Exhaust Clearance and Dimensions

What is the clearance (in inches) between the exhaust ports on an LS(x) head and the frame. I'm designing some headers in AutoCad. I'm 8000 miles away in Afghanistan, so I can't look at my car to measure the width of the frame.

Also, about how much room do I have to work with in both the vertical and horizontal planes. I'm assuming for vertical, it's about the height of where the engine mounts on the frame, but what about length? How hard would it be to fit 32" long tubes?

Thanks in advance for the help.

Here's some pictures of mine. Granted I have used a ol school SBC but you can see the basic configuation. My primary lenght target was 32-34 inches. I was easy to do this for 3 out of 4 pipes in my case. The 4th was difficult because I used a set of sprint car headers as donners. If I make them again and little better planning and it will be easy to get near equal 33 inch pipes. I think you could go as long as 36 inches if you wanted to. 32 is a pretty good number for a >7000rpm motor.

These are 1 5/8 then 1 3/4 into a 3 inch collector. The planned rev range is 3800 to 6600 and about 450HP.

A last one for the troops. Take care of yourself and your buddies.......and thanks.

Thanks for the pics,, esp the last one, that one might be the tightest fit..lol,, okay,, I digress.

About how many inches is it from the heads (exhaust flange) to the frame, Would you say I have at least 5-6" to work with before the pipes need to be going vertical?

My idea for exhaust headers is the following

1,7,4 & 6 will be the same length
While 3,5,2 & 8 will be approx 9 inches shorter.

I did this calculation figuring for 325fps exhaust velocity at 6000rpm. The exhaust actually travels at 9 inches per pulse, so to "even" up the firing order a bit, the pulse will be distance delayed/head started (depending on the side), to what should be close to one exhaust pulse.

With the slightly crude calculations I have, the left and right banks will be leaving the exhaust at exactly the same time, In essence, it will sound like 2 4cyl engines exactly synced up.

I "believe" you could stagger the exit (tailpipe) left and right exhaust pulses with distance, again, with having either the left or right side being longer than the other, I am not sure the distance, because I'm not sure what the exhaust velocities would be once they have passed the collector. The extra distance would have to be added before the mufflers. Otherwise it would not change anything because the sound is still traveling the same distance. I got a buddy of mine that should be welding up a set shortly and see if it makes a difference. I don't expect any power gains, though it might because of scavenging, but I hope the sound is differen

I don't see the point doing this without the car infront of you. When my friend built my exhaust it was a snug fit in order to get it equal length and be easily removable. I can see this would turn into a fitment nightmare without it there.

EFNFAST said:

I don't see the point doing this without the car in front of you.

Click to expand...

Ditto. I speak from experience building 3 pairs of SLC headers with the car either an hour or 3 hours away. I've screwed myself every time before they were finished.

You're much further away...stay safe.

I would recommend that you have the car with the engine in it before you begin building headers. Otherwise I would say you have less that a 25% chance of them fitting correctly. This isn't really hard to do but it does take a LOT of trial and fit, over and over again. You need the car for the trial and fit part.

I don't quite get the idea of purposely building unequal length primaries. I have never seen this done on purpose, although I freely admit I only know what I have read on header construction and theory and my limmited number of sets I made myself (1 V8 and a bunch of 2 stroke expansion chambers a long time ago). Are you trying to do a 180 design? I think it can be done with a Porsche size GRBX but not so much with a Recardo. I would steer you towards a H pipe design. Very little difference in performance and sound but less than 50% of the work IMHO.


The last thing is the area you are working with isn't square. The upper and lower chassis tubes are not equal distance from the head exaust port surface nor are they straight fore and aft as far as the same distance from the heads at each end. You also have quite a bit of additional clearance below the head ports and the block. Then where you mount the alternator and other accessories must be taken into account. There's plenty of room but its not a simple rectangle box you will need to work in.

Ditto on the comments. Wait until you have the car with the engine/gearbox in place.