Engine Knock

Jay_G
Jay_G Expert Adviser
edited November -1 in HUDSON
Ok, I think I am looking for a good engine guy in Southern California. Please let me know if you know anyone. Here is my problem and what I have done to date. I have a new stroked 308 it was built a few years ago and was waiting to go into the car. The car is to the point that the engine is in, wired, plumbed, and connected to the exhaust. I have started the engine and thought things were great until I got the exhaust on and discovered a low knock coming from the front of the engine. At this point the engine has less than an hour total running time and no miles on it. I have talked to a few people who have said that the fuel/vacuum pump may be to blame. The car has an electric fuel pump so I removed the mechanical pump and blocked off the hole in the block. Still got the knock! I am going to check the timing and the tappet adjustment but do not feel this is the problem. My guess is a rod bearing gone. Any thoughts? The engine is a twin H with headers, the carbs have been re-jetted to make up for the extra displacement. It has a double roller chain, a ½ inch stroked crank, a mild cam, a Clifford head, and it is a hydromantic. I plan on checking any additional suggestions this weekend then pulling the engine if nothing works. My goal was to have the car done by the National meet, now that is in doubt. Any help is appreciated. I have already been talking to Bill A who has been a great help. I would go back the engine builder but he has passed on, so I need someone who knows Hudsons, any suggestions? Oh, oil pressure is good.



Jay

Comments

  • [Deleted User]
    [Deleted User]
    A rod will "knock" when you let up on the gas. A main will knock all the time. A cam will also knock if the bearing is bad, you should be able to tell a cam by noise location. In the end, it is hard and sometimes you just have to take it down. If it is a main, it main not show from visual inspection and take clearance measurements. Good luck.
  • russmaas
    russmaas Senior Contributor
    Pull the pan and check each bearing. Could be a valve hitting the head by chance. If the builder put in oversize valves the clifford head must be machined to cover the clearance.
  • faustmb
    faustmb Senior Contributor
    You could do what a friend of mine did; Turn up the radio until the knocking goes away. I wouldn't have cared too much except it was my car.:mad:



    He said his method worked great, but I wouldn't recommend it. He did say that as he increased the volume, the noise shifted from the engine compartment to the interior door panels...
  • [Deleted User]
    [Deleted User]
    Its a quick check to pull the pan and check the bearings. While your at it see if you can move the crank back and forth if you can the crank shaft spacer might be missing.
  • Unknown
    Unknown
    Jay, Call Perry Spring. 909 460 0736
  • Jay_G
    Jay_G Expert Adviser
    Thanks,



    I planned on pulling the pan just to see what I can see. I don't think it is a valve the noise is comming from the wrong location and I know the head was worked on to be sure no problems. Thanks Danny I will call Perry later on this week and get his take.



    Jay
  • hudsonguy
    hudsonguy Senior Contributor
    Jay,



    Definitely pull the pan to further diagnose. For what it's worth, I had a similar 'knock' to the one you describe that turned out to be one of the connecting rod nuts. The bearing cap was all 'chewed up' underneath this nut, so it was obvious where the noise was coming from. I think what happened is that the nut/bolt was overtightened when it was 'rebuilt' (by someone else), which prevented the bolt from stretching correctly during use. This is what keeps the nut tight over time, the stretching/contracting of the rod bolt. Mine were torqued to 70+ lbs. when I discovered this. I believe the specification is something like 45 or 50 lbs. (not in front of me at the moment). Good Luck.
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