Valve Seat inserts

[8EL]

Originally Posted by Synchro909

My comment, for what it's worth, concerns both a rebuilt engine from a similar builder AND valve seats. First the valve seats. My opinion on what went wrong is that the builder ordered hardened seats that were too big and when they arrived, he fitted them to the block without checking them. Whether he realised what he had done when he came to assemble the engine or not, I don't know but it's hard to believe he didn't. When he installed the valves (standard Model A valves), they almost fell through the seats. They only seated at the extreme outside 1-2 mm. The engine could not be made to idle well (no wonder) and was noisy. The fact that within a few hundred miles, the bearings started to fall apart didn't help. The lady owner was on the ball enough to hear things going wrong in there so removed the engine and took it to another guy I recommended. He made new valves to suit, redid the bearings and a few other "little" things. The original builder has "retired".
My take away from her experience is that "improvements" sometimes are OK, other times .......... I have hard seats on only one of my six running engines ( a Burtz engine).

Probably the most important thing next to cleanliness and proper component selection is maintaining tolerances. You measure and when you think it is right, you measure just once more..... Any machinist or engine builder worth noting knows this and adheres to this.

I would not infer that the valve seats were in any way the problem here, rather the mechanic rebuilding this engine was. Provided this engine had proper lubrication, bearings and "other things" do not just fail on their own either.....do they?