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Indy CNC 300 heads

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DragRacingSpirit View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote DragRacingSpirit Quote  Post ReplyReply Direct Link To This Post Topic: Indy CNC 300 heads
    Posted: Mar/01/2019 at 2:56pm
Does anybody have a set of cnc300 heads that are not on the short block to measure the valve spacing and overall width of the intake and exhaust valves ?

Indy doesn't recommend running them on less that 4.375 bore and I was wondering how close the valves would be to the cylinder wall of my iron block which is 4.250" bore and hard blocked.

The CNC 300 heads have a valve size of 2.25X1.81 which is = 4.06".

That would leave .190" total clearance or .095 on each side to the cylinder wall depending on the space between the valves.

Any comments ? .095" to tight concerning valve shrouding ?

I don't think a 300cc port would be to big for an all out racing 442ci motor. 4.250"X3.9"
Best 1/4 mile 8.99, 1/8 mile 5.71, 60 foot 1.27, no power adders
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Post Options Post Options   Thanks (0) Thanks(0)   Quote PROSTOCKTOM Quote  Post ReplyReply Direct Link To This Post Posted: Mar/01/2019 at 5:14pm
I am sure Kevin (Stickshifter) can provide you the answers you seek. Since he did have an iron block and switch to the Indy block.

Tom
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Post Options Post Options   Thanks (0) Thanks(0)   Quote PROSTOCKTOM Quote  Post ReplyReply Direct Link To This Post Posted: Mar/07/2019 at 6:53am
Did you ever find the answer you were looking for?

Tom
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Post Options Post Options   Thanks (0) Thanks(0)   Quote amxron Quote  Post ReplyReply Direct Link To This Post Posted: Mar/09/2019 at 1:41am
Remember the valves are not in the center of the head so you don't get the full bore width.
 
Bolt a head to an empty block and turn it upside down on an engine stand and you can see the clearances.
 
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DragRacingSpirit View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote DragRacingSpirit Quote  Post ReplyReply Direct Link To This Post Posted: Mar/09/2019 at 2:25pm
I was wondering about the clearance before I bought them.

I was hoping someone that has a set could put them on an iron block and check the cylinder wall clearance.
Best 1/4 mile 8.99, 1/8 mile 5.71, 60 foot 1.27, no power adders
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Ken_Parkman Quote  Post ReplyReply Direct Link To This Post Posted: Mar/09/2019 at 3:11pm
I know it's not the question you asked, but 2.25 on a 4.25 is 53%, and that is really a lot for a wedge chamber. Especially with the 1.81 exhaust. Maybe the 275 cnc heads with the 2.19" intake might be a better plan.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote pfordamx Quote  Post ReplyReply Direct Link To This Post Posted: Mar/12/2019 at 7:10pm
i would do a 2.25 and a 1.65 thats the way every none amc head is going you put in as much intake as you can use whats left for the exhaust and adjust the cam accordingly. oh and people ran brewer heads with 2.25-1.81 valves on iron blocks and both heads are based off bbm valve placement i think they would fit the question is would it be shrouded enough to take away the advantage i'd think you would want all the valve area you could get. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tsanchez Quote  Post ReplyReply Direct Link To This Post Posted: Mar/27/2019 at 5:33pm
I looked into this at the PRI show and looks like the cnc 275 heads may be the better choice, but I want big so waiting till I can afford the cnc 300 and indy block and go from there. Currently moving the pushrod holes on my SR heads and going to a 2.15 intake valve, well see how it goes, should remove about .150 from the pushrod pinch area.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote tsanchez Quote  Post ReplyReply Direct Link To This Post Posted: Oct/18/2020 at 6:31pm
Well i have the cnc 300 heads here if you need measurements

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Post Options Post Options   Thanks (0) Thanks(0)   Quote DragRacingSpirit Quote  Post ReplyReply Direct Link To This Post Posted: Oct/19/2020 at 12:32pm
Bolt them to a block, roll it upside down and check it out visually at differing points of valve lift.

Best 1/4 mile 8.99, 1/8 mile 5.71, 60 foot 1.27, no power adders
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