right now I have 1.5 roller tip rockers from summit on my heads, i'm running a sum-1103 cam (214/224), would I be able to switch to 1.6 rockers without any modding, or would I need a diff cam to support the 1.6? would there be any gain from going to 1.6?

 

You will need to pin the press in studs on the 416s or you risk them pulling out with the higher gross lift the 1.6s offer. You can do this yourself with roll pins and an electric drill even with the heads on the motor if you are careful. You do realize what changing a rocker ratio does to gross lift, right? The lift and duration at the valves will be larger -- ie it will make your cam effectively larger. A cam size has nothing to do with "supporting" a different ratio rocker.

 

yes, i understand that, what I meant by changine the cam, was sometimes they list specs for the cam and they say for 1.6 rockers. Thats all. Are my studs screw in or pressed in? Is it possible for my to tap the head to all for screw in studs, or do I need a shop to do it? I understand the heads are steel.

I have flap top pistons with 2 valve reliefes, is there enough PVC to work with 1.6 rockers?

 

You have pressed in studs (I run the same heads). Yes you can tap for screw in studs, you would probably need a 3 pc tap set that has starting, intermediate, and bottoming taps to get enough thread depth. It is easier to pin the studs -- this involves drilling a hole through the stud boss, and through the stud, then out the other side, then installing a roll pin. This is not as strong as a screw in stud, but in applications up to low 500s lift is usually good enough. Your piston to valve clearance should be fine -- 1.6 ratio rockers makes your exhaust lift 0.496" instead of the .465" it is currently. I am running .485" lift w/ 1.5 rockers without pinned or screw in studs on the 416s because I'm lazy, and have no problems so far with high rpm use, but I do plan to pin them sometime soon.

 

which pistons are you running?

 

Just because you are close to the topic:

What is max lift on these heads prior to hitting the stock guide boss. Will he be ok with .496 lift on stock height guide bosses?

 

I'm at .485 on stock bosses and I'm ok. I can't say any more than that though, I don't know. I'm running a 1967 327 with Speed Pro Forged flat tops (not exactly useful to you but that's what I have)

 

You'll probabily not see any gain by going to 1.6's on the exhaust side, but will likely see a gain with 1.6's on the intake side. you may/ most likely will need to lengthen the pushrod guide slot in the cylinder head as with 1.6's the pushrod rides a little closer to the rocker stud than stock 1.5's. (The push rod may rub on the slot) There is a "louis tool" drilling guide just for this mod but I've done it many times by hand using a 5/16" rat tail file in an electric drill to elongate the slot. make it longer, not wider.

here is a little picture for ya.

 

thanks. I will think about this some more. I dont know if it's worth it or if I should just wait for votec heads. I will most likley end up doing it since I have no money for new heads