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manually turning engine after rebuild...


vintage_car

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I have the piston to TDC, the camsahft lobes on the first set of valves is pointed down, I bolted everything together and it does turn over manually. THere are a couple times in the rotations that it sticks a little and takes just a little more force to rotate the engine, not much, but I did notice it. What would be causing this, and is anything to be worried about?

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Is it "sticking" in the same spot every time? could it be when the pistons are half way between tdc and bdc? This is when a motor is the hardest to turn since mechanicle advantage is at it's lowest to move the new pistons and rings in un-lubricated boars.

John

Fresh squeezed horseshoes and hand grenades

1665778

 

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Okay I just went out and turned it and it sticks when the exhaust valve on cyl 1 goes totally down, that is when it gets more difficult to turn, once the valve reaches the point of going back up, I hear a small tick and it becomes very easy to turn again. It does this every time. So do I have a valve out of adjustment, or is this a bigger issue?

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You need to recheck your cam timing It sounds like your exhaust valve is hitting your piston, then check/reset your valves. DON'T START YOUR ENGINE UNTILL YOU FIND OUT WHATS GOING ON.

Marty

Don't worry about the world ending today,

Hell it's already tomorrow in Australia.

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it became noticeably harder when two of the pistons were at bdc. another source of the difficult turning could be a new camshaft that has yet to wear into the new rockers that you (might) have installed? also keep in mind that a new engine is tight and it's tolerances are measured in the tenth's of mm's.

mike r

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I will not be starting the engine till this goes away. I haven't done any head work or bottom end work for that matter. I replaced all the gaskets and cleaned it up...not a true rebuild, maybe a refresh is a better word? Either way, the tick doesn't sound like a tick from metal to metal, more like a tick of the valve sticking and unsticking. Adjusting the cam timing, is that meaning taking the front cover off and moving the chain on the upper gear? Is there a specific way to set this? Any marks on the gears or timing chain itself?

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for me it usually gets much tighter when you're trying to turn one of the cam lobes enough to compress a valve spring, which is really tough by hand, but it usually feels like a more gradual tightening. i'd expect you to notice this part for most every cylinder though....

but you took the head off and on, without knowing how the timing marks should align? that sounds kinda bad....so yeah, you gotta make sure the cam timing is right. i usually zip tie the timing chain to the cam sprocket and put some upward tension on it before removing the cam sprocket from the head, and that way you should never lose the position. but you should always double-check.

anyways, there's a big mark on the wheel of the camshaft, just inside from the cam sprocket itself. just need to pull the valve cover to see it. it needs to be in the exact center. then there's a notch on your crank pulley, and it needs to line up with a little needle sticking out from your block (offset from the center a little bit).

line both of those up, spin it a few times, make sure there's no resistance, and make sure the marks still line up.

Bring a Welder

1974 2002, 1965 Datsun L320 truck, 1981 Yamaha XS400, 1983 Yamaha RX50, 1992 Miata Miata drivetrain waiting on a Locost frame, 1999 Toyota Land Cruiser

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Well before I removed the head, I did mark the chain to the cam sprocket, but I didn't make a note of where the pistons were positioned. Is there a way to time it after the engine is installed or does it have to be done with the cam sprocket and crank pully first before turning the car over?

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now i haven't dealt with the crank pulley much on an 02, but I assume the crank sprocket is really small because it needs the reduced gear ratio. if there's no tension kept on the timing chain after you removed the head, the chain could fall off the crank sprocket, and may have now slipped into a different position than when you started.

So, you atleast need to take off the valve cover to check the cam timing and compare with crank pulley. if it is mis-timed, then take off front timing cover, take out tensioner, loosen/remove cam sprocket, and place chain on it so that it is right. shouldn't be a big deal, just those front timing cover bolts are hard to access sometimes if you leave the coolant hose there.

Bring a Welder

1974 2002, 1965 Datsun L320 truck, 1981 Yamaha XS400, 1983 Yamaha RX50, 1992 Miata Miata drivetrain waiting on a Locost frame, 1999 Toyota Land Cruiser

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ohh, then i dunno.. some cars can have a tendency for the crank pulley to wobble off its mark a little, but never heard that its a problem with 02s.

for a lot of DOHC engines you can verify the piston position by dropping the dipstick in the spark plug hole, and watching the vertical displacement. i'm not sure if anyone has figured out how to rig something up to do that with the 02 engine without dropping something inside. maybe a coat hanger or piece of utility wire bent at the right angle could give you a hint, without pulling the head again.

other random thought, be sure your cylinder walls are lubed a little. i cleaned off mine with brake cleaner by accident, so i replaced the natural oils with some 'lucas upper cylinder lubricant.'

i just put it on with my hand, but maybe some could go in the spark plug hole. it'll smoke like hell when you start it, but oh well.

other than that, i suggest a friend come look at it and see if its a normal kind of resistance or not.

Bring a Welder

1974 2002, 1965 Datsun L320 truck, 1981 Yamaha XS400, 1983 Yamaha RX50, 1992 Miata Miata drivetrain waiting on a Locost frame, 1999 Toyota Land Cruiser

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