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3 questions, valve gaping? Compressions? and detonation?

1158 Views 2 Replies 3 Participants Last post by  MI2600
Hey guys,

I just did a light overhaul on my 77 chevy 350, 1st I adjusted the valves by counting 3 threads from top down, the only way Ive been shown around this backyard shops is to do them by "HEARING" the valve, loosen it till it makes lil noise then tighten it 1/4 turn, what is the proper way to Gap the Valves. #2 I had the head rebuilt, i changed the rings and placed the opening of each ring in the proper place on the pisting(top ring 1030, 2nd ring 230, and the botton ones one right on top and the other one right in the bottom. the walls are good, you can still see the houning marks in them, so i did a compression test
(after i did all this)
1=120, 2= 120, 3=70,4=95,5=100,6=95, 7=90, 8=90
Im not a mechanic but I thought the compression after I did the rings and head jobs should be like at 130-150? 3rd what causes bad detonation? or something like that, ive been reading on here and it sounds like my friend my have that problem, he things its a bad rod bearing making a sound, but on here something else said could be the problem for making some kinda noise, so whats couses that detonation, and how can it be fix(FOR A 53 straight 6 chevy), thanks guys! this site has all the answers, LOL well most of them

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To set your valves, roll the engine to TDC #1 compression. Set both valves on #1 (tighten nut untill you have just zero lash, then an additional 3/4 turn). Turn engine in direction of rotation (the way it would turn if it were running) 90 degrees. Set both valves on #8. Turn engine another 90*, set valves on #4. Turn 90*, set #3. 90*, then #6. 90*, then #5. 90*, then #7. 90*, then #2. Try a compression test after resetting the valves, it should come up.

For your detonation, usual suspect is timing, and carbon buildup. If it is timing, set timing to factory spec. If timing is okay, and you suspect carbon, GM makes a kick *** product called Kleens. You set the idle to around 750 RPM, and fog this stuff into the carb, then let it run for 20mins. to 1/2 hour. Then go flog it for a few miles.
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Q#1: I agree with the valve adjustment procedures, as noted above, but I only go 1/2 turn after zero lash. Some even say 1/4 turn. After break-in, I go back and recheck them running and warm.

Q#2: Did you rehone the cylinders before you installed the new rings? They need a fresh surface. Have the rings even seated yet? It sounds like the engine is still fresh.
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