Headers

[Anonymous]

True duals would be nice... but I think its pointless. The only reason I would do true duals would be because I couldn't figure out how to even the collector length.

[Anonymous]

True duals would be nice... but I think its pointless. The only reason I would do true duals would be because I couldn't figure out how to even the collector length.

LOL good reason. It offers many performance gains, most TRUE sports cars have them, the GTO, the Corvette, the Viper, etc. Anywhere that exhaust comes together, ie collectors from primaries, or collectors period, is a spot where backups occur.

But it would be more expensive to do true duals.

[BowtieKid79]

A true dual does not offer the highest performance. If you do it right, merging the two banks together will gain a few extra HP. The theory is the same as the collectors for the headers. Yes two pipes will flow more than one (depending on size of course), but if you merge them together correctly the flow is increased after the merge. This is the idea behinh "x" pipes and "H" pipes. I wouldnt run a true dual if i were you... you will only have 3 cyl per muffler and that makes for a very weird and somewhat unattractive exhaust note. You should run 2.25 out of each header and then merge each bank to your stock system where the cat is. The system you have now should flow enough since its all mandrel bent. I dont think you will have enough room to run two 2.25" pipes in the stock location without them hanging down. you dont need to kill your ground clearance even more than you are going to by running the front bank under the subframe.

[Anonymous]

never thoguht about how it would sound, but you're right, it would suck.

[Cliff8928]

Ya, you can get a dual-in single-out catalytic converter for that specific application... A friend of mine has true duals on his 96 GMC Truck, and it sounds unique (has a whap whap whap sound) My mom's 96 GMC has a dual-in dual-out muffler and it sounds totally different (both trucks in question have Dynomax Ultra-Flo)... it definately makes a HUGE difference in sound..

Cliff Scott
89 BerettaGT
89 Volvo740

[Anonymous]

I turst Bowtiekid, he is a smart guy and knows his stuff.

But I have always heard that true duals is better, a lot better. Maybe not for sound, but for perforamnce.

It doesn't matter though, because I am going to keep my current setup to save money. I took an in depth look at the underside yesterday and here is what I came up with.

When KickinZ, (John), did his headers he ran the 3 front primaries UNDERNEATH the front frame crossover. This is where his clearence problems came from, since the frame is over 1 1/2" lower than the oil pan. I plan on running the 3 primaries over the frame, between the block and the frame. The front passenger mount blocks the space on the passenger side, but the driver's side, I believe they will fit if I run them side by side between the starter and the frame then collect them after 36" or around the back of the oil pan. One problem is the engine torqueing. Unlike RWD applications, our engine torques to the rear, lifting the front side up. Now this isn't noticable when in neutral and revving, my motor doesn't move at all. But I am sure it will under daily driving, especially hard driving. Thus the lower parts of the motor torque forward, whcih might put my starter through my headers. I do not know if it torques that much, I doubt it, but again I am not sure. Any comments would be much appreciated

As far as the rear goes, I have figured them out and will design them today in my drafting/engineering program on CAD. I also will have them be equal-lengh. Assume when I give directions that I am in front of the car, my right is the driver's side my left passenger's. the far left port(2) will turn to the right, cutting as close to the firewall as possible. It will run to the current collection area, then turn left and head down where the downpipe is for 36". The middle pipe(4) will go out, and immediatly cut left towards the left port, staying as close to the block as possible, then it will U-turn side by side the #2 pipe. Then it will follow suit back. The U turn will give me a few more inches to keep it equal with #2. As for #6, it will cut left, running just behind the #4 pipe. Then it will U turn, and run back with the other 2. I will collect the 3 after 36" is up. There is room back there as soon as I remove the entire EGR system.

Sound good???

[BowtieKid79]

I would reconsider your front design. I don?t think that there is enough room between the oil pan and subframe. The headers will move with the starter (since both are part of the engine and will move together), but the headers will get closer to the subframe as the engine rocks (not good). You can also kiss your starter good bye... they will not even come close to taking that much heat. Not to mention it will be impossible to change it without taking the front header off. Back to the drawing board!

The rear bank is made up of 1, 3 & 5 (not 2, 4, 6). Not that it matters really. Anyway, post a pic of your rear header idea when you get it CAD'd out. I am not quite following what you are saying (it?s late though so that could be part of the problem).

As far as true dual exhaust... they do not make the most HP (by TRUE I mean the two banks NEVER merge). Remember... just because some cars come that way does not mean it is the best. Usually packaging and money have priority over performance in a production car. Trust me... an X pipe on a dual system will work better. Not to mention a V6 with a true dual just sounds plain nasty.

Let us know what you come up with for a drawing.

[3.4Z24]

check out circle track mag. lots of tech info and stuff (not a plug).

i've gotten lots of header theory from them.

[Anonymous]

I am drawing it finally today in about an hour and I have an hour and a half so I should get it done unless CAD bes gay, which isn't uncommon. Using CAD I can measure the center of the pipes to ensure equillengh.

Bowtiekid, how much room between the rear exhaust ports(rear cyliner head) and the firewall do I have to work with? Disregard EGR, it is going bye bye on my car and since I have a good friend at Jiffy Lube, he will pass me for emissions.

I will rethink the front design, forgot about heat and I realized how much heat exhaust IMEEDIATLY produces when I tried to change plugs on a warm SBC

[Anonymous]

Ok ideas are a flowing.

For the front 3 (2, 4, & 6 ), what if I do the same for the front as I will do for the rear, wrap them back, then U-tun them. Then run them side by side in the trianglulated position for 36" around the stock crossover position. When 36" is up, probable before they even get to the rear head, collect them, then run that 2 1/4" pipe down on the right side of the current downpipe position. The current downpipe cutout is rather large, could fit 2 X 2 1/4" pipes side by side. when the rear set has its 36" done, then merge the 2 X 2 1/4" pipes together, Y-ing them to my current exhaust system. This will be good, and with ceramic coating and adequate heat shielding it should be the same if not less heat. I will draw both today, but it would help if I could get some other info.

I would like the distance, in feet and inches, from the front cyl head to the rear at the point, as far as heigth goes, of the exhaust ports, so about the middle of the actual head. If I do not get a reply, I am going to use about 20-24".



I am expecting my parents, for X-mas, to pay for about 200-300$ worth of parts. To include collectors, primary mandrel bent pipes, etc. Basically whatever I need to do it.

Bowtiekid, I know you know how to use a welder, and you aren't half bad at it, but do you have a welder or did you borrow one? I was thinking we could get together at my garage (heater, many tools, and space) and we could both do headers using my design if it works out ok. Sound ok?

[Anonymous]

I also need to know a few other things.

The distance between the center point of the exuast port on the left, to the center point of the port in the middle, to the point at right. I'm going to hypethetically assume it's around 4".

Also I need to know the exact port outlet size for the exhaust. Again just to get it drawn, I will use 1 1/8".

Lastly, what size for primaries? I don't care abotu low end, but pulling to 7k is a MUST. It can drop off after 7 I don't care, but if it meanse sacraficing 10 ft lbs for 5hp, it's worth it. I am going to use 1 3/8" for now, 1 5/8 seems big as small block chevy heads, a good set, will need 1 6/8".

[BowtieKid79]

I dont know how much room there is b/n the rear head and firewall. We'll just have to look at that later. I THINK the exhaust ports are roughly 1 5/8" square (or clsoe to that). I dont have a welder up here but i may go buy one soon since i will need one also. I dont know the center to center distance for the ports. I would go with 1 5/8" primaries. I think you are going to have a hard time fitting two 2.25" pipes in the stock downpipe location... remember you have to leave some room for it to move when the engine rocks. Anyway, check your PM. Will talk more about it when my finals are over tomorrow night.

[Anonymous]

Ok sounds good. About the welder, if the headers are going to be around that much for the kit, I may have to hold off on the welder or convince my dad that we need one.

[Anonymous]

with the 1 5/8" headers I am running into space problems. Also I have lost a way to make them equal lengh easily.

How essential is it to have them equal lengh?

[RacerX11]

Are you trying to make the individual runners equal length, or the total exhaust length (from exhaust port to tail pipe). I built a set of headers for my 3.4 pushrod engine in an X-11 (its not a DOHC, but the same principles apply).


Mine are 1-5/8? primaries, 26? long, with 2-1/2? collectors that taper down to 2-1/4? for the tailpipes. I routed the front header up and over the transmission, similar to the stock crossover routing. I used pictures of the Bearetta Indy Pace Car headers as a guide when building them. The rear header is a tight fit, with the collector ending up down in the tunnel. There was barely enough room to squeeze two 2-1/4? pipes down the tunnel. Maybe the W-body has more room.

With the longer 36? primaries, it will be a little trickier to fit the rear header.
The Chevy Power Manual calls out for 1-5/8" primaries, 26 inches long, with 2-1/2? collectors for the 660. Other header calculators I have used came up with very similar dimensions, even when using a 204cu in, ~220 HP engine as an input. I am wondering if the 36? primaries might be too long.

You reach a point where it might be better to get the headers on the car, even if the primaries are maybe not the ideal length, or the tube lengths differ by 1?, or some other design aspect is less than 100% optimum. Even a slightly compromised header design will be better than the stock cast iron manifolds.

Here?s a pic of my rear header to give you an example of how the tubes can be routed. I have several other pictures from different angles, and of the front, if you want to see them.