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Datsun 620 ultimate SS exhaust


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#1 Beastlikethat1

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Posted 11 January 2018 - 10:21 PM

Recently finished my 77 Datsun 620 custom SS exhaust. Most of it was tight welded but the whole system (welds, tubing, muffler and hangers are stainless steel) made by a co-worker and I. Flange was also machined by me with a harbor freight drill press!
2.5in the whole way and 1.75 2 out collectors
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#2 flatcat19

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Posted 11 January 2018 - 10:36 PM

That down pipe is sexy as hell.

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#3 racerx

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Posted 11 January 2018 - 10:47 PM

Nice job...

#4 FrankRizzo

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Posted 12 January 2018 - 04:59 AM

Sweet. How is the sound & any details on the muffler?


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#5 distributorguy

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Posted 12 January 2018 - 05:34 AM

Magnaflow mufflers sound great - and even better the further back they are placed on the vehicle.  Why not run the tailpipe all the way out the back?  That's a pet peave of mine.  And why not use pieces of mandrel bent tubing instead of sectioning a bunch of wedges together?  Think about how all of those sharp edges cause turbulence and hot spots inside the pipe, like the exposed ledge inside your collector.  I'm a firm believer in having "steps" in the system to prevent reversion, but not to restrict flow in the correct direction.  Its pretty, but not by any means an ultimate solution.  Also look at the direction air flows out of the 2 tubes in your collector.  The air is directed straight into a wall - an all too common mistake.    All this will work, but likely won't make any more power than a stock type system.  Why 2.5"?   That will lend itself to a significant loss in velocity and scavenging.  Did you keep the system at 96" overall length from the head as is ideal with a L-series port volume?  



#6 datzenmike

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Posted 12 January 2018 - 05:43 AM

With 2.5" pipe there won't be much air speed to worry about sharp edges. That's enough for a 3.5 liter engine.


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#7 Beastlikethat1

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Posted 12 January 2018 - 06:55 AM

Muffler is a 5x11 or 5x8 at 24 inches if I remember correctly. Sounds very deep, no rasp at all. I'll post some video of it, and as far as the miters go we use them on race cars all of the time when manderal bent tubing doesn't have a tight enough radius.

#8 datzenmike

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Posted 12 January 2018 - 07:14 AM

Mmmm SS!

 

distributor guy:  the stock 2 into 1 isn't great either. I had one that was likely Midas or w/e and it looked like the one pipe was slit and the other poked in from the side and welded up.

 

You obviously have an L16/18 manifold.... what did you use for the intake on a U67 head?


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#9 G-Duax

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Posted 12 January 2018 - 08:41 AM

"loss in velocity and scavenging"

Velocity & scavenging (gas column inertia) is primarily in the header primary tubes, and the first 12 to 20" after the collector.

 

I have one of, if not the fastest 3L, all motor Toyotas in the country, and I run an 80mm exhaust.

The header is a 6 into 2 into 1 system.

Primary tubes are 1-5/8", into a 3-1 collector. The secondary tubes are 2-1/4", about 16" long.

And they then combine into the 80mm drain pipe.

 

So, no, 2.5" isn't enough for a 3.5 liter, unless it's just a way to haul groceries home.

 

So by running the stock manifold, you have all the velocity needed to help scavenge the cylinder of a stock-ish L-series.

 

I like what Beastlikethat did, and think it's right on target.

I would personally like to see it all the way out to the back, and in some states, doing a short dump under the car is illegal due to the increased risk of death by exhaust. So just don't stop, leave the engine running while getting naked with your woman...

Besides, steamed up windows keep peeping toms at bay :)

 

Good job on the pie-cut shaping. If you ground the inside of each weld before moving on to the next, it will work just fine.



#10 Stoffregen Motorsports

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Posted 12 January 2018 - 08:52 AM

Nice looking setup. I'm not a huge fan of the small miters. When I build exhaust systems, I like to keep the welds to a minimum, mainly for aesthetics, but I get it. They definitely serve a purpose. It's hard to wrap a downpipe around the torsion bar.

 

As far as the 2.5" goes, almost every Datsun L4 powered car I've ever owned had a 2.5" exhaust. Even the whimpy 125hp L16 we used in our ITC racers had 2.5". Some say it isn't necessary, but the dyno loves it on a L4. Most of my cars had the Nissan Motorsports headers with custom collectors so maybe that's a distinction worth mentioning.



#11 Beastlikethat1

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Posted 12 January 2018 - 09:49 AM

I agree Stoffregen, and 2.5in is a great size where it will fit for covering high power. Maybe it's just me but I love the look of the miters, maybe it's just a teenager thing LOL.

And don't get me started on Midas or Mieneki.. haha

#12 G-Duax

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Posted 12 January 2018 - 10:24 AM

Some of the most powerful R34s in Japan use all miter cut exhausts.



#13 Str8jacket

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Posted 12 January 2018 - 11:03 AM

"loss in velocity and scavenging"
Velocity & scavenging (gas column inertia) is primarily in the header primary tubes, and the first 12 to 20" after the collector.

I have one of, if not the fastest 3L, all motor Toyotas in the country, and I run an 80mm exhaust.
The header is a 6 into 2 into 1 system.
Primary tubes are 1-5/8", into a 3-1 collector. The secondary tubes are 2-1/4", about 16" long.
And they then combine into the 80mm drain pipe.

So, no, 2.5" isn't enough for a 3.5 liter, unless it's just a way to haul groceries home.

So by running the stock manifold, you have all the velocity needed to help scavenge the cylinder of a stock-ish L-series.

I like what Beastlikethat did, and think it's right on target.
I would personally like to see it all the way out to the back, and in some states, doing a short dump under the car is illegal due to the increased risk of death by exhaust. So just don't stop, leave the engine running while getting naked with your woman...
Besides, steamed up windows keep peeping toms at bay :)

Good job on the pie-cut shaping. If you ground the inside of each weld before moving on to the next, it will work just fine.


How long are your primary tubes? Just wondering to compare what i have built for my 3.3lt

#14 G-Duax

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Posted 12 January 2018 - 12:04 PM

Not ideal by any means, as it started out as a Pacesetter, that I redesigned the lower half.

(next thing on the list - equal length tubes, and maybe slightly larger dia. primary tubes)

 

Right now they very between 18 and 20 inches.



#15 datzenmike

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Posted 12 January 2018 - 01:00 PM

If 1 7/8 pipe will flow an L20B then a 2.5 pipe will flow 77% more air or a stock 3.5 liter.  


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#16 G-Duax

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Posted 12 January 2018 - 02:41 PM

Mike, we are talking apples to oranges.

Yes, a dead stock engine can get by with tinny, restrictive piping.

But if you want to build an exhaust for something with cams, head work, and better induction, 1-7/8 won't cut it on a 2 liter,

and 2-1/2 won't work for a 3 liter, let alone a 3.5.



#17 tr8er

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Posted 12 January 2018 - 04:42 PM

That down pipe is sexy as hell.


Yup

#18 datzenmike

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Posted 12 January 2018 - 05:13 PM

Mike, we are talking apples to oranges.
Yes, a dead stock engine can get by with tinny, restrictive piping.
But if you want to build an exhaust for something with cams, head work, and better induction, 1-7/8 won't cut it on a 2 liter,
and 2-1/2 won't work for a 3 liter, let alone a 3.5.

 
I can't remember what the stock L20B pipe diameter is, may be 2" but there's no mention of cams, head work and induction. That said I doubt it will flow as much as a 3.5 liter engine. The cross section of a 1 7/8" pipe is 2.75 square inches. If you go to a 2.5" pipe the cross sectional area jumps to 4.9 square inches. Now that's an increase in area of 77% so if a 1/78 pipe works well enough for a 2 liter engine a 2.5" pipe will support a 3.55 liter engine.
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#19 Str8jacket

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Posted 12 January 2018 - 05:30 PM

Not ideal by any means, as it started out as a Pacesetter, that I redesigned the lower half.
(next thing on the list - equal length tubes, and maybe slightly larger dia. primary tubes)
 
Right now they very between 18 and 20 inches.


So your "header" length is roughly 34in long before the tail pipe merge?

This is a big difference to the cast manifold length maybe 12in - 14in plus maybe 6in of secondary in the pics above.

I wonder how it will effect torque? If you are only reving hard all the time it may be ok, i think being that short may hurt torque and could possibly cause some reversion issues with the carbs in certain rpms, be interesting if you have to change the jetting smaller once you tune it up.

Im running a 3.3 v6. 3 into 2 into 1
1 1/2in for 15in to 1 5/8in for 15in.
Merge to 2in for 33in before both sides join into a single 2.5in to the rear.

Im going for a torquey street car max revs of 6500rpm so is different to a drag set up.

#20 G-Duax

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Posted 12 January 2018 - 06:11 PM

My 7M will turn 9k or more.

Never leaves the driveway without running high rpm many times, even to just go to pick up burgers.

(can't help it, it is just too fun)

The only way to outrun pig iron V8s with out forced induction, or laughing gas, is to turn the daylights out of it.

 

The Texas mile, many years ago, smaller cams, less port work:

 

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