427/435 intake manifold casting mold crack

[Kerry A.]

I'm having my 67 427/435 engine rebuilt and during the process we discovered the tri-power intake manifold #3894374 has a repaired or patched crack on the bottom outer edge of the passenger side. Out of curiosity I was perusing eBay looking at manifolds and came across a used manifold with an identical crack. Within the description it states, the area is a production patch which is the result of the original casting mold breaking and was repaired. I was not aware of this. If this is not true, I find it strange to have an identical repair. Is anyone aware of this? I've included a link to the manifold on eBay. Thank you for your help.

http://www.ebay.com/itm/1967-CORVETTE-INTAKE-MANIFOLD-GM-ORIGINAL-427-435HP-L-71-TRI-POWER-3894374-/271813559478?hash=item3f4959c4b6&vxp=mtr

[Michael W.]

Re: 427/435 intake manifold casting mold crack

If it was the mold that was cracked, then the flaw will appear on every manifold produced afterwards. A decfective mold should not cause the manifold to crack.

[Paul S.]

Re: 427/435 intake manifold casting mold crack

There are a couple guys out there that can repair what you are talking about if you want to repair it vs replace it. I had one fixed

[Philip A.]

Re: 427/435 intake manifold casting mold crack

If it was the mold that was cracked, then the flaw will appear on every manifold produced afterwards. A decfective mold should not cause the manifold to crack.

Agree. It is either a casting flaw due to a cracked mold, just like the late C2 aluminum valve covers or it is a crack & repair of the manifold itself.

[Patrick B.]

Re: 427/435 intake manifold casting mold crack

Weren't these sand casting where the sand was packed around forms to shape the casting cavity. If the form broke, unlike a die, it would be very easy to fix because it was probably made of wood. If the flaw was caused by a piece of the formed sand breaking off, it would have been a random event not something that would happen from then on.

[Edward J.]

Re: 427/435 intake manifold casting mold crack

Kerry, did you have any running problems ?? If not, I would just use. it appears like a casting mark.how many years have you owned and driven ?

[Kerry A.]

Re: 427/435 intake manifold casting mold crack

The car was judged Top Flight in 2007, 2008 and 2010 and I have driven it approximately 200 miles and no running issues. The manifold is not currently cracked, it was repaired and looks identical to the picture of the manifold on eBay. This leads me to believe there was a casting issue or it's a highly unlikely coincidence. If it is a casting issue, I believe it occurred and was repaired at the time of the casting which would make sense. I don't believe it cracked later on because of a casting issue. Also, Michael is correct. All manifolds casted after the mold cracked would have the same defect. As I said in my original post I have never heard of such an issue so I thought I would cast it out on the forum. No pun intended. Well it was intended. By the way, low oil pressure and the inability to tighten some of the rockers led to the decision to do a rebuild. Thanks to all of you who responded.

[Michael W.]

Re: 427/435 intake manifold casting mold crack

If this is the flaw you're referring to

http://i.ebayimg.com/00/s/MTA2NlgxNjAw/z/~tkAAOSwaNBUjkru/$_57.JPG

I believe you're seeing the result of the repair made to the mold, not the manifold itself.

[Joe L.]

Re: 427/435 intake manifold casting mold crack

I'm having my 67 427/435 engine rebuilt and during the process we discovered the tri-power intake manifold #3894374 has a repaired or patched crack on the bottom outer edge of the passenger side. Out of curiosity I was perusing eBay looking at manifolds and came across a used manifold with an identical crack. Within the description it states, the area is a production patch which is the result of the original casting mold breaking and was repaired. I was not aware of this. If this is not true, I find it strange to have an identical repair. Is anyone aware of this? I've included a link to the manifold on eBay. Thank you for your help.

http://www.ebay.com/itm/1967-CORVETT...59c4b6&vxp=mtr

Kerry------



What is seen in the eBay item photos is a REPAIR. What the reason was for the repair, it's impossible to say. However, I have seen this type of repair on other original manifolds. It's not common, of course. In addition, I've never seen a field repair that appeared like this.

[Kerry A.]

Re: 427/435 intake manifold casting mold crack

Michael. Yes that is correct. After GM repaired the mold, it would've resulted in a flaw in the manifolds that were cast after the repair. If all of this is true, then what I'm see on my manifold and the one on eBay is the result of the mold repair. After rereading my last post, it isn't clear. It comes across as if GM repaired each manifold after it was cast. This of course would result in inconsistent repairs and would be labor intensive and expensive. All in all, I'm simply trying to ascertain whether anyone is familiar with this issue. I'm most certainly not an expert, but I've never heard of this.

[Kerry A.]

Re: 427/435 intake manifold casting mold crack

Joe. Thank you for your response. I just posted a response to Michael saying that after rereading my earlier post, it's point is unclear. When I stick my finger in the ports and run my finger over the area where the crack is, I can't feel the crack. It's the same as the other ports. So with this being said, I'm more curious than anything else to find out if the eBay person's story is true and the mold truly cracked and was repaired resulting in a flaw on the manifolds cast after the repair. The only reason I brought this up is the crack/repair on my manifold is identical to the one on eBay. Also, the fact I can't feel the repair from the inside would lend credence to the eBay cracked mold theory. It's a brain teaser and I was hoping someone could shed light on the matter. I'm going to send an email to the eBay seller and ask him were he got his information.


I don' think it was a field repair made by GM. If

[Steven B.]

Re: 427/435 intake manifold casting mold crack

In looking at the repair in the eBay photo, it suggests to me that this was a repair to the pattern. The light flashing of aluminum projecting out on the right side of the area in question in one of the pictures suggests that either some of the sand pulled out of the mold when the pattern was removed or the pattern had an identical shaped portion to the flashing. If the two manifolds mentioned earlier are identical, and I mean identical at the site in question, then it would indicate that both castings came from the same pattern. The casting looks as though the pattern had a patch of some sort. What would be the bigger question though, is what the heck happened to the pattern. Any pattern makers should be able to shed some light on this. I don't believe it to be a repair to the casting. It looks too clean. If a repair, how was it done? I could be wrong, and it wouldn't be the first time.

Steve

[Joe L.]

Re: 427/435 intake manifold casting mold crack

Michael. Yes that is correct. After GM repaired the mold, it would've resulted in a flaw in the manifolds that were cast after the repair. If all of this is true, then what I'm see on my manifold and the one on eBay is the result of the mold repair. After rereading my last post, it isn't clear. It comes across as if GM repaired each manifold after it was cast. This of course would result in inconsistent repairs and would be labor intensive and expensive. All in all, I'm simply trying to ascertain whether anyone is familiar with this issue. I'm most certainly not an expert, but I've never heard of this.

Kerry------


First of all, these manifolds were not manufactured by GM. They were cast by Winters Foundry in Canton, OH. I do not know if Winters performed the machining or if it was done by GM at the engine plants. However, machining is not an issue here. If a repair was done to the casting, I fully expect it was done at the foundry by Winters but it is possible it was done at the engine plant.

Second, these manifolds were sand castings. For a sand casting, the mold is made of sand which is basically held together by chemicals. The sand mold is made from a PATTERN. It is possible the PATTERN was somehow damaged and repaired in which case the repair could be visible in a cast part made from that pattern. However, I don't think that's what happened here. I think this manifold was most likely repaired POST-casting.

If the problem seen in the photo and, apparently, shared by your manifold were caused by a flaw or repair in the pattern from which the sand mold was made, then I would expect every manifold subsequently produced from this pattern would share the same flawed appearance.

[Kerry A.]

Re: 427/435 intake manifold casting mold crack

In looking at the repair in the eBay photo, it suggests to me that this was a repair to the pattern. The light flashing of aluminum projecting out on the right side of the area in question in one of the pictures suggests that either some of the sand pulled out of the mold when the pattern was removed or the pattern had an identical shaped portion to the flashing. If the two manifolds mentioned earlier are identical, and I mean identical at the site in question, then it would indicate that both castings came from the same pattern. The casting looks as though the pattern had a patch of some sort. What would be the bigger question though, is what the heck happened to the pattern. Any pattern makers should be able to shed some light on this. I don't believe it to be a repair to the casting. It looks too clean. If a repair, how was it done? I could be wrong, and it wouldn't be the first time.

Steve

I'm as curious as you. I'm going by what the eBay seller says in his/her description of the manifold. Unfortunately I'm unable to lay my manifold along side the one on eBay. However, looking at the picture the cracks seem identical to mine. Well close enough to prompt my original post. I'm going to look at mine again to make sure I'm not imagining this. If I'm not, I will take a pic of my manifold and will post it. There is a gentleman by the name of Jerry MacNeish of "Camaro Hi Performance" who can repair a crack or piece that has broken off. However, his repairs are virtually undetectable. Unbelievable work. But this is 2015 not 1967 so I agree with you about it being a repair. I can't feel it from the inside. So if it was repair to the casting it seems logical to me thatthat I should be able to feel it on the inside. I will keep you posted.

[Kenneth B.]

Re: 427/435 intake manifold casting mold crack

In looking at the repair in the eBay photo, it suggests to me that this was a repair to the pattern. The light flashing of aluminum projecting out on the right side of the area in question in one of the pictures suggests that either some of the sand pulled out of the mold when the pattern was removed or the pattern had an identical shaped portion to the flashing. If the two manifolds mentioned earlier are identical, and I mean identical at the site in question, then it would indicate that both castings came from the same pattern. The casting looks as though the pattern had a patch of some sort. What would be the bigger question though, is what the heck happened to the pattern. Any pattern makers should be able to shed some light on this. I don't believe it to be a repair to the casting. It looks too clean. If a repair, how was it done? I could be wrong, and it wouldn't be the first time.

Steve

I was a patternmaker starting in 1963 & I owned a pattern shop that made mostly automotive foundry patterns. It looks like the drag 1/2 of the sand mold was pushed out & cracked when the runner core was set. This would cause that piece of sand to push out past the rest of the casting mold causing that portion to stick up. If the core print was damaged it would cause the core to crush that portion of the mold outward. This is definitely NOT a repair but a brake in the green sand mold. That's why there is no crack on the inside because the core makes that shape.