swapping '69 2" to 2 1/2" exhaust system
I'm thinking about swapping out my 1969 2" exhaust system for a 68 design 2 1/2" system. I calculate that the cross sectional area would be 58% larger. Has anyone done this and what's the difference in performance? Thank you...Don
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Re: swapping '69 2" to 2 1/2" exhaust system
I'm sure there is a logical reason why the Division went to 2", but can't think of any. My 63 has the 2-1/2" for only 327 cu in, yet my son's L-89 427 69 has the 2". I thought it had to be a mistake as his has the side pipes, but later I learned that even the undercar system was 2".
Trust you are checking your manifold and hanger sizes. Be interesting to hear from others who may have done this too. Do you have BB or SB?
Stu Fox -
Re: swapping '69 2" to 2 1/2" exhaust system
Hi Stu...I have the base 427/390HP engine. I think they went down to 2" for smog control and noise reduction...DonComment
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Re: swapping '69 2" to 2 1/2" exhaust system
Get a chassis dyno test from 1500 to 6000. Install the 2.5" system and retest. There's your answer.
Pipe size has no significant effect on emissions, but smaller pipes can reduce noise, though not by a great amount. In 70 2.5" pipes were back. The reason for only 2" in '69 remains inexplicable.
DukeComment
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Re: swapping '69 2" to 2 1/2" exhaust system
If that's the case, Don, you should be able to find all parts needed from maybe a 68.
I know my son's 69 L-89 with the 2" side pipes is worst sounding SHP Corvette I've ever heard.
Stu FoxComment
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Re: swapping '69 2" to 2 1/2" exhaust system
There has to be some performance difference, but I have no information of how much it is. In the late 80's I removed the 1969 style side exhaust system from my 1970 that I installed in 1973 or early 1974. I installed the 2 1/2 inch 1968 style 2 1/2 inch system which my 1968 uses. On my 1970 I used two mufflers I got from ZIP Corvette parts and they are still in use today. I bought my 2 1/2 pipes from local Chevy dealer parts counter. Another part I bought from Chevy was the exhaust pipe support for 2 1/2 inch exhaust pipes that mounts under the end of the transmission at the cross member. Don't race my 70 and have never actually measured a performance increase.Comment
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Re: swapping '69 2" to 2 1/2" exhaust system
AS Jim Mentions you are going to need the 2.5" hanger bracket in place of the 2" unless you cut and modify it.
I went from 2"- 2.5" on my 69 and can't say much about the performance change. I have also run Chambered pipes-(waste of time and money), Headers and open sidepipes ( loud and hot but the eng did run better), so don't expect a huge difference unless you were going from a choked cat system back to real dual exhaust, then you would feel the difference.
There used to be a fellow named Jack Horner and he had a vette exhaust business. His pipes and muffler fit great but I don't know if he's still around doing it. Anyone know? His business was East Tenn Corvette if I recall.Comment
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Re: swapping '69 2" to 2 1/2" exhaust system
Don't have a spec book close at hand, but I heard from a reliable source that Chevy did offer a 2-1/2" off road system in 69 which included the 2-1/2" pipes (necked down to 2" at the manifolds) and mufflers that basically had fewer baffles inside.
Perhaps one of the numbers gurus can check into it - not that it is still available, but at least those worried about judging could justify it's use. I suppose it had an order code so that it would appear on one's tank sticker, etc.
Stu FoxComment
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Re: swapping '69 2" to 2 1/2" exhaust system
Don for mufflers on my 1968 with 2 1/2 exhaust pipes I bought two Walker guaranteed for life mufflers but only installed the right one in JAN 1990. It is still in use and great shape today. I installed the left side Walker in 1997. I delayed the installation because the original 1968 muffler sounded so good to me because most of the insides were gone but no problems with the rest of it. Finally fatigue attacked it where the inlet connected to the muffler body.Comment
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Re: swapping '69 2" to 2 1/2" exhaust system
Thanks all for your posts and responses. I have some older dyno runs with my 2" system and I'll have a 2 1/2" system installed probably in June and see what the difference is in torque and HP ratings, if any...DonComment
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Re: swapping '69 2" to 2 1/2" exhaust system
Stu-------
Your source was not too reliable. No such system ever existed for 1969. Such a system did exist for 1968, but NOT for 1969. However, all 1968's used 2-1/2" exhaust so the only real difference in the system was the lower restriction mufflers.In Appreciation of John HinckleyComment
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Re: swapping '69 2" to 2 1/2" exhaust system
Base 427, 390HP Auto THM 400 transmission. Mustang Dyno rear wheel 192.5 HP at 4250 rpm and 267.4 ft-lb torque at 3500 rpmComment
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