When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I am installing this N11 off road 2 ½ exhaust system. I am concerned because the front pipes come within less than 1” of the under body floor. My old pipes where much closer together with quite a different shape (see picture below) and maintained a much father clearance to the underside. Should I be concerned or is this proper? According to the exhaust distributor I received all the correct pipe parts so no mistake there. Also do my original pipes look like the Factory original pipes and/or correct shapes?
Hi Rick,
Here's all I have to offer.
These are GM 2" service replacement pipes from about late 72 or 73.
They are double wall and hard stamped with GM part #s.
Perhaps they'll give you some idea about the fit/clearances on your pipes.
Regards,
Alan
ed427vette: I believe your correct, maybe 68?? But I figure fitment clearance should still be the same.
Alan: My old pipes do look more like your GM replacement pipes.
On mine their are some numbers stamped on the inside area but are much closer to the exhaust manifolds so maybe they are original and the correct shape.
Also, your pipes seem to be approximately 2" away from the bell housing and father away from the under body. Where these N11 pipes are closer to 4" away from the bell housing and within 1" of the under body, again that concerns me regarding heat.
Maybe someone can post a picture of there N11 exhaust for comparison?
Hello Rick,
Clearance should be close. I don't know all the differences between a 68 and 69 frame but I think there were some minor differences by the kick ups. How that might affect the exhaust setup I'm not sure, if it does at all. But they do look a little closer to the frame then I might feel comfortable with.
Being Off Road exhaust it may very well be designed to stay close to the frame. Keep an eye on it to see if anything starts to melt!
Last edited by ed427vette; Dec 5, 2017 at 12:56 PM.
Hopefully someone can post a small block manual trans setup picture. Or can take a measurement of the above noted area. The clearance in that area with my setup is less than 1 inch.
Hi, Wondering how this worked out? I'm thinking about putting the N11 system on my car (69 350/300 auto hedman longs). I'm more after the sound than performance but still want it to look stock. Anyway, if you have an update, I'd like to hear. Thanks!
I do personally like the N11 exhaust system better than stock.
Regarding the exhaust sound volume at idle is different but not substantially louder, at cruise it is stock sounding, although when stepping into it it is significantly louder and free-flowing as a result of the size increase. I'll try posting a sound video in the future.
My particular concern after installing was that the driver side front pipe clearance distance to the underside fiberglass body was much less than the original exhaust system, this posed a serious heat issue.
I ordered my system from Corvette Central, exhaust system kit # 323106 (front set # 323539 & 323025 rear set) in the front set are part #’s 323607 driver side and 322532 for the passenger side. The folks at Corvette Central swapped out part # 323607 for 322533 which made a significant increase in clearance to the underbody.
I would recommend this substituted part number for a small block 4 speed set up.
So that part swap solved your concerns with being to close to the fiberglass? I was going to order the full system #323155. Mins an automatic and I'll be going to Hedman headers (longs). Front pipes will need to be cut and fitted for the headers. They have 3" collectors.
The body is of my car so I won't know there's a fitting issue for a month or so.
I did talk to the tech today and he assured me it will fit as factory, but clearly there was an issue for you. Assuming you have the aluminized vs carbon?
I do personally like the N11 exhaust system better than stock.
Regarding the exhaust sound volume at idle is different but not substantially louder, at cruise it is stock sounding, although when stepping into it it is significantly louder and free-flowing as a result of the size increase. I'll try posting a sound video in the future.
My particular concern after installing was that the driver side front pipe clearance distance to the underside fiberglass body was much less than the original exhaust system, this posed a serious heat issue.
I ordered my system from Corvette Central, exhaust system kit # 323106 (front set # 323539 & 323025 rear set) in the front set are part #’s 323607 driver side and 322532 for the passenger side. The folks at Corvette Central swapped out part # 323607 for 322533 which made a significant increase in clearance to the underbody.
I would recommend this substituted part number for a small block 4 speed set up.
We offer our Floor and Tunnel II material that will form to shape, cut easily, and has an aggressive adhesive for peel and stick installation. This material will help keep heat off of any area that you install it on. Check out P# 050501 at Designengineering.com. You could also wrap that section of the pipe with one our exhaust wraps to help keep the heat down in that area. Check out our Titanium Exhaust wrap and see what you think. Please let me know if you have any questions.
N11 Exhaust System
