What's a Backdrop Manifold?

[Dan Cary]

Extremely novice question's:

What is a Backdrop or Split Manifold? .. typically seen or heard on the Old Cummins. 

They sound great, imo. But do/did they serve a purpose. ie, Horsepower? Were they also available for Thermodyne's, Detroit's, early Cat's? 

If anyone cares to share, greatly appreciated. Thank you!

[mattb73lt]

No worries, we all have to start somewhere. The only way to find things out is to ask questions. The answer mostly had to do with Cummins engines and the NH series, 220, 250(although it's a NHC250 and 855 CI), 275 , etc. Most common exhaust manifold was the center dump, it was a three piece manifold and dumped straight down in the center section. The backdrop ran almost straight back to the rear of the engine with slight down turn, hence "Backdrop". There were two types of back drop, one with an internal baffle or divider. That one was meant for the NH/743 CI series. Then one without the baffle, meant for the NHC/855 CI series. The one with the baffle makes a particular exhaust note due to the fact the baffle prevents the exhaust gasses of the first three cylinders from mixing with the back three cylinders until they exit the manifold, giving the exhaust that particular "bark". There were many manifold made for both engines depending on its application and installation.

[mattb73lt]

Oh, and the split manifold was two pieces with two separate pipes. Three cylinders into each manifold. Ellis was the maker. I’ve seen homemade split manifolds, and only a couple of Ellis ones. Those are probably the rarest to find.

[Mark T]

Back drop was a Cummins thing.  I can't think of any other manufacturer that did much with exhaust manifolds other than where the outlet was in relationship to the application.  I don't know if the back drop was a performance thing , maybe it was like the grandfather to the pulse manifold (lol)   One thing for sure, on a healthy engine, they make a distinct note , and they sound great in my opinion.

[mrsmackpaul]

34 minutes ago, Mark T said:

  I don't know if the back drop was a performance thing 

That was gunna be my question 

Gardner had interesting manifolds on their straight 8's 

Big diesel truck motors from the UK, naturally aspirated straight 8's were 240 hp in their last editions in the 80's and around 320 hp turbo

Very basic low reving angine

http://www.classicmachinery.net/forum/viewtopic.php?f=58&t=10968&sid=ea221be3788a0d5b9d726ac98798f092&start=10

Here's a topic I started on them a few years ago

Have a look if your interested 

 

Paul

 

[1961H67]

O Lord,, I would probably be almost done with My LJ if I hadn’t went down the Backdrop road,, I spent days at that old trucking co getting Backdrops off old Emeryvilles , and I have changed mine 3 times, looking for the perfect sound, and there’s not much room under a LJ cab , I don’t think one I tried is on that list, it was off a Emeryville also, No baffles, it turned out the side. The one with the baffles has a sound of its own! 

I’ll try to find a picture of it.

[1961H67]

Some of my Backdrop experiences 

[Dan Cary]

18 hours ago, 1961H67 said:

Some of my Backdrop experiences 

Beautiful Project & Thank you, this is the 1st anyone has taken the time to explain. 

I need to become a member of ATHS ideally prior to moving forward on anything in this class. If you or anyone cares to answer, I'm also wondering when Cummins went to 855 CI Motors? 

I'm mixing up Small & Big Cams, hp, etc. To my understanding: (The 743's: 220/250/262/275?) 

Thank you, to all the above. 

[Brocky]

Dan

I cannot tell you when the 855's came out (early 60's??????) but the Big Cam 1 was in the late 70's..

As far as joining ATHS Personally I think ATCA (Antique Truck Club of America) is a better organization with a better Magazine. Their annual show in Macungie PA about 15 mile southwest of Allentown Is the better show with over 900 trucks displayed.

Also there is a newly revamped website, Just Old Trucks, which will have a lot more valuable information than the ATHS site!!

Brocky

Edited July 22, 2023 by Brocky

[1961H67]

I’m not sure about the 855 ether, i think the 220s came out in about 1959 (743 cu in ) I know that 743 block went on back , my 1951 LJ had a 200 Cummins, I’m with Brocky 855s probably early to mid 60s . I’m sure someone with way more experience than me will tell us. 

[Mark T]

855s were mid to later '60s.  Not sure exactly when.  It'd be a very large book explaining Cummins engines by the year and such.

[Dan Cary]

I found this on YouTube .. Excellent!

 

 

[Dan Cary]

On 7/23/2023 at 8:02 AM, Mark T said:

855s were mid to later '60s.  Not sure exactly when.  It'd be a very large book explaining Cummins engines by the year and such.

I have not Watched this yet, however, The 855's: Were they then advertised as higher HP than the 220-275 Cummins? 

Meaning is this when the 300 + HP surfaced? 

Thank you, respectfully. 

[Geoff Weeks]

The small cams, I don't know. I had a Bic cam1 that was a '78 build 400 (CPL 324?)

 There was also the long stroke version for a very short time 929? Cid Must had problems 'cause it didn't stick around long, Known as the super 250.

[Geoff Weeks]

On 7/20/2023 at 5:53 PM, mrsmackpaul said:

That was gunna be my question 

Gardner had interesting manifolds on their straight 8's 

Big diesel truck motors from the UK, naturally aspirated straight 8's were 240 hp in their last editions in the 80's and around 320 hp turbo

Very basic low reving angine

http://www.classicmachinery.net/forum/viewtopic.php?f=58&t=10968&sid=ea221be3788a0d5b9d726ac98798f092&start=10

Here's a topic I started on them a few years ago

Have a look if your interested 

 

Paul

 

Never got to work on an 8, but plenty of 6LXB's in the buses. Loved that engine,  slow turning and great on fuel. They were a work of art. I have a side cover with the Gardner script I was going to make into a belt buckle, and a piston from one on my "wall of shame".