There have been several topics recently that discussed the LT-1 exhaust system and I have personally received several inquiries on the LT-1 setup. I recently came into posession of an LT-1 system that was taken off of the car shortly after it was delivered and took a few detailed photographs. The original system differs significantly from both the service replacement system as well as the aftermarket systems that are available. Hopefully, those that were interested will enjoy the details of the original LT-1 exhaust system.



This is a photo of both forward pipes... The section of pipe close to the exhaust manifold has been swaged to reduce the pipe size from 2½" to 2" in diameter. You can also see that the pipes were mandrel bent as the diameter remains fairly consistent throughout and there are no compression "wrinkles" on the inside radii. There is some conjecture as to whether the front pipes were double or single wall tubing. These are single wall as are a set of service replacement pipes that are also in my posession.



This is a close up of the swaged section... While it doesn't look like much on the outside, the transition is relatively smooth and I'd be curious if there isn't a venturi effect provided by the shape of the swaging.



The front pipes had the part number stamped into the tubing near the rear of the pipe. This is the right side - FT 3877210; the left side was stamped FT 3913895.



This is a shot of both rear pipes... I am relatively certain that these were used under the same part number for all 1970-1972 LT-1s and big blocks. The pipe and muffler were welded together by Walker (the OEM supplier) and delivered to St. Louis as an assembly.



This is the standard method Walker used to bend most of the exhaust pipes it provided to GM. The compression "wrinkles" are quite evident. What isn't quite so apparent from the photo is that the rear pipe is actually flattened into an oval shape to provide ground clearance.



Photo of the exhaust tip... The chrome plating is terrible, but typical of what you received when you purchased a new Corvette. The pipe clamp points inward on both pipes since the line worker who tightened the clamps stood right in the middle. The centering tab for the exhaust tip can also be seen.



Part number tag for the rear exhaust pipe/muffler assembly. It's about 1" high by 2½" long with ¾" high black numbers. The entire muffler on this system was blacked out top and bottom; typically, only the bottom was painted.



Underside of exhaust tip... There is no seam on most 1970 (and some 1971) exhaust tips.



This is a photo of the locating tab for the exhaust tip... Simply a piece of metal tack spot welded to the muffler outlet.



Part number tag on exhaust tip... This is in the same format as the rear exhaust pipe/muffler assembly tag.



"W" embossed on muffler casing to identify it as manufactured by Walker. When installed on the car, the "W" on the left muffler faces up (and can't be seen) while the "W" on the right muffler faces down. No production LT-1 mufflers ever had a part number embossed on them; these are service replacements.



Single bracket for muffler hanger. Most service replacement mufflers have two brackets to allow for multiple applications.

Hopefully, those who posted on this topic found these photos interesting.

Regards,

 

But I thought the LT-1's used 2.5 inch ram horn manifolds? Or am I missing something here?

 

The last year of the 2 /12" manifolds was either 65 or 66. Every smallblock from then on used 2" manifolds.

 

Even my ZR-1 manifolds are 2" I believe, I guess I could always measure them as they are sitting on a shelf right now while I run with headers instead.

 

I asked this same question and found out that the 2 1/2 inch exhaust manifolds were only used for a couple of years in the mid 60`s. I have a set of these that are repros on my car made by the Allens Stainless Exhaust in Indiana that I am very happy with.


[Modified by Eddie 96, 5:51 PM 10/20/2002]

 

Great Post!! Good Info.
Thanks,
:cheers:

 

Thanks for the pictures, Stan and all the info on the '70 LT1 exhaust system.

 

Thanks Stan! That's a much better view than one would get crawling under the cars in the parking lot! :lol: There were many LT-1s at the Mawah show today, including a couple of blue convertibles that were fantastic (a 72 and a 70). So the tips were just clamped on? sheesh! :) MJ

 

Thanks for the feedback guys! Happy to post the photos and comments.

MJ,

That was my thinking as well. It is much easier to see the details with the system off of the car. Problem is, the few cars left with original exhaust systems are typically low mileage originals that the owner has no intention of ever disturbing anything on the car. This was an odd situation where the original owner of the car removed the exhaust shortly after he took delivery, which accounts for the part number labels remaining intact and overall condition of the exhaust system. The gentleman who purchased the system from its original owner was going to put it up for sale on ebay... Fortunately he asked me if I wanted it before doing so! :)

Sounds as though you NJ guys had a great show at Mawah... The photos in the other thread sure show some nice cars!

Regards,

 

Hey Stan, how ya doing? First, is this the system that someone wrote about in the restorer a year are so ago? Maybe Bob Cook? Second, how are you going to clean up the system to flight judge the car. Rust always gets a point or 2. I have the forward pipes and the middle pipes for the 70 LS-5 but the pipes were cut to install new GM over the counter mufflers. Maybe if I'm ready with the car before you I can use the system? HA HA Give me an update on the LT-1. Thad LeJeune

 

Stan-super info as always!!! Many people don't appreciate "originality" like that!!! You'll never see a "swage" like that on even Paragon or Corvette Central's BEST repro pipes!!! I saw an 1,800mi '74 exhaust system at Bloomington last year for $325!!!! Did'nt need it, did'nt buy it, but now wished I would have just to have had it!!!

Also, are'nt those "flattened rear pipes" what you would have got on a '68 with the "OFF ROAD" exhaust OR were those different yet????? :confused:

 

Paul,
Great history lesson.
Ed

 

Thad,

Great to hear from you! Hopefully we'll get a chance to catch up at the NCRS Regional in Louisiana next year... You guys always put together one heck of an event!

This is not the system that Bob Cook wrote about in the Restorer... To the best of my knowledge, that exhaust system is still on Bob's car. As for my plans for the exhaust, I doubt that it will ever be installed on a car. I have talked to some people in the restoration exhaust business (who currently do some pretty fantastic work) about reproducing some of the Corvette systems since there is nothing available that is really close to what our cars used originally. These guys were willing to take a look at the project; the only hangup in the whole deal was that we didn't have an original system to use as a template... That problem is now solved so I'm hoping the project can move forward.

My understanding from talking with these guys is that the swaged front pipes might be a problem, but they were pretty confident about the remaining parts of the system... Still, not a bad deal if it works out and the big block guys like yourself make out as well since the rear portion of the exhaust is the same as the LT-1 system from what I'm told. I'll let you know how things go on this project.

The LT-1 is coming along quite well... I've run into a problem with fuel and brake lines (doesn't anyone make a set that actually fits?), but once I get that squared away, the rest of the chassis assembly should go together quickly. The body is painted and is currently sitting at the body shop (waiting for me to get my act together with the chassis). I'm hoping to have everything back together in a couple months barring any major problems.

How about that '70 LS-5... How's that project coming along?


Paul,

All of the original rear pipes that I have seen on 1968-1972 cars are flattened (even the 2" diameter pipes)... GM seems to have been quite concerned with ground clearance at that area of the chassis.

I had an email exchange with Joe Lucia about a year ago regarding part numbers for exhaust systems. He seemed to think that while the part numbers would be different, the 1968 big block rear pipes/mufflers and those for the 1970-1972 LT-1 and big blocks were the same with the exception of the locating tab found on the 1970-1972 systems that was used for centering the exhaust tip. I believe the only difference in the 1968 N-11 system was the use of low restriction mufflers. I seem to remember that physically they appeared the same as the standard mufflers... the changes were internal.

Regards,

 

Over 20 years later - but I really wish these images loaded lol! Hard to find pictures of an entire non-service replacement LT-1 exhaust these days, even the judging manual has only a few small pictures.