468 ci exhaust question

[67chevy1]

Ok for you engine guys out there. I'm building a 468 for my 67 short bed. If you have a set of copo bbc manifolds would you use them or go with headers and sell the manifolds?

[davepl]

What makes a big block manifold a COPO manifold?

[Mick Je]

I would run headers.

[67chevy1]

Originally Posted by davepl

What makes a big block manifold a COPO manifold?

COPO Stands for corporate office production order, they were used on the high horsepower chevelles, camaros and maybe a few others. The number casted onto the manifold is how you can tell and they're supposed to flow better than the other production manifolds, but I don't know how much better or anything else. I think headers would look cooler, but it's kind of cool also knowing I have some copo parts on a pickup. They're kind of rare and expensive when you do find them.

[davepl]

Originally Posted by 67chevy1

COPO Stands for corporate office production order, they were used on the high horsepower chevelles, camaros and maybe a few others.

I know what COPO is, but I'm wondering what makes these "special". Wiper blades were used on the 9560/9561 COPO Camaros, but that doesn't make them COPO blades, I guess is my point.

I actually thought the COPO Camaros just used regular old 396 exhaust manifolds, hence my confusion about what makes them a COPO manifold and not just a 396 Impala manifold, for example.

If they're at all rare or desirable, sell them. No point putting them on a truck.

Edit: If SSTim is correct, I just saw his post, makes sense. So they could be used on a COPO build, but just because they happen to be the base part used on those cars (desirable), not a part unique to COPO cars (hen's teeth).

[67chevy1]

That answer Tim wrapped everything up in a nutshell for me. Basically the copo stuff anymore is just nostalgia more so than performance. Which pretty much means it's worth more but I'm not going to get anything performance wise from it. I now see what your saying. Does anyone have part numbers and brands of headers that fit these trucks the best? Performance pros and cons? I'm pretty sure I know which way I'm going now. When I started this project I just meant to have a good daily driver that I built myself. As far as built myself part is still true but not sure about the daily driver thing. I'm thinking more of a weekend warrior now.

[SS Tim]

If by COPO you are refering to the 9560 or 9561 427 Camaros, they used the stock 396 exhaust manifolds. Most people consider these somewhat restrictive on a stock 396 so why would you consider them for a 468? Unless you are building a low rpm torque engine they will probably not flow enough. Also might want to consider Chevrolet clearanced the frame in 68 to fit the production 396 engines in.

[67chevy1]

Originally Posted by SS Tim

If by COPO you are refering to the 9560 or 9561 427 Camaros, they used the stock 396 exhaust manifolds. Most people consider these somewhat restrictive on a stock 396 so why would you consider them for a 468? Unless you are building a low rpm torque engine they will probably not flow enough. Also might want to consider Chevrolet clearanced the frame in 68 to fit the production 396 engines in.

The set of manifolds I have are a set of 6178 and 9879 manifolds. One of them was casted from 67-70 and the other was casted from 68-70. I'm glad to find out about the restrictiveness though. I don't know that I'm building a massive power unit, but I don't want to bolt anything on that I know is going to take horsepower away either. I wonder why if they're stock 396 manifolds they would be listed as copo molds.

[SS Tim]

Can't help with the specific casting numbers off the top of my head. Its been too long.

But in a nutshell 427 COPO Camaros were assembled using as many stock parts as possible. They simply replaced the long block while retaining the production 396 exhaust and emission controls. This was done under the assumption (rightly so) that almost every end user was going to install some sort of performance exhaust specific to their needs.

As far as the stock Camaro L78/L89 manifolds being identified as COPO parts, they were. But they were also the same parts as used in countless other big block Camaros. Many other parts fall in the same spotlight. A great example are the base hubcaps. While they were used on the many of the COPO Camaros most were on basic strippers. But the guy selling them wants to get more $$$ (absolute most) and hypes them as a COPO part and often omits the base usage in sales verbage.

[SS Tim]

Exactly, a few parts were unique (application specific) most were simply production parts also used but so necessary for the "numbers matching" (though not original) builds.

On the other hand some of those unique COPO parts are rare and valuable....

[geezer#99]

Keep the sorta rare parts and hog them out.
http://boneheadperformance.com/extrude-honing/

They can be made to flow better than headers.

[El Dorado Jim]

I run headers on my 74 K20 and 73 Suburban, both have 454's...I have had stock exhaust manifolds crack quite often,and they are expensive and hard to find, so headers for me

[SS Tim]

Can't offer much more except to again point out they altered the truck frames to fit the 396 when introduced in 68. So what fits a later truck might not fit yours. Then you have to decide how its mounted, SBC, 68-71 BBC mounts, 72 only BBC or 73 up BBC altered. You need to have a common point of reference to say someone else's "it fit" will work for you.

Over the years I have been looking at exhaust manifold options for a 496, so far Sandersons look pretty good. But then I want to build a period looking 4x4 C30.

[Mike C]

I ordered a set of big block Corvette reproduction manifolds, they were $235 for the pair from Summit. I have searched and best I can tell the passenger side drops in. I am going to try and angle mill the drivers side and to run them on the 427 I am building for my '69 short step. Plan is to make it look like a bone "stock" 427. My donor is a '69 Corvette 390 or 400 hp single 4 barrel oval port head. I bought the smallest nitrous hydraulic roller that Comp offers and plan on running it NA through the 'vette manifolds, 2 1/2" exhaust with Walker Hemi Turbo mufflers. Hoping for 400 whp and stock truck sound. Cam ground on 113 deg LSA and is 224 at .05 on the intake so we will see...

[davepl]

I have a car with a ZZ502 that used to have headers, a decent intake, and a Holley 850. It ran a 12.9 (heavy car, one that ran 16.4 stock!).

When I restored it I dressed the motor as a "stock" motor complete with exhaust manifolds, iron intake, and Q-Jet. It's waaaaay slower now. I haven't timed it but you can really tell a difference.

So if you're stock enough appearing to fool people, great. If I were to do it again I'd get black ceramic coated headers, grind the Edelbrock logo off an intake and spray it orange, and get the Q-jet tuned for that setup.

Actually I still might not, because I really wanted stock appearing. But wow, what a difference. And you can keep 99% of those gains with discrete headers, intake, and so on just by how you dress them.

[BossHogg69]

If your truck is lowered more than say 2/4, you might think about using a set of A or B Body headers. 64-72. I used Hedman Elites #68198. 1.75" tubes, very nicely made. If it's not lowered, the Hedman Elite #69820 - I tried them too, but they hung down way below the framerails, so I changed to the A body headers. I would not use manifolds on a performance oriented big block, but I'm no engine guru either.

This topic has been covered many, many times around here. Here are a few with pics.

http://67-72chevytrucks.com/vboard/s...d.php?t=533692

http://67-72chevytrucks.com/vboard/s...d.php?t=450742

http://67-72chevytrucks.com/vboard/s...d.php?t=584177