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Car Forum / Driving, Maintenance, Tuning / Maintenance and Repair / July 2006chevy 350 cam question (moves in and out while turning)
Recently my distributor gear stripped. I pulled the motor a part to replace cam, and after replacing the cam I turned the new one by hand with a couple bolts in the end of it, and while turning I noticed the cam walks out about a 1/8 inch like it has a lobe at the back of it. this makes no sense to me and would explain the stripped distributor gear. Is this normal? Is this what makes the lifter rotate? Anyone heard of this? thanks for your replys. > Recently my distributor gear stripped. I pulled the motor a part to > replace cam, and after replacing the cam I turned the new one by hand [quoted text clipped - 3 lines] > gear. Is this normal? Is this what makes the lifter rotate? Anyone > heard of this? thanks for your replys. Does the cam try to walk the opposite direction if you turn it the other way? Is your distributor locked up and/or hard to turn? How about the oil pump? I bet you will find the problem in either the dist. or the oil pump. just pull the dist. and try to turn it by hand, it should turn very easily. if it does, stick a screwdriver down the dist hole and try to turn the oil pump, it should turn fairly easily as well. When reinstalling the distributor, make sure the engine is at #1 TDC on the compression stroke, then turn the rotor so it is pointing at #1 plug wire when it's dropped all the way into the engine. The gear is helically cut so the rotor will rotate as you drop the dist. down, this is normal (and I assume why your cam is trying to walk) once you have everything in place unless you got real lucky the dist. will probably not seat all the way because the oil pump drive will not be lined up, just leave it in there, use your remote starter switch to bump the engine over while keeping light pressure down on the dist. with your hand, it should drop into place before the engine makes a full revolution. check for oil pressure before allowing the engine to start. good luck, nate  Signaturereplace "fly" with "com" to reply. http://home.comcast.net/~njnagel > When reinstalling the distributor, make sure the engine is at #1 TDC on > the compression stroke, then turn the rotor so it is pointing at #1 plug [quoted text clipped - 11 lines] > > nate Two comments: take an old distributor and pop the gear off, and use a 1/2" drill and prime the engine first. Your bearings will thank you. And if you do this on an engine stand without the oil pressure sending unit hooked up at the back of the intake, you can spray 10W30 10 feet in the air. *(you can also buy a tool to do this.)* Do it until oil starts coming out the pushrods. Use a long screwdriver and turn the oil pump "tang" to line up with how you want it to be once you drop the distributor in. If it's all lined up right, it will all "drop right in" - no bumping the starter necessary. This is one of those things that I used to be very green at, but have gotten good at because of the race car. This time we managed to be at 8 degrees of timing and the motor started immediately - no cranking. Not bad, considering we were aiming for 10 degrees. :) Ray > > When reinstalling the distributor, make sure the engine is at #1 TDC on > > the compression stroke, then turn the rotor so it is pointing at #1 plug [quoted text clipped - 30 lines] > > Ray > >ray i have a question, I pulled a dist. from an olds 350 and marked where rotor pointed. dropping it back in i lined it all back up. now i have to turn the housing a lot farther than i think it should be to get it to fire. could i be one tooth off? Thanks Keith. >> >ray i have a question, I pulled a dist. from an olds 350 and marked >> >where rotor pointed. dropping it back in i lined it all back up. now i >> >have to turn the housing a lot farther than i think it should be to get >> >it to fire. could i be one tooth off? Thanks Keith. Yes. Often when you drop it right back in where the marks line up, it fails to mesh with the oil pump until it rotates a few degrees, at which time it falls the remainder of the way down. This can put you off a tooth. HTH, s >>>> ray i have a question, I pulled a dist. from an olds 350 and marked >>>> where rotor pointed. dropping it back in i lined it all back up. now i [quoted text clipped - 4 lines] > time it falls the remainder of the way down. This can put you off a tooth. > HTH, s which isn't the end of the world, because it'll still run. There's three problems with doing it this way... your plug wires may not reach anymore, adjusting the timing is a pain because the vacuum advance hits things, and the next owner will be cursing your name because what should be plug #1 isn't. But yeah, the best thing to do is pull it back out, rotate the oil pump drive back a bit and drop the distributor back in. Ray Look very closely at the distributor shaft for trueness. The cam may be getting a shove from a bent shaft... Signaturejeffcoslacker http://www.automotiveforums.com Ok, thanks for the replys. I didn't have the distributor in yet.. I just removed the pushrods and lifters and the cam turned fine, I put all the lifters back in and same problem, just not as bad....until a couple turns then one lifter stays up and cam turns smooth again. Everything seems ok no burrs etc when I put my finger in the hole. The lifter is a little snug, but I can move it in and out with my finger tips. I think I will just put it all back together and see how it is with oil flowing through everything. I will make sure that pushrod is turning when I start it up. > Ok, thanks for the replys. I didn't have the distributor in yet.. I > just removed the pushrods and lifters and the cam turned fine, I put > all the lifters back in and same problem, just not as bad....until a > couple turns then one lifter stays up and cam turns smooth again. I bet it's not a "roller" camshaft, right? The camshaft lobes are not flat (they're not supposed to be). The faces of the lifters aren't flat (they aren't supposed to be either). The lobes are ground on a bit of an angle, and the lifter faces are slightly convex (they bulge out). It's designed that way so that as the camshaft turns, the lobe rides against the lifter face off-center, making the lifter rotate in the bore, presenting a new surface for the next "lift". This evens out the wear across the lifter face, and greatly reduces the friction on both parts. When you turn it by hand, the lobes/lifters aren't sliding like they will when everything's fully lubed, so the "contact point" will tend to follow the rotation of the lifter, in or out depending on which way you're turning the cam. Here's another description, using highly technical terms: It's the same as using a finger to manually spin a disk on one of those pre-historic devices called "record players". If you move your finger straight across the record, it will turn a bit, and your finger will slide off the edge. If your finger encounters a blob of jam that fell off your toast onto the record, the increased friction will tend to glue your finger to the record, forcing your finger (lobe), and arm (camshaft) to follow the jam blob (contact point) on the record (lifter face) as it rotates towards or away from you. Hmmmm... I'm feeling a bit hungry for some reason. MasterBlaster Wrote: > > Ok, thanks for the replys. I didn't have the distributor in yet.. I > > just removed the pushrods and lifters and the cam turned fine, I put [quoted text clipped - 38 lines] > record (lifter face) as it rotates towards or away from you. > Hmmmm... I'm feeling a bit hungry for some reason. That's a good point. The slight beveling on the parts is supposed to make the cam ride to the rear slightly, but I didn't think about how lack of oil would affect it if you turned it over...I assumed he'd have proper assembly lube on the parts...but I think you are right... That's why I asked if it was a roller cam motor...ANY cam drift is bad news on them... Signaturejeffcoslacker http://www.automotiveforums.com |
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