Hi, First off, like the new message board! I have a newly rebuilt 302 with 1969 351W heads. I've noticed that i have a lot of valve noise...but how is that possible? The heads were completely rebuilt and the studs are fine. I have a new cam and new lifters. I have PLENTY of oil pressure. The rocker arms are non-adjustable and are properly torqued (to 20 ft-lbs)--and staying that way. I have new fulcrums. My only guess is that my pushrods might be too short? It's a 1980 motor, and i just reused the pushrods out of it. According to the computer at Autozone, the pushrods are all the same length from '70- at least '84. I bought a set just the same, and i will compare them tomorrow. Just wondering if i could have overlooked anything?? What could cause this? It seems like i'm barely getting any lift either (on a cam with about .450 of lift). ALL of the valves (or so it seems) are making noise. Thanks! Chris
Could be a couple scenarios here. First, I am assuming that this is a hydraulic flat tappet cam. Even though you are using non- adjustable rockers, there is certain degree of preload that is required. That is, after the valve train is set up the plunger in each lifter (when the lifter is all the way down the lifter bore or the valve is closed) must be compressed approximately .030". I noticed that you stated that the valves are barely lifting off the seat. That is cause for concern. Do the rockers seem excessively loose? I would then check for bent pushrods. Bent push rods are a sure sign of mechanical interference (i.e. coil bind, valve to piston contact, retainer to guide contact). If the pushrods are fine and interference is ruled out, I would turn my attention to the camshaft itself and determine if the lobes are in good shape. You would ideally want to put a dial indicator on each lifter and confirm that lobe lift matches the your cam card. The cam is gone if the actual lobe lift is less than the indicated lobe lift. Also, double check your oil to see if there are any obvious signs of metal contamination. Hope it all works out for the best.
THanks for the response, Fred! You are correct, it is a hydraulic flat tappet. The cam is brand new as well as the tappets (less than 1000 miles on everything). The rockers DO seem excessively loose. I will check for bent pushrods, but i'm having a little bit of difficulty believing that could be it....ALL of the valves are making noise, and my cam is not very large: 204/214 with about .450 lift. The pistons are only a slightly higher compression than stock, with my total compression being around ~9.5:1 (60 cc chambers on the heads). As far as adjusting the rockers, i don't belive there's much to do there! (is there?!?!). Following the firing order, on the compression stroke of each cylinder, i torqued the rockers down to 20ft-lbs (book lists 18-20). I noticed that they seemed excessively loose, even though the pump had been primed. What i'm wondering is if there is any difference with the 351 heads, i.e. if i need a slightly longer pushrod? To confirm my suspicions, i have very low vacuum....about 10hg at the carb.
Did the old engine or 351 us valve lash caps? Check and see. I had a 302 in an LTD, and when they did the engine, they did not put the lash caps back, and it made a lot of noise. Check it out and see. Good luck, Earl
chris, didn't anyone see this when assembling the valve train? The push rod length should be 6.905" in length. Remove one and check it's length. The valve needs to move about .430" +/- for a stock cam. Pushrods you used are for use with a different kind of rocker assembly.
It appears that I was a little unclear in my last post. I'll attempt to clear things up. First, check for proper lifter preload. With the lifter on the base circle of the cam, tighten the rocker arm adjustment nut to the proper specs. The plunger should be depressed about .030". Insufficient preload is an indication that longer pushrods are needed and stop here until you get the correct pushrods. If the pushrod situation is fine, then it would be necessary to check for excessive cam wear. I also do not think that bent pushrods are your problem but just wanted to let you know what all the possibilities are. I agree with Ken that it is more than likely pushrods that are too short since you apparently have no engine damage.
CACollo, Not to be blatently obvious, but is there any chance that the valve timing could be "one tooth off" on the timing chain? I've seen this before (on a 'Stang) and the valves were ever-so-lightly tapping the pistons. (Luckily) it didn't do any damage and re-stabbing the timing marks where they should have been cleared it right up. Judging by what your saying, that ALL the valves are making this noise leads me to think even moreso that this is the problem. I know its a pain to yank the timing cover,etc but might be worth a look. Also, (outside chance), check for bad lifters and broken valve springs (!). I know it sounds "out there" but better safe than sorry. Good luck, Tracy
