Can someone explain the steps for setting the valve lash (cold) on a GMC 228 or equivalent? My book says .020 intake and .012 exhaust. Also my gasket set came with two sets of manifold gaskets that seem to each be made of a different material. One set has larger intake openings. Do the larger GMC engines have larger intake ports? It would make sense. I just want to make sure that I'm not supposed to use both sets.
Depending on which book you use you will see different settings. I use .012 on the intake and .016 on the exhaust when hot. Cold start up can be set .002 looser and reset when hot. The 477-412 and 819 heads have the small ports. Some 270's use the 417 large port head (rare) and the 302's all use the large port 983 heads. Gaskets will not interchange.
Joe
just retired and finally making headway on my project truck. 1940 GMC AC152.
Just wondering if there is an actual documented procedure out someplace there for initial setup. Have looked many times, but never found one.
So, like gmc-is-me, I took the hot spec, added 0.002" - 0.004", then reset when hot.
BTW, made this in excel to know which valves can be setup on #1 compression/exhaust. Keep it on my smart phone so I (hopefully) can find it when I need it.
It is for the 2136000 cam, and is in 10 deg. increments, but should be close enough.
You can use a "technique". The advantage? It requires fewer crankshaft turns. Or, you can understand how the 4-stroke cycle works. The bottom line? You should only set a valve when it's closed. If you don't know when that is, you need a technique.
The purpose of specifying lash? It's an estimate of how hot the engine parts (especially the exhaust valves) will get, and from that how much will they expand in any service they're likely to experience. It's slightly more than enough to allow the valve close completely every time. Beyond that it just makes noise and wears out faster.
