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Yo,
The exhaust on the Slotus has presented me with a problem that I wasn't quite expecting...

I bought a set of "block hugger" headers because of the narrow space on the driver's side for the exhaust. As the name implies, they fit close to the block and the collectors/flanges on the ends actually point inward a bit. They work fine on the driver's side. However, on the other side, the collector/flange on the header points right at a frame rail, and needs to make about a 95 degree turn in a very small space.

James and I were looking at it the other day and came to a realization... A traditional "rear exit" header, like used on Mustangs, would fit just fine on that side and would move the collector rearward and point it slightly outward as well. But, that would mean the left and right side headers wouldn't "match" shape-wise. I can get a traditional header with the same size tubing as the hugger, but as far as pipe lengths and flow characteristics, I can't imagine they're anywhere close. These are not "equal length" headers by any means, but they'd be seriously mis-matched.

So the question to the group is: Would that make enough difference to matter? Will I be able to tell? Will it make the engine hard to tune? Will I burn all the exhaust valves on one side? Will all my children be born naked because of it??? What do y'all think?

JD "Enquiring Mind" Kemp

So the left side will make torque and the right one will make high-end power?

I am not actually sure if I am joking. Will you end up with a broader torque and power curve than otherwise, which might be a good thing for a hill-climb car, or will it be worse than either? In practice, all sorts of single-exhaust Vee engines have mismatched exhaust banks.

The equal length is a great goal, but matters less on the odd-firing v-8's. They still have power advantages, but I have not seen the gains on good design like you do on 180 degree crank v-8's, 4 cyl's, and 6's.
Since you are not able to run an x-pipe, you will for sure be giving up midrange power. How much? Not sure, but I've only seen gains when going from manifolds to headers no matter what the design.
On an n/a motor, the curves matter less than overall length. So, if the design is different, but you can get the lengths close, do it. Seems like a great reason to build your own!

Here is a set of equal-length, stepped headers for a 7 4age I did. Lots of room in this case, but with the sweep back he wanted, still had to get creative to get the lengths the same.

Gorgeous headers!

Yes they are, and excellent photography.

Thanks guys. The photography is just luck. I get a good one every few months that makes me think I have a clue, then the next one confirms the sad truth...Something I'm going to pursue in my later years for a hobby for sure though. I think it suits retirement well.

This is the essence of the problem. If anything like this is happening, it implies the banks are breathing different amounts of air. The power depend on the amount of oxygen you can burn. Then you need the right amount of fuel. If you have a carb feeding a plenum and then a manifold, like a 4 bbl, then each cylinder will pull what it needs and the mix will be the same - so that's OK. If you have a single barrel per cylinder or port injection things would be worse. For the carb case you could jet differently on each bank. The EFI is not so smart though. It could be but it isn't.

That's too bad. Do what you need to and go on. I don't think it will be so bad as to burn valves. If you go WOT on that thing for more then 10 seconds you'll be in the next state. We should re-visit this subject before we run the Daytona 24 hours though.

You could take a guess at how much the power difference between the banks would be. That should also be the difference in the air breathed and the fuel required. If the difference between banks came to 20-30 HP at WOT then the mix would be wrong by about %10. One bank could be at 12.5 and the other at 13.5. I guess this means you would need to be a little more careful, you will have less leeway in your mix since one side is always closer to trouble. If you use an oxygen sensor - I was gonna say put it on the side you think is lean but think you better get two sensors and one gauge...

Unobtainium, nice welding. The last time I saw welds that nice was like 25 years ago when my mechanic friend made me new arms for a corner I ripped off my car. The HAZ zone was hardly any bigger then the bead was.

Hey Marcus-
I was thinking on this earlier and came up with two O2 sensors and two gauges for "set up" purposes and tie 'em to one gauge thereafter. I could also measure the volume of each kind of header and see how they compare, but that won't really give me the flow rates which (I think) is what we're really after...

Maybe the answer is to bite the bullet and figure out how to make that rt side hugger header work. The modifications required might make more difference in flow than the mis-match would... Although, what we're really talking about is putting a tight 90 deg turn in the base of the header, just below where the four primaries come together.

Uncharted territory here, would somebody else like to go first???

Thanks for your help!
JDK

Hi Warren-
Sorry I missed your post, I was busy drooling over Unobtainium's headers!

You could be right, might see a net increase of torque and/or power... I kinda doubt it, but it could happen... Might be one of those "try it and see" moments. (Which are perilously close to the Redneck's last words, "Hey Y'all! Watch this sh*t!")


JDK

Gonzo,
This will be a little like the staggered intake ram tubes on some of the old Can-Am V8's, only on the exhaust side and bank-to-bank. IIRC this was done to broaden the torque curve of those big-blocks, as if they needed any more power.
So it should work ok. Instrument both sides with the O2 sensors to check, like you said. You can always build a custom set of headers later if need be.

can you shorten the block hugger to a similar length as the mustang one?

Hi John-
It's more the other way 'round... The stock one is the longer of the two. The block huggers are more like the "shorty" headers for Mustangs. If I go with a mis-match, that's what I'd use, because they have a better chance of being similar tube lengths.

I need to put up some pictures of what I'm talking about. I'll see if I got any runnin' around.

Thanks!
JDK

When it comes to headers, equal lenght does NOT mean equal flow. The tubes can be the same lenght, but a tube with more bends will be more restictive. Unless you have a dyno, getting within an inch or two is good enough and it will not have a noticable effect on HP for a street motor. Mod your current headers to fit.
Dave W

Come on JD! Just modify everything past the header flange on both sides. Meaning, use the headers for flange donors, cut off the pipes and start making new headers from scratch. You know you are dying to. We are just a support group validating your desires. Just do it! Come on in... the water's just fine.....Trust me......