Can 1.94 and 1.6 inch valves be put into 416 casting heads without modification, or what mods would I need?

 

you will have to bring them to a machining shop and they will cut the valve seats bigger. right now they are different diameters.

 

you need a carbite bit to cut the area under the valve seat

 

You don't "NEED" a carbide bit to cut the area under the valve seat, although it's a good porting mod - after the valve seats are cut by a machine shop.

 

I really thought you were better than that

not cutting the bowl is like putting a larger lid on a coffee can and expecting to get more coffee in the can

dont cut for larger valve unless you are going to do some major bowl shaping and yes you will need a carbite bit

 

ok ok, I mean physically he doesn't NEED to do that. He doesn't NEED to own the carbide bit and grinder while loading the heads in the trunk and taking them to the machine shop. However it's a VERY VERY VERY good idea to make sure to port the bowls before re-installing the heads.
I'm talking time-line wise. The valves will physically "go in" without the carbide bit work - although the coffee can lid analogy is very accurate.

 

To see the gain in airflow that you would expect from installing larger valves in the 416 heads, you need to "bowl hug" the area below the valve seat and do some porting. Don't be shy on the porting.
The bowl hog operation opens up the funnel under the valve seat. Needs to be 88%-90% of the new valve seat diameter. You can do it by hand or your machinist can rough it in for you before you do the head porting.
You'll need a new valve job and will also need to deshroud the chamber wall around the new valves a bit to physicly fit them in the head.
The chamber wall needs to be layed back about .050" where it is close to the valve edge.

You'll want to shorten the valve guide tops for high valve lift.
shorten by .200" for aftermarket posi seals. Drill and roll pin the rocker studs.
1.6 rockers need the 5/16" pushrod slot elongated toward the rocker arm stud.

 

 

If you were to replace the 76cc heads on a "stock truck motor"
(with factory dished pistons) with a head with a 58cc chamber and use a thin .015" steel shim head gasket (felpro 1094), your cr will be 9.8:1

 

trickflow has come out with a 58cc chamber a little wile back looked pretty good with flow numbers mid to high 240s maybe a little more money than reworking 416s an better flow they have 175cc int ports. chevy high performance used these on a beater 86 amaro with pretty good results. just another option.