Was helping a friend of mine swap the cam in his 302, 74 motor. put it all together, everything seemed good, the cam turned right around when put in, checked piston to valve clearence, .150 on both I and E. started it up last night, took it to 2100 r's to break in the cam, sounded great. 4 minutes into the break in it just stopped like someone shut it off. for some reason it sheared the timing gear pin on the cam. any ideas, any one ? what caused it ? Thanks, SS :confused:
Nothing in the oil that i can see, nothing on the magnetic plug on the rear sump. will check out the front one tommorow distributer seems fine, (other then the fact that it doesn't turn!!!) looked good when we pulled it out, turned freely ,will check out the timing gear tommorow( never thought about that one) thanks
Dumb question, but the cam bolt was plenty tight wasn't it? Another possibility would be the cam and crank gears not being aligned, causing stress on the cam gear. check the chain for wear on the inside of the links.(long shot). Was the dowel pin driven into the camshaft far enough?
A couple thoughts I have, when installing the cam did you leave the cam thrust plate a bit loose and then position the timing gear in it and check for free movement? I always do that and then carefully remove the gear and finish torquing the retainer bolts. This aligns the gear hub with the bore in the plate for smooth rotation. Also if the dowel is too long the gear retaining washer will not seat flush, most aftermarket cams come with two different lenght dowels. Something has caused an abrupt halt in rotation to shear the pin. ie, object caught in chain and gears, bolts, nuts, tools in rotating assy. Cam gear hitting timing cover etc. Last but not least would be a bearing failure or piston/cylinder problem. Did you clay the top of the piston to get the valve clearance readings? Was there enough lateral movement on the cam after installing the timing gear? Lots of stuff to look at, but I bet when you remove the front cover you'll find some answers. Hope it is something minor and fixable for cheap.
Well got it all the way apart today, the pin was sheared clean off at the cam. the center bolt was tourqed almost to totally breaking off, figure from the gear still spinning without the cam spinning? the gear has about an 1/8 of an inch of clearence to the thrust plate, and the gears seem to be lined up pretty darn close. Did do the clay method for the piston to valve clearence had about .150 on both, should be more then enough? bad cam bearing maybe?:confused: I don't know , any more things to check? thanks, SS
A bit late in this discussion but. . . Does the cam still turn or is it seized in a bearing? If it seized in a bearing it is possibly a bearing problem - oil hole line up on a crank main bearing or on the cam bearing. If it still turns then I am lost. I would expect something to show a red flag somewhere. PaulS
PaulS, honestly haven't got that far, got the timing cover off to check what OldGuy suggested, no luck, that is what i am thinking, but the motor wasn't rebuilt, just changing cams.we got that far the other night, he got discussded, slammed the hood and said we can play with it later!! will try to see tommorrow if the cam will still spin or not. as always , thanks for the Ideas everyone. SS
I hope you're not talking about camshaft end play being 1/8". That's about .115" too much! I think the specification is a minimum of .012", max is about .030" or something like that, but it wasn't 1/8". What about valvesprings? Are they dual or single springs? When breaking in a new cam, the inner spring on a dual spring should be removed. It's kind of a PITA, but your cam/lifters will thank you later on. Is it possible that one of the cam bearings might have been damaged upon removal of the old cam or installation of the new cam? You'll know when you pull the cam out of the block. I have also seen where the fuel pump eccentric will not seat cleanly against the face of the timing gear and the bolt will not tighten up like it should. I've seen that MANY times with Cloyes timing sets and 2 piece eccentrics. One piece eccentrics are thicker and will let seat the eccentric better against the cam gear. IMO it takes a helluva lot of pressure to shear that 1/4" dowel pin and definetly go through that thing with a fine tooth comb. Just some things to think about, FWIW.
Does this setup have a mechincal fuel pump? I know between 71 and 72/73 there was a change to the cam gear one is thicker and one is thinner. If you put the thicker one on the wrong application the pin is not far enough thr to the fuel pump drive lobe but if you don't seat the pin all the way in it will match up but I would guess maybe it could cause this problem cause the pin is not pressed far enough back came loose and then just got sheared?? If this was the case make sure pieces of the pin are not in the engine
Ok, well worst case, any one know how to get a siezed cam bearing off of a cam journal. it's the middle one, not having much luck getting the cam out (go figure). got the motor out last eve. want to try to get it out without killing the cam. what do you all think, the motor was running ok with the old cam, think it was the cam? SS
Boy was that a pain, ended up using a dremel to put a slit in the bearing to get it off of the cam. on the plus side looks like there is nothing wrong with the cam, we put it in a lathe and spun it with a dial indicator, no wobble. dropped the block off at the machine shop, the're going to check the cam bore alignment. hoping was just a knicked bearing. Thanks to all for the assistance, SS
