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We have just finished our set of C55 long tubes and it will be dyno tested tomorrow. It turns out all C55 shorty headers and SL55 shorty headers are exactly the same and interchangeable.
So next week we will have a SL55 in our shop for a test fit of our headers. If all goes well (I think it will). We will make some flanges and cats so you can bolt this header up to your SL55.
After running the SL55's engine specs in our header design software (bore, stoke, compression ratio, valve size etc..... It spit out the same date we used in designing these headers. Note: the software only tells us what size things need to be.
The headers will are build off the firing order on the 55k m113 motor to aid in optimal scavenging.
We do not have price set at this moment.
Here are some pictures of our headers we think will work for the SL55 and some of the steps we take in designing a performance header.
Looking really good Hooley...some questions for ya:
1) any idea on power and tq gains (guess you will have to fit it to SL55 and then test on dyno)? wanted to gauge your best estimate...
2) How does the header maching spit out the same build specs for a NA 5.5L V8 (C55) and an FI 5.4L V8-K (SL55)? They are two different types of engines alltoghether with different power/tq outputs.
Just added these headers to my 08 build, removed primary cats but left secondary cats plus mufflers installed. Sounds WONDERFUL at wot and no drone AT ALL at cruise. Additional power not bad either, hehe.
Just added these headers to my 08 build, removed primary cats but left secondary cats plus mufflers installed. Sounds WONDERFUL at wot and no drone AT ALL at cruise. Additional power not bad either, hehe.
Nice Bill!!!
Do you make any before and after videos?
I’m curious as to the connection to the existing exhaust, as I wouldn’t want to cut anything and retain the stock pieces intact.
I had the work done at a local MB performance shop. As far as I know there were no videos or pics taken.
They did say MBH provided a connection piece to step down the 3" headers to the 2.75" MB system downstream of where the cats were removed. I cut out the cats because I'm about to retire to FL where tailpipe emissions are not required, otherwise I'd have left them in (or substituted Kooks High Flow Green Cats).
I'd be happy to ask the shop to mark up a drawing of our exhaust system (I have an exact depiction) if that would help you. I also will post a video of a cold start and high speed pass when my son comes home to visit as he can be the "photographer".
"Butt dyno" says this was significant improvement in power/tq. The numbers should tell the story once I get another dyno done. Back end started to come around on wot acceleration the other day on I-40 on -ramp that was curved (fortunately the nanny's took over immediately and saved me ). Startled me at first, but then...... a BIG OL SMILE came across my face.
Just added these headers to my 08 build, removed primary cats but left secondary cats plus mufflers installed. Sounds WONDERFUL at wot and no drone AT ALL at cruise. Additional power not bad either, hehe.
Great! I have a set to install on my SL55 also.
So, you left the two cats located close the the drive shaft tunnel? And, the two resonators in the bend?
I'd love to remove both sets of cats, but concerned the removal may cause the dreaded Cat/Sulfur smell and possibly drone?
I would do a custom 3" stainless midsection with X pipe, if I could be guaranteed no smell or drone?
I have seen the videos of Brian Fishers (fisherfast on YouTube)latest exhaust configuration and see he is using the Kooks high flow cats, no resonators and Corsa Muffers?
I may tie into the factory exhaust like you did, then experiment with a custom X pipe midsection with not cats and resonators. If, I get smell add Kooks Cats. If it drones after Cats are added, use bullet style resonators. All using the factory AMG muffers?
Just added these headers to my 08 build, removed primary cats but left secondary cats plus mufflers installed. Sounds WONDERFUL at wot and no drone AT ALL at cruise. Additional power not bad either, hehe.
smithwn55 Good to hear this feedback. if you removed the primaries, did you use mini cat extenders like the one fabtech makes or did you need to do this for emmissions? i went back to read your follow up post about retirement so you just answered my questions.
Does anyone have experience using the mini cat extenders? Fabtech make one but there are others on the market that make these as well......they are "mini" cats as advertised but on extenders....so not real small cats.
Last edited by Ajai Thomas; 04-21-2021 at 08:27 AM.
@smithwn55 how do you like the performance gain from the pulley and the tune? What tuning company did you go with? did the pulley and tune pass the "butt dyno" test?
I am expecting delivery of my red anodized UPD 77mm SC pulley today and I'm considering tunes. UPD recommended some tunes so may just go with them (their tune provider that they've been working with for over 12 years). I also ordered a PLM XL heat exchanger but i'm only expecting delivery of that first week of May. Maybe the split cooling and Needswings intake will arrive before then so i plan on installing the intake and the cooling side first.
06-24-2009, 11:18 PM
...some questions for ya:
