The 336 GMC/Pontiac engine in my 1958 GMC 100/manual trans has developed a chirping/squeaking noise and I am at my wits end where it could come from... I overhauled the engine over the last winter with new camshaft, lifters cam bearings, conrod bearings, re-ground valves and seats, new piston rings etc. and the engine initially ran more or less fine. After driving the car for maybe 60 miles the strange chirping noise first occurred when the engine was hot. I first thought it was a bad alternator bearing and renewed the alternator but without success. I have now driven the car maybe 250 miles and the noise is now always present, right after startup of the engine. It tried to catch the noise on video and it can be heard here: http://youtu.be/ChBEPZHVPsw At idle it chirps about once a second (a bit faster) and increases in frequency parallel with engine revolutions. The following I have already tested: - Took of the belt, so that alternator and water pump don't turn - noise stays the same - Took out the distributor. It turns freely without any noises. Lubricated everything and put it back in...still the same noise - Removed the flywheel cover to check for any contact between flywheel and starter, checked the pressure plate bolts - everything o.k. - Checked the intake manifold and carburetor bolts - all fine The noise is very hard to pinpoint but checkign with a stethoscope it seems to come more from the rear part of teh engien than the front I am now more or less out of ideas what else to check...for me it does not sound like a damaged bearing. I would really appreciate input from anyone who maybe experienced the same and/or can point me in the right dircetion what to look for. As the noise seems to be increasing I do not like to continue driving the car, fearing to cause any furhter damage..
Someone recently had this same issue. Look under the truck for anything that is contacting/rubbing the exhaust system.
You may want to check it for an intake leak, they can churp and make you go nuts until you find it! Gary
..I would pull the valve covers off and run the motor listen/looking for the sound coming from the rocker arms,push rods etc....
While running pull the plug wires one at a time if the noise stops it'll have something to do with that hole,but it does sound like a manifold gasket,check the intake with wd40 while its running if it changes rpm pitch that would be the prob,and check flywheel bolts one may have backed up a bit and is rubbing.
Sounds like you might have a dry rocker ball.Isolate the side that it is on(you can use a long screwdriver like a stethoscope)and pull the valve cover to check to make sure all are being oiled.
I'd double check what has been mentioned about the rockers. They are stud oiled and the passage may be blocked. They get oiled from number 2 and 4 cam bearings so long as you got them lined up properly.
X2 I've had this problem years ago. the oil passages in the studs are small and prone to clog up. worst case scenario is your cam bearings.
Great tips everybody...thanks! As always the H.A.M.B. provided the solution quickly... As repeatedly suspected above it was a dry rocker ball/arm. The rearmost rocker****embly on the right hand cylinder bank was completely dry and the ball in the arm already pretty scored. I would never had thought that a dry rocker****embly would make such a chirping/squeaking noise. The pushrod was supplying some oil upwards but nothing came out of the rear rocker stud... I ordered a new rocker arm and ball to replace the scored parts but I have yet to figure out a way to free/clean the blocked oil passage. Hopefully it will be possible without dismantling the whole cylinder head Thanks again everyone for the helpful comments.
Questions.....How does the oil get to the rocker arms?..I have never seen gm rocker arms like you have in the picture,..all the rocker arms I have seen have a hole in the area where the push rod makes contact and the oil comes up from the lifter through the push rod and then into/onto the rocker arm and ball stud....does this motor have a different way to get oil to the rocker arms??...thanks miller
Try running the engine without the 2 rocker arms installed, and see if the crud in the oil system will blow out of the passage from the oil pump pressure. May want to remove the plug in that cylinder also when doing this.
On the older Pontiac type motors the rocker/ball nut is oiled via the rocker stud. A (real) small oil hole is located about halfway up the rocker stud and gets oil from the longitudinal oil passage in the cylinder head. I do not know when the design was changed to oil supply from the pushrods (I know my '65 Pontiac does not have the rocker stud oil supply). Fortunately only one single aft rocker was dry, so the main oil passage in the cylinder head seems to be free. I will remove the ball nut and rocker arm and run the oil pump with a drill to see if I can push out the blocking crud...
try a piece of wire in the stud hole first to see if the crud is right there , , you could try a oil in the can with a straw ( CRC or WD40) and try to blow any crud back and/or loosen / break it up . compresses air with a rubber tipped blower nozzle might also do the trick . the inside passage is about 1/16th Dia ( 1.5 mm ) often when a set of heads are rebuilt if the builder is not familur with them they do not blow them out backwards when they clean them and all the crud plugs them up when they see oil pressure . only other way is to pull the stud and then have a new one pressed back in ( freeze the new stud so it will go in easy , they don't reccomend reusing the studs because they will not grip because they were compressed , you could use a hollow pushrod and newer style hole in rocker if you lifters pump oil . but I would only do that in a extreme case .
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