Vacuum Leak



After all the pain I went through, change oil, sparkplugs, timing, carb adjustment, new oil filter etc. My pony runs somewhat half powered. My mechanic said the number 5 and 6 valves might be clogged and not working at all. I end up buying a set of Detroit Gasket for my engine. I'm still in the process of learning of how my engine works.

Now my question are:

1. Given the case the two valves are not pumping, what are the steps?
2. Do I have to replace ALL my gaskets? I bought a new gasket for my water pump a month ago til I stumbled on this set which is a lot cheaper.
3. Should I got for a top overhaul or go for the complete one?

It's a 66 pony C4 200. Thanks :D
I would start with a compression check of the engine to determine which cylinders are not working properly. Compression should be around 140-150 assuming this is a stock engine with quite a few miles on it. You should not have more that 10 pounds difference between cylinders. I would buy the entire gasket set. If you pull the head and find damage to the pistons, rings, or cylinders, you are going to need the rest of the gaskets.

I assume your mechanic used other words than clogged or not pumping when talking about your valves. When you have low compression in 2 adjacent cylinders, you may have a blown head gasket. Since they are both the rear cylinders, it could be from burnt exhaust valves that are leaking or the head could be warped causing the head gasket to leak. I'm sure there may be another possibility or two also.