 exhaust ports. Also I need a point relatively close to the engine for the O2 sensors. The aftermarket headers for LS1s provide collectors with O2 bungs, but they all appear to either be kindof long i.e. the collector sits back near the bellhousing or the truck type from S&P place the collector straight down mid engine which is really painful.

So with the Z06 manifold I have a O2 sensor bung, they are short and then I use a single connecting pipe to route the exhaust from the bellmouth of the manifold down and out to the frame rail. I'm planning on frame clearance tubes from Dr. Gas to minimize the lost ground clearance. Dr. Gas Frame Clearance Tubes

I'll be stepping up to 3" or 3.5" as soon as possible with either 3.5" or 4" sidepipes under fiberglass covers. I'll be using JCL Spiral Turbo Baffles instead of glasspacks or reverse flows.

My engine is a 2000 crate motor in the stock configuration with the 2000 Corvette (y-body) cam. Since I'm into so many other modifications on the car I can't really focus on the motor at this time so starting point is around 350 - 370 HP at crank with a good tune, 5-wire MAF, free mods, etc. End point will be either this engine improved or an LS6, either solution will be targeting 425-450 RWHP.

How much performance am I leaving on the table if I use the Z06 cast iron manifolds instead of some type of header arrangement?

Thanks,

Ryan

John B

iTrader: (10)

Too much! Go with a custom header!

Scooter70

iTrader: (1)

Ryan,
I'm still wrestling with the exact same thing right now. I actually bought my STS baffles when I thought that I was going to build a 383. I've seen O2 sensors mounted in the collectors of Hooker sidemounts, but on one car they were sticking straight up with the wire going thru the side vent. Technically this is correct but it's also very ugly. They could also be mounted on the inboard side of the collector so that it's relatively hidden under the rocker panel but I don't think that you can get it to be above the horizontal to keep moisture out.

I've asked a few people about putting the O2 sensor on a primary and not the collector. I haven't received a definitive answer. ASSuming that the cylinders are all close enough to use for feedback of the entire bank, I would think that it should work. I have a few contacts in the world of LS1 racing, so if I find anything I will let you know.

-Matt

Mark IXZD 150

iTrader: (1)

I'm in the same boat. I'm building an LS6 powered 1963 Grand Sport so my intention was to have my headers custom made at FLP (Finish Line Performance - forum sponsor) near me here in Naperville, IL who said they could do it in a matter of a few days. My chassis will be a full tube frame so I'm not sure if the same headers will work on the factory frame. I was going to have them keep the templates for anyone else in need of these headers for LS powered Grand Sports but maybe they'll work for any midyear - I really don't know. I plan on 5/8" flanges, 1.75" primaries to a 3.5" collector with the O2 bung facing the rear of the car and then fully ceramic coated inside and out.

Frame >> http://www.hpphoto.com/servlet/LinkP...590b3486&size=

Scooter70

iTrader: (1)

Mark,
I think that if you were to do something like GS #3 has, it would work just fine.


However, the Hookers have the collector outside of the body, so that's where our issues lay.



Chris (69MyWay on CorvetteForum) has a fuel injected BB in his car and posted some things on Corvette Forum, but I didn't find when he posted his final solution. You can check this out though: http://forums.corvetteforum.com/zerothread?id=243016

I just e-mailed him and asked a few questions.

(Sorry about the big pics)

Scooter70

iTrader: (1)

Ok, I figured out what Chris did and I don't really like it. Look at the collector on the roadster, right in front of the door cutline. See the O2 sensor sticking up with the wire going through the gills?

reidry

Hmm... didn't realize Chris's car was fuel injected. I really like his work, but that O2 sensor location doesn't do it for me.

I went searching this morning and there are several shorty LS1 header manufacturers ... BBK and JBA along with others. The JBAs are are equal length with 1 5/8" primary tubes. The BBK unit is 1 3/4" primary tubes but I haven't found anything saying that they are or are not equal length.

I don't think mid or full length "off the shelf" LS1 headers are gonna work.

The best solution would definitely be custom.

What did those custom headers cost?

Ryan

Mark IXZD 150

iTrader: (1)

I think customs will be in the $1000-1200 range but I'm not certain of that. They only told me "time and material" when I inquired.

reidry

Wow .... just custom headers not mufflers for $1000. I don't know if I can dedicate that much of my project budget to headers.

Any thoughts on the shorty headers?

Ryan

70 LS1

iTrader: (1)

Don't waste your time with shorties. Here is my suggestion for you.

Pick up a set of hedman or stahl side exhaust headers and have them modified to fit the LS1. You will be able to run your 3.5" pipe (4" would be too big) under the fiberglass covers. I also don't think the Dr gas squished pipe would work either. Those are designed for undercar exhaust that needs to go under the frame instead of through it like ours does. By the time you get those pipes under the side frame rail and put in a 90 bend to run the pipes along the body, your pipes will be 6" from the body. Maybe a little exageration. There should be enough room to run at least a 3" pipe under the frame. Don't forget the frame kicks up for more clearance just behind the front wheels.

reidry

70LS1

I see where you're coming from, but let me explain a bit more about my project.

I'm not just repowering. I'm building a dedicated Prepared Class Autocross car from the ground up. I'm starting over with new suspension - I'm literally cutting off the old mounting points and starting over. Those spring pocket things on the front cross member ... lets just say they are gonna be history.

I'm working with another gentleman who has already done a similar build on a 73. He originally modeled the suspension using the Performance Trends package. He is on the 3rd iteration of the design and has managed to place in the top 3 at Nationals twice in the last 5 years. The suspension uses common circle track construction, heim joints, coil over shocks, etc.

I have converted the model over to Suspension Analyzer 3D and verified the dynamic characteristics. I'm taking it to the next level and designing all the new components in CATIA. Instead of a steel rear upright like the previous generation, mine will be machined from solid 7075 Aluminum billet. Even though he is running a coupe with the windshield and t-top portion cut away I should be able to match his weight by using alternate materials including the LS1 engine instead of a iron block 350.

My ground clearance at the frame rails will be around 4 to 4.5 inches.

Looking at the rolling chassis in my shop I see where the frame rails kick up toward the front crossmember. It's pretty gradual and that is where I intended to pass under the rail with the clearance tubes. I recently contacted Dr. Gas and got the measurements on the various tubes. I intend to mock the whole thing up with PVC and other various components before ordering the clearance tubes, headers and STS baffles.

If I were to consider the modified Stahl or Hedman's, I can machine the flanges - what kind of shop modifies the primaries?

Ryan

Scooter70

iTrader: (1)

Where is the collector on the Stahl & Headman headers?

-Matt

Edit: Ryan, send me a PM with your e-mail address. I have something for you to read.

reidry

Here's a link to a picture of the Stahl headers. The collector is is near the frame rail, I'm not sure from the picture below if it falls inside the engine compartment enough for an O2 bung or not.

Stahl Sidepipe Headers for 350

Ryan

feldmanj

I have just finished the exhaust on my LS1 powered cobra kit. The exhaust is slightly different except the problems are the same. My set up cost 190 bucks and are exactly what I wanted. I ordered a kit for ford small block as the spacing is similar from www.schoenfeldheaders.com minus the flange and bought the flange from GM. They have all sorts of applications that look similar to yours and they were able to modify mine to fit. O2 bungs and the works. I tack welded in place for a perfect fit as It will vary from side to side because the exhaust ports are off set from side to side. A local welding shop welded and grinded to a smooth complection for 40 bucks. I may have them ceramic coated as I have everthing else on the car powdercoated.

Scooter70

iTrader: (1)

Got any pictures of the positioning of the bungs? Is the collector inside of the engine bay or outside of the body like the real Cobras?

grooves12

For V8 cars equal length headers largely do nothing, because of the uneven firing order. In an I4 or I6... they are a huge asset, because the exhaust pulses come in even cycles, so en equal length header improves scavenging. But, on a V8 the erradic exhaust pulses negate the need for an equal length header. It's largely just a marketing ploy to get people to pay more for headers imo.

Here is a good website that has TONS of information on optimal header/exhaust design: http://www.headerdesign.com/login/header.asp

Most people are surprised to find that 99% of all headers sold are FAR from optimal for the typical combinations people run... but thats what you get when companies make ONE or TWO header designs per vehicle. And typically they oversize the headers to make their peak numbers more impressive on all-out race vehicles, because NUMBERS are what sell... even if you aren't going to see those same numbers on your vehicle.

I know a few people that have modified an off the shelf set of headers to more closely mimic those of what that website recommends with GREAT results.

Sorry... I know this was a topic about sidepipes... and I went off on a tangent, but I think some people will find the info useful.

70 LS1

iTrader: (1)

I am going to have to disagree, sorta. Let me explain. What you said is entirely true if you limit the header to one side of the engine. However, if you pair the appropriate cylinders together as in some from one side and some from the other and use a 4-2-1 design, then equal length headers can do wonders. Unfortunately, this is not feasible in most cars due to the lack of space for the headers. Have you ever seen the headers from a Pantera or GT40? They have criss cross headers that pair up the cylinders optimally. I am not trying to say your are incorrect, there is just more to it than you stated.

grooves12

I agree... so, let me change that. Equal length headers don't do much in 99.99999% percent of vehicles with V8's.

There might be some SMALL benefit if you are using an optimally designed equal-length headers along with an X-pipe crossover, but I think by the time it gets to the crossover most of the scavenging effects are largely lost. But, in a true dual configuration as most people with V8's run, it is not worth the extra expense (or fitment hassles) for equal length headers.

BTW: Those "criss-cross" headers are called 180 degree headers... and they make some for Small Block Chevy's and other applications, but they largely don't fit in anything besides a purpose-built race chassis.

feldmanj

The collector is inside the fender and comes out with 3.5" tube. I went this way so I wouldn't have to have the o2 sensor on the side of the car. I may regret it as it doesn't look original but hell, either is the LS1 or the 6 speed or the car itself.
I will see If I can attach a pic latter today.
Josh