My '69 needs a new exhaust. It currently has either a 2 or 2.25 inch exhaust on there. Can I go to 2.5 inch with no problems? The motor is relatively stock..no headers, no radical cam, just basic 350.

Can I expect any problems like the carb needing to be readjusted, or anything???

Thanks,



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JR
TC #1098
My 69 Convertible (http://www.erols.com/ruther/69conv)
Body work and interior started June 02 - UPDATED 9/29/02 (http://www.erols.com/ruther/69conv/bodywork)

My 2001 Z28 - LS1 (http://www.erols.com/ruther/z28_5.jpg)

I was told by several knowlegdable people that with a stock or relatively stock SBC that anything larger than about 2 1/4" would be pulling the plug on your power. I went with 2 1/4" and was amazed at how much more power I got over the stock diameter which I think is 1 7/8". You should measure yours and see how big it actually is before to much farther. If you are planning on building your SB than that would be another story.

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Want to make your car really unique and stand out? .... Finish it!

Jeffry Bakken
ACES Memeber # 3994
TC Member # 1755
www.Jeffry72.50megs.com

67 Malibu in Wolf's
Clothing
70 Radical SS Clone
71 El Camino
72 4-door Sport Sedan

I can only offer a word of caution from my own experience but unfortunately it is with a stock big block 396/350HP motor. I put 2" primary headers into 3" pipes and 2.5" tails and lost my low end torque. The power range has shifted now that I put an RPM Manifold and Rhoads lifters on a year after the exhaust change (getting about 500 additional RPMs on the top end) but my low end torque is noticeably less by the seat of your pants feeling. I used to be able to break 'em loose at a low RPM roll and then jumping on it. Not any more.

I discussed this with other's more knowledgeable on this board and it appears that the 2" primaries on my headers are probably more the culprit than the 3" pipes. If I were to do it all over again I might have stayed with 1 5/8" primaries (maybe 1 7/8") but I doubt I would have gone with more than 2.5" pipes. Too much breathing is not always good if you don't have the motor to back it up.

Seeing as though you will be running stock exhaust manifolds I personally would not see the need to go larger than 2" or maybe the 2.25" as mentioned above.

Robert



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My 67 SS396 (http://chevelles.com/showroom/Mytmouse/Mytmouse67SS.jpg)
My 70 SS396 (http://chevelles.com/showroom/Mytmouse/Mytmouse70SSback3.jpg)
My 68 RSZ/28 (http://chevelles.com/showroom/Mytmouse/MytmouseRedZ28.jpg)
All 3 Together (http://chevelles.com/showroom/Mytmouse/MytmouseAll3.jpg)
Mytmouse A.K.A. Robert Stacho
ACES Member # 04359

Somewhere on this site, and somewhere in the past, there was a chart showing various horsepower levels, then various header sizes, then exhaust pipe sizes, muffler selections, then exit pipes. It may have shown "H" Pipe and "X" Pipe comparisons also.

It is here somewhere!

It may have been a chart from one of the car mags also. CHP? HOT ROD? CAR CRAFT? ?????


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Team Members Forever #341

Richard, Judy, MAXX2

'69 Elke (Frame Off); GM HO 350/330-Mildly Ported Vortec Heads-Manley Severe Duty SS 2.02/1.60 Valves, Comp Cams Full Roller Package (Magnum)-Custom Grind CS 3315/3316 HR112-.510/.520 Lift, Edelbrock Air-Gap W/750 Performer Manual Choke-Performer 100 HP NOS, March Pulleys, 4L60 (Non Computer) W/Lokar Shifter, 12 Bolt Posi., Full Aluminum Bed With Full Tubs, Aluminum Firewall, Custom Aluminum Dash/Gauge Bezel.

I am a bit old school,,,,running 1 5/8" headers on my mild 350ci to 2" pipe to Cherry Bomb glass packs,,,good combo.

I had a feeling the 2 inch would be better, which is why I asked the question. I certainly don't want to make it run worse, it runs really well now. I bought a pair of the "SS" chrome tips I would like to use, but the opening for the tips is 2.5 inches... How can I still use these if I go with the 2 inch exhaust???

Thanks,

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JR
TC #1098
My 69 Convertible (http://www.erols.com/ruther/69conv)
Body work and interior started June 02 - UPDATED 9/29/02 (http://www.erols.com/ruther/69conv/bodywork)

My 2001 Z28 - LS1 (http://www.erols.com/ruther/z28_5.jpg)

[This message has been edited by jerryr (edited 01-03-2003).]

Car Craft did an article on this issue. Basically it stated that 2.25 is good for mid cubic inch V8 engines in the 200-250 HP range, and 2.5 is for engines in the 250-300 HP range. I'd use a guesstimate of HP at the CRANK. Exhaust size has nothing to do with driveline loss of power. If your going to do any upgrades, I'd go with the 2.5.

Actually for a 350, I'd go with 2.5's BEFORE the muffler and then 2.25 after the muffler.

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BUZZBOMB (http://www.azlyrics.com/lyrics/deadkennedys/buzzbomb.html)

jerryr if you want to use them jsut get the 2 1/4 from the manifold to the muffler and then the 2.5 from the muffler to the bumper and then you can use them. on my set up wich is a stock 307 with manifolds im running 2in fromt eh manifolds to the muffler and 2 1/4 the rest of the way, ( the 2 1/4 rest of the way is mainly a look thing so the pipes dont look really tinny at the bumper..

Jerry,
Just out of curiosity, what kind of muffler's are you using?
My opinion go with the 2.5 w/flowmasters.

[This message has been edited by chevelledude71 (edited 01-03-2003).]

Let us know what you decide if you don't mind.

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Wallace L. Allen
SSgt USMC
Proud owner of a
1971 Chevelle
350/400 Turbo
Zinc Yellow w/Black Stripes (soon to be painted)
Weld Pro Stars
BF Goodrich T/A

My ORIGINAL plan was to go with 2.5 inch all the way with 2.5 inch Flowmasters (not sure which series yet) or the Dynomax mufflers. I guess my biggest concern was if I ended up going too "big" if that would hurt the car, or mess up the way it runs (i.e. too lean, or something) and end up having to tinker with it just to get it back to "normal".

The car doesn't see any strip duty, it's not really even a daily driver. It's a summer daily driver, when I don't have a project going on with it. This spring I plan on removing the exhaust manifolds, sandbasting them, coat them, and reinstalling, all while replacing belts, hoses, etc. I figured this would be the best time to replace the exhaust too.

So, can a 2.5 inch on a basically stock 350 hurt me in any way??

Also, is it possible to run 2 inch all the way and "flare" the end to 2.5 so I can use the tips?

Thanks,


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JR
TC #1098
My 69 Convertible (http://www.erols.com/ruther/69conv)
Body work and interior started June 02 - UPDATED 9/29/02 (http://www.erols.com/ruther/69conv/bodywork)

My 2001 Z28 - LS1 (http://www.erols.com/ruther/z28_5.jpg)

[This message has been edited by jerryr (edited 01-04-2003).]

Jerry, when I replaced the exhaust on my mostly stock 396 I did have to change the jets in the carb.

I had 2.5 head pipes out of stock manifolds into stock mufflers, then 2.0 out of the mufflers into resonators, and 2.0 out of those to the rear. This was the stock configuration.

I installed 2.5 head pipes off the stock manifolds into a 2.5 X pipe, 2.5 out of the X into DynoMax large body mufflers, and 2.25 out of the mufflers all the way to the rear. This set up is very quiet but the engine developed a lean miss. re-jetting solved the miss.

Jeffry72 mentioned 1 7/8 as the stock dia for the tail pipes and I beleive that is correct so a stock set up would be 2.0 out of the manifolds and 1 7/8 out of the mufflers. On a stock-ish 350 that isn't being spun high I'd think 2.0 or 2.25 out of the manifolds and 2.0 out of the mufflers will be absolutly fine without hurting performance, especially if you are running the stock single snorkle air cleaner.

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Awww, fer cyrin out loud, there's that IMPALA guy again.

http://photos.yahoo.com/bc/ss3964spd?d&.flabel=fld1&.src=ph

The old 300HP 327 used 21/2 in exhaust and it wasn't a radical motor by any means.

This may seem like a silly question, but do the mufflers come with different sizes on each end? I mean, some here say they are running one size BEFORE the muffler and another size AFTER the muffler. I always thought the inlet/outlet size was the same.

Sorry if this seems to be beating adead horse, but this is something I want to get right.


Thanks,

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JR
TC #1098
My 69 Convertible (http://www.erols.com/ruther/69conv)
Body work and interior started June 02 - UPDATED 9/29/02 (http://www.erols.com/ruther/69conv/bodywork)

My 2001 Z28 - LS1 (http://www.erols.com/ruther/z28_5.jpg)