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Old 10-23-2011, 06:23 PM   #1
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Default Lg3 exhaust manifold questions

I'm going back out to the u-pull where i saw a set of LG3 exhaust manifolds and pulling them on monday. The plan was to run them into SSEI 2.5 full exhaust and hi-flow cat.
After reading on here some say 2.5 exh may hurt low end.
Even the 2.25 n/a Bonneville exhaust looked bigger than mine. There was a full exh on a n/a Bonne from resonator to tail pipe.

Whell i need to find someone to port my L27 heads and LIM that i plan on running on this LN3 . Any thoughts or advise ? Should have asked sooner but what the heck. Pulling the LG3 mani'* anyway if still there.
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Old 10-24-2011, 06:11 PM   #2
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[IMG][/IMG] Well i did pick up the LG3 exhaust today. Also got a downpipe from a Lesabre L27 motor. It is larger than the older models. Obviously not an SC motor. There was another LG3 car (Lesabre) but same exhaust as my LN3 .

[IMG][/IMG]

The downpipe on the bottom is the L27 Lsabre and it fits the LG3 exhaust. The bigger downpipe also has better bends in it.
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Old 10-25-2011, 12:10 AM   #3
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A straight pipe will flow 115CFM per square inch of area (using inside diameter of the pipe). You need 2.2cfm of flow capacity per horsepower. so basically anywhere between 2.25 and 2.5 you will be fine as far as low end torque yes you could lose some but also pick up a small bit of top end hp this is a trade off you make when going to a bigger exhaust.also if you were to upgrade your air intake system you could level it back out some and i like how your bigger downpipe is mandrel bent instead of standard crushed restricted bent lol
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Old 10-25-2011, 05:33 PM   #4
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I like the way they bent the exh on the newer cars. Read after 92 and up. . There was a Bonneville n/a car with 2.5 exh, mandrel bent and with a resonator. That might be the way to go for me. I still have one more trip out to the u-pull before it gets too cold.





These are the photo'* of the rear manifold exit. They look better than the LN3/L27 style exhausts.
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Old 10-25-2011, 09:51 PM   #5
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yes they do
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Old 10-28-2011, 05:24 PM   #6
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Update on the exhaust manifolds is that they do not fit. They will not bolt up. I am going to have the mounting flanges off and reweld the LN3 flanges on to them because the ports do match up but the bolt holes do not. If i can get another front manifold i will have that modded into a rear manifold. Then i can use the stock round port manifold gaskets.




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