Front Y Pipe
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Heel & Toe
Joined: Mar 2006
Posts: 21
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From: Greenwood IN
Front Y Pipe
I am not interested in getting headers for my '87, however, I can pick up pre-catless front Y pipe dirt cheap. Is the gain worth the trouble of installing it? Thanks to all.
Burning Brakes
Joined: Nov 2000
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I have the Walker cat-less front Y pipe and 3 stage converter. If installed as an assembly then its suppose to meet EPA smog requirements for the 49 states. You can guess what state won't allow it. I think adding system was helpful, but I can't say I saw any HP gains. The exhaust note was different without the pre-cats. I'm overall satisfied.
Race Director
Joined: Nov 2003
Posts: 12,220
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From: Overland Park Kansas
2020 Corvette of the Year Finalist (appearance mods)
C4 of Year Winner (appearance mods) 2019
Originally Posted by 87vette
I hear its very restrictive and I will be getting rid of mine soon.
But the LT1 with a redesigned engine (50 more HP) isn't that much faster than the L98. I gather it's something in the neighborhood of 8-10mph in the quarter mile. And, actually, the difference might be less.
For such a difference in improved engine design -- combined with the much bigger and less restrictive exhaust on an LT1, I'd expect the L98 to be way slower the the LT1s -- but they're not.
It's for this reason, I haven't jumped onto the redo your exhaust bandwagon. At some point, I'm positive it's useful, but it sounds like you need to open up the intake before it'd make a real difference in HP.
Team Owner
Joined: Sep 2001
Posts: 62,126
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From: Athens AL
C7 of the Year - Unmodified Finalist 2021
C4 of Year Finalist (performance mods) 2019
you should get about 5-10hp back, so you might as well if you wont get full headers
it'd be best to replace the cat at the same time
it'd be best to replace the cat at the same time
Instructor
Joined: Sep 2004
Posts: 122
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From: Salt Lake City UT
I did the straight pipes with the car being true dual. No cats and no mufflers. with no mufflers its loud but wicked especially in the mid to high RPMs. drove it for a few weeks here in salt lake with no trouble from law enforcement. i finally through the magnaflow mufflers on and its queiter than it was before with three cats on and muffler eliminators. It felt faster, but maybe because it sounded faster. i dont know if there was a performance gain or not.
Advanced
Joined: Jan 2004
Posts: 96
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From: Yardley PA
I recommend it! I had 40k on my '87 vert when I first did exhaust mods. My first mod was a RT cat and cat-back exhaust. I definitely noticed a little SOTP difference as well as a nice "V8" sound. Secondly, I replaced the stock front-Y with a 2.5" catless Y. I noticed even more SOTP difference than my first exhaust mod, and an even better "V8" sound!
I don't think the cats were clogged since I only had 40k on her. I simply think everyone's right on the money when they say the L98 3-cat system is truly a HP robber. Go for it!
I don't think the cats were clogged since I only had 40k on her. I simply think everyone's right on the money when they say the L98 3-cat system is truly a HP robber. Go for it!
Race Director
Joined: Nov 2003
Posts: 12,220
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From: Overland Park Kansas
2020 Corvette of the Year Finalist (appearance mods)
C4 of Year Winner (appearance mods) 2019
Originally Posted by vader86
you should get about 5-10hp back, so you might as well if you wont get full headers
I've heard that anything less than a 10% gain in HP is difficult to impossible to feel. 5-10 HP on a 230-240+ HP car is less than 10%. Recommending the elimination of pollution equipment for such a small gain seems unwarranted.
Your website is one of the sources which lists the L98 exhuast as rediculously restrictive. I would suggest that you amend the language. When I first read it, I would conclude that taking the cats out would be readily felt. But the HP gains mentioned don't bear that out. At the very least, calling them extremely restrictive seems like an overstatement.
Not trying to challenge your knowledge -- because you list mucho good info on your site! In this case of the L98 exhuast restriction(s), I wonder about HOW the info is presented.
gp
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Team Owner
Joined: Sep 2001
Posts: 62,126
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From: Athens AL
C7 of the Year - Unmodified Finalist 2021
C4 of Year Finalist (performance mods) 2019
read 65Z01s site
i'm not amending the language, its correct as it stands,
you cannot debate 'feel', only numbers
i'm not amending the language, its correct as it stands,
you cannot debate 'feel', only numbers
Last edited by vader86; Mar 3, 2006 at 02:35 PM.
Race Director
Joined: Nov 2003
Posts: 12,220
Likes: 446
From: Overland Park Kansas
2020 Corvette of the Year Finalist (appearance mods)
C4 of Year Winner (appearance mods) 2019
If you want to take that approach, I can appreciate it. In that line of thinking, the amount of restriction induced by the L98's exhaust restriction should be given and the amount introduced by other cars (i.e., LT1, should be provided side-by-side). That would give the reader an indication of what they're dealing with.
Merely saying that the system of "so restrictive it's not funny" provides an unsubstantiated claim. Especially when 5-10 HP is all that numbers back that claim up. Geez, I gotta believe the LT1 cat/exhaust system introduces at least a 5HP loss. Where's the fact?
I'm not saying your wrong -- cause I'm not doing measurements on my own. However, the general info doesn't seem to add up. In this case, that info is ENCOURAGING people to remove polution control devices from their cars. If it's really that beneficial, I'm not against it.
gp
Merely saying that the system of "so restrictive it's not funny" provides an unsubstantiated claim. Especially when 5-10 HP is all that numbers back that claim up. Geez, I gotta believe the LT1 cat/exhaust system introduces at least a 5HP loss. Where's the fact?
I'm not saying your wrong -- cause I'm not doing measurements on my own. However, the general info doesn't seem to add up. In this case, that info is ENCOURAGING people to remove polution control devices from their cars. If it's really that beneficial, I'm not against it.
gp
Team Owner
Joined: Sep 2001
Posts: 62,126
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From: Athens AL
C7 of the Year - Unmodified Finalist 2021
C4 of Year Finalist (performance mods) 2019
The LT1 cats do cost about 5hp, thats in Lingenfelter's book. If you read carefully you see that I dont mention much of the LT1 yet, because I havent had time to write everything I know down.
Tests have shown that the L98 will give back 10-12hp (or more in special modded cases) from the total removal of cats. Tests in articles of Hot Rod Magazine, Super Chevy Peformance, and one other I fail to recall....show that typical catbacks (borla, B&B, PE, Flows) give 10-15hp on bone stock cars. I cant scan these articles in to give everybody proof of everything, I cant please everybody who demands the numbers, I can only state from memory. 65Z01s test shows that you can get some power back from removing the restriction of the precats, which I conservatively estimate to be between 5-10hp. Any expected power results I give people here or there will be the most conservative estimates I can.
Tests have shown that the L98 will give back 10-12hp (or more in special modded cases) from the total removal of cats. Tests in articles of Hot Rod Magazine, Super Chevy Peformance, and one other I fail to recall....show that typical catbacks (borla, B&B, PE, Flows) give 10-15hp on bone stock cars. I cant scan these articles in to give everybody proof of everything, I cant please everybody who demands the numbers, I can only state from memory. 65Z01s test shows that you can get some power back from removing the restriction of the precats, which I conservatively estimate to be between 5-10hp. Any expected power results I give people here or there will be the most conservative estimates I can.
Advanced
Joined: Nov 2005
Posts: 54
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From: Mountain Home AR
No Cats!!!!!!
Vader, I agree with you 100% 
. I live in Arkansas where we have NO money wasting test. I bought my 86- Z51- 4+3- 6 months ago with 76 K on her. The original cats were rattling and blocked. Went to the local shop and told them that all I wanted left was the two mufflers. When I left I went through the gears---Wow!!! It sounded good, and really felt good getting that L98 kick in the pants feeling. Let them say what they want, but I know how I think it feels.
. I live in Arkansas where we have NO money wasting test. I bought my 86- Z51- 4+3- 6 months ago with 76 K on her. The original cats were rattling and blocked. Went to the local shop and told them that all I wanted left was the two mufflers. When I left I went through the gears---Wow!!! It sounded good, and really felt good getting that L98 kick in the pants feeling. Let them say what they want, but I know how I think it feels.
Race Director
Joined: Nov 2003
Posts: 12,220
Likes: 446
From: Overland Park Kansas
2020 Corvette of the Year Finalist (appearance mods)
C4 of Year Winner (appearance mods) 2019
My main point (here) concerns your website comment that the L98s exhaust being so restrictive that "it's not funny". After reading this, I (for one) began researching in earnst headers, removing cats, increasing exhaust, etc... etc...
After learning more, I'm not quite as inclinded. I now realize that exhaust changes can be hit/miss. They can have pitfalls. They can be disappointing. The can SEEM faster just due to noise increases (false perception). And, backpressure (with cats) can even be a good thing. Or at least -- not so bad.
While I absolutely, 100% appreciate the information you've compiled on your website, this particular comment seems blown out of proportion. Had I blindly plowed forward, I probably would have had false expectations and I'd be driving an illegal car.
I'm not even saying that I probably would have ended up unhappy. I'm just pointing out my observations and providing some feedback.
After learning more, I'm not quite as inclinded. I now realize that exhaust changes can be hit/miss. They can have pitfalls. They can be disappointing. The can SEEM faster just due to noise increases (false perception). And, backpressure (with cats) can even be a good thing. Or at least -- not so bad.
While I absolutely, 100% appreciate the information you've compiled on your website, this particular comment seems blown out of proportion. Had I blindly plowed forward, I probably would have had false expectations and I'd be driving an illegal car.
I'm not even saying that I probably would have ended up unhappy. I'm just pointing out my observations and providing some feedback.
Race Director
Joined: Nov 2003
Posts: 12,220
Likes: 446
From: Overland Park Kansas
2020 Corvette of the Year Finalist (appearance mods)
C4 of Year Winner (appearance mods) 2019
Sorry for the sidetrack. For those still considering this conversion, I would suggest that MAM sells (what they describe) as a front catless Y pipe in 2 1/2". Since I assume this still has a 3" connector, I have to assume this part provides a 1/4" increase in diameter over factory -- in addition to providing an option that doesn't include the front pre-cats.
Finally, I want to add that my Corvette SEEMS to be cleaner than both of my newer Jeeps. On both of those vehicles, I can clearly see carbon build-up in the exhaust pipes (black soot). My Corvette is a light-to-medium brown color and seems more devoid of soot despite the extra power/displacement.
Kinda makes me wonder if they actually went into overkill during those years.
Finally, I want to add that my Corvette SEEMS to be cleaner than both of my newer Jeeps. On both of those vehicles, I can clearly see carbon build-up in the exhaust pipes (black soot). My Corvette is a light-to-medium brown color and seems more devoid of soot despite the extra power/displacement.
Kinda makes me wonder if they actually went into overkill during those years.
Intermediate
Joined: Nov 2005
Posts: 44
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From: Jacksonville Arkansas
I have a 87 convertible auto with the dynomax front y pipe w/o pre-cats and a high flow dynomax cat going into dynomax super turbo muffs. I hate it, I had the mufflers with the stock cat and pre cats and loved the full sound and low resonance, but had a pre cat start making noise. So I replaced them and the cat. Now I have a terrible resonance and a strange noise, chatter or shuddering, coming from the front y pipe right at the y. I don't know what to do. I wish I had just replaced the pre cats now.
Advanced
Joined: Jan 2004
Posts: 96
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From: Yardley PA
Originally Posted by triple_E_Farm
I have a 87 convertible auto with the dynomax front y pipe w/o pre-cats and a high flow dynomax cat going into dynomax super turbo muffs. I hate it, I had the mufflers with the stock cat and pre cats and loved the full sound and low resonance, but had a pre cat start making noise. So I replaced them and the cat. Now I have a terrible resonance and a strange noise, chatter or shuddering, coming from the front y pipe right at the y. I don't know what to do. I wish I had just replaced the pre cats now.
Maybe the exhaust is too close (or touching) your x-brace? Mine was at first, but a quick trip back to the shop had it fixed in about 5 mins.
Racer
Joined: Nov 2004
Posts: 445
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Originally Posted by 87droptop
I am not interested in getting headers for my '87, however, I can pick up pre-catless front Y pipe dirt cheap. Is the gain worth the trouble of installing it? Thanks to all.
As for performance...let the experts with experience debate that.
I gutted my pre-cats, then sleeved them the same size as my pipes, 21/2", have no centre cat, but have two straight thru resonators, a psuedo x-pipe, and a pair of straight thru mufflers...
It all sounds nice to me, and I am happy with it. I have no proof, but feel that it must be more efficient and less restrictive than the original equipment.
If it was me, I would definitely take the trouble( and it is no big deal) to fit the cat-less front pipe...
Intermediate
Joined: Nov 2005
Posts: 44
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From: Jacksonville Arkansas
Originally Posted by stick91
Maybe the exhaust is too close (or touching) your x-brace? Mine was at first, but a quick trip back to the shop had it fixed in about 5 mins.
I haven't re-installed my X brace yet, Just finishing up a complete rebuild, the car had a bad fire in the engine compartment. The exhaust does seem to hang down more now. I had to cut some of the flang off of the new cat because it would drag the ground when I hit a bump.
