MTFCA Forum

I have a rebuilt engine and when in operation there is a knock when i advance the timer sounds like a loose piston [new pistons..20 over] .003 rebore== on this rebuild the rods are good clearance the next thing i can think is rod side to side clearance i never checked them i ordered from Langs

forgot to add the crank is standard original

likely a bent rod or loose bearing

Are you maybe just getting too far advanced?

Another thing that sounds like a crank knock is the cam shaft, any more than several thou end play (float) on the front bearing will do it. A thrust washer kit can be bought to stop this.

Kerry , will the cam shaft movement do this only on a retard position ?
the bearings are good , a bent rod that is what also comes to mind
i got the set from langs , don>t they correct this on this rods when you get them ??

Likely a slightly bent or twisted rod. The re-babbitted rods from the major vendors do need to be checked for alignment and often require adjustment before installation. A minor bend or twist will likely be quiet at first and show up sometime in the 1,000 to 2,500 mile range. A properly aligned rod, even with excessive side clearance generally will not be noisy.

Some people do not hold the wrist pin in place when tightening the wrist pin bolt and you bend the rod causing a knock?

I did the pin bolts with a rod in the pin hole held on a vice as to not bend the rod
could i have gotten 7.5 advanced cam gear instead of standard ?
just wondering .... i will have to check

Describe the conditions under which the knock occurs. Is it at idle? Is it pulling such as accelerating or going uphill? Is it going downhill? Is it going along without either pulling or slowing down, just a steady speed? Different conditions cause different knocks to appear. If you have the oil inspection plate off, crawl under the car and have someone slowly turn the crank as you look upward toward the rods. If you have front to back movement of the rod on the crankshaft, which changes direction when the rod goes either up or down, you have side movement in the rod. Some knocks occur when the spark is too far advanced for the driving conditions. Such as pulling with the spark fully advanced. Try retarding it a few notches and see if it helps. That type knock is normal and can be regulated by slightly retarding the spark. The more modern cars with a distributor have a vacuum advance which advances as the vacuum increases. Since the vacuum drops as you accelerate, the spark automatically retards on those cars. On a T you must do it manually.
Norm