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Need Source Recomendations for New Exhaust Manifolds

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Old 02-04-2017, 10:15 AM   #1
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Default Need Source Recomendations for New Exhaust Manifolds

1966 coupe... The exhaust manifolds are in pretty bad shape. One of my winter projects is to replace these with new. As near as I can tell the casting numbers are 3747038 and 3749965. Anyone have good luck with new imported castings? Most of the used ones I see on eBay are in pretty bad shape.

Thanks in advance
Greg
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Old 02-04-2017, 10:22 AM   #2
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are they cracked or broken ears? if not I would sand blast them and paint them with PRO 15 cast blast or anther high temp pant
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Old 02-04-2017, 10:56 AM   #3
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are they cracked or broken ears? if not I would sand blast them and paint them with PRO 15 cast blast or anther high temp pant
Not cracked or broken but severely corroded and pitted.
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Old 02-04-2017, 10:58 AM   #4
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New ones won't be any better
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Old 02-04-2017, 11:00 AM   #5
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If you have a 2 1/2" system, these manifolds from Brzezinski Racing Products would likely be a bolt on proposition. If you have a 2 1/2" system from 2" manifolds, all you would need to do is change out the top of your header pipes to the 2 1/2" header pipes to fit. (The 2 1/2" system on '66 and later uses a 2" header to adapt to the 2 1/2" system a few inches down from the manifold.)

Brzezinski takes an imported (2 1/2") manifold and CNC machines it to flow as well as the original 2 1/2" manifolds.

If you are not in a big hurry, you can also find quite a few old 2 1/2" manifolds at Carlisle in August and perhaps even a few at Corvette Expo in March in Sevierville, Tennessee. The problem with many of the old originals, is that they are often pitted pretty badly and also frequently have broken and welded ears on them. These start as new cast iron manifolds.

Good luck... GUSTO
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Old 02-04-2017, 11:42 AM   #6
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I've used the imported Dorman brand manifolds. They seem to be good. Not and exact copy for the man with the magnifying glass but close enough.

They are available for various years and sizes. Many retail outlets for these.

https://www.google.com/shopping/prod...HZVgDqoQrhIIXQ
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Old 02-04-2017, 03:48 PM   #7
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If yours are salvageable and original then restore them unless you don't car about the original aspect. The repros often are missing the casting ridges; there are several along the top from front to back on factory manifolds....a dead giveaway that they're repros....
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Old 02-04-2017, 06:38 PM   #8
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Quote:
Originally Posted by MikeM View Post
I've used the imported Dorman brand manifolds. They seem to be good. Not and exact copy for the man with the magnifying glass but close enough.

They are available for various years and sizes. Many retail outlets for these.

https://www.google.com/shopping/prod...HZVgDqoQrhIIXQ
me too...
ill
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Old 02-04-2017, 11:00 PM   #9
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Quote:
Originally Posted by Tigershark3 View Post
1966 coupe... The exhaust manifolds are in pretty bad shape. One of my winter projects is to replace these with new. As near as I can tell the casting numbers are 3747038 and 3749965. Anyone have good luck with new imported castings? Most of the used ones I see on eBay are in pretty bad shape.

Thanks in advance
Greg
I have always found that Long Island Corvette Supply sells the best products.
Go to section 33 of their catalog and you'll find new, NOS and used manifolds that fit your needs.
There was a time when the nubs on the top, which are very important, were ground off prior to sale because of casting flash. Times have changed and judges and buyers have gotten more sophisticated.
If you don't like them, then just send them back.

http://www.licorvette.com/

Download the "print catalog"

Go to section #33
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Old 02-05-2017, 08:54 AM   #10
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Paragon Corvette Reproductions has exhaust manifolds listed in their catalog. I'm not sure how correct they are.
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Old 02-07-2017, 11:34 AM   #11
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Quote:
Originally Posted by MikeM View Post
I've used the imported Dorman brand manifolds. They seem to be good. Not and exact copy for the man with the magnifying glass but close enough.

They are available for various years and sizes. Many retail outlets for these.

https://www.google.com/shopping/prod...HZVgDqoQrhIIXQ
I'll check these out but site says that they fit 62-63
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Old 02-07-2017, 11:35 AM   #12
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Some good info here.... Won't be a judged car so they don't have to be factory perfect.

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Old 02-07-2017, 11:44 AM   #13
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Quote:
Originally Posted by Tigershark3 View Post
Some good info here.... Won't be a judged car so they don't have to be factory perfect.

Not sure if it is left or right you need. You should check Ebay too.

Here is a 2 1/2 inch left side.
https://sacramento.craigslist.org/pts/5988588670.html
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Old 02-07-2017, 12:04 PM   #14
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I'll check these out but site says that they fit 62-63
That was just a sample. Dorman retails many different manifold configurations for SBC. Talk to the counter man.

I don't know if Paragon and LIC sell the same manifolds for an inflated price but it's possible.
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Old 02-07-2017, 12:24 PM   #15
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Quote:
Originally Posted by Tigershark3 View Post
Some good info here.... Won't be a judged car so they don't have to be factory perfect.

Well, that changes a few things.

You can buy the cheaper replacements, which work just as well. They will be fairly close enough to original that most won't be able to spot.

Rockauto.com has what you need for $77.99, overseas made.

Paragon, Zip, LICS, etc use USA made parts.

BTW, here is what you have now:
3749965 manifold..................283 & 327 1958-63 Corvette left 2"
3747038manifold....................283-327 1958-65 Corvette right 2"






Last edited by 65tripleblack; 02-07-2017 at 12:58 PM.
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Old 02-07-2017, 12:24 PM   #16
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Quote:
Originally Posted by Tigershark3 View Post
1966 coupe... The exhaust manifolds are in pretty bad shape. One of my winter projects is to replace these with new. As near as I can tell the casting numbers are 3747038 and 3749965. Anyone have good luck with new imported castings? Most of the used ones I see on eBay are in pretty bad shape.

Thanks in advance
Greg
I believe 3747038 is a 2" RH (not a 2.5"). I have a used one with a casting number of 3747038X I'd sell for a very reasonable price. Let me know if you have any interest and I will send you some pictures.

I also have a pair (LH and RH) of used 2.5" manifolds that I'd sell as well.

Last edited by AkrHack; 02-07-2017 at 12:29 PM.
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Old 02-07-2017, 12:26 PM   #17
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I believe 3747038 is a 2" RH (not a 2.5"). I have one with a casting number of 3747038X I'd sell for a very reasonable price. Let me know if you have any interest and I will send you some pictures.
All 1966 SBC used 2" manifolds.
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Old 02-17-2017, 02:11 AM   #18
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Quote:
Originally Posted by Tigershark3 View Post
1966 coupe... The exhaust manifolds are in pretty bad shape. One of my winter projects is to replace these with new. As near as I can tell the casting numbers are 3747038 and 3749965. Anyone have good luck with new imported castings? Most of the used ones I see on eBay are in pretty bad shape.

Thanks in advance
Greg

You have gotten some solid advice regarding the inexpensive Dorman replacements. They get the job done but are not perfect.

The reproductions sold by Paragon are much closer to the original style but they cost a lot more. It is true that the "nubs" along the parting line are not identical to the originals, but otherwise the Paragon reproductions are excellent.

If NCRS judging is not a priority and you decide to purchase new reproductions, I suggest that you purchase the versions with 2.5" outlets and also purchase new 2.5" header pipes (the pipes from the manifolds to the transmission crossmember).

For some reason (cost savings, I suspect), GM changed to 2.0" passenger car outlets on the '66-'67 manifolds after using 2.5" outlets for 1963-65. There are 2.5" versions of the '66 style manifolds that will bolt right in to your '66. I'm away from home right now, but I can provide the correct casting numbers next week if you like.

If you decide to purchase new manifolds and you would like to protect them from corrosion, I suggest that the you get the "Jerry MacNeish" coating or possibly the Jet Hot coating to protect them from rusting. This will prevent any future rust and will make you engine bay look much nicer than it would with rusty, corroded exhaust manifolds.
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Old 02-23-2017, 10:01 PM   #19
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You have gotten some solid advice regarding the inexpensive Dorman replacements. They get the job done but are not perfect.

The reproductions sold by Paragon are much closer to the original style but they cost a lot more. It is true that the "nubs" along the parting line are not identical to the originals, but otherwise the Paragon reproductions are excellent.

If NCRS judging is not a priority and you decide to purchase new reproductions, I suggest that you purchase the versions with 2.5" outlets and also purchase new 2.5" header pipes (the pipes from the manifolds to the transmission crossmember).

For some reason (cost savings, I suspect), GM changed to 2.0" passenger car outlets on the '66-'67 manifolds after using 2.5" outlets for 1963-65. There are 2.5" versions of the '66 style manifolds that will bolt right in to your '66. I'm away from home right now, but I can provide the correct casting numbers next week if you like.

If you decide to purchase new manifolds and you would like to protect them from corrosion, I suggest that the you get the "Jerry MacNeish" coating or possibly the Jet Hot coating to protect them from rusting. This will prevent any future rust and will make you engine bay look much nicer than it would with rusty, corroded exhaust manifolds.
I don't see that Dorman has replacement 2" manifolds that will fit my car. 674-500 (I don't see how the square flange would work to mount the alternator), 501 (mounting holes don't look right), 503, or 504. Both 503 and 504 are 2.5"

Any and all helpful comments are welcomed

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Old 02-24-2017, 07:57 AM   #20
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Is your alternator mounted like this?
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