Big block rockers

http://www.clubhotrod.com/photopost/...0/MODEL-A4.jpgHello

I am new to this site so be gentle please. Anyway I put a 454 bored 100 over in a model A and exhaust valve on cylinder 8 kept backing out - I pulled it and found it was missing a chunk of metal - so rather than mess around too much I bought a set of full Roller compcam ultra gold rockers. I went through each rocker and adjust I thought appropriately but I seem to be getting so popping coming back through the carb. I am wondering is a tall valve cover required or perhaps I have an intake valve too tight - thoughts please? Thanks!!!

Welcome to CHR. You don't say what method you used to adjust your rockers, but I like the zero lash method where you back off the adjustment on all of them, then go down the line bringing each one down while lifting and spinning the pushrod to pull it away from the lifter, stopping when you just feel it make contact. When you've done them all rotate the engine 90 degrees and go through them again - the ones that were up on a cam lobe will be loose, others still just making contact. Repeat 8 times, through two full revolutions of the engine and all rockers will be at zero lash. Now tighten every one your prescribed amount of pre-load, I like 1/2 turn but many use 3/4 - you're wanting 30 to 35 thousandths of compression of the lifter plunger. It takes a little longer, but no tricks about firing order, intake or exhaust valve, and it's foolproof.

Here's a video showing the process, and there's another one like it from a really good Marine Engine shop down on Lake of the Ozarks. This one is kind of long, and if you don't want to listen to all of the "wrong ways to do it" skip ahead to 8 minutes - https://www.youtube.com/watch?v=5EGlb_VpTAw