Help with 253FMM Engine.

ben2go · 05-30-2017, 04:23 PM

Bronze sounds like the valve guides are breaking up because of to much play between the valve stem and the valve guide. The valve will rock in the guide and break it over time. There should almost be no play in there. If there is, oil will leak past the valve and directly onto the back of the valve. The valve seal is there to slow down the oil flow onto the valve stem, not stop it completely, which could also the problem. The valve isn't getting any oil and it's chewing up the guide.

If that engine has hardened valve seats, running lean could cause the valves and seats to run hot and recede into the head quickly. This usually happens over time and why engines require valve adjustments ever so often.

Bending valves is from them hitting the piston. The valve timing is off a tooth or two. It will still run some but kill the valves.

05-30-2017, 04:23 PM	#1
ben2go Join Date: Jun 2011 Posts: 1,335	Bronze sounds like the valve guides are breaking up because of to much play between the valve stem and the valve guide. The valve will rock in the guide and break it over time. There should almost be no play in there. If there is, oil will leak past the valve and directly onto the back of the valve. The valve seal is there to slow down the oil flow onto the valve stem, not stop it completely, which could also the problem. The valve isn't getting any oil and it's chewing up the guide. If that engine has hardened valve seats, running lean could cause the valves and seats to run hot and recede into the head quickly. This usually happens over time and why engines require valve adjustments ever so often. Bending valves is from them hitting the piston. The valve timing is off a tooth or two. It will still run some but kill the valves.
	2