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Best diameter Y pipe for 305 tbi

Old 07-05-2019, 08:09 PM
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Best diameter Y pipe for 305 tbi

I am considering replacing the exhaust on my tbi Camaro from the manifolds back to help it breath better. I would like to know if I would benefit from increasing the diameter of the Y pipe, and back. I have a hollow cat. Input would be appreciated.
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Old 07-05-2019, 10:02 PM
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Re: Best diameter Y pipe for 305 tbi

After reading and being in a few discussions here I became convinced that the factory T-Pipe is a significant restriction. (It's not even a Y). I ordered a MAC Y pipe for a little over $200. Haven't put it in yet but it's a real Y. Members here say that it is by far the best thing we can do for a stock exhaust.

https://www.teambeefcakeracing.com/mac-48692.html
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Old 07-05-2019, 10:26 PM
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Re: Best diameter Y pipe for 305 tbi

Yes, T pipe is a more accurate discription, and I believe it's 2", and the Mac is 2 1/2". This is a bolt on and go, or does it need fitment? From the Y on back I figure 3" is what is recommended. I have a shop that might be able to fabricate this, I just need to ask about cost.
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Old 07-05-2019, 10:54 PM
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Re: Best diameter Y pipe for 305 tbi

Originally Posted by Tootie Pang View Post
After reading and being in a few discussions here I became convinced that the factory T-Pipe is a significant restriction. (It's not even a Y). I ordered a MAC Y pipe for a little over $200. Haven't put it in yet but it's a real Y. Members here say that it is by far the best thing we can do for a stock exhaust.

https://www.teambeefcakeracing.com/mac-48692.html
I wonder if that fits both 2" and 2.25" exhaust manifolds.I believe one of the exhaust ports, (passenger side?) is orientated differently than the other.
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Old 07-06-2019, 09:06 AM
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Re: Best diameter Y pipe for 305 tbi

Originally Posted by chazman View Post
I wonder if that fits both 2" and 2.25" exhaust manifolds.I believe one of the exhaust ports, (passenger side?) is orientated differently than the other.
Good question. I am in the process of calling the company, they are open 7 days. I'll see what they say if I can get a technician who knows the answers
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Old 07-06-2019, 12:35 PM
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Re: Best diameter Y pipe for 305 tbi

Originally Posted by Stevolwevol View Post
Good question. I am in the process of calling the company, they are open 7 days. I'll see what they say if I can get a technician who knows the answers
I had to have my Y-pipe modified on my '83 when I went from 2" to 2.25" manifolds.
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Old 07-06-2019, 03:55 PM
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Re: Best diameter Y pipe for 305 tbi

Originally Posted by chazman View Post
I had to have my Y-pipe modified on my '83 when I went from 2" to 2.25" manifolds.
What engine were the 2 1/4 from? Do they dump in the same place the previous ones did?
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Old 07-06-2019, 04:30 PM
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Re: Best diameter Y pipe for 305 tbi

Originally Posted by Stevolwevol View Post
What engine were the 2 1/4 from? Do they dump in the same place the previous ones did?
From an L69. One of them dumps in a different place, enough where the Y pipe needed modifying.
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Old 07-06-2019, 04:59 PM
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Re: Best diameter Y pipe for 305 tbi

Alright chazman, I'm sure my l03 has a 2" diameter. I would like to know If I would benefit from a larger, better designed y pipe with the restrictive manifold that's on the engine.
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Old 07-06-2019, 05:40 PM
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Re: Best diameter Y pipe for 305 tbi

Originally Posted by Stevolwevol View Post
Alright chazman, I'm sure my l03 has a 2" diameter. I would like to know If I would benefit from a larger, better designed y pipe with the restrictive manifold that's on the engine.
It does. L03, LG4 and LU5 all had the 2 manifolds.
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Old 07-06-2019, 06:10 PM
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Re: Best diameter Y pipe for 305 tbi

Yes Chazman, but would I benefit with a better Y pipe using the existing manifolds?
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Old 07-06-2019, 06:15 PM
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Re: Best diameter Y pipe for 305 tbi

Originally Posted by Stevolwevol View Post
Yes Chazman, but would I benefit with a better Y pipe using the existing manifolds?
I think you would. But the 2.25 intermediate pipe is also a restriction.
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Old 07-06-2019, 06:24 PM
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Re: Best diameter Y pipe for 305 tbi


It's not often I get the chance to contribute on this forum (I'm usually the one asking all the questions), but I thought this might help. I happen to have a set of manifolds off an LO3 as well as a set of L98 manifolds. I have attached a photo of them side-by-side.
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Old 07-06-2019, 09:51 PM
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Re: Best diameter Y pipe for 305 tbi

The driver's side manifolds are close enough. The passenger's manifold on the HO cars is longer, and the outlet extends at a different angle.

The solution is simple... Get the manifolds from an HO car. By HO I mean a LB9 between 85-87, or a later car with dual cats, or any L98 with G92 or R6P, pretty much any of the GOOD tuned port engines. The only exceptions are the later cars with single cats, because GM neutered them with the TBI/LG4 exhaust that's the same diameter as the V6 trash. The cars to avoid are also the ones that had 2.73 gears... Feels like I'm trying to drive through Jello just thinking about those slugs... Disgusting.

If you absolutely can't find a used set of HO manifolds, Rock Auto has new ones for less than a set of headers.

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Old 07-07-2019, 01:18 AM
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Re: Best diameter Y pipe for 305 tbi

The definitive post on factory 3rd gen exhausts.

Originally Posted by TransamGTA350 View Post
There were only 2 different manifolds for the V8's throughout the years, but they were different depending on what motor and gearing package they came on. Here is the breakdown.

2" outlet manifolds with single 2 1/4" y-pipe
82-87 305 LG4 (VIN H)
88-92 305 L03 (VIN E)
82-83 305 Crossfire
90-92 305 LB9 w/o G92 axle (VIN F)

2 1/4" outlet manifolds with single 3" y-pipe
83-86 305 L69 (VIN G)
85-89 305 LB9 (VIN F)
88 350 L98 (VIN 8)
89 350 L98 w/o G92 axle (VIN 8)

2 1/4" outlet manifolds with dual 2 1/4" cats
89 350 L98 w/G92 axle (VIN 8)
90-92 350 L98 (VIN 8)
89 305 LB9 w/G92 Axle (VIN F)
90-92 305 LB9 w/G92 (Vin F)

The manifolds from the single 3" cat and the dual 2.25" cats are interchangeable. On the passenger side manifold, some will have the heat riser butterfly valve, some will have a spacer, and some will just have a donut gasket. You most likely have the wrong manifold for your application. If you have the larger manifolds, then it may be worth it to get the larger y-pipe for some more performance.
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Old 07-07-2019, 01:31 AM
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Re: Best diameter Y pipe for 305 tbi

LG4/LU5/L03 Y-pipe vs L69/LB9/L98 Y-pipe.

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Old 07-07-2019, 08:02 AM
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Re: Best diameter Y pipe for 305 tbi

Originally Posted by chazman View Post
LG4/LU5/L03 Y-pipe vs L69/LB9/L98 Y-pipe.


Bad example. The wide-mouth 4-bolt cat was long gone by the L98. 85 was the last year for that.
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Old 07-07-2019, 09:49 AM
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Re: Best diameter Y pipe for 305 tbi

Originally Posted by Drew View Post
Bad example. The wide-mouth 4-bolt cat was long gone by the L98. 85 was the last year for that.
I know, but it was late and that pic was handy.
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Old 07-07-2019, 12:56 PM
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Re: Best diameter Y pipe for 305 tbi

So it looks like I should be OK with the MAC Y I cited. I have an 89 LB9 with the 2.25". I'll report back how it fits.
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Old 07-07-2019, 07:38 PM
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Re: Best diameter Y pipe for 305 tbi

The Magnaflow is less buckaroos than the MAC and it's stainless. If you're into that kind of thing.

It's a bit shocking that MAC still makes anything, more of a shock that anyone sells an upgraded Y-pipe for stock manifolds. It'd be utter insanity if anyone offered one for the low output manifolds.
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Old 07-07-2019, 08:31 PM
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Re: Best diameter Y pipe for 305 tbi

I've had the MAC Y-pipe on my 87 TPI for many years. Two 2-1/2" pipes into a 3" pipe to the cat; nicely-made; perfect fit. So precise, that both sides had to be raised into position at the same time, which wasn't easy without any help, while laying on my back underneath the car. And retainment of the passenger side spacer IS necessary, which also added to the complexity of my one-man installation.

When such Y-pipes have come to topic in past years, it was mentioned that the passenger side manifold on dual-cat cars angles downward differently than the manifold on single-cat cars. True or not, I, personally, have not confirmed. But IF true, and if someone's plan is to switch from dual cats to a single cat, then the MAC Y-pipe(or any other such past or present Y-pipes--Magnaflow used to offer one, Jegs used to offer one, and Hawk's offers one for no cat "off-road" use) isn't likely to fit those dual-cat manifolds.

MAC states 86-92 single-cat fitment. Aside from the fact that the Y-pipe is obviously feeding just one cat, the angle of the dual-cat manifolds, if, in fact, different, is probably also a factor in their fitment claim. But I can say with 100% certainty that it fits my 1987 TPI perfectly.

MAC deals mostly with Mustangs, but it does still offer our Y-pipe. On a side note, it also still offers ceramic coated headers/Y-pipe and a 3" cat-back for our cars, too. So when Dyno Don eventually stops producing his headers and Y-pipes, which will be soon, and if I haven't gotten his by that time, then I will probably go with the MAC headers/Y-pipe, given that its stock-fitting Y-pipe fits so very well.
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Old 07-07-2019, 09:18 PM
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Re: Best diameter Y pipe for 305 tbi

Originally Posted by LAFireboyd View Post
When such Y-pipes have come to topic in past years, it was mentioned that the passenger side manifold on dual-cat cars angles downward differently than the manifold on single-cat cars. True or not, I, personally, have not confirmed. But IF true, and if someone's plan is to switch from dual cats to a single cat, then the MAC Y-pipe(or any other such past or present Y-pipes--Magnaflow used to offer one, Jegs used to offer one, and Hawk's offers one for no cat "off-road" use) isn't likely to fit those dual-cat manifolds.

As already explained there are two sets of manifolds, large and small. The reason some people say dual cat manifolds are different, is because sometime after the dual cat system came around, GM decided that anything that didn't warrant the dual cats, didn't warrant the better manifolds or 3" cat either. Without digging into the books, it's 90-92 if the car doesn't have dual cats, the 305 TPI has the tiny exhaust. That's why the dual cat cars are rated 25hp and 15ft lbs higher than the single cat version.
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Old 07-07-2019, 09:41 PM
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Re: Best diameter Y pipe for 305 tbi

Originally Posted by Drew View Post
As already explained there are two sets of manifolds, large and small. The reason some people say dual cat manifolds are different, is because sometime after the dual cat system came around, GM decided that anything that didn't warrant the dual cats, didn't warrant the better manifolds or 3" cat either. Without digging into the books, it's 90-92 if the car doesn't have dual cats, the 305 TPI has the tiny exhaust. That's why the dual cat cars are rated 25hp and 15ft lbs higher than the single cat version.
But that isn't what I was talking about.

I'm talking about the angle of the manifold where it goes down to meet the Y-pipe(the downpipe, if you will). That's what people were saying is different about the dual-cat manifolds, the angle, not the size of the openings. And because everyone who posts on TGO is always right LOL, the discussion got ugly. What a surprise! Someone even posted a pic with a manifold from a dual-cat exhaust next to a manifold from a single-cat exhaust, and the angles of the downpipes did appear to be different. So if that pic was accurate, then the size of the openings is irrelevant to fitment, in this case, as it would be the angle, which would prevent the Y-pipe from meeting the dual-cat manifolds properly. So, again, IF that's true, as several people on this website will fight to their deaths to prove that they're right LOL, then that would mean there are more than two sets of manifolds. Just saying...

As for the pic of the manifolds in this thread, while the diameters of the openings do differ from each other, with one being larger than the other, the overall diameter of the mounting "ball" looks similar to each other. If that's the case, then it looks like the MAC flanges might fit properly on the manifolds with the smaller openings. That's just from looking at that pic, without having dimensions to verify.
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Old 07-07-2019, 09:53 PM
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Re: Best diameter Y pipe for 305 tbi

Originally Posted by LAFireboyd View Post
But that isn't what I was talking about.

I'm talking about the angle of the manifold where it goes down to meet the Y-pipe(the downpipe, if you will). That's what people were saying is different about the dual-cat manifolds, the angle, not the size of the openings. And because everyone who posts on TGO is always right LOL, the discussion got ugly. What a surprise! Someone even posted a pic with a manifold from a dual-cat exhaust next to a manifold from a single-cat exhaust, and the angles of the downpipes did appear to be different. So if that pic was accurate, then the size of the openings is irrelevant to fitment, in this case, as it would be the angle, which would prevent the Y-pipe from meeting the dual-cat manifolds properly. So, again, IF that's true, as several people on this website will fight to their deaths to prove that they're right LOL, then that would mean there are more than two sets of manifolds. Just saying...

As for the pic of the manifolds in this thread, while the diameters of the openings do differ from each other, with one being larger than the other, the overall diameter of the mounting "ball" looks similar to each other. If that's the case, then it looks like the MAC flanges might fit properly on the manifolds with the smaller openings. That's just from looking at that pic, without having dimensions to verify.
The N10 dual cat manifolds are the same as the single cat 2.25" manifolds. See the the post I quoted from TransAmGTA350 above.
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Old 07-07-2019, 09:56 PM
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Re: Best diameter Y pipe for 305 tbi



I understand what you're saying, but that rumor doesn't match the facts. The dual cat manifolds, and the HO manifolds from a single cat car, are exactly the same manifolds. Both Y-pipes will bolt up to the HO manifolds. The reason people think that dual cat manifolds are different, is because in most of the years the N10 exhaust applies, the single cat TPI cars got the low output manifolds. I don't need to fight to the death to prove it, I've uploaded the catalog pages with the part numbers before. I've had a set of 92 Z28 L98 manifolds (dual cat) sitting next to an 86 LB9, the manifolds were/are the same thing.

Person also needs the HO spacer to fill the gap of the EFE flapper valve. Note the "HO" cast right into the spacer.


Last edited by Drew; 07-07-2019 at 09:59 PM.
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Old 07-07-2019, 10:41 PM
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Re: Best diameter Y pipe for 305 tbi

All of that is good. It makes my case for the MAC even better. It means the aftermarket Y-pipes that fit stock manifolds, like the one from MAC, will fit manifolds of single cat exhausts(86-92, as MAC states), and manifolds of dual-cat exhausts where the owner might want to change to a single-cat. I doubt many people make such a change, but it's probably happened.

Regardless of any of that, all I'm confirming for this thread is that the MAC Y-pipe fits my 87 perfectly. That's hands-on, not from quoting anything I, or anyone else, might've said or read. Beyond that, people will have to take their own chances. The apparent bad info I mentioned, in question, was info that I've read here on TGO, and now that's been clarified for everyone.
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Old 07-08-2019, 12:15 AM
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Re: Best diameter Y pipe for 305 tbi

Originally Posted by LAFireboyd View Post
It makes my case for the MAC even better. It means the aftermarket Y-pipes that fit stock manifolds, like the one from MAC, will fit manifolds of single cat exhausts(86-92, as MAC states), and manifolds of dual-cat exhausts where the owner might want to change to a single-cat.
Nope, still not getting it.

90-92 TPI single cat cars use the low output manifolds. TPI Single cat cars before 90 use the HO manifolds. The same Y-pipe won't bolt up to both LO and HO manifolds because the passengers side manifold is different.

It has nothing to do with single or dual cats, it has everything to do with HO and LO manifolds. Early TPI cars with single cats, and late cars with dual cats use HO manifolds. Late single cat cars use LO manifolds.

MAC is wrong. Their Y-pipe fits HO manifolds. They don't realize that 90-92 TPI cars use the LO manifolds. Plenty of people around here don't realize that distinction either, hence the confusion.
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Old 07-08-2019, 09:11 AM
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Re: Best diameter Y pipe for 305 tbi

I'll post this again.




Originally Posted by TransamGTA350
There were only 2 different manifolds for the V8's throughout the years, but they were different depending on what motor and gearing package they came on. Here is the breakdown.

2" outlet manifolds with single 2 1/4" y-pipe
82-87 305 LG4 (VIN H)
88-92 305 L03 (VIN E)
82-83 305 Crossfire
90-92 305 LB9 w/o G92 axle (VIN F)

2 1/4" outlet manifolds with single 3" y-pipe
83-86 305 L69 (VIN G)
85-89 305 LB9 (VIN F)
88 350 L98 (VIN 8)
89 350 L98 w/o G92 axle (VIN 8)

2 1/4" outlet manifolds with dual 2 1/4" cats
89 350 L98 w/G92 axle (VIN 8)
90-92 350 L98 (VIN 8)
89 305 LB9 w/G92 Axle (VIN F)
90-92 305 LB9 w/G92 (Vin F)

The manifolds from the single 3" cat and the dual 2.25" cats are interchangeable. On the passenger side manifold, some will have the heat riser butterfly valve, some will have a spacer, and some will just have a donut gasket. You most likely have the wrong manifold for your application. If you have the larger manifolds, then it may be worth it to get the larger y-pipe for some more performance.
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Old 07-08-2019, 09:12 AM
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Re: Best diameter Y pipe for 305 tbi

So I have a 91 TPI with the single cat 2.25" pipe. Will I need a spacer like the one pictured to make this work? I don't believe I have a "flapper" in my passenger side manifold but it is hard to see down there.
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Old 07-08-2019, 11:24 AM
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Re: Best diameter Y pipe for 305 tbi

Originally Posted by vinny R View Post
So I have a 91 TPI with the single cat 2.25" pipe. Will I need a spacer like the one pictured to make this work? I don't believe I have a "flapper" in my passenger side manifold but it is hard to see down there.
You would need HO manifolds, a matching Y, and something to fill the EFE flapper valve gap.

By 91, thirdgens didn't have the EFE valve anymore, but the manifolds they used were designed for the valve. Scroll up and note how the passenger's manifold outlet is flat instead of a tapered flange like the driver's. You probably already have some kind of adapter on the stock manifolds/Y-pipe to fill the gap. Earlier cars used the cast spacer in the pic I posted, later cars used a cast iron donut, the ZZ3/4 used a donut. You just need something to take up about .5-1" gap and adapt the flat outlet to a ball flange/flared pipe.


Last edited by Drew; 07-08-2019 at 11:30 AM.
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Old 07-08-2019, 12:03 PM
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Re: Best diameter Y pipe for 305 tbi

So here's a question: How much (if at all) do cars that already have the HO manifolds benefit by replacing the stock Y-pipe with a mandrel-bent 2.5" in/3" out pipe?
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Old 07-08-2019, 01:04 PM
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Re: Best diameter Y pipe for 305 tbi

Originally Posted by DaveyDug View Post
So here's a question: How much (if at all) do cars that already have the HO manifolds benefit by replacing the stock Y-pipe with a mandrel-bent 2.5" in/3" out pipe?
Every little thing helps. On a stock car, would it be worth 5 horsepower? Maybe less?
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Old 07-08-2019, 01:14 PM
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Re: Best diameter Y pipe for 305 tbi

Originally Posted by DaveyDug View Post
So here's a question: How much (if at all) do cars that already have the HO manifolds benefit by replacing the stock Y-pipe with a mandrel-bent 2.5" in/3" out pipe?

Considering the low output Y-pipe is a crush bent, constricted monstrosity with a T-pipe where the pipes come together, a proper Y-pipe with smooth bends and larger pipes helps a lot. You can dig a bit and probably find some exact numbers.

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Old 07-08-2019, 01:58 PM
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Re: Best diameter Y pipe for 305 tbi

Originally Posted by Drew View Post
You would need HO manifolds, a matching Y, and something to fill the EFE flapper valve gap.

By 91, thirdgens didn't have the EFE valve anymore, but the manifolds they used were designed for the valve. Scroll up and note how the passenger's manifold outlet is flat instead of a tapered flange like the driver's. You probably already have some kind of adapter on the stock manifolds/Y-pipe to fill the gap. Earlier cars used the cast spacer in the pic I posted, later cars used a cast iron donut, the ZZ3/4 used a donut. You just need something to take up about .5-1" gap and adapt the flat outlet to a ball flange/flared pipe.

Got it, Thank you Drew!
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Old 07-08-2019, 03:20 PM
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Re: Best diameter Y pipe for 305 tbi

Other than 3.42's, my car is a stock auto 305 TPI. I'm putting in a 5-speed, cam, and custom tune so I figured the Y pipe would be a good complement to the other stuff.
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Old 07-08-2019, 04:22 PM
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Re: Best diameter Y pipe for 305 tbi

Originally Posted by vinny R View Post
Got it, Thank you Drew!
Just for a picture reference, these manifolds came from my 92 Z28 non G92 car, there was not a spacer, just an ordinary donut. Vinny, yours should be the same?

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Old 07-10-2019, 02:12 PM
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Re: Best diameter Y pipe for 305 tbi

Originally Posted by Tootie Pang View Post
Other than 3.42's, my car is a stock auto 305 TPI. I'm putting in a 5-speed, cam, and custom tune so I figured the Y pipe would be a good complement to the other stuff.
if you're doing all that , why not just put a nice set of headers on too?
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Old 07-10-2019, 02:27 PM
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Re: Best diameter Y pipe for 305 tbi

I've thought about that. Lots of little reasons but mainly pain of install, spark plugs and I don't think they will make much, if any difference on a near stock LB9. I wasn't going to do the Y-pipe but then I thought about that T-Pipe and that's just plain wrong.
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Old 07-10-2019, 02:51 PM
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Re: Best diameter Y pipe for 305 tbi

well if I was swapping manifolds for .25" I would also have to consider headers providing a benefit too.
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Old 07-10-2019, 03:00 PM
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Re: Best diameter Y pipe for 305 tbi

Headers are a pain in the ***. They don't fit. Everything that interacts with the manifolds, don't fit once you replace them with headers. Headers rust. Headers leak. Headers melt all lumpy and greasy... Wait, are we talking about headers vs manifolds or cheddar vs Velveeta? Anyway, there are plenty of reasons to go with the HO manifolds. It's a quick and affordable way to free up some power, if you're resourceful, without the headaches and expense of headers.
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Old 07-10-2019, 03:08 PM
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Re: Best diameter Y pipe for 305 tbi

Originally Posted by Sierra6 View Post
well if I was swapping manifolds for .25" I would also have to consider headers providing a benefit too.

.375" if you want to get technical. By GM's own words, the low output manifolds have 1 7/8" outlets, vs 2.25" on the HO manifolds.

With limited exceptions, you can't touch a bolt in set of headers and Y-pipe that are worth a damn for much under $500. A set of used HO manifolds is usually a $50 proposition, and another $200 for the Y-pipe. The gain of the manifolds isn't HUGE, but the gain from a mandrel bent Y-pipe and larger pipes at that, is a good upgrade for the money. It's just an unpopular mod because it's not flashy, and it goes against the traditional socially acceptable headers or nothing view point.
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Old 07-10-2019, 03:11 PM
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Re: Best diameter Y pipe for 305 tbi

point well taken
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Old 07-10-2019, 05:23 PM
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Re: Best diameter Y pipe for 305 tbi

Originally Posted by Drew View Post
Headers are a pain in the ***. They don't fit. Everything that interacts with the manifolds, don't fit once you replace them with headers. Headers rust. Headers leak. Headers melt all lumpy and greasy... Wait, are we talking about headers vs manifolds or cheddar vs Velveeta? Anyway, there are plenty of reasons to go with the HO manifolds. It's a quick and affordable way to free up some power, if you're resourceful, without the headaches and expense of headers.
Well, I put long tube headers on my Vette, and they fit like a charm. Made it easier to get to the spark plugs, and I used good gaskets. All you need to do is re torque a couple of times, and your good to go. Both Camaro, and Corvette are gen 1 small blocks, so once their installed, they are better than stock manifolds if you ask me. ! 7/8" outlets are just plain pathetic no matter what engine.
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Old 07-10-2019, 09:54 PM
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Re: Best diameter Y pipe for 305 tbi

My HO manifolds are already on there. If I had the smaller ones, I might consider...
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Old 07-10-2019, 09:56 PM
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Re: Best diameter Y pipe for 305 tbi

Originally Posted by Stevolwevol View Post
Well, I put long tube headers on my Vette, and they fit like a charm. Made it easier to get to the spark plugs, and I used good gaskets. All you need to do is re torque a couple of times, and your good to go. Both Camaro, and Corvette are gen 1 small blocks, so once their installed, they are better than stock manifolds if you ask me. ! 7/8" outlets are just plain pathetic no matter what engine.
I've done long tubes, short tubes, equal length. It depends on who makes them and luck whether they fit well and whether they seal well as a bolt on. Also, better or worse access to things- its usually less with the headers...

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Old 07-11-2019, 08:01 AM
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Re: Best diameter Y pipe for 305 tbi

here's a tip for anybody. I highly recommend remflex gaskets. sealed like a charm on my v6 when the felpros kept failing me. I also used ARP bolts.
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Old 07-11-2019, 12:10 PM
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Re: Best diameter Y pipe for 305 tbi

I have a set of HO manifolds. If I were to get the magnaflow Y-pipe i would still need the spacer? If I do where would I find one or do any of you guys have one for sale? I have a set of headers but am not opposed to using manifolds on my 350 swap.
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Old 07-11-2019, 01:17 PM
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Re: Best diameter Y pipe for 305 tbi

Originally Posted by dmccain View Post
I have a set of HO manifolds. If I were to get the magnaflow Y-pipe i would still need the spacer? If I do where would I find one or do any of you guys have one for sale? I have a set of headers but am not opposed to using manifolds on my 350 swap.
Does magna flow still make a Y-pipe? I looked into theirs awhile back with no luck, like it was discontinued.
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Old 07-11-2019, 01:25 PM
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Re: Best diameter Y pipe for 305 tbi

I have an exhaust man that will fabricate a y pipe, and a three inch single pipe all the way back for under 300 dollars. The question is; with a 2" manifold, will it help??
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Old 07-11-2019, 02:26 PM
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Re: Best diameter Y pipe for 305 tbi

Unless your exhaust guy has a mandrel bending machine, it'd be worse than the stock stuff.

Magnaflow had their Y-pipe unavailable for awhile, but it's been back a couple years now.

Walker, and I'm sure AP, and Felpro offer donut gaskets. I'm sure one of them would fit snug in the manifold. Or check out what you have now, if it doesn't fit as is it can probably be bored out to match the larger manifolds.
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