hello. i would like peoples opinion on my setup i plan to have. i have an 84 camaro with a carbbed 350 in it. i plan on putting a pair of 416 heads that i have laying around on it. the heads have 2.02 valves and springs good for a .600 lift cam and have been ported/polished. and i want a cam with anywere from a .480 to .500 lift. my only concern is that the 416 heads will increase my compression to 11.1. but i had heard that the 2.02 valves would decrease my compression and i could run a bigger head gasket. is this true? would i have to get forged internals? and would the cast iron 416 heads be able to hold up to that compression? just lookin for some input on my build.

 

If those excessively large valves were ANYWHERE NEAR PROPERLY installed, the chambers won't be ANYWHERE NEAR their original size. With the more sensible 1.94" intakes and correct de-shrouding, they usually come out to around 62cc; I'd expect them to be even larger with the larger valves.

Here's what the CORRECT chamber work looks like, with 1.94" valves. Note that if the chamber wall isn't laid back around the valve, the edge of the valve is RIGHT UP AGAINST the "wall" of the chamber, meaning that the larger valve will actually flow LESS than a properly-sized one. I'm not sure you can even eat enough material out of there for 2.02" valves without hitting water, so you might have a set of basically ruined heads.



Not sure why you would think you're going to end up with such high compression anyway. That's probably a DRASTIC overestimation based on inadequate information. What's the short block? (piston part #s especially, please)

 

Yes you can run a 0.038" (crushed) head gasket which will help some on dropping a little compression. You probably have nothing to worry about and do not need forged internals.
For street gas just keep your tune under control and run a bit colder spark plugs to manage the higher cylinder pressure. If your cooling system is working well and you're not towing or anything like that you should be ok.

Make sure you don't have any sharp edges exposed in the combustion space. This would include the outer mating surface of your combustion chambers, the edges of the valve heads, and keeping any spark plug threads from being exposed. There are some photos in my sig link below for spark plugs and what to look for when test-fitting them into a head.

Higher compression generates more combustion heat, so you adjust your plugs accordingly. This is the case no matter what type of internals you are running.

edit: Every 416 head I have worked with has the EGR holes in the exhaust port bowls. I weld those up and regrind the bowls. For performance you want to keep the exhaust in the port and the heat away from your intake charge.

 

another question that i have is if i can put these heads on my stock 350 motor right now with the bigger valves and a very mild port polish job and still gain horsepower? because i heard that if you put done up heads on a motor that doesnt have a bigger cam in it then the motor will actually be slower and in some cases run bad. just wondering

 

What you heard is very false. Yes you will gain power with the ported heads.
Bowl porting and a performance valvejob increases flow at all valve lifts.
The ports are identical between the 305 and 350 heads. The only difference is in the valve and valve seat size, and the chamber width and volume.
Do good bowl work with a quality valvejob and you will have a great power gain.

 

Iv'e read other threads from sofakingdom before the guy seems pretty sharp, one thing I harp about is your quench area, with dished pistons your in trouble, but with flat tops measure how far the piston is at TDC, its usually about .020, pick a head GSK that gives you around .036-.040 clearance to the head.

When you get your quench right even though the compression is higher your detonation problems decrease. Remember good quench produces turbulence in the chamber making for a better burn.