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I'm planning on putting on full exhaust from the headers to the tailpipes this spring. I'm on a limited budget and want to get the most bang for each buck. Would the extra money spent on 3" pipes instead of 2.5" pipes be worth it?
Also, I haven't been able to find anyone who sells a 3" mandrel bent intermediate pipe (the one from the cat to the muffler). I could have sworn Dynomax made one but I can't find it. Does anyone know?
Dyno Don headers, DD's dual (2 1/2") cat "Y" merged into a 3" cat back. Dynomax 3" in/dual 2 1/2" out, with Walker aluminized tail pipes. IMHO, the stock style tailpipes (30*-ish bend, angle cut, slash tip), like these Walker ones, are the best looking option for third gens.
On even a 305, you want a 3" exhaust - headers to 3" cat, to 3" cat-back. 2.5" single pipe restricts the power so much, it is not even worth it - unless it is a six cylinder.
Thanks for the comments! I was hoping to go with theHedman 68470 headers but the y-pipe is only a 2.5". I would either have to get a more expensive header that makes a 3" y-pipe or pay to have the hedman y-pipe changed.
So those walker intermediate pipes go straight from the cat to the muffler? That sounds like exactaly what I need.
On even a 305, you want a 3" exhaust - headers to 3" cat, to 3" cat-back. 2.5" single pipe restricts the power so much, it is not even worth it - unless it is a six cylinder.
On a 305 that won't even get to 5000RPM you need a 3" exhaust?? Totally ridiculous statement. I'm betting a 2.5 pipe will make more power and torque at all rpms.
On a 305 that won't even get to 5000RPM you need a 3" exhaust?? Totally ridiculous statement. I'm betting a 2.5 pipe will make more power and torque at all rpms.
So your saying that a 305 that's going to run a set of "lets say" Dyno Dons Headers and "Y" Pipe, should keep the 2.5in piping the rest of the way back including the muffler ?
Most guys that use parts like "Dyno Dons" are prepping the car "hopefully" for bigger and better things
This is Dyno Dons and IMHO the best there is . No way I would put 2.5in pipe on it =
Last edited by Ron U.S.M.C.; 02-15-2016 at 02:36 AM.
When you can only run a single exhaust on these cars it only makes sense to go 3in. From the factory a lot of things on these cars didn't make sense. Personally I think they all should have had 350s and a true dual exhaust setup.
On a 305 that won't even get to 5000RPM you need a 3" exhaust?? Totally ridiculous statement. I'm betting a 2.5 pipe will make more power and torque at all rpms.
Fail, BTDT. DynoMax cat-back with L69, Performer EGR intake, ported big-valve heads, with Comp 12-388-4 cam, Hedman shorties. Should have easily pulled strongly well past 5000 RPM, was essentially dead by 4500. Just one test-run with open headers proved the small piping was the choke.
When you can only run a single exhaust on these cars it only makes sense to go 3in. From the factory a lot of things on these cars didn't make sense. Personally I think they all should have had 350s and a true dual exhaust setup.
True dual 2.5s weigh more than a single 3.5" without flowing more. Thus single is better.
If you only want a WOW!! factor go with the 3 inch stuff. Oh yeah and be sure to get the 1.75 header pipes. Put up with all the hassle of installing it too. It won't do anything to improve performance but the Wow will be there. But then your limited budget will be gone.
If you want to see some performance improvement , buy a set of 350 camaro manifolds, that will increase the flow out the manifold from 1.75" to 2.5" ($50), then get the magnaflow Y pipe 2.5-3" off Ebay ($205, free shipping) 3" cat, in and out, then a 3"-2.5" reducer, then the 2.5 pipe kit. This is what I put on my 305 5speed car, I took the 3" pipes off and am going with 2.5. My 350 car will get the 3" pipe.
My 406 sb runs 1.75 headers into 3" pipe and operates between 5K- 7K rpms. The heads have 230 runners, it runs 9.40 in the 1/4 mile. Do you think your stock 305 1K - 4.5K rpm comes anywhere close to this? According to post here, I guess I should be running 3" headers and 5" stovepipe for pipes.
Enjoy your car, just providing some info to think about.
Everyone appreciates decent advice here but there is "Nothing wrong" with the "WOW" factor.
and crying about the "hassle" of installing parts is something that I never do.
I have been on this site for 10 years now and the two thing that come up over and over again is replacing the "air in" and "exhaust out" components with those that flow better than stock.
No one is saying run 5in stove pipe.
Last edited by Ron U.S.M.C.; 02-16-2016 at 12:36 AM.
I had a 1990 Formula LB9/700r4/2.73 gear, originally had a 2 1/4" exhaust. I added Edelbrock headers/Y-pipe, 3" Magnaflow cat, and 3" exhaust. It made a huge difference in performance. Think my best time was 15.2(stock) after exhaust best was 14.7(once) but would run 14.8 all night
First of all, the reason the 305 had problems above 4000rpm was the exhaust - just changing it to a TPI 3" from the manifolds back is going to be worth 25 to 35hp with stock OEM junk.
For those (like myself) that have done the stock 2.25 LG4/TBI system to a free flowing 3" system have all dropped off more than a second vs. the stock one.
A few idiots I know thought the same way as you - 305 only needs a 2.5" pipe, so go for that. Instead of running in the low 15's, those cars were stuck haplessly in the 16's.
Originally Posted by Blizzard Bill
On a 305 that won't even get to 5000RPM you need a 3" exhaust?? Totally ridiculous statement. I'm betting a 2.5 pipe will make more power and torque at all rpms.
First of all, the reason the 305 had problems above 4000rpm was the exhaust - just changing it to a TPI 3" from the manifolds back is going to be worth 25 to 35hp with stock OEM junk.
For those (like myself) that have done the stock 2.25 LG4/TBI system to a free flowing 3" system have all dropped off more than a second vs. the stock one.
A few idiots I know thought the same way as you - 305 only needs a 2.5" pipe, so go for that. Instead of running in the low 15's, those cars were stuck haplessly in the 16's.
It's very difficult to understand what you've posted. I can't make any sense of it. A 3" pipe from the manifolds back gives you 25-35 HP???( I don't see how you put a 3" pipe on a manifold with a 1.75 opening) At what RPM?? What exactly is a 3" system??? Why are they idiots, cuz they don't agree with you??? I don't buy this BS about 1.75 headers and a 3" pipes for a stock 305 and your post does nothing to prove me wrong.
You went from a 25 year old exhaust system to a new system and you pick up a second??? What exactly does that prove?? Was your old exhaust restricted internally? Then you went to 350 manifolds and a after market Y pipe and 3" cat (like I suggested)and 2.5 pipes, still no improvement, then you got the 3" pipe and then the second improvement, is that how it went in testing??? You still haven't offered any proof that a 305 needs a "3" system". Enjoy your 15 second car!
This is exactly what I did in 1990 to my 1984 LG4 Camaro - the car was barely 6 years old:
Banks 3" cat-back
TPI 3" cat (hollowed out)
Banks y-pipe to mate Lg4 manifolds to the 3" cat in the stock location.
There was no 2.25" intermediate pipe left - all replaced by the banks 3", y-pipe was 2.5" per pipe into the merge at the cat. Car went from 16.5 to 15.3 with just that change and added 9 mph (82 to 91mph). Headers may have given it another 5 or 10hp vs. the manifolds and if I knew how to tune the carb to compensate back then - maybe another 5 to 10 hp.
Keep in mind that a single 2.25" pipe with no bends is only going to support 150hp free flowing at most - put some bends and OEM kinks and its not going to get that high. GM purposely strangled the LG4 down to 140 to 160hp by using a super restrictive exhaust, retarded spark curve, clutch fan, and single snorkel air cleaner. GM took out about 50hp by these restrictions alone.
The car ran 15.0/15.1 all day back in 1991 and was in the mid 13's by swapping out the 305 with a 1990 L98 with headers and ended up in the mid 12's with ported heads and a larger roller cam.
Originally Posted by Blizzard Bill
It's very difficult to understand what you've posted. I can't make any sense of it. A 3" pipe from the manifolds back gives you 25-35 HP???( I don't see how you put a 3" pipe on a manifold with a 1.75 opening) At what RPM?? What exactly is a 3" system??? Why are they idiots, cuz they don't agree with you??? I don't buy this BS about 1.75 headers and a 3" pipes for a stock 305 and your post does nothing to prove me wrong.
You went from a 25 year old exhaust system to a new system and you pick up a second??? What exactly does that prove?? Was your old exhaust restricted internally? Then you went to 350 manifolds and a after market Y pipe and 3" cat (like I suggested)and 2.5 pipes, still no improvement, then you got the 3" pipe and then the second improvement, is that how it went in testing??? You still haven't offered any proof that a 305 needs a "3" system". Enjoy your 15 second car!
Open up the sinuses, and give it an enema! But a man convinced against his will, is of the same opinion, still.
The WOW factor ain't all looks, either.
What's 1.75 + 1.75 again? Just wondering. I know that formula isn't an exact science and there is far far more to consider in exhaust size; (ei, flow, backpressure, scavenging etc.) Single 2.5" may be fine for the 305, but to say there is no gain from running up to 3" is hard to swallow. 2.5 is great for my V6 pick-up though.
(Of all the things I could of made my first actual post here about lmao)
I replaced a stock exhaust once on a 350 vortec I had in a 3rd gen. Went from 14.2s- 13.7s immediately after new headers, y-pipe , and 3in exhaust. I hope this year to replace my bottleneck exhaust manifolds and tiny y-pipe on my car this year. From the y-pipe back I have 3in Flowmaster system.
Magnaflow 12267 shipped from Advance Auto for $123.99
Walker 43243, 43244, 53061, 54064 and clamps shipped from RA for $183.63
I've gotten the Dynomax system for under $200 in the past (after $50 rebate which is usually offered in the Spring) and put it on an LG4 but it necks down to 2.5" at the muffler. For a hair over $300 there's no reason not to go with 3" on the cat-back.
I replaced a stock exhaust once on a 350 vortec I had in a 3rd gen. Went from 14.2s- 13.7s immediately after new headers, y-pipe , and 3in exhaust. I hope this year to replace my bottleneck exhaust manifolds and tiny y-pipe on my car this year. From the y-pipe back I have 3in Flowmaster system.
Well there your problem right there.....Every body knows Headers and 3"pipe is for 305 engines, not 350 engines you need a larger exhaust pipe and headers........ according to the info I've gained from this thread.
What's 1.75 + 1.75 again? Just wondering. I know that formula isn't an exact science and there is far far more to consider in exhaust size; (ei, flow, backpressure, scavenging etc.) Single 2.5" may be fine for the 305, but to say there is no gain from running up to 3" is hard to swallow. 2.5 is great for my V6 pick-up though.
(Of all the things I could of made my first actual post here about lmao)
Interesting first post for sure, You know the terms, backpressure, scavenging, flow, now do some research on atmospheric pressure, why engines need backpressure to run, also a little on exhaust flow stall when the piping is too large.. Bigger is not always better. Oh yeah and I am saying there is no gain going to 3" over 2.5" If I used your theory of 1.75 + 1.75 the 305 would need 5" pipe 2.5+2.5.. or 3"+3" 6"???
Kind of odd,on an exhaust thread, the exhaust is holding the 305 back. On a cam thread, the cam is the problem. On a head thread, it's the crappy ports. 305s I love 'em !!!
Well there your problem right there.....Every body knows Headers and 3"pipe is for 305 engines, not 350 engines you need a larger exhaust pipe and headers........ according to the info I've gained from this thread.
I can guarantee you it does not hurt a 305 either. They are both air pumps and you are taking away air restriction going 3in.The one intermediate pipe is a lmitation at 2.225 or 2.5 Sure a 350 will gain more but a 305 will definitely have some to gain by going 3in. It has been proven time and time again. One reason those 80s Mustangs give a lot of 3rd gens fits was simply because they had true dual exhausts.
Magnaflow 12267 shipped from Advance Auto for $123.99
Walker 43243, 43244, 53061, 54064 and clamps shipped from RA for $183.63
I've read that the walker intermediate pipes might neck down to 2.75 or 2.5 where it connects to the muffler. Do you know if thats true?
I ended up purchasing the 3" hooker 2055 headers. They were almost double the price of the hedmans that I was originally looking at, but based on what most of you said I think it will be money well spent. Thanks for everyone's input!
So a question for exhaust gurus, is there much of a gain with 3" collectors on the headers, or should it be fine having smaller than 3" for each bank merging into 3" on the Y-pipe? At what HP would it start to be a problem?
Exhaust pipe diameter is about airflow requirement. And that is less about engine size, and more about horsepower/potential.
A 100hp engine whether 50ci or 400ci can use the same exhaust because they will flow the same amount of air.
I found this chart to provide a guideline. A single 3" will support 250-300hp. 2.25" factory pipes will try to choke an engine down to 150hp. A stock 305TPI around 225hp doesn't NEED 3". Add some bolt-ons, such as a cam and StealthRam and you could easily be looking at 275hp, where anything less than 3" is limiting hp.
[QUOTE=ZsTransAm;6010037]I've read that the walker intermediate pipes might neck down to 2.75 or 2.5 where it connects to the muffler. Do you know if thats true?QUOTE]
The 17495 has a 2.75" intermediate pipe that necks down to 2.5" where it enters the muffler. This fits later TPI models with the two bolt flange connection to cat.
the 17494 has a 2.5" I pipe into the same 2.5" muffler inlet. This system fits the HO and early TPI that has the four bolt flange/gasket connection to cat.
From the Dynomax catalog, there are no 3" kits for third gens.
From the Dynomax catalog, there are no 3" kits for third gens.
Aren't Walker and Dynomax the same company now? Walker has a 3" intermediate pipe available (2 pieces).
WLK-53061 INTERMEDIATE PIPE $63.97
WLK-54064 INTERMEDIATE PIPE $46.97
So according to the chart, as long as the collector pipes match or exceed the diameter in the "dual" column corresponding to the "single" column's size that I'll be using after the y-pipe, it should work ok? So for a 3" catback I would probably want 2.5" collector pipes?
The two biggest bang for the buck things I installed on my car - when I had the 305 in it was a set of Edelbrock TES shorty headers and a Hooker 3" cat back exhaust. Seemed to make a huge difference from mid range up...and I lost no torque at all. But this is on a carbed engine. Granted, the Y pipe on the TES isn't the best, but still better than stock.
Factory exhaust systems on these cars are just plain restrictive. Hell, even my original "HO" exhaust was only 2-1/4" diameter....
Magnaflow 12267 shipped from Advance Auto for $123.99
Walker 43243, 43244, 53061, 54064 and clamps shipped from RA for $183.63
I've gotten the Dynomax system for under $200 in the past (after $50 rebate which is usually offered in the Spring) and put it on an LG4 but it necks down to 2.5" at the muffler. For a hair over $300 there's no reason not to go with 3" on the cat-back.
naf,
Any feedback on how this all fit up? im thinking i would need another 45 elbow and straight pipe to go from the I-pipe to the cat on our cars.
Any pictures you have would be great, or any other feedback.
Thanks!
Fitment was perfect. The only adjustment required was to locate the driver's side exhaust hanger rear-ward about 1 1/2 inches to square up the muffler. I used the rear bolt hole on the frame to install the forward bolt hole for the bracket, then drilled a second hole for the rear bolt hole on the bracket.
This located the muffler assembly slightly to the rear but still provided plenty of clearance between the heat shield and muffler. The Magnaflow muffler may be smaller in profile than other mufflers, so no guarantee it would work with every muff.
The I-pipe fit with plenty of clearance in the stock frame mount. Shifting it forward was not a good option as this affected clearance over the panhard rod assembly.
I connected the other end of the I-pipe to a straight pipe that was installed in place of my failed cat. There's plenty of play side-to-side to get it to line up.
I plan to re-install a cat in the future with a new y-pipe. I'll probably have to fab it up in order to get the correct length cat to fit everything without any more cutting and pasting.
Fitment was perfect. The only adjustment required was to locate the driver's side exhaust hanger rear-ward about 1 1/2 inches to square up the muffler. I used the rear bolt hole on the frame to install the forward bolt hole for the bracket, then drilled a second hole for the rear bolt hole on the bracket.
This located the muffler assembly slightly to the rear but still provided plenty of clearance between the heat shield and muffler. The Magnaflow muffler may be smaller in profile than other mufflers, so no guarantee it would work with every muff.
The I-pipe fit with plenty of clearance in the stock frame mount. Shifting it forward was not a good option as this affected clearance over the panhard rod assembly.
I connected the other end of the I-pipe to a straight pipe that was installed in place of my failed cat. There's plenty of play side-to-side to get it to line up.
I plan to re-install a cat in the future with a new y-pipe. I'll probably have to fab it up in order to get the correct length cat to fit everything without any more cutting and pasting.
I'm planning on putting on full exhaust from the headers to the tailpipes this spring. I'm on a limited budget and want to get the most bang for each buck. Would the extra money spent on 3" pipes instead of 2.5" pipes be worth it?
Also, I haven't been able to find anyone who sells a 3" mandrel bent intermediate pipe (the one from the cat to the muffler). I could have sworn Dynomax made one but I can't find it. Does anyone know?
I hate to piggy back onto your post but I asked this on a new thread and didn't get a response. I bought my son (first car) an 86' sport with the 2.8. The car came with a cat back OBX Maximizer 3" new in box for a third gen 5.0/5.7. My question is can I put this on his car? I know the factory pipes are smaller and the flange at the cat wont line up so it will need cut, reducer and weld. It shouldn't change back pressure or trip a code since it will be after the o2 sensor and cat. Long term i plan to "tune" it to try to squeak a little more hp for him but i dont want to give a 16 year old 300 or 400 hp with a v8 swap just yet. The car is solid... Barn stored 35k original. Let me know your thoughts and thank you!
Exhaust size is my opinion, the 5th cycle of an internal combustion gasoline engine.
If you plan your exhaust correctly, you can pock up lots of power with a properly sized and routed exhaust.
However of you just think that you need a certain size exhaust without knowng things like bore, stroke, piston speed, etc. It is just a shot in the dark.
An example is:
Would you say a192ci, 4 cylinder engine that makes 400 Natural aspirated hp, at 8000 rpms., would need the same size exhaust as a305ci, V8 that makes the same 400hp. at 6000?
If you say,"Yes", youd be wrong.
Why? because the 4 cylinder engine is moving more air to do the same work as the V8.
The piston speed is higher, the valve action is faster, etc.
Why do you think a 500ci.Pro Stock engine runs 2 1/4"-2 1/2" stepped headers with a 5 or 6" collector to make 1400 hp. NA, at 9200 rpm.
And a 632 will make the same power at just 8000, with a 2 1/4" non stepped header with a 5" collector.
The 632 is 132ci. larger, but doesn't require as many rpm. or as much piston speed as the 500.
A 305, 327, 350 all share a 3.48 stroke.
They l share the same piston speed to move "X" amount of air per revolution.
The bore diameter is different between a 305 and a 327 or 350.
But does it make enough difference to matter.
Usually not.
How do I now that?
Here's how.
I have at this moment a 358ci. engine which made 497hp. at 6400rpm. It made 458lb. of torque. Ported Alum heads, roller cam, the works.
It made more overall "torque" through the mdrange for a wider rpm.,with 2 1/2" exhaust than it did with 3". Up to 26lb.ft. more at 4800rpms.
The exhaust is and was built for one purpose and that was to improve power.
The headers alone were almost a thousand dollars. The exhaust pipe was specifically built with butt connectors to match the headers merge flange. Walker Dynomax mfflers round it out only because and this is a big one.THEY FLOW THEIR ****.
Flowmaster doesn't list a flow rating. Neither does Thrust,Summit,Jeggs, Borla,etc.
Also note :All pipe," is not the same". Wall thickness, type and shape all contribute to flow.
Both in and out. Bet you didn't know low pressure gasses will follow the wall of the exhaust and try to move back to the exhaust valve.Now did you?
They will.
Just like,"Swirl" happens in the combustion chamber, it happens in the exhaust.
One of the things I've seen on this site is advice stating, when adding external parts to a 5.0 take into consideration the possible upgrade to the 5.7 in the future. Ether because you want to (increased performance) or because you need to (5.0 gives out on you). The 5.7 being the replacement.
Putting on parts that will help the 5.0 even if it’s only a small benefit, but will help the 5.7. a lot when the time comes IMO is the smarter move. Why invest money into parts that are not going to benefit a 5.7.
Last edited by Ron U.S.M.C.; 03-30-2016 at 10:28 PM.
One of the things I've seen on this site is advice stating, when adding external parts to a 5.0 take into consideration the possible upgrade to the 5.7 in the future. Ether because you want to (increased performance) or because you need to (5.0 gives out on you). The 5.7 being the replacement.
Putting on parts that will help the 5.0 even if it’s only a small benefit, but will help the 5.7. a lot when the time comes IMO is the smarter move. Why invest money into parts that are not going to benefit a 5.7.
It's odd to me why it is always assumed if someone wants to enhance 5.0 performance one needs to keep in mind that he needs to only buy parts for a possible 5.7 swap... later. If a 5.7 swap is the next step why do anything to a 5.0.
If you are buying parts to improve a 5.0, I would suggest buying parts for a 5.0. Why put something on this engine when it's not the most results driven part for the engine your working with. Especially when the OP is often wanting the most bang for the least dollar.
Why don't you fill in your profile under your user name.
Hell, why do any thing nice to a 5.0. Why even put headers on it.
According to you he might as well keep it stock.
When it comes to offering suggestions I like to point out items that are a "step up" from stock.
I guess this is directed at me.
Why fill that out?
If you're short on cash, why do stuff geared towards an event that may never come, 5.7 swap.
I don't know why headers on a stock 305. Short on cash... 350 manifolds, real 2.5-3" Y pipe, 3" cat, 2.5 exhaust. $550 and done, you can't get headers for that little bit of chump change and you still need another $600 + to finish the exhaust, plus fabrication. I see pictures of exhaust on this site with two or three 90* bends in one pipe and that is supposed to be exhaust improvements because the pipe is three inch. When someone post: Yeah I put a bigger cam in it, ported the heads and larger valves and the 2.5 " exhaust was holding it back, it really woke it up when I went 3" exhaust so everybody needs 3" pipes. If you want that large and expensive exhaust, go for it.
Don't see any post I made that says leave it stock.
My post are an alternative that is easier, less expensive and are remove and replace, with a performance gain. When a post starts out, "short on cash", I give an economic response, If it starts out "I want to improve my F body performance and I got a ton of cash to spend on it", I think that warrants a different type of answer.
If you would like, PM for this type of dialogue, but I think I covered it.
01-08-2016, 11:30 PM
