I am planning to upgrade the iron double hump heads on my 383 stroker. If the only change I am making now is the roller rockers do I need to install guide plates? What determines the need for guide plates? I have asked around but most of the answers are rather vague.
Depends upon the heads. Some heads were machined for screw in studs (required for roller rockers) and had guide plates beneath the screw in studs. The earlier pressed in studs used slots machined into the head casting to guide the push rod. Late model Vortec heads have screw in studs (metric) but they do not have a hex on the base to hold a guide plate. Instead they rely upon a slot that restricts both valve lift as well as push rod diameter.
If you are going to go to roller rockers I recommend stepping up a diameter in your push rod size (jump from the 5/16th size to at least a 3/8th diameter chrome moly push rod). This requires having a larger slot in your guide plate to match the push rod's increase in diameter.
I have had two different customers drag their car into my shop complaining about brand X cams only to discover they had bought a high lift roller cam with bigger push rods but kept the old stock 5/16th inch guide plate slots. The lifters were trashed the cam lobe wiped and three push rods were bent but it was all that *7^%$ cam companies fault of course.
These were the same guys that were usually Holley experts that later changed over to an Edelbrock carb because Holley makes junk. No need to read the instructions if you know everything already.
You can get self aligning roller rockers. The bigger issue is that there are much (much) better heads out there than the old double humps, especially to use on a big 383. Do your stroker a favour, and put the money into a set of dressed heads instead of throwing expensive parts on old tech.
Thanks for the responses guys. I fully understand that my heads are not good for horsepower, but this whole thing is a process. I've owned this car since 1978 and did some drag racing in the early 80's with a 327. In the mean time university, marriage and kids got in the way of hotrodding, but now I have some more $ to spend on the car. I built the 383, then broke my driveshaft. Now I am working from the back to the front, so heads will be the last thing. I just wanted to finish the valve train with roller rockers to compliment the roller cam.
I think I should update and answer my own question. I purchased my roller rocker from Summit and got them installed last week without guide plates and without any problems. Because the Chevy heads have pushrod holes in them there was no real need for guide plates. I will probably need them when I upgrade to aftermarket heads.