L71 exhaust manifolds

[Kerry A.]

I recently purchased a NOS L71 RH exhaust manifold P/N 3880828 dated 8/31/66. I was so excited about the part that all I paid attention to was the part number and condition. However, upon receipt of the part and closer examination I noticed something that to me is unusual. In the pic below the manifold in the back is my old one and the new is in the front. If you look closely my old manifold has a raised angular boss below each of the AIR undrilled bosses. The new one does not have the angular bosses. Any input would greatly appreciated. Thank you in advance for your assistance.



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[Donald A.]

Re: L71 exhaust manifolds

My L71 manifold looks like your old one, with the raised angular areas. I have photos of cars I have owned before, and both 66 427s had the same manifold appearance. The 3880828 manifold was used in many big block applications and years but my concern is the new one you have obtained is not the typical appearance of big block manifolds for a 67 Corvette. Just my opinion!

[Joe L.]

Re: L71 exhaust manifolds

I recently purchased a NOS L71 RH exhaust manifold P/N 3880828 dated 8/31/66. I was so excited about the part that all I paid attention to was the part number and condition. However, upon receipt of the part and closer examination I noticed something that to me is unusual. In the pic below the manifold in the back is my old one and the new is in the front. If you look closely my old manifold has a raised angular boss below each of the AIR undrilled bosses. The new one does not have the angular bosses. Any input would greatly appreciated. Thank you in advance for your assistance.



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Kerry------


Please post full photos, front and rear, of both manifolds.

[Kerry A.]

Re: L71 exhaust manifolds

As soon as I get over to the shop, probably next week, I will take pics and post them on the forum. I purchased the part from the UK but there is no special markings to indicate it is a special manifold. However, it shouldn't matter what part of world it came from. I look forward to figuring this out. I do know it has halted the final assy. of my engine.

[Kerry A.]

Re: L71 exhaust manifolds

Attached are pics of the manifolds you requested. I was incorrect about the UK. It was a different part. I confused myself. My manifold is dated F 29 6 the NOS is dated H 31 6. At first glance the NOS 6 looks like an 8 but if you zoom it's definitely a 6. So they were casted 2 months apart. The NOS has a round boss at the base of the furthest rear tube just above where the exhaust attaches to the manifold. Mine does not. However, I see more manifolds with the boss than without it. Mine has excess material at the casting seam and the NOS is smooth. The angular bosses below the AIR bosses are missing on the NOS. They're present on mine and every other 67 BB manifold I looked at except the NOS manifold I have. On the engine side of the NOS it sates RH1 and mine is RH3. On the outside face of mine it says GM and the NOS is GM1. However, I've seen GM2 and GM3. It's my understanding the numbers after the GM represent replacing a worn out mold with a new mold but no changes were made to the actual pattern. You will see slight shape discrepancies between the two because mine has been significantly repaired as you can tell by the pre-repair pic. The repair was powder welded. The coating on mine is a porcelain coating and is going to be stripped. The person that did the coating and I weren't on the same page. Unfortunately I will still need to coat it because of the repair. This is where the NOS manifold comes in. It was to replace my repaired manifold. The manifold meets all of the NCRS judging standards. However, the NOS is missing the angular bosses but there is nothing mentioned in the 67 IMJG. look forward to receiving comments. Thank you.

[Joe L.]

Re: L71 exhaust manifolds

Attached are pics of the manifolds you requested. I was incorrect about the UK. It was a different part. I confused myself. My manifold is dated F 29 6 the NOS is dated H 31 6. At first glance the NOS 6 looks like an 8 but if you zoom it's definitely a 6. So they were casted 2 months apart. The NOS has a round boss at the base of the furthest rear tube just above where the exhaust attaches to the manifold. Mine does not. However, I see more manifolds with the boss than without it. Mine has excess material at the casting seam and the NOS is smooth. The angular bosses below the AIR bosses are missing on the NOS. They're present on mine and every other 67 BB manifold I looked at except the NOS manifold I have. On the engine side of the NOS it sates RH1 and mine is RH3. On the outside face of mine it says GM and the NOS is GM1. However, I've seen GM2 and GM3. It's my understanding the numbers after the GM represent replacing a worn out mold with a new mold but no changes were made to the actual pattern. You will see slight shape discrepancies between the two because mine has been significantly repaired as you can tell by the pre-repair pic. The repair was powder welded. The coating on mine is a porcelain coating and is going to be stripped. The person that did the coating and I weren't on the same page. Unfortunately I will still need to coat it because of the repair. This is where the NOS manifold comes in. It was to replace my repaired manifold. The manifold meets all of the NCRS judging standards. However, the NOS is missing the angular bosses but there is nothing mentioned in the 67 IMJG. look forward to receiving comments. Thank you.






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Kerry------


I've been anxious to see the photos of your manifolds. However, your photo attachments did not work and I cannot see them. I get an "invalid attachment" when I click on your attachments.

[Kerry A.]

Re: L71 exhaust manifolds

Joe, I screwed up and did the pics as attachments instead of inserting. I've done this before. I'm frantically working to resolve my error. I will repost soon. Thank you.

[Kerry A.]

Re: L71 exhaust manifolds

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[Joe L.]

Re: L71 exhaust manifolds

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Kerry------


You've posted a lot of photos and that's good. However, the one photo that's most important is missing. I cannot see clearly the foundry marks on the front of the NOS manifold. Would you please post a good photo of the front of the entire NOS manifold, as close-up as you can and still get the whole manifold in it?

[Kerry A.]

Re: L71 exhaust manifolds

Joe,

This is a close up as I can get with my camera and also capture the entire manifold. I hope you are able to zoom. I cleaned it up some as well. Hopefully that will help. look forward to hearing from you.





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[Joe L.]

Re: L71 exhaust manifolds

Joe,

This is a close up as I can get with my camera and also capture the entire manifold. I hope you are able to zoom. I cleaned it up some as well. Hopefully that will help. look forward to hearing from you.





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Kerry-------


It's the FRONT side of the manifold that I need to see and, in particular, the portion with the casting marks which include the "GM", casting number, and other markings. So far, I've seen virtually everything except that.

[Kerry A.]

Re: L71 exhaust manifolds

Joe,

I just logged in to see if there was a reply from you and I can see why not. My reply never posted. I seem to be having trouble with this particular area of the board. I'll try again.

[Kerry A.]

Re: L71 exhaust manifolds

Joe I do apologize. After posting my last reply all of sudden all of the threads are visible. I read your message and I will post the pics you requested.

[Kerry A.]

Re: L71 exhaust manifolds

I hope these help.





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[Joe L.]

Re: L71 exhaust manifolds

I hope these help.





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Kerry------


Yes, they do. You will note that there is no large cast "T" on the manifold. Most big block cast parts were cast at the Tonawanda Foundry. Tonawanda was usually very good at placing the "T" casting mark on their castings although even your apparently original manifold lacks the "T". I have noted that some Tonawanda castings do lack the "T" but the VAST majority have it.

The Tonawanda foundry shut down in 1984. After that time, big block cast iron parts were cast either at the GM Danville, IL foundry or the GM Defiance, OH foundry. Those cast at Danville usually have a large "D" casting mark together with the Central Foundry Divison "wagon wheel" symbol. Danville was usually very good about these casting marks, probably the most reliable of all GM foundries at including these marks on their castings. On the other hand, the Defiance, OH foundry usually did not place any foundry identification casting marks on their products. I have no idea why.

In any event, as I mentioned, the Tonawanda foundry shut down in 1984 and big block castings were transferred to the other foundries. So, castings made at those foundries in 1985 or, even, 1995 could carry a "5" casting year symbol and castings made in 1986 or 1996 could carry a "6" casting year symbol.

I believe that due to the lack of the 4 "nubs" on this manifold and the lack of the "T" casting symbol, this manifold was likely cast at Defiance, OH in 1986 or 1996. I can tell you that SERVICE manifolds without the "nubs" are quite rare; I have rarely seen them. I have NEVER seen a known original PRODUCTION big block manifold without the "nubs". I'm not saying they never existed but I have never seen one.