oversize valve question

super duty04

super duty04

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Aug 4, 2009
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Can anyone tell me what is the largest valves that will fit in a stock cummins bore? I am looking into a set of 1.870" intake valves and using the stock 12 valve intake valve on the exhaust side which I believe is a 1.775". Will these fit without notching the bores? Any help is greatly appreciated.
 
My valves are only 3mm larger than stock and the machine shop that installed them said i could have went bigger. Those valves would most likely fit with out notching
 
I wouldn't recommend putting the stock intakes in the exhaust ports. Because of the 30 degree seat angle and thinner head of the intake valve. I've installed several sets of the mountain high valves they are nice pieces if you are looking for a direct replacement.


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jupton said:
I wouldn't recommend putting the stock intakes in the exhaust ports. Because of the 30 degree seat angle and thinner head of the intake valve. I've installed several sets of the mountain high valves they are nice pieces if you are looking for a direct replacement.


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What is their pricing like for the 12v sets? I am on the fence about going bigger and couldnt find it on the web page
 
bigstacks95 said:
What is their pricing like for the 12v sets? I am on the fence about going bigger and couldnt find it on the web page
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I'm not sure what the pricing is currently, I believe it is going up a bit due to an increase in material cost or something. I think I paid around 360 a set for the last few sets I got. That's for valves and seat inserts.


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Remember when going over valves, don't think about just the size. Think about the following too

Port restrictions
~wall and roof limitations
Angle from the stem to the head
~tulip verse nailhead etc
Stem diameter
~can there be a more narrow stem employed?
Discharge Coefficients
~can you flow more EFFICIENTLY with a SMALLER or LARGER valve? Would the rule of thumb in wall to valve clearance be slightly different??? Or would it stay the same.
 
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