Exhaust help 1980 720 (l20b) "Early non-smog manifold work up"

[ericsb210]

Working on a 1980 Datsun 720 King cab 2wd.

 

I went and bought a 1971 510 exhaust and intake manifold and have them mounted on the l20b. I have a part of the 1971 510 y-pipe and I bought a flange to create a new down pipe. This is where it sits. The local exhaust shop wants $250 to create a down pipe to mate to my existing exhaust pipe (cat).

 

I was hoping to avoid spending another $250 on this set up. I do not weld. Does anyone have a down pipe or can fabricate one for a better price? or suggestion.

 

I am in Olympia, WA

[KlassicMotion]

I've got this.  It's NOS. I paid $85 for it off eBay, then it turns out I didn't need it.  I painted it hi-temp silver to keep it from rusting in storage.  I had it on my "For Sale Ad" at Make offer.  I would estimate shipping to be about $20.

 

[ericsb210]

I have that same Y-pipe the problem is it doesn't clear the torsion bar.

 

I keep thinking the best answer would be to have the machined piece (looks like the gasket, but thick stainless steel) welded up with the two into one as short as possible to meet up with the existing downpipe. or run the two pipes at the same bend as the original downpipe and have the y-pipe under the truck.

 

Was hoping someone else has created one of the pieces i described above and would be willing to weld up one for me :-).

 

If anyone out there could do this I would supply the machined piece that mates up to the 510 manifold and the original downpipe off of the 720.

[bananahamuck]

Call or better yet go to his shop and talk to the guy at Hubbs muffler in Aberdeen he is very fair with his prices,, and by fair i mean frickin cheap.. .. It seems like we talked to him about making one of those from scratch and running two pipes all the way out the back on a wagon and the quote was $250. for everything... but my memory is foggy sometimes... We were going to supply the flange also.

 

 

Hubbs muffler

2208 Sumner Ave  Aberdeen, WA 98520

(360) 533-1957

 

 

I might have a old rusty one i could sell you if you are desperate ,,,,,, if i could find it... :lol:

[KlassicMotion]

Ah... This is what you need.....  I sold it a few months ago though.....  I think it may be Datsun 620, but I'm really not sure.....

 

If you find one, cut it off closer to the Y, and then weld up your 2" Pipe to it..... Or just have the shop cut off the flang and make one.... Although I see where they would want $250 to do that.  It wouldn't be difficult, but it would take time. 

 

[ericsb210]

Update:

 

Midas is going to bend (matching original downpipe) two 1 1/2 pipes with the flange end's flared to 1 5/8 for $99.00. The front side pipe will have an additional bend as to have them be parallel under the truck. After I get them in the truck I am going to measure out the remaining distance to exit and have them bend two additional pipes and attach two glass packs and then exit. If this goes as I hope I will have two continuous pipes (no Y-pipe) from the manifold to rear exit both being 1 1/2 with each pipe having it's own glass pack. After all of the piping is in the truck and working I will have it all welded up.

 

Is there any arguments as to why this would not work? I have no exhaust experience.

 

I will also be posting pic's of my good times with the Datsun on friday.

 

Also, thank you for the quick reply's and help.

[KlassicMotion]

In short, yes.  Back pressure and equalization of the exhaust flow for one.  Even when you have dual exhaust on a V8, at the very least you want an equalizer tube, if not an "H" pipe or "X" pipe.  Naturally aspirated Gasoline engines need back pressure and equalization of gas pressue between All the cylinders.  The way you are talking about setting it up,  There will only be equalization between 1&4 and 2&3. Next, you will have an equivilent of a 3" pipe, when the L20B runs good on a single 2" pipe... There are plenty more reasons like sound and other things.  Not to mention you will be paying twice as much $$ to run two pipes versus one.

 

It will run, but you won't get the most performance out of it.

[KlassicMotion]

By the way, the stock manifold really isn't a bad manifold.  It has a nice big chamber for equalization and it flows down into a 2" outlet.  I've seen a lot worse designs.