Hercules engine knock

[harry chapin]

I have finished rebuilding my HG 42 and it drives well with the auxilary gear box added. BUT...just running the engine that was suposed to be OK for about 15 minutes, it has developed a KNOCK !!! Using a stethascope...the worst noise comes fron the front of the oil pan. Is there a way to tell if the main bearings or conrod bearings are at fault??

[Dusty]

In many cases if it is a crank bearing it will be more of a rumble than a knock, A rod will be more of a consistant knock with RPM. piston slap will tend to quiet down when warmed , but not all the way. wrist pin will sound high while rod bearing will sound low. any way you look at it, its best to pull pan and check out rods and mains before you run it any more. I just went through crank grind, sleeves pistons, bearings rings etc... its extensive and expensive, in many cases if you catch it early you can save save save$$$ with that said there are numerous things to cause a knock. If you have High oil pressure when cold and drops extreme when warm it generall points to main bearings in combination with rumble down low and or main oil seals leaking. A spun or extremly worn bearing will usually just create constant low pressure low or no oil pressure and a low knock would send me straight to rod bearings, This is not always the case but as general observation. hope this helps, Dusty

[John Schwiebert]

I can not believe nobody jumpered on this a couple of days ago. First question and I hate engine noises. Have you shorted out at least the front 2 plugs(one at a time) and then what happened to the noise. How much backlash did you have on the timing gears?

[harry chapin]

Thank you for your inputs....I did a pressure diferential check yesterday....NOT GOOD ! # 1 cylinder  16/24 lbs....#2,3,4  00/24 !! there was blowby through the head gasket on #4 .  So...it will be a major overhaul....!!??
No I did not ground out # 1 & 2 cylinders to hear the difference sounds. I would much rather just drive the little crawler than take it all apart,but it has to be. Are head gaskets still available