Engine rattle noise under load

[Tony Clifton]

so im looking at this spark plug hole, and the 1/2" drill bit required to drill it out to tap to 14mm for a helicoil repair, and theres just no way thats happening. would need a drill press to get that drilled straight and square. crazy how you can just trash a head completely by stripping some threads.

Yeah, there is no way I would contemplate coming at the cylinder head with a drill and a big ol' bit...that's an LOL right there

At the risk of sounding like TimeSert's marketing guy, there is no drill bit required with their system for the spark plug thread. You simply start a standard tap which drags the larger tap behind it as you continue to screw it in. And then the tool that cuts the insert seat and a new spark plug seat fits around the tap, keeps everything perpendicular and true to the world. Something to consider

Even a hamfisted idiot like me had success and it has good instructions, for what it's worth

 

[tmross]

Doing a proper valve job is an important part of getting the engine to run its best. Take off too much material, cutting that new valve seat, and the valve is sunk deeper into the head. Sunken valves will adversely affect airflow, also the resulting extra combustion chamber volume is going to lower the compression ratio by a fraction of a point. Skim the head in order to reduce the combustion chamber volume and that slightly retards the valve timing. Retarded valve timing means the intake is closing later, at the cost of low end cylinder pressure and lower torque.

I looked closely at the valve seats again, comparing to old head, and now im thinking maybe the angles ok. But your comment on sunken valves lowering compression has me wondering if thats whats causing my low compression.

Any thoughts on this? You can see valve on right, outer ridge around wide angle shows how much material was shaved off. Could that explain 130 psi compression?

 

[EzPete]

Do you have any marking blue? Just thinking that you could use that to check the width of the contact surface between valve and seat.

Just mathematically, that valve would have to sink pretty far to create a +10% variance in compression. It would show up trying to adjust them as the valve stem would be longer.

 

[ericfreeman]

Something looks off with that seat towards the right side of the pic. Maybe just an illusion but it appears the 45° part of the seat gets larger. Or my old eyes are playing tricks again!