Exhaust, Muffler, and Cat Questions

[ColtonMelson]

hello fellow Datsun enthusiasts  :thumbup: 

 

       My plan with the exhaust is too free up the restriction a little with out making the truck super loud or annoying. i plan on buying a new muffler and keeping the pipe about 2in or a lil less.  Now what i need to know is how much of a difference will I see in performance, if i remove the cat, And will it be really loud with just a muffler and no cat.  If there is no point in removing the cat and all im gonna do is make it loud as hell, please let me know :poop:  . But if you guys notice a big difference with a cat delete and performance muffler let me know   :devil:

[metalmonkey47]

It all depends on the muffler you use.

 

Ditch the cat and use a nice Magnaflow for the best tone/volume control. 

 

 

Performance gain is marginal. Noticeable but nothing to brag about. Totally worth it for the awesome Z24 sound. 

 

 

 

My L20B with header, 2.25'', and Flowmaster super 10. Pretty obnoxiously loud, and it's not hardly even close to singing yet either.. I need a resonator. 

 

[elmerfudpucker]

I have had the Z22 and now a Z24, on a pacesetter header, 2 1/4" to a magnaflow, no cat, on my 720. If i stay out of the secondaries it isn't really loud but still growls. You only really feel it in the top end that you have a bit more leg to get up the hill without having to downshift if I am over 3.5k. I would think the added back pressure with 2" would work for a touch more bottom end, but I wouldn't go any smaller. But I built mine for heavy long haul ability not for off the line jumps. I had my truck (3k tare) and trailer and my household belongings (6K+) 2600 miles in the middle of June from WA to KY at 75mph all day with no bad issues other than popping an old coil and replacing a fuel filter after some bad fuel. And MM is right, it does sound bad ass when I open it up!

 

http://s762.photobucket.com/albums/xx268/elmerfudpuckered/trip/?action=view&current=VID_20120611_111128.mp4

[Scurrvy]

So I was thinking of the same thing for my 720. I have the z24. So Magnaflows are best or?

[ColtonMelson]

cool well if deleting the cat is not really going to make a difference then i thing my plan will stay with stock headers, and a cat back, 2in pipe to a nice short, less restrictive muffler. As soon as tax money comes in, im goin for the Weber 38dgav baby! cant wait. no more vacuum line bullshit running my second barrel. I want those suckers to open together!

[_chiefjt]

I got a Weber 38 not too long ago. Glad I didn't get the 32/36. Now I got to free up my exhaust flow so I'm gonna go with the '86-'89 HB 4-1 long tube headers with a 2 1'4. removable cat so I can smog it and a Flowmaster 40 series. 

 

And yes I got my z24 with the Weber 38 to pass smog. The only thing is I have to wait for it to fully warm up but summers coming up so that shouldn't be a prob.

 

Once summer comes though I have to get a a/c compressor and custom fit the lines 'cause I got all my a/c stuff from the junkyard.

[ColtonMelson]

 here are some pics of my truck from today

[datzenmike]

I think the 720 already has a 2" down pipe to a cat. The cats I've looked at are see through. It's like looking down a double hand full of drinking straws, but a lot smaller like a fly screen. Because the cat is 2x or 3x larger than the 2" pipe any restriction is very minimal. You could remove the cat and run straight 2" pipe back to a muffler. Turbo type are good and packed with 'glass to absorb the sound. Straight through are a no no... they just don't do anything for the sound, and believe me a loud exhaust get's old REAL quick. A cheap resonator in line won't hurt either.

As soon as tax money comes in, im goin for the Weber 38dgav baby! cant wait. no more vacuum line bullshit running my second barrel. I want those suckers to open together!

Good luck with that. The 38/38 is a V6 carb. Not saying it won't work but with as 38 you will have to step into the carb slowly or it will bog. This is the advantage of the vacuum secondaries... they add more carb as you need it making driving much easier on the street. The 38 is more for mid and high speed performance than off the line.

[_chiefjt]

Nice truck, If my dad saw it he would ask where your at and if you'd sell it. He had one like that too.

[ColtonMelson]

always appreciate your input datzenMike  Thx

[ColtonMelson]

Yeah, my girlfriend would never let me sell it. Her dad bought it brandnew back in 84' and put 200,000 miles on it him self. He also did a full rebuilt on the engine about 30,000 miles ago... But that was 15 years ago! When he gave me the truck (for free) about 3 months ago, it had been sitting for 13 YEARS!  So i pulled it out of the bushes and gave it a lot of love under the hood and around the body. She is comin together great though, Runs like a champ (except for the carb problems i had).

[datzenmike]

Overall the Z24 will respond very well to the 38. 720 owners rave about them. The stock carb is quite small for the 2.4 liter motor so a 38 will really boost passing performance on the highway. You may be able to adjust the accelerator pump rod for more throw and a bigger squirt to cure much of the low speed bog. Ask Sealik I think he has one. Otherwise a week of driving and you'll have it figured out.

[ColtonMelson]

Cool thats what I was really hoping to hear.

[_chiefjt]

yeah, highway is amazing. I barely have to press he pedal and it still picks up speed.