Ajgkirkwood Posted December 1, 2017 Report Share Posted December 1, 2017 (edited) Hi there. I was wondering if anyone know the shape and size of the intake and exhaust ports on the 25" block. Block is question is a 265 from 54 but im assuming the 25" blocks all had the same port sizes and shape? Im getting an intake and dual exhaust for my engine but i plan to make my own intake and exhaust header. What i like to know is the size and shape of the ports on the block so i can use measurement from the intake and exhaust header im getting put know the diameter/shape of thr engine ports to match them as close as possible together. I dont want to remove the intake off my car just yet to keep it mobile till i get closer to be done it Edited December 1, 2017 by Ajgkirkwood Quote Link to comment Share on other sites More sharing options...
Brad47 Posted December 1, 2017 Report Share Posted December 1, 2017 Adam h just posted about making his own for a 230 , maybe you could ask him ? He looks like he knows what he’s doing they turned out mint !! 1 Quote Link to comment Share on other sites More sharing options...
martybose Posted December 1, 2017 Report Share Posted December 1, 2017 Just buy a gasket set and use the manifold gasket as a guide. Marty 1 1 Quote Link to comment Share on other sites More sharing options...
Ajgkirkwood Posted December 1, 2017 Author Report Share Posted December 1, 2017 2 minutes ago, Brad47 said: Adam h just posted about making his own for a 230 , maybe you could ask him ? He looks like he knows what he’s doing they turned out mint !! I just sent him a msg so ill hear back from him hopefully Quote Link to comment Share on other sites More sharing options...
Ajgkirkwood Posted December 1, 2017 Author Report Share Posted December 1, 2017 3 minutes ago, martybose said: Just buy a gasket set and use the manifold gasket as a guide. Marty Haha i didnt think of that. Do the gasket set sizes match up to the motor? I guess if i was even bigger then the gasket diameters. The gasket size would restrict it Quote Link to comment Share on other sites More sharing options...
dpollo Posted December 1, 2017 Report Share Posted December 1, 2017 The gasket holes match the manifolds. The block's ports are a little smaller . I use the gasket as a template to enlarge the block's intake ports so they match the manifold. The 25 inch engine has larger ports than the 23. Quote Link to comment Share on other sites More sharing options...
Matt Wilson Posted December 1, 2017 Report Share Posted December 1, 2017 (edited) I went out to the garage just now, where I have a bare 251 block, which I'm going to convert into a 265. I used calipers to measure a couple of intake ports and a couple of exhaust ports. The intakes are 1.375" or very close to it. The exhausts are 1.310" or very close to it (probably actually 1-5/16). I also took two measurements of each port, 90 degrees apart from each other, and got the same numbers, so they are circular in shape. Edited December 1, 2017 by Matt Wilson Quote Link to comment Share on other sites More sharing options...
Matt Wilson Posted December 1, 2017 Report Share Posted December 1, 2017 I also have a 230 block (23" block, of course), so out of curiosity, I measured its ports, and the intakes are 1.312" (probably actually 1-5/16), and the exhausts are 1.25". Quote Link to comment Share on other sites More sharing options...
Adam H P15 D30 Posted December 1, 2017 Report Share Posted December 1, 2017 Funny, my 230's ports were all 1.25. I'll remeasure when I get back into town. The gaskets were larger and if I didn't have a freshly rebuilt engine I would have matched the portsto the gaskets also. The headers I used were the small primary tubed SBC headers, I think 1 5/8 and they were plenty big for my 230 Adam Quote Link to comment Share on other sites More sharing options...
Ajgkirkwood Posted December 1, 2017 Author Report Share Posted December 1, 2017 1 hour ago, Matt Wilson said: I went out to the garage just now, where I have a bare 251 block, which I'm going to convert into a 265. I used calipers to measure a couple of intake ports and a couple of exhaust ports. The intakes are 1.375" or very close to it. The exhausts are 1.310" or very close to it (probably actually 1-5/16). I also took two measurements of each port, 90 degrees apart from each other, and got the same numbers, so they are circular in shape. Wow thank you for measuring it out! Everyone replying thank you. Looks like i sparked some interest in the sizes for others too. Glad to know they are just round circles. Gonna make things alot easier. If the gaskets are alittle bigger then the ports then i could round the corners of the ports to smooth the air flow on them Quote Link to comment Share on other sites More sharing options...
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