Jump to content
Cardinal Grammeter

1974 620 Ultra Quiet (like OEM) Exhaust: Adapt 720? or?

Recommended Posts

I do interstate driving over 4500 rpm and do not want any kind of exhaust drone - seems like I have an OE muffler on mine an it gives off only the faintest hum at that speed.

 

Even sticking with OEM style mufflers is not a guarantee.  For instance, the Suzuki Swift variants Walker SoundFX is terrible - very noisy mufflers.  Only the Walker stainless steel mufflers are quiet.

 

I was looking at Ranger and S10 exhaust parts and it looks like both are RHS systems (620 is LHS.)

 

The 720 might be good for the muffler/tailpipe?  Bosal has a welded 283-903 for about $110 shipped from RA.  (muffler has a front flange, but that could be cut off or welded.

05838380.jpg

 

 

I don't want to go to a muffler shop and get something bent because I would be really

pissed for a $300 job for muffler/tailpipe that was loud - which is what most people want. 

I could weld up a tailpipe but that leaves the muffler.

 

So that leaves me sourcing a muffler.

 

I looked at a lot of threads and one referenced a quiet muffler choice for a King Cab.  It didn't have much in the way of responses.

 

NOTE on PIPE SIZES:  The S10 and Rangers use a 2.25 exhaust and 2.0 tailpipe for their 2.0 liter engines.  I'm guessing they are 100 hp, so the 70 hp L18 could manage with a 2.0 and 1.75/1.50 pipe sizes.

 

____________________

 

EDIT:  I'm guessing 520/521 exhaust might be a direct fit more or less.  Yes, older, but past discoveries would apply.

 

NOTE:  It doesn't seem like there is any attempts to find modern parts that will fit w/minor modification.  Everyone is getting loud / performance stuff either DIY or from muffler shops. 

 

I admit working on exhaust is a RPITA and virtually impossible if you don't have the tools/equipment.  I have all the tools/welders but not the lift.  I've done fabbed exhaust working off jack stands and I just don't have the stomach for it anymore.  But it backed into a corner, I guess I'll have to submit...

Edited by Cardinal Grammeter

Share this post


Link to post

Add a good thick layer of sound deadening, like DynaMat, to underside, doors, back of cab, and under the whole bed.

These trucks were not made to be as quiet as a Lexus while driving.

All that tin amplifies any noise made by the engine.

 

Either that, or remove the dirty, noisy internal combustion engine, and replace it with a Green Planet electric motor, then fill the bed with 1000 lbs of batteries.

  • Like 2

Share this post


Link to post

I just built a new exhaust for my Land Rover and I wrapped the muffler with some sound deadener from DEI.https://www.summitracing.com/parts/dei-010455/overview/   I ran the truck before and after I installed the muffler wrap and it was both quieter and cooler with the muffler wrap.

 

Rover_Exhaust_Small_02_zpsvjt9noxz.jpg

 

Rover_Exhaust_Small_03_zpsd0m5fj0m.jpg

 

Rover_Exhaust_Small_04_zpshyqhgu6u.jpg

 

Rover_Exhaust_Small_01_zpsdinolxvj.jpg

  • Like 2

Share this post


Link to post

Your going to struggle to quiet the engine noise itself, the exhaust is a different noise all together.

  • Like 1

Share this post


Link to post

To be silent the exhaust can't come out of the pipe in puffs, it has to come out in a steady stream all slowed down. The very explosive pulse has to be spread out and released over a longer time. This requires a lot of resistance to flow through the muffler and is impractical as the engine has to work harder to push it through. If you were running at a set RPM the muffler can be designed (tuned) to cancel out the exhaust pulse frequency but this is also impractical. Exhaust sound can also be lowered by absorption into a sound deadening material lining the inside of the 'muffler'.   

 

 

Stick with the 620 pipes, you know they fit and work. Good news is it's a truck with lots of clearance under it so there is leeway for a larger muffler. If you can afford it a 2" 620 system custom bent at a muffler shop. A larger pipe diameter will be the first step in slowing down the exhaust speed. If the 620 pipe is 1 3/4" going to 2" is a 30% larger cross section. I would put a resonator up behind the down pipe under the cab. A glass pack 'Cherry Bomb' style will work, but they don't last the life of the system. A better choice is a newer car resonator that is a straight perforated pipe inside an empty shell. This allows the high pressure spike a place to expand and slow down without too much turbulence in the flow. For a muffler the largest 2" inlet you can find. Does not have to be for a truck. Look inside as some makers have 2" on the outside but it necks down inside the muffler. It's just a generic muffler with different inlets welded on. You could even go 2 1/4 inlet with a pipe adapter. This is what I did on my 710. A muffler with extra outside layers or internal sound absorbing materials will also reduce sound in the muffler casing. These 'mufflers' tend to be surprisingly heavy. As mentioned wrapping might be an option too. Definitely run a tail pipe to get the sound as far to the rear of the truck s you can.

  • Like 1

Share this post


Link to post

I'd look at a sedan setup, eg a 4 cylinder Honda Accord. Anything 4th generation up should be fine as those were 2 liters. They are quiet up through 7k rpm, so shouldn't be a problem.

  • Like 1

Share this post


Link to post

See this thread, I made an exhaust system for a 521.
http://community.ratsun.net/topic/49698-my-dragon-datsun-521/page-3

To be honest, I have not yet had this truck on on the freeway yet, it is a too long term project that I am currently working on.  I also put a new exhaust system on another 521 that is running, but not really good, it burns too much oil.  I used a similar muffler on it, both trucks use a baffled design muffler.

 

I believe the drone at certain RPM ranges is caused by a specific length of pipe.  I do not know if it is the length of pipe before or after the muffler.  For example, the truck that is running not really good had a drone at about 1900-2000 RPM, then again at 3800 -4000 RPM. 

 

Like Mike said, a resonator between the engine and muffler may prevent the drone.  I might try it someday.  If you do try a resonator, I would try to place it so the length of pipe between where the runners on the exhaust manifold come together, the resonator, and length of pipe to the muffler are different.

  • Like 1

Share this post


Link to post

Thanks for the tips.

 

FYI, the exhaust on the truck is just fine as far as quiet goes - and that is with a rotted off tailpipe.  My Suzuki Swift references are probably not completely comparable since that system has a mid-resonator and a muffler at he very end (no tailpipe.)

 

RE:  Large Case Mufflers:

 

Another thing I learned about mufflers from my 1989 LS1 Z28 which had a long tube header system made by a company I can't remember, 3 initials, Txx, and not TSP which is Texas - I think this outfit had a misleading name like "turbo marine" or something - they had the first 1/2in flange long tubes you could buy for the LS1.  But the crux was that when they designed the system, they discovered mufflers with a small case did not have strong resonances  - an example of the worst muffler you could choose would be a Walker school bus muffler.  Does anyone remember "racking off?"  Some loved it, but it was really the worst possible exhaust sound out there.

 

So a large case muffler might be problematic, however, the current muffler on my 74 is a big round one (no dimensions at this time.)

 

I do like the idea of getting Honda pieces - or even S10 or Ranger mufflers.  But it might be best to find a muffler from something with 70 hp instead of over 100hp.

 

Off to check out that 521 thread...  wow, lots of nice work!  The exhaust crosses over to the RHS?  Is the 521 tank on the RHS like the 620?

  • Like 1

Share this post


Link to post

521 tank is behind the driver.

Share this post


Link to post

1.  Run a cast iron manifold at the head.  

2.  Have a custom front pipe made of VERY heavy wall tubing.  

3.  Run a cat under the driver's floor 

4.  Run very heavy wall tubing to a rear mounted muffler - as far back as you can.  The further back it is, the more "high notes" it removes

5.  Ask your local muffler shop for a suggestion on a very quiet muffler.  They likely either know what you need.  Its what they do for a living (if its not some douche-bag Midas type shop.)  

Around here you're talking about a $300 system including a cat.  A smaller 2" system will be quieter than larger - maybe even choke down to a 1 7/8" tailpipe.  

 

The resonance you normally here is through the pipe.  Thin 14 or 16 gauge pipe is loud.  OEM systems are a little heavier, and the pipe is softer so it absorbs more noise (like cast iron manifolds).  

  • Like 1

Share this post


Link to post

UPDATE:

 

My tailpipe is gone and the muffler, while pretty solid, has some pin holes below the outlet I found when I ran a needle descaler (one of my favorate tools) looking for weak spots.

 

So that leaves a big, long exhaust pipe that goes from the manifold to the muffler - the muffler is located just front of the axle (tailpipe will require a sharp 90* up bend to get over the axle tube.)

 

While the muffler and tailpipe fail sooner than exhaust pipes, I'm still  thinking maybe I should do the entire exhaust.

 

Thoughts on doing an OEM whole exhaust :

  • Exhaust pipe "Y" at the manifold flange:  can this be bought new?  If NO, that means hand fabricated or reuse it.
  • What was the OEM config?  Mine is a muffler just ahead of the axle and 1.5" tubing for the whole system.
  • Was considering the Walker 22266 which is a cheap Honda turbo style muffler w/1.5" in/out and 18" total length.
  • Does anyone make a SS system?  There is this Swedish outfit Raka Rör KB makes a complete system for the D21 King cab hard body.
  • Like 1

Share this post


Link to post

I am pretty sure the OEM parts are non-existent, but it may be worth a shot.

 

A few years ago, I was able to source am entire OEM exhaust for our '72 240Z from the Nissan dealer. Everything from the manifold back.

Share this post


Link to post

BACKFIRE!  Got a bang out the end of the muffler when trying to loosen tailpipe stub with oxy-acetylene torch.  That had never happened to me before.  I started again, and then got a "whoosh".  I had the truck jacked up sideways pretty good (frame 24" high) - don't know if that was part of it.

 

I suspect I have a leak in the carb which isn't working right anyway...

 

Right now I'm trying to contact Columbia River Mandrel Bending since they appear to have supplied the little Y-pipe at the exhaust manifold in that 521 Exhaust thread.  However, they just do not pick up the phone...

  • Like 1

Share this post


Link to post

I would add to whichever muffler you do get, that you can get large rolls of fiberglass wrapping, and wrap from the header and all on the muffler to deaden resonance.

 

Larger mufflers for newer trucks usually have more internal tubes and material matting to deaden sound, like from a Frontier would work.

  • Like 1

Share this post


Link to post

I was told by a tuner for a high performance dual exhaust w/X pipe, the best arrangement is:]

  • Muffler as far back as possible.
  • Then using thermal paint or something that will burn off, paint the exhaust pipes and find where the hot spot is - that is where you put the X pipe.  

Perhaps in a single exhaust, that hot spot would be where the resonator location?

Edited by Cardinal Grammeter
  • Like 1

Share this post


Link to post

 Get a muffler shop to custom bend up a system. Search around for someone who knows what he's doing. It's more of an art than anything. Specify the pipe size (2" for an L18 is lots) and resonator (2" in and out bullet style glass pack) and muffler (here I would just get the largest 2" muffler that will fit in the space and a 45 degree bend outlet. A turbo style with lots of sound absorbing filler is also good if louder is needed) Do not get anything that is straight through. You're looking for lower restriction mostly and quiet is also good.

 

You have the early 4 into 2 manifold with the down pipe as a 2 into 1 collector.  You could have the shop extend the two pipes down under your feet and join it into one there just ahead of the resonator. It's not like dual pipes are going to make a stock L18 any faster. Indeed, lowering the restriction in your exhaust will alter how well the cylinder empties.... you may need to reject your carb.

 

mRhIAwH.jpg

 

I cobbled this 240sx dual down pipe onto my L16 manifold equipped L20B using one of Mklotz's L16 exhaust flanges. It's around 32" or so from the exhaust valve to the collector to single pipe. 

  • Like 1

Share this post


Link to post

BAND CLAMPS:  Does anyone know where to get 1.5" stepped?

 

I talked to one shop that also does SS and he quoted $425 to fab the little Y-end at the manifold.  $500 in SS.

 

Argh....

 

I'm going Lo-Buck.  22266 Walker SS Honda 1-1/2" muffler and buddy mechanic friend says he likes to bend exhaust for the tailpipe.

 

NOTE:  I can fab all this stuff.  While I love to weld, I TOTALLY HATE DOING EXHAUST WORK UNDER JACK STANDS  (ewww... don't like these new Emoji's)

 

If it was a Studebaker, I could buy a read to go, complete SS system for any Lark, Hawk, or Avanti - models going back into the 50's.  I guess I've been spoiled being a Studebaker guy...  

 

I CANNOT figure out the 620 market.  Back here in SW PA, when I drive my 620, it's like I'm Jack Nicholson with all the attention I get.  You'd think people would be crawling over each other to get one of these trucks.  But it seems like all the Big $$$ interests are in Custom renditions.   And while most people like to have a fly ride that gets attention, I don't know of anything that would beat out the 620 as far as that goes.  Ironically, no one wants to pay for a 620.  What's a flawless resto worth?  $10k?

Edited by Cardinal Grammeter
  • Like 1

Share this post


Link to post

Its the Datsun market as a whole, not just the 620 trucks but the older and newer stuff also.

 

I think its the Datsun gene pool, not much is getting passed down to the next gen, and good vehicles and parts are rotting away or horded from the rest.

 

I had complete restored a 73 620 with a L20B completely rebuilt with 0 miles, and couldn't get over $2500 for it, just how it is.

  • Like 1

Share this post


Link to post
On 7/25/2018 at 10:53 AM, Cardinal Grammeter said:

Right now I'm trying to contact Columbia River Mandrel Bending since they appear to have supplied the little Y-pipe at the exhaust manifold in that 521 Exhaust thread.  However, they just do not pick up the phone...

I buy from them frequently. They are mostly an online business so be patient. I have called them though.

 

I doubt they sell a collector ready to bolt on. All you need to know is the inlet and outlet tubing size as well as the centerline of the two inlets, then go to their collector page and see what they have available.

  • Like 1

Share this post


Link to post

See Mklotz70. He had the CAD for water jet, hell he may still have one laying around. I used one of his and it was a spot on fit. I think the pipes were 1.5" (outside) could be wrong might be inside.

  • Like 1

Share this post


Link to post

Here's the pic the 521 guy got from Columbia:  That looks like some manufactured/stamped 2-1 collector flange:

 

NewPipe.JPG

  • Like 1

Share this post


Link to post
12 hours ago, nl320what said:

Its the Datsun market as a whole, not just the 620 trucks but the older and newer stuff also.

 

I think its the Datsun gene pool, not much is getting passed down to the next gen, and good vehicles and parts are rotting away or horded from the rest.

 

I had complete restored a 73 620 with a L20B completely rebuilt with 0 miles, and couldn't get over $2500 for it, just how it is.

 

$2500?  Oh man, that's HORRIFIC.  Where and when did this occur?

  • Like 1

Share this post


Link to post

8 years ago in Sacramento CA, also had a Weber and EI matchbox on it.

 

Have to hit the right people at the right time to buy/sell a Dat.

  • Like 1

Share this post


Link to post

The collector in the pic looks like garbage. Is it even split in the middle? Or does it just dump into an open chamber?

Share this post


Link to post

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×

Important Information

By using this site, you agree to our Terms of Use.