Only the very early 2 port 76 CVCC had the bolt together cast manifold, I happened to have one on a car that I owned, It leaked.
The major redesign in the 75 to 76 porting was to siamese the exhaust ports to eliminate the auxiliary port in the intake manifold from plugging up, as well as a few other emission related troubles. Honda also updated the 75 replacement mainfold to utilize the auxiliary plenum and a more gradual angle to the runners.
We welded a lot of the later exhaust manifolds, for cracking, with generally good results. But it turns out that it was illegal along with removing the baffle, and voided warranty... But then Honda came out with a campaign to cover the later manifolds and it all became a corporate problem.
By all means get a good one! it will save you many headaches!

By John S. (152.163.100.199) on Monday, July 04, 2005 - 05:16 pm:

I believe the only manifold that bolted together was the '75 model...1st yr for the CVCC. It tended to clogg the CVCC passages due to running too cold, so in '76 honda came out with the "new" design. It was a welded cast design. and as talked about earlier would eventually burn out its innards, and also could crack along the welded seam. This tended to happen often enough to mention it. The one I have IS in good shape in both areas, and Kevin, I will eMail you about it.

By Kevin (Kman) (68.40.207.194) on Thursday, June 30, 2005 - 09:59 am:

My preheater tube comes off of the 1st exhaust pipe (the flexable one) which is still good so I am inclined to just replace the 78 exhaust manifold. John. My e-mail is kevkev(at)hotmail.com (use the @ symbol). Stainless exhaust manifold ???. Yeah I'll take one of those :-)

By Username (Username) (68.116.93.157) on Tuesday, June 28, 2005 - 08:39 pm:

There were actually 5 different manifolds, varying by material and design. Early ones bolted together, later stainless were welded, some had preheat shrouding on the manifold, some on the pipe. We finally found one that would work in all applications, sold so many I still remember the Honda Code for the manifold and shield...

By Brass N Wood (172.128.64.171) on Tuesday, June 28, 2005 - 08:06 pm:

that inner lining was missing and collapased in places i couldn't reach .. gave up and went junking ...this was back when the yards had plenty of them to pick over ,,, learned they made 2 very different exhaust manifolds .. been so long i'm not really sure if this is off a 76 or not but the preheater tube is correct for the 77s ,,, this is easy double the weight of the 77s. double wall stamped steel vs cast iron i think ..and this one is clean .. lining in intact including the area where the lining flares into 2 rings that the head side clip rings mate too ... kept it when i tossed the 1500 cause i remembered what a time i had finding a good one .. yours for the shipping ,, or come n get it ,,so calif area

By Kevin (Kman) (68.40.207.194) on Tuesday, June 28, 2005 - 01:14 pm:

John. $50 is a steal compared to a new one. I already looked. My 78 is nice too. Check out the eyes on design thread or the civic77 site. The only comperable trade I might have is a couple of original spares I thought I'd show it with (near mint with nubs) or a set of well aged deluxe gauges. If you don't need these $50 is a deal. E-mail me. Right clicking on my name will show my address under properties.

By John S. (207.160.168.243) on Tuesday, June 28, 2005 - 12:32 pm:

I have a good one off of a "78 CVCC, but I want 50.00 for it and you pay shipping. Don't know if you have priced one from Honda, but you'd better be sitting down. Good ones are rare, and that it why I have had this one for so long, I wasn't about to throw it out. You might be able to get me to trade for some Honda something, if I need it. Let me know what you might have. I have a nice '78 CVCC, and a nice "83 Civic S.

By Kevin (Kman) (68.40.207.194) on Friday, June 24, 2005 - 03:36 pm:

Jonathan. Thanks for the offer. I think I'll have to pass. It looks just different enough in the drawings that I know it'll drive me nuts trying to put it back together. I think I'll be able to rethread the old one without too much trouble.

By Jonathan (68.193.6.173) on Friday, June 24, 2005 - 03:07 pm:

Kevin, I've got one from a '77 CVCC you can have for the cost of shipping. It's a little different from the 78/79 versions, but may work fine. Only change I know of is the heat riser tube was on a shroud around a manifold for the earlier models, but came off the exhaust pipe below the manifold on the later models.

I think it's called a thermal reactor because it works sorta like a catalytic converter does for emissions. The manifold gets real hot, continuing the combustion process and cleaning up the tailpipe end of things.

By Kevin (Kman) (68.40.207.194) on Thursday, June 23, 2005 - 05:39 pm:

Yep. CVCC. I removed the rest of the liner today. Quite a chore. When I put it back together one of the bolts came out! *&^%$#@! manifold. Still noisy, cause I couldn't get the gasket to seal fully. I'll have to put in a larger bolt or get a new exhaust manifold. Anyone got a good one?

Kevin

By John S. (207.160.168.243) on Thursday, June 23, 2005 - 01:07 pm:

Kevin,
You are talking about a CVCC right?
If so then be aware that if those sheet metal inner liners tend over time to rust to pieces and can fall down into, and block the exhaust tract, which will cause the exhaust manifold to get HOT, and I mean cherry red hot. Enough to set the engine compartment on fire.
Find a good exhaust manifold, and throw the bad one away. Or even better swap an 80-83 four port Head and exhaust manifold onto the car,(your early intake will still work on the later head). It will breathe better, and also eliminate the sheet metal problem once and for all.

By Username (Username) (68.116.93.157) on Wednesday, June 22, 2005 - 05:07 pm:

The inner baffle was most likely cut because it had dropped and began to block the outlet of the manifold. It will not harm anything to cut more of it out. The original intention was to retain heat to transfer to the intake manifold to aid atomization in the CVCC system, since it runs so rich it takes more energy to atomize the fuel. Some have refered to it as a thermal reactor, which it kinda is, it reacts with heat... But not in the sense that, say a Mercedes thermal reactor does.

By Kevin (Kman) (68.40.207.194) on Wednesday, June 22, 2005 - 04:55 pm:

My exhaust manifold's thin metal interior seems to have a human made hole in it (not rusted, looks like it was cut with snips). The rest of the metal in there seems loose and I worry about it interfering with exhaust gasses. The gasket going to the exhaust pipe seemed to burn through as a result of it getting too hot. My question is if there would be any major harm done by removing as much of the thin metal interior as possible before reconnecting the exhaust pipe. I know many of ya'll get rid of the stock exhaust manifold alltogether. What is the function of the thin metal. Heat disipation?