L72M21

I a recent earlier thread I described how my loss of power was attributed to a blocked main converter. At first I thought the ceramic material in the main converter had broken up and blocked the entrance to it. On closer inspection it appears that one of the pre-cats has let go of it's ceramic material and blocked the main converter. Question #1. Is there a good way to determine which pre cat has lost it stuff? The main cat, now, has many small particles in it, #2. Should I just back wash it with air or water & re-install it? #3. Or Knock the guts out of it & re install? Other experiences & suggestions welcome! Oh I forgott, 86 L98 coupe 21K miles all orig. system.

corvetteronw

Purchase a new "catless" front Y pipe and be done with the dang things.

Bobby Brewsky

Here's an option:

Eastern Catalytic Catalytic Converter
Sale Price:
$225.19
FREE Shipping

Part Number: 3219-05245006
Notes: Catalytic Converter -- 49 STATE DIRECT FIT - UNDERCAR; Y-PIPE ASSY; Not For Sale Or Use In The State Of California
Condition: New
http://www.partsgeek.com/gbproducts/...FUxMMgodej8ANQ

GREGGPENN

If you are trying to stay stock (NCRS) and/or save the OEM cat, you SHOULD be able to dislodge most/all particles using water/air as described. Magnaflow makes some nice ceramic (bullet) pre-cats as replacements. For about $65 ea, they will retain stock sound too.

Any exhaust shop should be able to "hook you up" and clear out the main converter. (by clear out, I don't mean gut).

bogus

I must throw this out there...

Any good exhaust shop worth his salt will not gut a cat... the federal fines are killer steep, $25k worth of steep.

This is what I would do... find an LT1 cat back and do an LT1 style exhaust.

Winnin'

I bought my car with Gutted CATs. I replaced mine with 2 MagnaFlow High flow cats for $165 a peice. Sounds great and no more black exhaust sut all over the back of my car.

GREGGPENN

Metallic CATs are higher priced...definitely more durable too. OEM is ceramic.

I burned up ceramic with my 383...but it's also higher compression.

81c3

Great time for headers,hi flow cat if you desire.

65Z01

I'm thinking of that for a true dual system; does the LT1 exhaust bolt up to a L98 car??

mcm95403

My LT-1 manifolds bolted right up to the L-98 front y-pipe, BUT I had to oval the 3 bolt holes out by about 1/8" - the LT-1 pattern is slightly wider/larger. Aside from that, it should be fine, but remember that the LT-1 resonator goes to single pipe inside (and it's also restrictive), plus the stock Lt-1 mufflers go down to 2" at the muffler outlets.


Keep in mind that system was built to satisfy Federal sound regulations more than performance people. If you could find a complete system (cats and all) for cheap it would be worth doing.


And don't forget you'll need the offset oil filter adapter and will need to run an small LT-1 oil filter from then on as well.


Also, the Magnaflow y-pipe that I bought SUCKED! It cost me $150 to fix the problems. The drivers side inlet pipe was canted over about 15 degrees, so it missed the manifold outlet by half of the opening diameter. Also, the point where the two 2.5" pipes join to the 3" section drops down to a single 2.5", THEN necks up to 3". Totally LAME production. I documented all of this (plus several other posts on the forum about similar product problems with this part) to Magnaflow. They said they'd get back to me - that was almost 2 years ago and NOTHING.

leesvet

Go to ANY of the Corvette catalog stores and buy a new bigger front Y pipe minus the pre-cats.
Its LEGAL. There were only a couple years that used pre-cats. They stopped because of the many problems pre-cats caused.

Install the new front Y and buy a NEW main at the same shop. They WILL do the work. If they grumble about the Y pipe tell them to look up other yr vettes and see for themselves that precats were discontinued.

The Y pipe will be about $250. No way around that. Its jail time in some states if you 'gut' a cat...even a pre-cat. The fine comes on top of that.....
Nobody in his right mind will talk to you about gutting a cat. Unless its got fur.

Again,. BUY the new main (even if you can wash out the old one, its OLD and due to be replaced) and you will NEVER get ALL the fragments out...so its half blocked already and WILL get worse.

Buy the new cat at the shop that's doing the Y install. The fact that you are buying a new main will motivate them to do the work even though its grey area with the Y pipe....

Yes, LT exhaust manifolds DO fit the L98. You can install LT ex manifolds and them the NEW Y will bolt right up. From there back its cake,. and the LT manifolds are easy to come by and a BIG performance bump. You'll understand why/how after you see the L98 manifolds off the car.....

miker2

I see you're in Michigan. I have a 1990 exhaust y-pipe with cats and the main cat.about 20,000 miles on it. the car has about 37,000 but I had lingenfelter headers on it for quite a while. $220.00 if you come and get it in central Michigan. if interested,pm me.

GREGGPENN

FWIW, I bet they'd have reason to grumble. I believe specific wording states that no one can alter emissions systems or configuration as delivered from the factory. That's EPA regulations.

Though State "statues" vary. We all know California is the most strict. It sounds like that state WOULD grumble...and do so loudly.

California isn't the issue here, but in reality, it still the discretion of the shop whether they want to accept that type of work/conversion. I doubt you'll force them into anything they normally wouldn't do. Citing that different model years didn't have precats probably won't sway their decision.

leesvet

True Greg, but they WILL make "exceptions" when you are buying new parts from them,(main Cat) and having them install it...so they feel better about the whole deal.

I did this exact thing in So Cal...Anaheim.

Its a simple explanation to say that pre-cats were d/c and the factory "fix" was simply to eliminate them. That's not far from the truth....it was only a couple yrs that used precats on the L-98 cars and after that they just used a single main cat. The muffler shops don't know the diff between L98 and LT.

It might take going to a couple shops, but someone will do it. Its the "sale" of a new part that seals the deal...that way the shop can cover their *** to some degree. You won't find ANYBODY that will cut those pre-cats out, but replacing the whole Y assy is not too hard to sell 'em on. Its the factory replacement...that simple.

L72M21

Thank you all for your help and suggestions. After back washing the converter, the small particles came out. Then I was able to re install it with just the replacement of one mounting bolt and the front clamp. Now when/if the other pre cat lets go I'll know what to do. This Vette is my two month a year "Dream Cruise" summer driver. With 21K miles on it, I doubt it will see 30K in my lifetime. I'm trying to keep it all original and not spend a lot of money on it. It got an NCRS top flight last month. The other ten months I drive a couple of mid years, and they are always eating a hole in my wallet! Thank again.