Paragon Repoduction Exhaust Manifold

[Joe R.]

Re: Paragon Repoduction Exhaust Manifold

Hi Clark:

As promised, attached is a photo that compares an original 3846563 exhaust manifold with two others. The one on the bottom is either an early repro or a GM service replacement. It's a nice casting but the supplier got a little carried away with grinding off the flash at the casting seam.

The one in the middle is an original. Note the five small "nubs" along the casting seam.

The one on the top came from Paragon in 2010. Note that there are only three nubs and they are larger. To my eye comparing the Paragon part to the original, this was the only difference I could find.

[William C.]

Re: Paragon Repoduction Exhaust Manifold

I'd say service replacement for the bottom one based on what I've bought 40 years ago.

[Kenneth B.]

Re: Paragon Repoduction Exhaust Manifold

Hi Clark:

As promised, attached is a photo that compares an original 3846563 exhaust manifold with two others. The one on the bottom is either an early repro or a GM service replacement. It's a nice casting but the supplier got a little carried away with grinding off the flash at the casting seam.

The one in the middle is an original. Note the five small "nubs" along the casting seam.

The one on the top came from Paragon in 2010. Note that there are only three nubs and they are larger. To my eye comparing the Paragon part to the original, this was the only difference I could find.

The nubs your are refering to are in gates that was used to feed iron to the casting. Flash is where the mold parting didn't seal off & iron finned out. Why Paragon didn't make the Foundry use the same # of ingates I don't know. Some machine shops require the ingates to be ground off & some don't if it dosn't interfire with machining or fixturing. Othes want it groung off for looks.
KEN

[Patrick H.]

Re: Paragon Repoduction Exhaust Manifold

In addition, for the original I note that the large boss just left of center is two-humped whereas it is one smooth boss on the Paragon unit.

The shapes of the square bosses on the head side of the center seam also appear to differ slightly in shape between the original shown and the repro.

Not sure if these items are relevant to all years or not, however.

[Joe L.]

Re: Paragon Repoduction Exhaust Manifold

Yeah, you are correct. I just decided that I did not want them painted and then burned off. I did not paint my bell housing either which cost another point of two, but I like it.

Jeff------


From 1955 to 1981 at least a little engine paint is seen on virtually all bellhousings which were originally part of an engine assembly. There was one notable exception, though. 1969 ZL-1's didn't have a spec of engine paint on the bellhousing. That's because for that application there was no engine paint.

So, how come bellhousings after 1981 don't have engine paint on them? Well, after that time GM went to component painted engines. In this process, the major engine castings are painted after the foundry and before machining and assembly. Since this eliminated engine plant complete engine painting, there was no "overspray" to get on the bellhousing. Aluminum bellhousings were never separately painted.

[John D.]

Re: Paragon Repoduction Exhaust Manifold

The early Paragon repro had the grinding marks as mentioned above. The last ones GM sold over the counter were super ugy as they have the grinding marks also. I think I have a set around here somewhere that I bought from Chevy in late 70's or so. They have boo coo grinding marks.
I didn't realize the new Paragon repros were so nice.
I made the mistake of not listening on my 63 FI trailer queen and painted the exhaust mans gray. Should have listen to Jorjorian and Hanson and had them dipped in orange. JD