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Old 11-14-2002, 10:07 AM
Super Streeter Super Streeter is offline
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The bigger valves wont effect where your engine makes power,but it might hurt performance all over.When putting larger valves into your heads you need to make sure you have suficient clearance around the valve inside the combustion chamber,as well as proper clearance between the edge of the valve and the cylinder wall if the camshaft is really big.Bigblock combustion chambers are wider thn smallblock chambers which gives the valve more room to breathe,and the valve are canted toward the middle of the chamber so that they open away from the cylinder wall,and any 396 built for performance will benifit from having the top of the cylinder bore relieved in the area of the intake valve.In the case of the smallblock,most stok production heads dont have enuff material to support installing the bigger vlaves because if you relieve the chamber as needed you will cause the head to become thin.On many small aftermarket heads you wont have enuff room for a bigger valve,but you usually can have the chamber cut to clear the valve.400's have a big bore so you might be able to keep the reshaped chamber matched to the size of the bore.After installing the bigger valves,you need to blend the bottom seat angle into the bowl area as well.any time you can put bigger valves in any chevy engine and do the job right,the engine will make more power all over the rpm range and more torque as well.In all chevy engines,both bigblock and smallblock,the intake valve is a bottle neck,and as long as you are putting the bigger valve in right,the engine will kep making more power.Good luck.
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