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jamie2370 08-15-2020 03:38 PM
intake castings
 
Hypothetical question. I know with sbc intake castings(iron) the castings vary a good bit. So, 2 intakes, same casting number, obvious diff production dates. One has around .070 avg wider ports at gasket surface on all ports. is this much variance normal?

Adger Smith 08-16-2020 01:06 AM
Re: intake castings
 
Let me make a guess... the wider/bigger one has an earlier date code..

SSDiv6 08-16-2020 03:00 PM
Re: intake castings
 
Core shift due to an acid trip??? :D:D:D

jamie2370 08-16-2020 05:26 PM
Re: intake castings
 
Quote:
Originally Posted by SSDiv6 (Post 621100)
Core shift due to an acid trip??? :D:D:D
By the amount of views and lack of response....I have my answer:D:D

Adger Smith 08-16-2020 08:21 PM
Re: intake castings
 
OK, here is what my friend JV Brotherton (Owner of Brodix) told me when I was complaining about port size/Vol matching specs.
As the molds are used the ports shrink due to the wear on the mold.
I'm not a mold maker so I took him at his word. He said the early part of the production run will be on size and the tail end will be smaller.
I was hoping someone that knew the mold process at GM would take the bait and tell us. I hope that helps. BTW I always flow the manifolds to be sure.

SSDiv6 08-17-2020 01:14 AM
Re: intake castings
 
Quote:
Originally Posted by Adger Smith (Post 621119)
OK, here is what my friend JV Brotherton (Owner of Brodix) told me when I was complaining about port size/Vol matching specs.
As the molds are used the ports shrink due to the wear on the mold.
I'm not a mold maker so I took him at his word. He said the early part of the production run will be on size and the tail end will be smaller.
I was hoping someone that knew the mold process at GM would take the bait and tell us. I hope that helps. BTW I always flow the manifolds to be sure.
He is correct. This happened with the old days casting processes.

SDT1DYI 08-17-2020 12:49 PM
Re: intake castings
 
Best to test intake manifolds on a dyno. They can be different. In one case 15 "stock' CI manifolds same casting #, were tested on one engine , same day. HP varied 15 .

Steve Teeter STK/SS 620.

Glenn Briglio 08-17-2020 03:46 PM
Re: intake castings
 
Quote:
Originally Posted by Adger Smith (Post 621119)
OK, here is what my friend JV Brotherton (Owner of Brodix) told me when I was complaining about port size/Vol matching specs.
As the molds are used the ports shrink due to the wear on the mold.
I'm not a mold maker so I took him at his word. He said the early part of the production run will be on size and the tail end will be smaller.
I was hoping someone that knew the mold process at GM would take the bait and tell us. I hope that helps. BTW I always flow the manifolds to be sure.
Wouldn't the ports be bigger if molds wear and get smaller?

SSDiv6 08-17-2020 03:55 PM
Re: intake castings
 
Quote:
Originally Posted by Glenn Briglio (Post 621162)
Wouldn't the ports be bigger if molds wear and get smaller?
No. As the intake runner pattern wears with use, the runners get smaller and more material surrounds the pattern.

Ralph A Powell 08-18-2020 07:55 AM
Re: intake castings
 
With wear the sand core gets larger therefore a smaller port

curtis reed 08-18-2020 03:42 PM
Re: intake castings
 
Quote:
Originally Posted by Ralph A Powell (Post 621205)
With wear the sand core gets larger therefore a smaller port

That doesn't sound correct. If the core box that they use to make the cores was getting worn then the core would be getting larger. The core is what makes the plenum and runners, so they would also be larger.

SSDiv6 08-18-2020 05:34 PM
Re: intake castings
 
Quote:
Originally Posted by curtis reed (Post 621246)
That doesn't sound correct. If the core box that they use to make the cores was getting worn then the core would be getting larger. The core is what makes the plenum and runners, so they would also be larger.
In sand casting, the core box and the core are two different items.

For an intake manifold, the core box (drag), contains the sand and the intake runner core (mold). When the intake runner core wears, it reduces the dimensions of the core. That is the reason why many times you have core shift on new intakes, requiring further machining to make them fit on the engine.

https://www.meskan.com/Uploads/Images/Olds455Intake.jpg

curtis reed 08-19-2020 07:35 AM
Re: intake castings
 
Quote:
Originally Posted by SSDiv6 (Post 621257)
In sand casting, the core box and the core are two different items.

For an intake manifold, the core box (drag), contains the sand and the intake runner core (mold). When the intake runner core wears, it reduces the dimensions of the core. That is the reason why many times you have core shift on new intakes, requiring further machining to make them fit on the engine.

https://www.meskan.com/Uploads/Images/Olds455Intake.jpg

Gotcha thanks. We run thousands of castings through my shop each year and obviously I am confused about what I thought I knew. LOL


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