more exhaust questions

[Tisk Tisk]

I have read through all of the posts about the headers JBrady designed and had built, very impressive. This has lead me to do alittle redesign of the exhaust on my 92 SC400 project car. I have run into a few problems and would appreciate any feedback.

First my car was winter driven in the northeast and all of the exhaust fasteners were completely rusted to hell and it took 3 days with various sockets, an impact chisel and eventually the sawzall to remove them to drop the exhaust. Now comes the real problems, the car was driven for about 20 miles with only one ignition coil functioning, car ran fine as it has dual distributors and is balanced to run on 4, but the obd1 computer did not shut off fuel to the remaining 4 cylinders and the cats were glowing white hot by the time i got home. I wish I had some pictures of the large chunks of glowing metal that were bouncing down the road behind me, it was fun.:Eyecrazy:
Anyway the result of this was a complete melting of the material in both cats and a broken weld on the center resonator, also after i removed the center resonator section i noticed that it makes a rattling sound when i shake it...

I have already removed the rear main mufflers and replaced them with straight pipes which look real nice and are alot lighter although didn't really effect the noise at all. My guess is because of the 2 cats and 3 resonators before them...

So on the list of things to do are:
gut, or replace cats
do something with that center resonator...

sounds good so far right? here are my questions;
1. I have read several places that JBrady and others have warned about simply gutting cats as this can reduce power if done improperly, am i right in assuming that by gutting the cats you mean to simply remove the catalyst material and leave the hollow chamber open? My plan was to remove the catalyst material and replace it with a straight through tube so it would look like a cat and thus pass visual inspection, but flow as if it weren't there. would this be the best choice or would a high flow cat work better, what exactly are the down sides of gutting the cats?? also will the noise be that much louder without the cats?

2. Because the center resonator rattles i am assuming that the sound deadening material is shot? unless someone has any better ideas i am going to buy one of those cheap little glass packs and weld it in place of the stock resonator...

Thanks
-Jake

 

[jibbby]

Those S&S headers ain't going to fit properly so be pre-warned. Better have a good exhaust mechanic...I got those headers on my 92 SC400 and it wasn't an easy install...Your gonna have to delete your two small down cats and fab some new down pipes to properly fit in the headers and connect to the rest of the exhaust.. That also includes a connecting flange. Ouch......

Gutting the cats and installing straight pipes inside to run straight thru the cats is going to give you great flow... I don't see any problems with that, but it seems like a waste of time and effort to me... Why not just dump the cats altogether and install a straight pipe in it's place? What do you need visual inspection passage when the car is never going to pass with the headers in and or deleted cats? I don't see the logic in that....

 

[Tisk Tisk]

Thanks jibby i read your posts on CL about installing your S&S headers grats on getting them to work at all!
im not ready to do headers yet, im just trying to make my old system work better cause im not sure if i want to do cams or FI, ill build a complete system at that time.

As for the cats, we dont have to pass sniffer tests here in texas(atleast in my county) yet so all they do is check (visualy) that the factory emmissions equipment is still in place, thats all they can do so if it looks like i have cats then i have cats

-Jake

 

[jibbby]

Wow, you got it good in Texas...Here in California they test and practically strip the car down to make sure it meets up to smog emmissions.. Very anal here in Cali.....

Yeah, I got banned from the CL about a year ago...I got into it with the senior moderator GSDave and his forum god like complex....I am glad some of my ancient posts over there are still helping people like you...

 

[Chase]

I have read through all of the posts about the headers JBrady designed and had built, very impressive. This has lead me to do alittle redesign of the exhaust on my 92 SC400 project car. I have run into a few problems and would appreciate any feedback.

First my car was winter driven in the northeast and all of the exhaust fasteners were completely rusted to hell and it took 3 days with various sockets, an impact chisel and eventually the sawzall to remove them to drop the exhaust. Now comes the real problems, the car was driven for about 20 miles with only one ignition coil functioning, car ran fine as it has dual distributors and is balanced to run on 4, but the obd1 computer did not shut off fuel to the remaining 4 cylinders and the cats were glowing white hot by the time i got home. I wish I had some pictures of the large chunks of glowing metal that were bouncing down the road behind me, it was fun.:Eyecrazy:
Anyway the result of this was a complete melting of the material in both cats and a broken weld on the center resonator, also after i removed the center resonator section i noticed that it makes a rattling sound when i shake it...

I have already removed the rear main mufflers and replaced them with straight pipes which look real nice and are alot lighter although didn't really effect the noise at all. My guess is because of the 2 cats and 3 resonators before them...

So on the list of things to do are:
gut, or replace cats
do something with that center resonator...

sounds good so far right? here are my questions;
1. I have read several places that JBrady and others have warned about simply gutting cats as this can reduce power if done improperly, am i right in assuming that by gutting the cats you mean to simply remove the catalyst material and leave the hollow chamber open? My plan was to remove the catalyst material and replace it with a straight through tube so it would look like a cat and thus pass visual inspection, but flow as if it weren't there. would this be the best choice or would a high flow cat work better, what exactly are the down sides of gutting the cats?? also will the noise be that much louder without the cats?

2. Because the center resonator rattles i am assuming that the sound deadening material is shot? unless someone has any better ideas i am going to buy one of those cheap little glass packs and weld it in place of the stock resonator...

Thanks
-Jake

Sorry to bring up an older thread, but i just signed up and figure i'll give it my 2 cents.

Dumping the pre-cats and going with just plain piping will help with the air flow but your car will get a bit louder. Also you have the main cat in the center of the whole exhaust system (if you are a 92-95 model). My suggestion is to replace the pre-cats with new after market cats and do the same with the main cat. Weld on some custom piping in between and you should be fine for a little while. The other option is to remove the cats all together and weld on a new main cat (same location as your stock main cat) to quiet down the system. This would be the cheapest way to go and still keep some kind of balance in your exhaust system.

The first option would cost you a little more money but it will be the quietest and best balanced option. The 2nd option is a good temporary fix until you are able to upgrade to after market headers and exhaust system.

 

[JBrady]

I have read through all of the posts about the headers JBrady designed and had built, very impressive. This has lead me to do alittle redesign of the exhaust on my 92 SC400 project car. I have run into a few problems and would appreciate any feedback.

First my car was winter driven in the northeast and all of the exhaust fasteners were completely rusted to hell and it took 3 days with various sockets, an impact chisel and eventually the sawzall to remove them to drop the exhaust. Now comes the real problems, the car was driven for about 20 miles with only one ignition coil functioning, car ran fine as it has dual distributors and is balanced to run on 4, but the obd1 computer did not shut off fuel to the remaining 4 cylinders and the cats were glowing white hot by the time i got home. I wish I had some pictures of the large chunks of glowing metal that were bouncing down the road behind me, it was fun.:Eyecrazy:
Anyway the result of this was a complete melting of the material in both cats and a broken weld on the center resonator, also after i removed the center resonator section i noticed that it makes a rattling sound when i shake it...

I have already removed the rear main mufflers and replaced them with straight pipes which look real nice and are alot lighter although didn't really effect the noise at all. My guess is because of the 2 cats and 3 resonators before them...

So on the list of things to do are:
gut, or replace cats
do something with that center resonator...

sounds good so far right? here are my questions;
1. I have read several places that JBrady and others have warned about simply gutting cats as this can reduce power if done improperly, am i right in assuming that by gutting the cats you mean to simply remove the catalyst material and leave the hollow chamber open? My plan was to remove the catalyst material and replace it with a straight through tube so it would look like a cat and thus pass visual inspection, but flow as if it weren't there. would this be the best choice or would a high flow cat work better, what exactly are the down sides of gutting the cats?? also will the noise be that much louder without the cats?

2. Because the center resonator rattles i am assuming that the sound deadening material is shot? unless someone has any better ideas i am going to buy one of those cheap little glass packs and weld it in place of the stock resonator...

Thanks
-Jake

Removing the catalyst "guts" and welding a tube inside is easy and effective. You will also be able to bolt on replace with cats later if needed or sold. Downside is that the pipe will probably cost a little low speed torque. This because it allows more reverse flow. Top power will probably rise slightly. Noise will increase noticably.

Do not use a cheap louvered glass pack as a resonator. You should only use a perforated tube glass pack, wire pack or true resonator. Perforations are holes drilled in the tube wall. Louvers are punched flaps of metal that reduce flow and cause turbulance.

The SCs came with 2 styles of middle mufflers. Round straight through and oval muffler style. Muffler style are heavier and more restrictive. Round are less restrictive and louder.

 

[jibbby]

I found that any exhaust mods that you do on stock SC400 will bring about topend power only... The more exhaust mods you do the more lowend power you will lose slightly... For a stock SC400 that's bad because of the stock torque converter stall rate... They are slugs off the line at stock as is... Topend will flow very nicely though, especially with aftermarket headers...

Just my two cents, for what ever that is worth...

 

[Tisk Tisk]

thanks guys

Thanks everyone!
I had an oval shaped straight through center muffler stock but when I cut it open all the sound deadening materials were melted together. I replaced it with this:
http://store.summitracing.com/partdetail.asp?autofilter=1&part=WLK-24234&N=700+0&autoview=sku
Should be a decent improvement, also with the tubes in the cats and the straight pipes replacing the rear main mufflers it should flow pretty well even if losing alittle low end torque. I have the factory stall TC but I also have the lower 4.272 supra LSD and 285/40-17 on stock supra rims and I can break them loose in second if I really get on it so alittle less torque would actually be all right.
I'll see if I can borrow a camera and get up some pics of the install, I need to replace the header to cat studs before I put the piping back up.

Cheers,
Jake

P.S. Jbrady, do you still live in houston? If so I might have to come visit you some day.