di speed issue

[jimfleming88]

01 gtx di. Just did a top end rebuild at .40 over, have done them with no issues before. I have a hard time getting past 53, 54 mph. Pump is pefect, impeller appears fine, idle and acceleration seems normal. Top end lacks. I did clearance the raves, took about a thin marker line off (hopefully not too much). Any ideas?

[Waterluvr]

Fuel pressure, if your not hitting the magic number the top end is no where to be found. Di pumps are dropping like rocks this season we've had more bad ones this year than the previous ten combined.

[Myself]

Pump, which was probably also the cause of the first top end failure. Possibly just need to change all the fuel filters.

[jimfleming88]

Thanks, I'm going to tee in a gauge and see if pressure holds @wot. The pumps I've had go bad went from working to nothing.

[jimfleming88]

Not sure about top end failure as result of lean condition. Every di I've done it's been front cylinder damage, all of them very similar, damage on top edge of piston around rings. Unlike carb engines or other makes where piston is squeezed due to lack of oil or overheat. Kind of weird. I don't think they receive enough top end lubrication since they're direct injected. I increase the piston to cyl clearance a little and haven't had a rebuild come back yet.