View Full Version : 1948 pan head engin noise

03-10-2006, 06:43 PM
after startining no noise after bout 5 min. when warm to oper.temp. a lot valve clater runs fine! down the road @ 50 mph no noise is there a fix for this?? nothing lose inside! seems like when cyl.length grows the hyd.pushrods do not compensate!

03-24-2006, 07:58 AM
I was hoping that someone more knowledgable than I would chime in, but not so. So, my experience with top-end noise. If you have the original valvetrain with the hydraulic lifter at the top of the pushrod, what you are hearing is perfectly normal. It was for that very reason that H-D changed over to the later style with the hydraulics in the lifter body itself - it takes a while to get the oil warmed up and functioning as it should, especially with the hyd. at the top of the pushrod.

If your motor has been changed over to solids and aluminum pushrods as my '48 has, you will hear a bit of noise that will gradually diminish as the motor warms and the pushrods soak up the heat and then "stretch" (perhaps "expand" is a better word). The noise should become more quiet then.

Perhaps due to the aluminumm construct and the pans themselves, my pan motors seem to be a bit noisy in general. If the pans do not have the felt glued to the top (which sometimes can come loose and just sip atop the valvetrain if not properly glued), the noise is worse as the pan becomes a big echo chamber.

However, be sure to check out the integrity of the entire valvetrain. My '50 had a lifter roller freeze up, wiping out the top of the cam lobe. It was noisy cold, less so warm.

Also, it seems that if you have excessive clearances at the rocker arm block, between the rocker and the block, you will also have a noisy situation. You can check that by fiddling with the pushrods (pressure off the valve by rotating until valve closed, etc.).

Lastly, if you have the stock oil pump on an early pan, be aware that they do not seem to supply a lot of oil at idle and it is not uncommon for the light to come on at an idle when hot.