70 Corvette 2 1/2" welded pipes

[Patrick H.]

Re: 70 Corvette 2 1/2" welded pipes

I have been debating what to do with my 71 LT1 for the exhaust...

I was wondering about buying the midyear 2-1/2 inch head pipes and having them swaged down to 2" like the originals, using original BB midpipes with the creases and running NOS mufflers, welding the mid pipes and mufflers.... but it is going to cost somewhere around $2,000 to do it like this... would I lose points with a system like this?

AM I better off buying the 2-1/2 CC welded system?
OR the Gardner system...
Last gardner I bought was for a 69 Z28 and it was $2,000 so if I could do an original vette system for the same I considered it a good deal.

FWIW I have ordered the judging guide and everything else NCRS has for the 1971 year model...

What is your goal with the car?

[Patrick B.]

Re: 70 Corvette 2 1/2" welded pipes

Tom, I would like to do exactly what you did on my 71 SB 4spd car. Were you told that the 65 4spd front pipes would work had your car been a 4spd car? I could not tell if the CC pipes were "flattened" where they pass under the rear differential from your picture. Do you feel you still have sufficient clearance with stock sized tires? Just FYI, 73 used a different muffler and extension than the 70-72. The off road muffler they offer is the 68 which I think works with the 70-72 extension. That is probably why they told you to order the 72 system.

[James G.]

Re: 70 Corvette 2 1/2" welded pipes

As correct as possible...
FWIW ZINC plated parts can be made to appear as bare steel... tumbled with steel shot rubs the ZINC to a nice bare steel sheen which doesn't rust.

[Joe L.]

Re: 70 Corvette 2 1/2" welded pipes

I have been debating what to do with my 71 LT1 for the exhaust...

I was wondering about buying the midyear 2-1/2 inch head pipes and having them swaged down to 2" like the originals, using original BB midpipes with the creases and running NOS mufflers, welding the mid pipes and mufflers.... but it is going to cost somewhere around $2,000 to do it like this... would I lose points with a system like this?

AM I better off buying the 2-1/2 CC welded system?
OR the Gardner system...
Last gardner I bought was for a 69 Z28 and it was $2,000 so if I could do an original vette system for the same I considered it a good deal.

FWIW I have ordered the judging guide and everything else NCRS has for the 1971 year model...

James------


The forward pipes you are describing do not have to be specially made. The original forward pipes for LT-1 were essentially as you described. So, you can get these "off the shelf".

The rear pipes (midpipes as you refer to them) were exactly the same for LT-1 and big block. They are in no way exclusive to big block.

The 2-1/2" mufflers were the same for any 2-1/2" system.

If you were to seek out NOS pipes and mufflers I think you'd be talking about more than $2,000, probably quite a bit more.

[Patrick H.]

Re: 70 Corvette 2 1/2" welded pipes

As correct as possible...
FWIW ZINC plated parts can be made to appear as bare steel... tumbled with steel shot rubs the ZINC to a nice bare steel sheen which doesn't rust.

OK, let me restate....

What is your judging goal with the car? And how many points are you willing to gain or lose, especially on a points-per-dollar ratio?

No one makes an entirely correct system, as currently no muffler externally looks like the originals.
From a points-per-dollar aspect, an aluminized system is the cheapest as you take the 25% judging deduction and move on. They just had a free shipping deal, and if you watch they do that a few times per year.
Even a current Gardner system takes a similar hit due to configuration differences, and you'd have to be sure you get the carbon steel system if you want to look authentic.

Short of NO$ pieces, there will be a points loss. And, it will take $1500-2000 to get the 8-10 points you'd lose from a CC aluminized system.

In the end, its your choice how to spend your money.

[James G.]

Re: 70 Corvette 2 1/2" welded pipes

Do any of the welded aluminized systems have the correct forming wrinkles? Are points deducted for this?
To me the 2 into 2-1/2 head pipes from CC do not look very much like the originals... are there points deducted for this?

FWIW I would gladly pay 2k for AN EXACT REPRODUCTION of the original.

[Patrick H.]

Re: 70 Corvette 2 1/2" welded pipes

Do any of the welded aluminized systems have the correct forming wrinkles? Are points deducted for this?
To me the 2 into 2-1/2 head pipes from CC do not look very much like the originals... are there points deducted for this?

FWIW I would gladly pay 2k for AN EXACT REPRODUCTION of the original.

No, maybe and maybe.

You need to read the Judging Reference Manual with regard to the standard deduction for exhaust, specifically aluminized and stainless.
When the standard deduction applies, it works differently than the usual CDCIF judging format.

[Joe L.]

Re: 70 Corvette 2 1/2" welded pipes

Do any of the welded aluminized systems have the correct forming wrinkles? Are points deducted for this?
To me the 2 into 2-1/2 head pipes from CC do not look very much like the originals... are there points deducted for this?

FWIW I would gladly pay 2k for AN EXACT REPRODUCTION of the original.

James-----

As I've mentioned previously, I believe the original (and, GM SERVICE) pipes were die-formed. That's why the fitment was so good. It's also the reason that the "wrinkles" were formed in the pipes. Die forming of exhaust pipes is really only practical in an OEM situation in which the pipes have to fit perfectly at the time of factory installation and the cost of the tooling to do so is off-set by the aforementioned requirement and the very high volume of pipes to be manufactured. I believe that all aftermarket or reproduction pipes are mandrel bent. This does not produce as precise of a final configuration but it's the only practical way to produce low volume, SERVICE pipes.

[Paul D.]

Re: 70 Corvette 2 1/2" welded pipes

Would NOS rear pipes and mufflers (if they could be located) not still receive a configuration deduction since SERVICE replacements were never available as welded assemblies? Even if welded and no clamp, configuration is different due to the slip fit connection between muffler and mid pipe. Chip.

[James G.]

Re: 70 Corvette 2 1/2" welded pipes

No, maybe and maybe.

You need to read the Judging Reference Manual with regard to the standard deduction for exhaust, specifically aluminized and stainless.
When the standard deduction applies, it works differently than the usual CDCIF judging format.

I ordered the Judging Manual, the complete Restorers collection for 70-72 on CD, and the 71 assembly manual on Tuesday...


Apparently I was wrong in the way I thought deductions were assessed.
I thought that the material was a deduct-
Aluminized was a 25% deduction -
Stainless 50%,

The lack of embossing on the mufflers was a deduct, the muffler beads were a deduct, the forming wrinkles were a deduct, the welded reducers 2- 2-1/2 not being correct was a deduct.

I guess if it's just a 25% deduct for a welded 2 to 2-1/2 CC system then that's the way to go.

[Patrick H.]

Re: 70 Corvette 2 1/2" welded pipes

There are those who argue that exhaust should be judged as you describe, that the 25 or 50% is a starting point and the rest is added to that. However, that is not how most of us interpret the standard deductions. Most chassis judges deduct 25% for the exhaust pipes as "the" deduction for those and move on.

Note that more than one item is in each line of the exhaust category on the judging sheets. So, you might lose points on the other items. The reproduction hangers, bolts, exhaust tips, etc all warrant deductions as purchased.

Patrick

[James G.]

Re: 70 Corvette 2 1/2" welded pipes

I would eliminate the service configuration, mate the pipe and muffler, cut a butt joint, tig weld it, then finish the weld and sand it smooth.
Fortunately I've got more time than sense and love a challenge...

[Joe L.]

Re: 70 Corvette 2 1/2" welded pipes

I would eliminate the service configuration, mate the pipe and muffler, cut a butt joint, tig weld it, then finish the weld and sand it smooth.
Fortunately I've got more time than sense and love a challenge...

James------


If you're talking about a butt joint at the muffler, you can only do what you suggest if you start with original rear exhaust pipes. SERVICE pipes, both GM and aftermarket, are shorter to accommodate the extension on SERVICE mufflers.

[Richard T.]

Re: 70 Corvette 2 1/2" welded pipes

I installed the CC 2 1/2" off road system with welded mufflers on my 1968 with L 36. Easy to install and fit was fine. I bought them during one of they're sales that offered free shipping so that wasn't an issue. I like the sound and it gets better with age. You can hear the radio or talk to a passenger and there's no drone . Wide open throttle sounds great. I'm happy with it.