BBLM 38181 exhaust info

Hi all,

It looks like 38181 got some upgrades from Carobu a few years back – including an exhaust. From what I've been able to gather, this car dyno'd over 500HP (not sure at crank or wheels). Any info / thoughts on this header design? Looks like larger diameter, with earlier collectors – maybe solving the pinched 6 & 7 cylinders problems as well as providing clearance to lower the car? I think the video below is of 38131; which has a different tone that other BBLM (at least to my ears).

I am considering having a custom exhaust made for my BBi. It may sound crazy, but I'm even considering 3D printing Inconel as the costs have come down considerably. Probably cheaper than a stock header reproduction from Tubi. Trying to do some R&D before really digging in.



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The original LM manifolds are one piece open pipes was my understanding and they look great, those above are a modern interpretation? Carobu manifolds could be for dyno use only and produce the best results but dont fit a car properly - Im speculating on that because thats how most dynos are. I've considered open manifolds on a road car but these engines sound like crap in street form with them uncorked, unless you have your foot into it all the time but otherwise they sound like an import with a broken head pipe.

 

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I ran my car with open headers when installing a Nouvalari Sport exhaust. It sounded pretty horrible. Major let-down. I didn't even bother recording it was almost embarrassing. Quickly moved on with the rest of the install.

Good point about the headers for just the dyno. It does seem like the car is running something different than other LM cars though, as the collectors appear to be side-by-side vs stacked?

I wonder at what point a road car needs to be modified before it "deserves" LM style manifolds.

 

Cams and significant compression would be a game changer but then it would be a drag to drive on the road unless you lived out in the sticks like me

 

When I owns #38179 (#70 LeMans 19830 I drove it on the street here in Alabama.--mostly on the interstate. Epic experience.

 

I spoke to Tate at Carobu briefly (he was on the road). I got the sense that the exhaust was a bit of a nightmare and that he would not do it again. He confirmed that the exhaust used on the dyno was the same used in the car and added that they really only made the exhaust out of necessity because of the engine work they had done.

 

How many similarities are there between an LM car and our BB/BBi street cars?

 

I'm really not qualified to answer this, as I only know what I've read. I think the short answer though is that they're more similar than they are different (even by the time they got to the Series 3 versions). Obviously, the stand-out differences are the Pininfarina Silhouette body and Lucas injection instead of carbs / K-Jetronic.

Beyond that, it's my understanding that the changes were actually pretty mild (or at least when compared to the Porsche road vs race versions). Basic things like higher compression pistons, race cams (P6?), beefed up transmissions (quite a few DNF due to transmissions), and overall lightening of components (eg, holes drilled in suspension arms, bell housing, etc.).

I could be way off base though, and welcome corrections / additions from someone with more knowledge.

 

You are pretty correct. Only so much beefing up of transmission was possible though. Making them live had a lot more to do with driving style. The basic architecture is the problem. Oil temps were a very real problem even on street BBs not having an oil cooler so the nose was configured to put a large cooler up there. I remember running them in the shop. Back then none had mufflers and off idle the noise was intolerable. It was ear piercing.

 

I drove a couple around the property and worked on a few. As endurance cars they were not real cammy. I think with mufflers and a conventional clutch and usable ride height it could be driven on the street. Visability sucks though. Even to the front. I was told by an owner at Daytona on the banks you have very limited visibility ahead and you really need a spotter. Stuff can happen in front that you'll never see until its too late.

 

You could go your Iconel route for styling, and add some cherry bonb mufflers along the way to the rear. Years ago franklin parker did a BIi with cherry bombs sounded great,

The stock header apparently flow well and powder coating them white gives it s 512s look, aft of the headers imo the single can bell exhaust sounds best and is still streetable.

the tubi headers look nice and fit the car. Remember though stainless bits dont sound the same as mild steel.

the motor and exhaust being behind you means its hard to get that classic ripping canvas sound in the cockpit, however intakes done right add a whole dimension to the symphony.

i understand you're going for a bit of BBLM on street mechanical look overall. However a car too noisy, becomes hard to use on the street as its aggravating to yourself and others, and you announce your arrival miles off. How to get great tone and sound through the rev range, race motors run near redline all day.

we're all different so this is my opinion only. Tuneful tonal sound is the way to go over sheer volume. Im trying to think of a modern car that does this, most seems to have those baffled mufflers which are really quiet untill the baffles open and then mostly loud, I guess the departed aston v12 vantage do it well. Maybe the z06 and hurricaine come closest now.

Tuneful motors imo, a euro spec alfa GTv6 was sublime as was surprisingly the early 70s 365 gtc4 ferrari.

 

Yes, I am essentially creating a "modificata" version of the BB as-if Ferrari brought some of the learnings from the BBLM program back to the road car. Maybe it could be called a "restomod" because I am using EFI instead of Lucas injection, but I am trying to stay respectful to the brand and the period (fine line to walk).

Per the exhaust, I was particularly interested in the collectors being side-by-side, as well as appearing to collect sooner than most I've seen for the BB. Tate said a lot of time / engineering went into designing these; so I am guessing primary length / collector position was designed around pulses, cam lift, scavenging, etc..

IIRC, the Tubi sport headers are ~$7k, and I don't think they cure the bottoming out problem (particularly if the car is lowered), and I'm not sure they cure the pinched 6 and 7 primaries either. Also, for that kind of money, I can design custom headers in CAD, and 3D print out of stainless steel (Inconel is still quite expensive).

I reached out to Bell, and never heard back. I have Nouvalari on my car; which sounds "ok". I've read that the glasspack / cherry-bomb style sounds great. Regardless of the mufflers, I think it's the chop / lope of more aggressive cams is what I'm after. The BBi is just too smooth.