Let's Talk Exhaust - Building My Own

[nogoodwithusernames]

Alright so it was a busy 2018 and I didn't get much VW time in so my motor currently stands as it was in my last topic (https://www.thesamba.com/vw/forum/viewtopic.php?t=672230) though I have decided to start properly setting some money aside to buy some panchitos heads and along with that I would like to improve my exhaust. (Currently stock heater boxes with a 1-3/8" tri-mil header/muffler.)

If you don't want to read through that thread the motor is a 76mm x 90.5 (1956cc) T1 block setup with T3 tins and cooling for my square back.
Cam is a CB 2250 and stock ratio rockers.
Heads will be a set of Los Panchitos.

I've got the welding and fab skills to physically get it together but I want to get some input regarding the design of it.

First off, I have easy access to sanitary stainless tubing but it's only really available in either 1", 1.5" or 2". I would assume that 1.5" would be pretty good for a 1956cc motor but want to confirm. I think 1-5/8" would be too big for this motor anyways even if I could get it?

For connections I plan on using sanitary tri-clamps with hi-temp gaskets so that I can rotate bits around if it's ever on a different motor that's a little wider or narrower. Nothing fancy there, but easy for me to get and easy to usel.

For the actual design I'm not sure about tri-Y or just straight 4-1 header. Thoughts?

If I went tri-Y my thought is bring both ports to meet in the middle under each head then 90 them back to another Y just behind the sump plate. I know that's not a proper tri-Y where opposing firing ports join at the first Y's but looking for feedback.

Another theoretical question is for an equal length header, does the length matter or is the volume of the leg what it's about? AKA could I use some reducers and larger tubing for a section and have a shorter leg with the same volume and have it work well?

Finally (for now, every answer will bring new questions I'm sure.) I plan on making my own heat exchangers. Hoping to keep it fairly simple and weld on some strips as fins outside the 1.5" tubing and then splitting some 2" or 2.5" tubing and clamping or welding or somehow affixing it around the fins and running up to some heater box flapper boxes. Any tips on this from past experience etc?

Now go ahead and school me on this, I'm ready to learn and have plenty of time before I actually get around to this. (Probably be a few months before I can buy the heads) Or if there are other good threads/videos/etc regarding this please point me their direction.
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71 Squareback, 1.7l T4 w/ crank trigger fuel and spark
(Conversion thread https://www.thesamba.com/vw/forum/viewtopic.php?t=732508&highlight= or https://shoptalkforums.com/viewtopic.php?f=1&t=151375&sid=f0542d44a322d290c29d6609fac7f215 )
74 914, 2.0L w/ D-Jet

-Derek

[modok]

Did you read this one?
https://www.thesamba.com/vw/forum/viewtopic.php?t=708541

[nsracing]

You trying to save money or just wanting to be different?

There are headers out there already proven... and they look freaking awesome. IN any flavor.

[oprn]

[nogoodwithusernames]

Modok, I have but I read through it again and it looks like a lot has been added since I last read it. I’ll keep tabs on that one, looks like a good discussion.

I’d like to save money, be different, and I like building things. And like oprn mentions type 3 systems are not as available as T1.

It sounds like the tri-Y would be the most difficult but most rewarding on the low end which is where it’s important in the heavy squareback.
I’ll try to find some other threads to read through too.
Any input on the equal leg vs equal volume?
With tri-Y would the second leg (after the first Y) need to be equal to 2x the 1.5” tubing? Or since only one cylinder is exhausting at a time would keeping it 1.5” through to the final Y be okay?
_________________
71 Squareback, 1.7l T4 w/ crank trigger fuel and spark
(Conversion thread https://www.thesamba.com/vw/forum/viewtopic.php?t=732508&highlight= or https://shoptalkforums.com/viewtopic.php?f=1&t=151375&sid=f0542d44a322d290c29d6609fac7f215 )
74 914, 2.0L w/ D-Jet

-Derek

[Vanapplebomb]

Although there is only one primary exhausting at a time, there is still a significant pressure wave traveling through the primary that is not exhausting. So, there is a good deal more volume flowing through that secondary branch than there is in the exhausting primary alone.
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1800 Type 4 Berrien 295

http://www.thesamba.com/vw/forum/viewtopic.php?t=487021

[mark tucker]

I would recomemnd not usint stock ratio rockers with that .420 lobe camshaft. i would use the 1.34 ratio ( 1.25 with the adjuster on the pushrod side of the rocker, and curved foot on the valve end.) thats too much lift for the 1.1 rocker saftly. I have over 120000 miles on that cam&1.34 rocker combo with no issues at all, and set the rocker side play at .003, lower the rocker's .040 ( cut the rocker shaft blocks.040-.050" shorter). use lash caps. cut flats on the pushrod ends at the holes, and deburr the pushrod cut hole. add oiling groove inside the rocker bushing going down about 1" long in a C or S shape from the oil hole staying 1/4" from rocker sides. do not groove the top side!! good luck and have fun.

[modok]

My best configuration with the longtube tri-y so far, shooting for about 5500-6k shift point, is
1.5x 30-32 primaries,
1.75x 14 secondaries,
2 1/8 straight collector into muffler

I tried....longer secondaries, smaller and larger secondaries, stepped and reverse stepped secondaries, and 2 and 2 1/4 final size, and fancy collectors shapes..... have not tired stepped primaries yet but that is next on the list, I have not tried shorter secondaries but I prefer to stick near 1/2 primary length, or at least 1/3 of it, to make it kick in strong and early......tho you can do very short secondaries and achieve a kind of different effect.

it may be that smaller diameter secondaries could work IF I could make the primaries shorter, but....... it's not really possible to make them any shorter.

If you change the tri-y so the other cylinders are paired, it acts very different, and to get into the same RPm range you will need much LONGER primaries believe it or not, which is a curse and a blessing yes even longer than the formula V ones!....because of the CAM duration. Would be interested to see how that works, very few people doing that, but that's probably not what you want to do this time, at least for this application.

[nogoodwithusernames]

Mark, I was hoping to avoid that expense but it would probably help wake up the motor even better and since it'll be out of the car already I might as well. I just read through the slipper foot geometry thread and think I can manage getting those setup properly. I'll add those and new pushrods into the budget.

Modok, how does that configuration feel on the low end? Sounds like it's not too high a shift point so that should play well with the heavier car keeping the torque and power down lower?
Those dimensions help a lot as it gives me something to shoot for when I build it, so thank you for putting the effort to testing and seeing what works best.
_________________
71 Squareback, 1.7l T4 w/ crank trigger fuel and spark
(Conversion thread https://www.thesamba.com/vw/forum/viewtopic.php?t=732508&highlight= or https://shoptalkforums.com/viewtopic.php?f=1&t=151375&sid=f0542d44a322d290c29d6609fac7f215 )
74 914, 2.0L w/ D-Jet

-Derek

[mark tucker]

not really for waking it up but so it will work and last. as far as the tri Y header....where is the 4th tube going to go

[67rustavenger]

[earthquake]

I like to build headers, I have built at least 2 dozen sidepipe headers for 427 Cobra's while working for a Shelby dealer at Las Vegas Motor Speedway. I would like to build a header for my class 11 look a like that gives a bit more ground clearance one of these days, I found the best place to buy bends at this place...

http://www.mandrelbends.com/
_________________
74 CLASS 11 LOOK-A-LIKE
69 DUNE BUGGY
79 INTERNATIONAL SCOUT II
05 SCION XB SERIES RELEASE 2[#437]
95 Chevy C3500 dually
98 Ford E150
Link to Kelly J. Nolte 3/20/53 - 11/6/08
https://time-zonelabs.blogspot.com/p/about-kelly.html
DEATH TO CHINGERS!
[From a military recruitment poster in the novel "The Stainless Steel Rat" By Harry Harrison]

[mark tucker]

I like the cb oe type rockers over the others...but not for a .420 lobe or more.IMHO a .380 lobe is pushing it for that style rocker to "work", but the bugpoop/empi cheep sliper foot would be my choice...like what I run..for long time.

[bugguy1967]

[DeathBySnuSnu]

I also built my own headers. I have an odd app and the desire to be different also. Mine wound up being a 4 into 2 split header. It seems to work, but I dont have anything to compare it to. I did get on a wheel dyno once and made good numbers. But since then I have changed a good bit of stuff with the tuning. I have become more concerned with making it fun to drive instead of peak hp on a dyno.

So with a 2387 and fk10.
1-5/8 out of head for the first few inches.
Then an anti reversion can.
Then 1-3/4 short tube (calculated length using online sources) of 34" long from valve.
Then a steep tri-y style (2 into 1) with a 2" collector.
Then a 2-1/2 anti reversion can with a 2" outlet.

It made good numbers.....but nothing to compare it to......would it make better with a store bought header? I will never know (wont fit) and I am happy with the results.

Bottom line.....if you like building headers and want to give it a go.....then by all means do it....make something that is yours and will make you happy.
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[oprn]

[67rustavenger]

[oprn]

I have found that muffler shop bends have a huge radius anyway. Impossible to make a compact system with their bends.

[67rustavenger]

[DeathBySnuSnu]