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OK, here's where I'm at: I believe Chazman stated , the Y pipe on the L69, LB9, and the L98 was a 3" diameter. So, for my L03 I should go with a 3" Y pipe, or a 2 1/2" Y pipe into 3" exhaust? I just got back from the shop, and I could have it done for just under $300. I would like to be positive on the Y pipe diameter before I do this.
OK, here's where I'm at: I believe Chazman stated , the Y pipe on the L69, LB9, and the L98 was a 3" diameter. So, for my L03 I should go with a 3" Y pipe, or a 2 1/2" Y pipe into 3" exhaust? I just got back from the shop, and I could have it done for just under $300. I would like to be positive on the Y pipe diameter before I do this.
3" Y pipe might be too big. Are you changing to HO manifolds?
3" Y pipe might be too big. Are you changing to HO manifolds?
I'm keeping my stock manifolds for now. My exhaust guy said he can't do much with the angle of the Y pipe forming a T. I would need the Summit Y250300, or something similar. I don't know if the Y250300 will fit, cause it's universal, not specific for third gens. He could do 2 1/2" into 3", but the T angle is troubling to me. I'm concerned about the design causing back pressure. I want to reduce back pressure of course.
I'm keeping my stock manifolds for now. My exhaust guy said he can't do much with the angle of the Y pipe forming a T. I would need the Summit Y250300, or something similar. I don't know if the Y250300 will fit, cause it's universal, not specific for third gens. He could do 2 1/2" into 3", but the T angle is troubling to me. I'm concerned about the design causing back pressure. I want to reduce back pressure of course.
Below is a pic of your exhaust. What if your guy fabed you a pipe. Where the T comes in the drivers pipe. that pipe bends to the side, the drivers pipe. The pass pipe comes down now along side the drivers pipe, not in the top, and 90's to run parallel with the drivers for a few inches.
So you will have 2 pipes side by side that end just beyond the original T At this point weld in this...
From there he can make the sweep around that would eventually go into the cat. Maybe 2.5" throughout. This would at least get that T out. I was thinking on doing this to mine if I was not going to switch manifolds so I have had this idea floating around. Below is the Magnaflow design. It looks like they took a similar approach.
It's possible he could reconfigure the Y pipe as you explained. What can you tell me about the Y250300? I called Summit and they told me it's a universal, and the tech didn't know If it would fit a third gen. I would have to have it put back on the hoist to reexamine.
It's possible he could reconfigure the Y pipe as you explained. What can you tell me about the Y250300? I called Summit and they told me it's a universal, and the tech didn't know If it would fit a third gen. I would have to have it put back on the hoist to reexamine.
If this is the Y250300 than I would say no. Right off it looks to have a 3 bolt flange and ours are 2 bolt. The T is a little better but still a concern as you stated. It is not mandrel bent. The fitment would cause me concern just from looking at it. That black collector Y I pictured came up in a search using the above numbers so maybe that is the Y he referred to. The stuff is made by Flowmaster.
Yeah you would think Magnaflow would have a mandrel bent replacement, but that's the way it is I guess. Since my last post I called Magnaflow, and they have part number 10778, a Y pipe specific to third gens. It's a collector, not the pipe, designed for 2 1/2 into 3" exhaust pipe. About $50 delivered. My guy can fabricate the rest of the system from the engine all the way back. This brings the price to about $350 for the performance exhaust.
So does this imply horsepower gain, or is this adequate for a 5 or 5.7 ? I don't quite understand the chart.
The chart indicates the proper pipe sizing for you CID and horsepower rating. The left side is your engine and the right side is the pipe size you want to use.
This alone will make a huge difference. Even with LG4 manifolds. The flow from both banks is in the same direction.
While it was not a L03 I switched a my LE9 305 in my old G20 van from the factory 2" outlet truck manifolds, factory Y-pipe and single 2.5" cat to the factory 2.5" tubular manifolds and the complete 2.5" factory stainless catless dual exhaust. I added a DrGas X-pipe (this was back in 2004 and they were about the only ones making them then) to the factory dual pipes. Made a big difference. Later I also swapped on a performer rpm Q-Jet manifold and rebuilt the Q-Jet. Finally I swapped out the stock distributer for a used MSD Streetfire HEI. I swapped out my stock air cleaner for a 10x4 open element. I knocked more than 3 seconds off the 0-60. The 218/218 cam I put in it knocked another second off it. Literally felt like I unhooked the trailer I was dragging around behind me. All in all I went from 165 hp at the crank to 210 at the wheels. 0-60 dropped from 11 seconds to 7 seconds. Fuel mileage went up 3 miles to the gallon from averaging 13 to averaging 16.
The chart indicates the proper pipe sizing for you CID and horsepower rating. The left side is your engine and the right side is the pipe size you want to use.
The part that connects the Y pipe to the exhaust pipe is Magnaflow #10778. My exhaust guy will fabricate the rest. It's for 2 1/2" into 3". I am ordering one on Ebay for under $35.00
The part that connects the Y pipe to the exhaust pipe is Magnaflow #10778. My exhaust guy will fabricate the rest. It's for 2 1/2" into 3". I am ordering one on Ebay for under $35.00
Dual 2.5 or dual 2.25 to single 3" both work exceptionally well on a 305 or a 350 under 400 hp. I would avoid dual 2.5 to single 3" as the 3" pipe has a substantially smaller area than the dual 2.5". If you go with a Y-pipe fed with 2.5" pipes it needs a 3.5" pipe after the Y. I had that on my Titan. 340 cid but overhead valves. I had that stock engine making about 420 hp and over 500 tq with intake/exhaust and tuning. Stock exhaust was dual 2 1/8 to the muffler with a 2.75" tail pipe. I opened it up to 2.5" to match the manifolds and ran it into a Vibrant 2.5 to 3.5" merge Y and then out through a single 3.5" magnaflow and tail pipe. Picked up nearly 30 hp at the 6,200 rpm rev limit with almost no torque lost down low. Even at that power level the stock 2 1/8 piping exhaust held its own under 4,500 rpm.
The 305 Vortec in my 99 Tahoe had 1 5/8" headers with 2.5" collectors, 2.25 reducers to 2.25" pipe, dual thunderbolt 2.25" cats and a dual in/single out muffler into a 3" tail pipe with a 4" tip. Sounded great and had great power throughout the whole RPM range. I had a Lunati High Efficiency 268 flat tappet cam in it with Rhoads original lifters. Even before I put the S10 converter in it the truck drove great around town and on the highway. After the converter it would usually outrun 5.3 trucks and Tahoes. The cammed 305 had alot more top-end pull than the stock cam 350 vortecs with choked exhaust and similar midrange grunt.
Dual 2.5 or dual 2.25 to single 3" both work exceptionally well on a 305 or a 350 under 400 hp. I would avoid dual 2.5 to single 3" as the 3" pipe has a substantially smaller area than the dual 2.5". If you go with a Y-pipe fed with 2.5" pipes it needs a 3.5" pipe after the Y. I had that on my Titan. 340 cid but overhead valves. I had that stock engine making about 420 hp and over 500 tq with intake/exhaust and tuning. Stock exhaust was dual 2 1/8 to the muffler with a 2.75" tail pipe. I opened it up to 2.5" to match the manifolds and ran it into a Vibrant 2.5 to 3.5" merge Y and then out through a single 3.5" magnaflow and tail pipe. Picked up nearly 30 hp at the 6,200 rpm rev limit with almost no torque lost down low. Even at that power level the stock 2 1/8 piping exhaust held its own under 4,500 rpm.
The 305 Vortec in my 99 Tahoe had 1 5/8" headers with 2.5" collectors, 2.25 reducers to 2.25" pipe, dual thunderbolt 2.25" cats and a dual in/single out muffler into a 3" tail pipe with a 4" tip. Sounded great and had great power throughout the whole RPM range. I had a Lunati High Efficiency 268 flat tappet cam in it with Rhoads original lifters. Even before I put the S10 converter in it the truck drove great around town and on the highway. After the converter it would usually outrun 5.3 trucks and Tahoes. The cammed 305 had alot more top-end pull than the stock cam 350 vortecs with choked exhaust and similar midrange grunt.
So you believe the chart Noemissions posted was too restrictive for performance exhaust? M concern is; will it fit on a third gen?
Dual 2.5 or dual 2.25 to single 3" both work exceptionally well on a 305 or a 350 under 400 hp. I would avoid dual 2.5 to single 3" as the 3" pipe has a substantially smaller area than the dual 2.5". If you go with a Y-pipe fed with 2.5" pipes it needs a 3.5" pipe after the Y. I had that on my Titan. 340 cid but overhead valves. I had that stock engine making about 420 hp and over 500 tq with intake/exhaust and tuning. Stock exhaust was dual 2 1/8 to the muffler with a 2.75" tail pipe. I opened it up to 2.5" to match the manifolds and ran it into a Vibrant 2.5 to 3.5" merge Y and then out through a single 3.5" magnaflow and tail pipe. Picked up nearly 30 hp at the 6,200 rpm rev limit with almost no torque lost down low. Even at that power level the stock 2 1/8 piping exhaust held its own under 4,500 rpm.
The 305 Vortec in my 99 Tahoe had 1 5/8" headers with 2.5" collectors, 2.25 reducers to 2.25" pipe, dual thunderbolt 2.25" cats and a dual in/single out muffler into a 3" tail pipe with a 4" tip. Sounded great and had great power throughout the whole RPM range. I had a Lunati High Efficiency 268 flat tappet cam in it with Rhoads original lifters. Even before I put the S10 converter in it the truck drove great around town and on the highway. After the converter it would usually outrun 5.3 trucks and Tahoes. The cammed 305 had alot more top-end pull than the stock cam 350 vortecs with choked exhaust and similar midrange grunt.
I did the math on the square inch of the exhaust system. If you have 2 1/2" duels all the way back, that would be 39.27 square inches of pipe. With a 3" exhaust pipe it would give you 28.274 square inches, with a single 3 1/2" exhaust pipe you would get 38.485 square inches. So even with 3 1/2" single exhaust you would have less than duel 2 1/2" pipes. so yes it stands to reason a 3 1/2 inch single exhaust would give almost the value of duel 2 1.2" pipes, so it would be a viable option. Still my concern is fitment. Around the tranny pan is tight as it is already.
True duels would be the best. It would cost me $450 for duels, and under $300 for performance single exhaust. The first thing that comes to mind is rattles from the pipes running so close together.
True duels would be the best. It would cost me $450 for duels, and under $300 for performance single exhaust. The first thing that comes to mind is rattles from the pipes running so close together.
Weld metal straps across them in a few places to tie them together.
Those sure do look like them, at least the passenger side. The drivers side will look the same in a picture.
Yes you will for sure need the spacer to make the y-pipe fit. The spacer you will have to find through this site from one of the third gen scrapers. BethsCamaro is one of them. I list a couple others in the post above.That Magnaflow pipe is the right one as long as you have the HO manifolds and the proper spacer, Which is pictured in a above post also.
Magnaflow should probably thank this thread as it seams they have sold a few pipes from here, me being one!
07-25-2019, 09:29 PM
