I believe i have a nasty lifter.. or a wicked rod knock. Im bettin more on the lifters tho. When i fired up the beast (70 mav 200 c.i.) it was makin a repetitive percussive sound. if i revved it slightly, the tempo would increase. I gave it a few sharp stabs with the throttle, and it ceased. Would this be a starved lifter? and if so, i believe i could use a fresh set anyway. It seems to peter out around 3300 RPM's.. as in just all out "die" but once it gets back to 3000 rpms she's back in action (im assuming valve float). should i used a magnetic pickup tool to fish them hydraulic lifters out or what? Thanks for any info fellow mav/comet lovers, Kyle B.
good luck with the magnetic tool. i replaced the lifters in my 250 last week. i had to buy a lifter tool. about $9 bucks at auto zone. jmo i would work the head while i have it off. i also did a rering, rod and main bearings. did the dura spark II also. i have a bad case of can't quit when i get started. i am doing the front disk swap today. the car with the donor disks has a new tailpipe and muffler i am getting it also.i told myself this is all i am doing for now. this started out replacing a freeze plug in the head sorry about getting off of the lifter subject.(cain't quit)..frank...
try the old screwdriver to the ear trick. Get a long screw driver and place the steel end on the valve cover above each piston and listen for noise. put the plastic end to your ear, screw driver works just like a stethcascope. If you can safely get under the car, do this with the oil pan. Do exercise EXTREME caution doing this, but you should be able to hear exactly where the noise is coming from. Generally a lifter will tap a lot faster than a rod knock. Rod knocks tend to be quite slower.
If you are a little freaked out about getting your grape under the hood you can use a broom stick . I think you can actually hear better because you are farther away . Also dont forget the fuel pump . Sometimes they are noisy too . The above post is also partly correct in the frequency of the noise . The camshaft will make noise at half the speed of the crankshaft because its gear is twice the size of the crankshafts . Or crankshaft noises will make noise at twice the speed of the camshaft . Depends on how you look at it .LOL
other way around, actually, the cam spins twice the speed of the crank. the valves can usually be heard tapping at twice the speed of a rod knock. For simplicity sake, picture the size of the crank next to the cam. Good idea with the broom stick, I always did get nervous putting my face so close to the spinning fan.
Thanks for the info guys. I believe that im just gonna go ahead and replace all the lifters... for peace of mind. It hasnt done it since yesterday, but its definitely something for me to worry about considering this is my daily driver (it becomes more and more apparent everyday ). And another thing... i noticed something strange today because my engine does seem to idle kinda rough. I went through the spark plug wires starting with #1... when i took it off it obviously started acting like it was missing, i replaced and did this with each and every wire. When i got to the fourth wire... i pulled it... and no audible or visual changes in the running engine. the spark plug wire throws fire. The plug is firing. The cylinder is filling. so i replaced it and will be making the venture to work tomorrow. I dont understand this. If anyone has any insight on this phenomina i would greatly appreciate it. (my 200 sounds rather worn out doesnt it LoL) Kyle B.
If a valve is hanging open because it's bent, or a bent pushrod, bad lifter, worn cam, etc., that cylinder isn't contributing to running the engine. You won't see a change in the idle when you remove the spark.
It's the other way around, the cam spins 1/2 crankshaft speed. That's why the crank gear is 1/2 the size of the cam gear. Rod knocks generally occur at a steady speed, give it some gas and accelerate and the noise goes away. Let off to slow down, and the noise goes away. Lifters are usually noisy in the morning at startup, then shut up after about 30 seconds of running. But, sometimes a piston can do the same thing. Confused yet? Good luck
you have a "dead cylinder" engine may or may not be shot. Could be the source of that noise....hmmmmm. before pulling ANYTHING apart to replace lifters, etc, run a complete compression test and/or a leakdown test on the cylinders. That will be an excellent starting point, as it will help lead you in the direction you want to go.
when you take the head off have it .030 or you will lose hp becaus the new head gasgets are .25 - .30 thicker than the original so you will lose compresson and hp
when i had my 170 in the car... i ran a bottle of rizlone... and the ticking went away... you could also use lucas oil stabilizer... if you didnt want to fix it right away that is
