I'm putting a whole new exhaust on my 70 gs 455. Is a 3 inch exhaust alright to use with a basically stock engine? I'm planning on building a higher horsepower engine in the next year or so. So my question is if the 3 inch will help or hurt the performance of the stock engine?
3 inch exhaust would be overkill on a stock engine..2 1/2 inch mandrel bent exhaust is good for around 500 hp..TA sells a great 2 1/2 inch Mandrel bent exhaust system and the long case Hemi mufflers..sounds great and very free flowing..i have had both the 2 1/2 and 3 inch systems and i preffer the 2 1/2..it sits up under the car better. .Bob
It'll hurt torque alot, BUT if you think that the new engine (as in a HOT STREET/STRIP, or strictly STRIP) will require or like the 3"... maybe buy it and not put it on until the new engine is ready. If you think that you are going to build an "average" 455, you might consider going with a 2 1/2" system. You can go as fast as low 11's with this size later. This way you can immediately enjoy an increase in power right now.:3gears:
Johnno, I'm assuming you have headers. What I did was put on a 2 1/2" system with the long case Walkers. Later I added a Dr. Gas hybrid X pipe. The headers are 3 1/2". The front half of the X is 3", and the rear is 2 1/2" which connected to the rest of my new exhaust. It is nice and quiet until you lean on it. Just suggesting this as a compromise.
Bob... I just gotta ask about your avatar. Is that a nailhead with a cross ram intake ?? :eek2: Tell us more! :Brow:
So how would 3" exhaust reduce torque? It just seems odd to me that you would get better performance from 2.5" than 3"(with a stock 455). I would expect no noticeable difference, but to reduce torque, sounds strange, sorta like my car runs better with manifolds than headers.o No: uzzled:
If you run to large of pipe you loose the scavaging effect, which is what gets the exhaust out of the pipe. Basically causing the engine to push the exhaust out of the pipe thus reducing power. At least this is my interpritation of the info I have read.
Scavaging, with a stock 455 (I assume manifolds)! How much "scavaging" can you get with the iron manifolds?
Dan, I think, with exhaust manifolds dumping into a 3" pipe, you would loose some velocity of the exhaust gases. With manifolds, the 2 1/2" is gonna work better, hands down. Now with headers, it's another story entirely.
How about headers WITH a 2.5 inch exhaust and a mildly built 455 (i.e. to stage one specs)? That will be my scenario.
I agree Larry I just think if he is going to rebuild the 455 next yr, (where 3" would be an edge), why not buy it now and have it ready? I don't think it will hurt the performance that much. In fact, use an X pipe too.:TU:
Hello. I put on the Summit Racing 3" X-pipe kit ($99.00). I had a set of Flowmaster 3"-2.5" cone reducers hanging around. So I have all 3", cone reducers right before the 2.5 Flowmasters. After the mufflers, I got 2.5 tailpipes (Summit). This set up is much quieter than the 2.25/h-pipe set up i had taken out. I copied this exhaust system from that 11 second maroon 71(?) Pontiac wagon that was in a car craft recently. The guy said he tried every possible exhaust system. He finally go best results with 3"-X-Pipe-cone reducers-(3 or 2.5 mufflers, I forgot)-3"tailpipes. I did not spring for the 3"tailpipes, and since I all ready had 2.5 mufflers on the 2.25 system, I kept them ($$saver). FYI.
Ok I have a question for you Exhaust experts... I recently bought a '67 GS400 and I'll tell you what it has and then tell you want I want from it. It currently has TAPerformace headers - 1 7/8 primaries, 3 1/2 collectors. TAPerformance FULL 3" aluminized dual exhaust with a 3" (H) cross-over pipe, 3" in and out-flowmaster mufflers with 3" tail pipes dumping behind the rear bumper. I am going to build the engine to be a Daily driver, so I'm concentrating on building it for low-mid range torque, (maybe a TA113 or TA118 cam). I drive the highway everyday to an from work so I currently have 3.08 rear in it. So I gather from what I've read here and elsewhere that the 3" is going to cause my low-mid range torque to suffer. So I'm open to suggestions.... I was wondering if replacing the tail pipes with 2 1/2" pipe would help? I don't know so please, any help is appreciated. Also I'm on a tight budget so I am limited for now... Thank you, Todd
Hi Todd, Yes it will suffer somewhat on LOW range torque. I don't know if just the 2 1/2" tailpipes would make a enough of a noticable difference. I say leave it alone... and get the gears you want!!! Sending you a PM, BTW!:grin:
I'm definetly putting new headers on the car. Either TA's or mickey thompsons (any insight guy's???). I'm also putting in a new X-pipe. So is it going to be 3 inch all the way, 2 and a half all the way, or 3 inch up front and 2 and a half tail pipes??? Thanks for all the info Jeff, Eric, Larry, Ken, Dan, John, and Todd...keep it coming!
Hi all, I'm also thinking of running a 3" exhaust as well. I was wondering if its a good I dea for the engine I'll be running?? I've got a 455 stage 1 engine I'm planning on getting the heads ported, the combustion chamber deburred, and the bowls polished, I'm planning on using the SP 1 intake, I'm getting a 3 angle valve job done, I'm using a TA 413 cam and lifters, I'm using Hooker super comp headers with 2" individual pipes and a 3.5" collector, I was planning on using a H-pipe with one chamber flowmasters and turndowns after the mufflers. Will I benefit from the 3" exhaust or will this hurt my torque as well?? Gerald
edit: Haha, I found it! April-June '1994 The Torque Sheet Tom Haeffner, 11.38 @ 116 mph - still using 2 1/2" exhaust! 3" sounds VERY COOL, and its hard to get a good fit, and most times it hurts low-end torque.o No: So its been said anyways... Lot of times it's made up in the mid-range. It REALLY depends on the combo, so dang many variables!ou: Unless you're racing, and want it ALL, don't worry about the 1/2" difference! The minimumal amount of torque loss will only help the poor tires hook!!!:Brow: :TU:
Read above post. H-pipes are great, X is better!:TU: 2" pri tubes, you're getting close to Stage 2 requirements with those... Have you already bought them?
Dan, I've never had either one. 3" exhaust, and I'm convinced that either one would be better than nothing! But I agree, if you're going to spend the effort and expense, go for the best!:Brow:
