Dark Ember

This was a much bigger project than I realized. Installing them was a pain to be sure, but nothing out of the ordinary for a 3rd gen project. I did not want collector gaskets however, and so I welded the header to the exhaust. This decision... not a good one to make lol. I do not have access to a lift, and I did the exhaust work myself. But it a done project now and for any brave(stupid) souls who want to follow in my shoes, you can follow along below.

First lets talk about the results. My sig link will tell you whats done to my car if you want to know. Basically its got every bolt on except heads, cam and power adders. The car had a best et of 13.889@99.57mph with factory cast iron manifolds and cats. It did that time with a 2.037 60ft time. I bolted on these long tubes, and dynomax high flow 3" cats. Then the car went 13.710@101.42mph, with a 2.063 60ft time. My math puts that at about a .18 tenth gain, and 1.9mph faster. I have never had a car gain so little from a set of headers. But I will say that this car is not consistent at the track. On a given night I usually see about a .4 tenth and 2mph difference, not counting 60ft variations. Don't ask me why, If I knew I would correct it. Now that the dissapointing improvements are out of the way, I will talk about how I got them in and show some pics of the modifications.



Step 1: Getting the Headers In

1. A: Things to Remove

Everyone has a different list of things to remove in order to get them in. Here is mine: Oil pressure sending unit, A/C compressor(unbolt it and move it out of the way, but dont remove the lines), coolant temp switch, all 8 spark plugs, oil dip stick, Mini starter(even though its smaller, it still had to come off), transmission torque converter dust cover, both motor mount bolts(I had to jack up the engine) and finally I also had to remove the passenger side valve cover. Once I did that, I was able to get the passenger side in. Passenger side goes in from the top. Driver side goes in from the bottom. Sticking a pillowcase over the headers before install is highly reccomended to prevent scratches. Headers are in, the easy part is done.

1. B: Frame Clearance

You can install these headers and bolt them to the heads without notching the chassis, or denting any primarys. The first time you get on it, the engine will do some denting for you though because they are resting against the chassis. I actually attempted this, just out of curiousity. When starting the engine you could hear and feel some knocking noises as the engine was shifting around and the headers were hitting the frame. So, I marked with white paint everywhere that I saw a header touching a frame. Here are the best pics I could get to show you the 2 driver side frame notches. I dont have a pic of the passenger location.

Just below the master cylinder and towards the passenger side a bit.



Bottom of the car, the control arm mount has some extra meat on it that has to be removed.



You will probably need to install it in your car anyway just so you can mark exactly. Also, there is an evap line that runs over the trans to the passenger side. This line was touching the header, but it was not hard to bend up and out of the way just a little bit. The driver side hit header hit in 2 places. The passenger side only hit in 1 place.

Headers are in, the easy part is done.

Step 2: Ground Clearance

2.A: Explaination of Factory Exhaust Routing

The factory exhaust manifolds tuck under the body just infront of where the inner framerails begin. Shorty headers can have a Y-pipe that utilizes this wonderful design and not sacrafice ground clearance at all. Long tubes collect a few inches beyond this point and there is no room to do a 180 degree bend to get back up front in order to utilize the factory clearanced location.

2.B: Under the Chassis

The header collectors come out between the transmission and the inner frame rails. There is not enough room between the 700R4 and the frame for exhaust piping, so the pipe has to go under something. The most convient thing is to curve outward at 45 or 90 degrees and go under the inner framerails. The passenger side is easy once its on the other side of that inner frame rail, because thats where the stock exhaust ran. Thats also why your passengers ask you why there is a big hump in the floorboard where their feet should go. Plenty of room for pipes here.

The driver side also has a small area on the other side of that inner frame rail for the pipe. Ground clearance is not an issue until it comes time to get to the back of the car. It must once again cross over the chassis, or go under the floorboard where the rear, driver side passenger would put their feet. Both points are among the lowest points under your car. This is really why ground clearance suffers so much with long tubes.

2. C: Through the Chassis, SFC Required

My wife is the primary driver of this car, so ground clearance was a huge priority. It is not a high stress, racing application and so I decided to do something that I have not seen anyone else do. I notched and welded in new material on the inner frame rails and ovaled the exhaust pipes. Then I ran through the newly created gap. Now before you shout "hack job" into your monitor, allow me to explain the process.

2. D: Frame Rails Explained

3rd gen F-bodys have 2 sections of frame rails. The first, inner, main set starts just after the factory y-pipe, contours around the transmission tunnel and terminates just after the cross member. The inner frame rails(they are not normally called this, its just a term I am using) only exist on the rear subframe. These 2 main sections of frame never contact one another on a factory F-body. Also note, the rear sub frame also has an outer frame rail. This is where the factory trailing arms mount.

Sub frame connectors like the ones from Top Down Solutions mate the rear sub frames, inner frame rails to the central body inner frame rails(Rear subframe to the transmission contoured frame).

Sub frame connectors like the ones from BMR mate the rear subframe outer frame rails to the foward most point of the body's inner frame rails. When these are both installed you end up with all of the previously mentioned sections of frame being connected into one.

Example Driver side. Note I added a metal bar to create an H between the sub frame connectors.

Dark Ember

2.E Chassis Notches and Braces

I notched the factory chassis by removing an approx. 1 1/2" X 5" section of frame. The factory frame I removed was composed of 2 sheets of thin steel(maybe 1/16" each?). The 2 sheets are only connected "here and there", and for the most part are seperate pieces. I do not have before pics, but the chassis is allready perforated here with large holes. I cut right through the center of one of those large holes.

Passenger side notch, note the dual sheet metal:



Driver side notch:



I would never remove that much chassis material without putting something back. I used bumper bracket steel. It was much thicker than the factory metal.



The bottom one is oriented the same way that they were welded together and installed inside the factory frame rails. I welded the 2 factory sheets together, c-clamped them against the newly installed braces, and welded them together. I had to be careful and stop in order to give the carpet right above all this welding time to cool. This could have easily caused a fire in the interior, but luckily did not.

The braces, after welding and priming them.

Passenger Side:



Driver Side:



After this was done, I added some more braces to better mate the BMR outer frame rails to the factory inner frame rails. The driver side SFC allready mated to the inner frame rail just 1 inch infront of my newly made notch. The extra steel bar that I installed between the BMR sfc and the TDS sfc to form the H, was a few inches behind the newly made notch. Both sides of my frame are supported by thick aftermarket braces. This is why I say this method would only work with sub frame connectors. Without those I would have a massive weak point in my frame.

The passenger side BMR sfc did not have that connection. They sell 2 types of SFC's, and the one I bought had to work with the factory exhaust, so I had to make my own braces on the passenger side. I have the extra steel bar on the passenger side, just as I have on the driver side, forming the H. But now I needed some extra bracing just infront of my newly made notch. I purchased some L shaped steel, cut to fit, and welded those on. Pics were taken before I finished painting it all.

Its hard to tell what you are looking at in this pic, but there are actually 3 braces which come from the BMR piece and connect to the factory inner frame rail. At the bottom of the pic, you see the bar that formed the H, connecting to the inner frame rail just a couple of inches after my frame notch. The other braces coming over to the inner frame rail are L shaped pieces, although you cant tell that in this pic. They are welded to the inner frame rail just before the notch. So again on the passenger side, the notched factory frame is supported both before and after the newly made notches.

Dark Ember

3.F: Exhaust Pipes

Now with approx 1 1/2" more ground clearance to work with, I began to oval my exhaust pipe. Remember that part about welding the collectors to the exhaust, instead of using the 3 bolt flange? Well the collector is 3", and this engine doesn't need dual 3" exhaust. I planned in advance having to oval out pipe for ground clearance. The sections of pipe that go under the chassis oval out to about 1.5"X4.5". It took a C-clamp, a hammer and a lot of effort to get this done right. Right behind a car lift, the 2nd most important tool for this job that I wished I had was a nice bench vice. The next step was to install the exhaust itself. This was tedious. Most of my welds are not that pretty, largely because of how cramped I was under this car. Its really hard to weld in tight spaces. The passenger side cat is mounted in the factory cat location. The driver side cat is back near the drive shaft, just under it actually. I installed new heat shields along the driver side as well.

Step 4: Smog Pump Delete

This was the easiest part of the whole project. Removing the pump requires 3 or 4 bolts. The pulley comes off with 3 more. Then the pump itself can be removed. I removed mine from the bottom. I had to purchase a slightly longer belt also. I have an underdrive crank pulley, and ended up needing a belt that was about 1" shorter than the factory belt. Even with the underdrive pulley, the factory belt(which I still had laying around, despite changing it for the smaller crank pulley a couple of years ago) was too long.

Finished

I need to get some pics of my car from a distance so you can see the ground clearance. I lost about 1" - 1 1/2" of clearance on the driver side. There only needed to be 1" lost but when I welded up the exhaust it was hanging lower than it needed to. It barely scrapes on our driveway, and only sometimes, if you are at just the right angle. Nothing else in the Houston area has scraped with the lack of clearance, our driveway is just evil. I should mention that I have not tested any speed bumps. Obviously, some of those were too high for a factory 3rd gen, so we learned to avoid them.

As for the minor 1/4 improvements. I have 2 things that I need to look into which could have something to do with it. #1 An exhaust pipe runs very close to the fuel lines now at the driver side notch, and I intend to install a heat shield between them and the exhaust pipe. #2 This car needs a TUNE! No more A.I.R., so the O2 sensor is now reading a straight exhaust shot, instead of a diluted mixture. The factorm ecm is not going to know to compensate for that. Although if o2 sensors are not used by the ecm at WOT, then this would have no effect on 1/4 times, but it sure would help the mileage. It runs stupidly rich and did even before the headers.

I'll update again sometime with ground clearance pics.

InfernalVortex

iTrader: (4)

http://www.wallaceracing.com/et-hp-mph.php

These calculators are just theoretical, but I always use the same one because I have a reference point with it, and that's all I need.

But regardless, assuming your car weighs 3500 lbs with you in it, going from 99.5 mph to 101.4mph is a 15-20hp gain. Not really sure how you could have expected more... Especially without a tune on a Speed Density car. Wouldn't be a HUGE change, but to get the most out of it you'd probably need to richen up the mixture a bit since your VE probably went up.

The 350 cars got the best manifolds of the thirdgens and the intake and factory cams are just as much a restriction as the exhaust system.

sailtexas186548

iTrader: (2)

Glad to see you finally got the m installed! almost 2/10 of a second is a pretty solid gain IMO, especially with out a tune modification.

FYI the ball and socket collectors that come on the 68460's do not require a gasket, they are actually very easy to hook up and keep leak free - just bolt the "socket" (cone looking things) onto the collectors and weld your exhaust to them. Then it's just 6 bolts to put on/remove the exhaust and they pretty much self align when you reinstall so it's nice and easy

Dark Ember

I had these installed a few weeks ago Sailtexas. I made these passes at the track the night before the Pontiac Show down in Galveston. Unfortunatly I have been too busy on other projects to get the bird to any local shows.

My friends 92 camaro always had the collector bolts backing off. I recall changing those out 2 seperate times. I'm a fan of locktite and have had good luck with that on header bolts on every header car I have ever owned. But on his collectors for some reason, even locktite could not keep the bolts in place. I was just trying to avoid that hassle. If I could do it over again I would probably just use the collectors and try locking nuts + locktite

Infernal Vortex, I suppose I had set my sights high. My car actually weighs about 3500lbs without me in(it has about 100lbs worth of aftermarked braces), 3650 with me in it. Let me explain why I hoped for more.

I got .7 tenths quicker from jet hot coated edelbrock tes shorty headers and y pipe, and an underdrive pulley on a 96' V-6 full size truck. I got .7 tenths quicker again on an 85' 305 monte carlo ss with the same mods, jet hot edelbrock tes shortys w/ Y-pipe and underdrive crank pulley.

Both of these cars were in the high 14-15 second range, so its easier to get big gains when your that much slower. But I thought with long tubes + high flow cats(which I was only thinking would give about 5 hp over the factory dual cat setup), and a more free flowing pre cat exhaust pipe would have done closer to .4 to .5 tenths and 3-4mph. Apparently I was being too optimistic. I was figuring that if the engine was moving enough air through restrictive cast iron manifolds to run 13.8's(which does not often happen), that headers would do more than the normal 10-15hp gain, + the 5 or so I was expecting from the bigger spread high flow cats. This is to say nothing of what the Jet Hot coating would add. The engine bay is probably 40 degrees cooler than it used to be and that's worth something also. I usually make my track passes with the engine somewhere between 160-190 degrees.

This car does not need any more fuel. It runs so rich it burns your nasal passage if you smell the exhaust. Driving around with the windows down is also a bad idea because of the strong fuel smell you get when coming to a stop. I adjusted the fuel pressure regulator from about 45psi down to 40psi and made a pass. I lost a mph and a tenth. Then I changed the fuel pressure up to the max, 55psi. Ran identical ET and mph to the 40psi. Next time, I will move 2psi at a time, I just was hoping to get a general idea about whether or not the pressure needed to move up or down.

One more thing I wanted to explain a little bit better is how hot the fuel in the car gets. I need to add a heat shield between the gas tank and the exhaust pipe. Now the fuel gets heated at another source too, the exhaust pipe next to the fuel pressure and return lines. With the Jet Hot, all that heat that used to escape into the engine bay is now going out the tail pipe which is going to further exacerbate the problem of heat soaking up into the gas tank. Making matters worse, the evap line is plugged inside the tank. So there is no vent atm for the tank when under positive pressure. The actual "vent" line coming off of the tank only vents into the tank for negative pressure situations. The evap is meant to vent out positive pressure. This is how I know the fuel is getting so hot, because when you open the gas filler cap at a gas station, hot gas fumes bellow out the spout. I am suspecting this could be my huge inconsistent et problem. The less fuel in the tank, the faster its going to heat up on the hour drive to the track.

I guess what I am trying to say is.. this car needs some tuning, and needs some fuel issues worked out. For all that's done to this car it should be going faster than it is. I guess I figured headers would somehow magically fix the problems lol. It was also a ton of work for a measly .19 tenths heh.

InfernalVortex

iTrader: (4)

Locking nuts will solve that problem in no time. I've had no issues since I went to those. These are the all-metal locknuts, not the nylon ones. These have deformed threads, they're what the factory uses on suspension parts, like the lower control arms.



http://www.sears.com/shc/s/p_10153_1...=SPM5988743401

InfernalVortex

iTrader: (4)

Dont pay so much attention to ET's, that revolves around launches and gearing and 60 foot times. And 60 foot times arent nearly as linked to power as the trap speed.

With a car that heavy, you're actually doing pretty well in my opinion.

3650 lbs
99.5 MPH - 295hp - Ideal ET: 13.47
101.4 MPH - 312hp - Ideal ET: 13.22

The jet hot coating probably wont do much for power. The engine bay heat is still gonna be a factor... Try to fab up a cold air intake and see how much of a difference that makes.

And remember, primary diameter determines flowrates. 1.75 primaries will flow more air than 1 5/8 primaries will. The hedmans are still 1 5/8 primaries. I think that's plenty for a moderate 350. I'd probably run these hedmans on a 383 without too much concern too, but a lot wouldn't. Regardless, the advantage of long tubes is not more horsepower. Long tubes do have an advantage over shorties (with the same primary size) in horsepower, but it's not much, maybe 2-6hp. The advantage of long tubes is that they make more power through the RPM range, especially before peak torque, after peak torque long tubes and shorties are about even on a dyno. They make more torque in the low-mid RPMs than shorties which will in theory get you a better ET gain than shorties, even if it isnt a huge amount.

Dont get too hung up on ET's, there's a LOT of factors involved with that. Instead, focus on trap speed, and get an idea of how much power you're making. From there you can get an idea of what ET range you should be hitting with the car set up perfectly, and you can do what you can to achieve that. At least, that's my approach. I would get some 3.42's.

VincentZ28

iTrader: (2)

We had a 92 GTA 350 Dual Cats went 13.7@102 with just Dyno Don's Shorty headers with a 3in Magnaflow cat-back. The same with a 92 350 Z28 with SLP 1 3/4 dual cat, Magnaflow cat-back, 3000 stall converter went 13.18@102. Both cars were stock with no other bolt-on. Longtubes are not worth the hassel for a street car

InfernalVortex

iTrader: (4)

102mph is really high for a "stock" car with exhaust. That's 300 fwhp for a 3500 lb (with driver) car. You're telling me an L98 was pushing 300 fwhp with just a 3 inch catback and headers? That's a 50hp gain. Not saying it's impossible, but it's not normal.

Generally I agree with you, long tubes are not worth it, but remember, Dyno Don shorties are expensive, and hedman LT's are less than $200 a set. If you can fab up an exhaust system on your own its a lot more cost effective to go LT's. The practicality issue is something else, and to me there's no point in trying to run LT's with an auto unless you do some trick stuff to the crossmember to tuck the pipes up higher. If you run a T5 or a T56 you have tons of room to run a pipe right up beside the trans and keep your ground clearance.





So the hassle of driving a car with no ground clearance isnt an issue. But I'd never recommend anyone who cant do some custom work to run LT's. The sacrifice in ground clearance by just running pipes under the crossmember is awful and makes it much less worthwhile in my opinion.

Dark Ember

VincentZ28, I also am thinking that your cars sound like they are . I have had 2 friends who have owned l98 3rd gens.

92 camaro 5.7, ram air mod w/ removed fog lamps, short headers, high flow cats, muffler, underdrive crank pulley, air foil, adjustable fuel pressure regulator = 2.1 60ft time 14.2@99.8mph

89 formula 5.7, 1.6 rr, 2200ish rpm torque converter, sticky tires, shorty headers, single high flow cat, muffler, underdrive crank pulley, k&n in the stock air box, shift kit, adjustable fuel pressure regulator, polished plenum, + MSD timing advance unit=1.9 60ft time, 13.7@100.

I have everything the above 89 had done + a ram air+ 1LE aluminum driveshaft + ported upper & lower intake with SLP runners + long tubes instead of shortys. I do not have the MSD timing advance unit on mine though I have advanced timing 4 degrees base. These 2 cars are the reason why I was thinking that my 13.7 at 101 was not as fast as it should be.

As for the suggestion on getting 3.42's. I am actually planning on eventually doing 2.73 gears for better highway mpg. I know it will get a little slower in the 1/4 but as mentioned in my sig, this isnt the race car. Every dollar I can save on gas can be spent on the "other" car.

InfernalVortex

iTrader: (4)

Just remember the advantages of long tubes is more power under the curve, not more peak power (there is a little more, but on the order of 1 or 2 percent). So just enjoy having more low end grunt than the guy with shorties of the same primary size.

https://www.thirdgen.org/forums/exha...long-tube.html

If you really end up going to 2.73 gears (I dont know that you'd really gain much mileage except on the highway, but if you do it post up and let us know what happens!) the extra low end will help tow the car through those gears a little better than shorties.

At the end of the day I paid $100 for my hedmans, and those shorties are big money, and still a little less power, and a little less low end torque...

VincentZ28

iTrader: (2)

Well all of our cars in SoCal has 1 3/4 primaries tubes shorties either Dyno Dons or SLP wiith a custom chip tune. And making 251-255whp. So yes it's possible.