Engine Knock and ISSUE

S

Sailormike

Member
hey guys,

Not to beat a dead horse but this weekend I was driving my a and she was running fine nice and cool and all of a sudden she over heated. I pulled over let her cool down and filled up radiation and rest of trip to carshow she ran fine. after the show cranked her up and had a knocking in the engine that I didn't have. I ran her back about an hour trip ran great didn't knock around 40 to 45 mph. only knocked when speeding up. I pulled pan no metal in it. also found there is about 35 to 40th play in crankshaft. would i rebuild motor as it was recently rebuilt. run it till it gets worse ect what do yall think?
 
You scored number 3or4 piston when it got hot. The engine was still a little tight and you were probably run it faster and maybe to lean, and the timing a little slow. Also you could have lots of rust in the water jacket on that cylinder. I think you will find it knocks most when cold.
 
I still don't know what 35 to 40th means, it was not answered.

Kinda hard to diagnose an issue without answers or good description.
 
I have .035 to .040 of play from front to rear in my crankshaft. Pistons and cylinder walls look good no scoring I guest what I should ask is should I pull engine rebuild it or run it as it is and rebuild if it gers worse
 
are you saying you have over a 1/32 end play, if so it will leak oil like mad out the rear main. If you mean .0035 to .004 it will be fine.
As far as the knock I would run it for a while and see what happens. I'm 95 percent sure you scored a piston.
 
With that much crank play, it may be the small rod end(s) are hitting the piston. The spec clearance there is .040 as I recall, but have seen less. You can check it out from the bottom. Move the crank from one extreme to the other. Move the rod big end from one extreme to the other. May need a soft hammer for this, depending on rod clearance. Sometimes you can eyeball that there is plenty of clearance with the piston at the bottom of the stroke. Easy to do if you are removing the caps to measure clearance which is not a bad idea so long as you have it down and there seems to be problems anyway.
 
old fashioned choke cable is termed bowden cable. It is still available in neighborhood parts stores such as Napa, Oreilly, etc.
Cut off a 1' piece. Remove the central wire that would have been connected to the choke butterfly. Now all you have is a flexible spiral wound outer sheath; stronger than speedo cable, and small and strong enough to get into tight spots in the water jacket
 
Bike or motor bike stores are a good source of Bowden cable. You might get old damaged ones for the price of a cup of coffee.
 
Even a short length of steel cable also makes a good tool to stick into the holes and spin around to knock out rust flakes and junk.
 
Update I looked at pistons the best I could with them still in the block I did not see any signs of scaring I think it is a tribute to a poor rebuild by previous owner I will look for a new engine to put in it
 
Sailormike said:
Update I looked at pistons the best I could with them still in the block I did not see any signs of scaring I think it is a tribute to a poor rebuild by previous owner I will look for a new engine to put in it
Click to expand...

You are not going to see it without taking out the piston. The way you tell is shorting out the cylinders one at a time and see if the knock goes away or makes less noise..
 
You must log in or register to reply here.
Back
Top