Supererogator's questions

[Supererogator]

Since I am new to the whole over seas made vehicle thing, not to mention working on something newer than the early 70's, I have found that I have a lot of questions...so, on the lead of breadbox, I am going to toss them all here.

Upon the recommendation of all of you kind folks, I crawled under my cute little truck, to check out the cat situation. I believe nothing in my state over 25 years gets smog tested, so I should be safe to strip it (I am in need of renewal registration by October)......So, the cat is still there. I want it gone, as I am still lacking some power....like really. She drives fine, idles at 1k perfectly after a 5 minute warm up, and even gets to 70mph relatively well for a truck with almost 200k on her and nearly all original parts.

Alas, I still take what feels like 15 minutes to reach any reasonable speed, and I can be beat by a school-bus off the line. Even for an OLD automatic this is rough. I have done timing, vacuum tube replacement, and some other general tune up stuff. I still have an oil pan gasket to put on, and a few rinky dink things, but really, she is tuned up. Keeps me from getting tickets however.

So, I wanna remove the cat, and boost her up a touch.....the mufler is kinda not good. I want it gone and replaced too.

So, do I take it to a shop? I can turn many a screw, and can even access many types of welding apparatus if I need to. Do I use my knowledge to do it myself? Do I pick a muffler of some sort for some reason I do not know? I wanna replace everything from in front of the cat on back.

Last time I had a muffler done, it was in my Stang, and at a shop to factory specs....not quite what I am looking for this time.

Any suggestions? I have found a zillion mufflers out there, but do not know the difference. I want more acceleration (hence more clearing of air right?), but small noise and pollution.

[breadbox]

So, the cat is still there. I want it gone, as I am still lacking some power....like really.

Gut your cat and put it back on. As we all know the cat is a straight pipe filled with a honey comb that gets hot and burns up the remaining crap in the exhaust. The two ways to gut a cat.

One take something and hammer it through breaking the honey comb and knocked it out the other side, it may take a bit to break it up.

Two cut the bish open and remove stuff and weld it back, be careful to make it look like it was factory welded or they can slap you with a ticket for not having a proper cat. Only heard of this happening like once though.

Or Three get a "test pipe" A striaght pipe the exact length of a cat, aka Cat delete.

the muffler is kinda not good. I want it gone and replaced too.Any suggestions? I have found a zillion mufflers out there, but do not know the difference. I want more acceleration (hence more clearing of air right?), but small noise and pollution.

Well gutting a cat on a NA vehicle makes it louder, especially because we don't have mufflers per se, just a pipe to direct the exhaust out from under the vehicle. Yes there is a "muffler" but that kinda seems more like a tiny resonator more than a traditional muffler.

So in essence you could do your own custom exhaust and have a 18" to 22" resonator added in to make it quieter. Exhaust isn't that major, make sure it can go somewhere but not to fast and your good.

[PEZi]

well depending on how loud you want it will be the deciding question here

i say that you should remove the cat and put in just a straight section of pipe there

as far as the muffler i use the maganaflow round body... its described as a resonator as there is no flow restriction inside... its just packing around the center similar to a glasspack

the exact one i use is the second one down below the 4" round body stainless steel (part 14415) http://www.hottexhaust.com/StainlessRound.htm

i also have the pacesetter header

its the header up to 2" piping to the magnaflow high flow cat... then from the cat back its 2.25" through the resonator... i have no piping after the resonator and it ends right before the axle pointed slightly down so it doesn't actually hit the axle

its loud as s*** as is... i've hit 95 decibels at autocross before... and daily driving i'd say its around 80-83... this is something to think about because a lot of places have noise limits

i've been thinking of removing my high flow cat for a little more power but i'm worried about how loud it will be considering that some auto x sites have noise restrictions... the one we usually go to has a limit of 103 decibels... but there is one in denver we go to that has a limit of 93 decibels and i'm already having to be careful there

[Supererogator]

Gut your cat and put it back on.

this is genius....I never would have come up with that. May be what I do. Gonna have to go the hammer rout as I am a s***ty welder, and it would definitely show.

As for loud....well, I really don't want loud. We do have noise laws in our state, so I think the option of leaving the cat to help with a bit of the sound reduction should be a good idea.

Thanks for the suggestions. Y'all rock.

[breadbox]

Once you gut a cat, it is a straight pipe so I don't think there will be any noise reduction, but you should still have that resonator.

[breadbox]

I gutted a cat for you and took pics, in case you were unsure what exactly you need to do.

zerothread/427942
Modified by breadbox at 5:03 PM 5/30/2009

[Supererogator]

Yup....you're a rockstar. Thanks.

In other news, I scored a new old stock driver's side orange light and lens (this has been missing), and I finally found an '80 factory maunal....$2+about 7 in shipping. Blessed ebay.

[breadbox]

Nice price on a FSM.

[breadbox]

Have you figured out your exhaust yet?

[Supererogator]

Honestly, unless I have some dramatic changes in life and plans, I am slating it for late July.... I get super busy in Summer with festivals and such.

[Supererogator]

OK, so I was using my truck to haul me about 120 miles round trip to a festival. On the second day, second trip home, I had some trouble. Almost like the exhaust wasn't clearing, and the truck was hesitating or would die at an idle. This all after another trip to another festival and the truck magically started running WAY better. After a few heavy revs and some smoke clearing, the truck started running well again, and is still.

Now, I have noticed a bit (well billows of smoke) coming from underneath my cab. I chalked it up to the leaky oil-pan gasket that I have, but have not put in yet. I am now starting to think that my cat is all rotted out inside and that pieces are floating around causing intermittent exhaust blocks and hence the stalling and such.

Before I go ripping the thing out and making it a straight pipe, as I have wanted to do, but it appears need to....do yall think I am on the right track? All my vac lines are new, and they are intact. The general tuning stuff has been done... should I go for it? Not that it can hurt, but if I end up out of commission at the wrong time because of a compounding problem, then I could really lose money this year. I would rather limp and pray for two more weeks and then get at it when the vehicle is not so important and can be taken apart. Like I said, it runs better than it has since I got it, save this intermittent issue that has not left me stranded for more than 15 minutes.

[flinterman2000]

breadbox has it straight. the silencer from the a33 Cifero would work and keep the decibels down. I used the resonator and silencer from a Primera on my Wingroad with 2.25 front to back exhaust. the cat has also been removed. decibels are around 80, not much louder than stock.

[breadbox]

^lol. It'd be hard to find those JDM parts here. I want a GTiR.

[Supererogator]

Hey Yall! I have been trolling, and loving the new site set-up. The FAQ (please read before posting) has grown to a veritable odd knowledge library. Thanks.

An update. I still have my beloved '80 720 (fast coming into 2nd favorite vehicle ever owned). I rammed out the cat, put on a auto parts store "muffler" and have been having a great time. A few other tuning things also, but they are small change. She runs great, but keeps me from getting tickets.

What I am running into now is a classic case of "butt-first syndrome". But first I need to do this to ultimately do that.

Currently, it is the driver's side tail light and assembly. The metal has rusted and there are no longer electrical conncetions. It even seems to be causing a trickle leak in my charging system ( I am guessing the bad ground is doing it).

Long story long, I have found tail lights, and am actually bidding on a NOS piece now. That has been the "simple part". The Butt-first comes because once I get the piece, I have almost no metal left in my rear valance to attach it to. I cannot find the valance. I cannot find it Sam I Am. Anyone have a clue where to look?

I have searched for Datsun parts, have searched for mini-truck parts (as I would be fine with a plastic custom deal as long as I don't get a ticket), I have searched using every word combo I know. Anyone have a rear valance from an '80 720, or know of another easier to find part I can mod onto it? Does the 620, which looks like the pre '82 720's rears fit?

You folks have been gurus before, can you help a brother out before he starts to fabricate pieces?