The brass is part of the head gasket. That is a composit head gasket. Originals were copper clad so someone has been in that motor before you. On the subject of valve guides for your head redo, there is a difference of opinion on this topic. Quite a few years ago I was having original valve guides removed and replaced with stock type new cast Iron guides. They have to be essentially pounded out and pounded in. The head that this process was being performed on cracked during the process and I turned a perfectly good 848 235 head into an instant boat anchor.
So I no longer replace them unless absolutly necessary. Instead, the stock guides get drilled out and bronze liners are installed. From there, a good machinist can dial in the correct clearance between the valve stem and the guide. This is important (even more so if you are going to use stock style guides) because if the clearance is too tight, you run the risk of overheating the guide and the valve stem and they sieze up. I believe the bronze is easier on the valve stems, helps with the lubricity better then cast iron, and is more forgiving if the clearance is not 100% spot on. On the other hand, too loose and you are drawing oil down the valve and smoking out the tail pipe. I also think the bronze guides are easier to replace and easier to service.
Valve seals are another area to discuss with your machinest. The stock type seals are these crappy O rings that get installed on the valves. They lasted about an hour back in the day, with todays rubber, they last about 10 minutes. There are two alternatives. The first is to use what is known as an umbrella seal that goeves over the guide. They work pretty good. But if you have a machinest that is decent, you can also machine the top of each valve guide to install a more modern teflon seal, or what you may hear referred to as a PC seal (PC stands for Perfect Circle who I think developed these types of seals). These work really well. The one caviat, you machinest has to be sure the seal is not over efficient. The valve stems need some lubricant.
If you are having trouble finding springs or retainers, no worries. Its the seat pressure that is the important factor. So if you can't locate proper 261 springs, your machinest can use springs from another application, even if a larger diameter spring, by simply enlarging the seat in the head. I dont know that this will be an issue as there always seems to be decent GM offerings on eBay. One piece of advice I will give you is do not buy springs from anyone, including ebay, if those springs have any corrosion on them. Its not worth the risk of having a failure, particularily on the intake side as a spring failure will result in a dropped intake valve that the piston will then hit and bend and you are back to square one.
\Look for GM springs with the paint completely intact. Different years took different spring pressures, and there are differences between 235 and 261 motors also even though they look identical, so be particular and get the correct springs for your 261 (i.e., find the correct part number for your application).
Just my own two cents and opinion.
Last edited by Dragsix; 03/18/2022 1:52 PM.
