Valve timing problem on a 450E the valves are hitting the pistons
Hi and welcome to HEF. Have you done any work to engine recently? Could it be assembled with incorrect toming? May also have a damaged or sheared the key on crank or camshaft. I would verify the timing by matching the rockers in no. 4 cylinder to the timing marks and top of piston travel.
Kinda makes it time for an overhaul then.
Thanks Cliffy I work on all kinds of engines but this one has me baffled. I have gone over the timing many times, checking timing marks and sheared keys, used a dial indicator for TDC. With the head off the pistons have light exhaust marks showing, when i turn the motor over by hand, when the piston goes up to exhaust the cylinder, the exhaust valve was open and is slowly closing but the valve is still slightly open and the piston approaching TDC hits the piston. I have to raise the rocker shaft to allow the motor to turn over. The valve lash is 18 thousands . If I increase the gap another 16 thousands the piston clears.this happens on all 4 cylinders.
Deere machine ? What is the piston protrusion measurement ? What is the valve recess measurement ?
As above, measure piston protrusion to spec. Had an mitsubishi engine do that once. Would randomly break rocker arms. Turns out direct injection pistons where put into a pre combustion chamber engine. No valve recess in the pistons.
Sorry, to be clear I was referring to cylinder head valve recess measurement.
Welcome to HEF, Hubby ! Was the head R&R recently ?
Has this engine run since you have owned it? We need the full story on this project. We can't be there looking at it.
This dozer was dropped off for me to check it out. It had a miss I drove it up on blocks and pulled the engine out took off the head and saw how the exhaust valves were leaving marks on the flat part of the pistons, the intake valves have recesses. 4 bent push rods. Checked the lower end , it was nice and tight. all I have to do is advance the cam gear one tooth and the engine rolls over with out hitting the pistons. I was hoping some one would say that John Deere had a problem with their timing marks but I guess not ! Dave
Let me give u my 5 cents of it... as i have no idea on the 450E engine, but i have done others and they´re same arquitecture give it or take it. IDI engines do not have much space in the beetween head chamber and piston crown, due to higher C/R and the volumetry of the prechamber. Usually pistons have flat tops and use recesses for valve exactly to avoid that "kissing" expecially on exaust valves, and depending on how much overlap the manufacturer gave it, u may have to measure it on assembly. Specially N/A engines may have only 2/3 tents of mm clearence for a closed valve. In DI engines is not that problematic as valves very often have space in piston Bowl. If not one can make it as the piston top has a lot of thick materiel. A lot of fellas, do not pay much atention to this and very often they flat out Blocks and Head assys, as much as a 5 tents may be lost easily, cuting 2 tents is usually aceptabe. At the same time many machine shop do not care about valve seat protrusion, cause they say we have to cut the seat lock so no problem( and that is true), what they do not pay atention too is sometimes the Manufacturers sell a seat that has to be finished ACC to valve seat protrusion, and they don´t do it. If u sum .2 from deck clean, .2 from head surfacing, another .2 from valve protrusion, u have .6mm and bang. And i´m not mentioning the HG, cause that would last for a week of discussion. Measure this 3 key points: Piston Protrusion Valve protrusion, or Valve seat height. Check the gasket was /is right thickness That taking acount the cam is the right one, and gear timming is on the right place. Note that Cams Shafts may have diff lobes if that eng has a N/A and TD version.
With the 1 tooth advance, what is the valve to piston clearance? With unbent push rods of course. Oh and how many cam or crank degree's is that one tooth advance?
It won't have been hitting from new . Something has been changed has it a different cam in it . May even be con rods . Different height pistons would do it but thats been covered . Past head gasket problems needing the head and block cleaned up might be enough
Somebody did something to cause this, engines don't leave the factory like this. Some history is needed, someone somewhere knows who worked on it until it was fubar. Joe H
Last seller had a pretty good idea .
Moving the cam gear one tooth is a poor choice to stop those valves from contacting the pistons. Did you straighten one any of those bent push rods and measure the length of them for comparison to new OEM push rods.