Valves Floating And Rod Knock???

Jonathan Villines · Jul 8, 2017

Hi all... new to site. Have an issue that no one can diagnose. Please help!!

Full PI swap on 97 block.

1st b- did not rebuild lower end, just put heads on.

Canton road race pan
degreed cams
Ford Racing high volume oil pump
Windage tray
admittedly went cheap!!

Put it on track, valves seemed to float around 5000 rpm. 5th lap, rod started knocking and lost all power.

2nd b-

block worked
DSS balanced rods and pistons
stock crank balanced and turned
All clearances within tolerances (on the loose side)
removed and inspected all valves
removed oil/water cooler for standard neck

Put on dyno- same exact issue. Started missing and lost 50 HP at 5500. 3rd pass on dyno- rod knock!

I'm not an expert, but several at the scene and no one can figure it out. Thinking it is a head related issue? Too much pressure to valve train? But then why are the rods not getting oil?

Any ideas???

Jonathan Villines · Jul 8, 2017

More info- Fuel /air rates are textbook and not spark/timing issue.

Sluggie24 · Jul 9, 2017

Was the same crank used both times? Almost sounds like there is a blockage in the oil passage in the crank that feeds that rod bearing if it's the same rod that failed again.

Jonathan Villines · Jul 9, 2017

Sluggie24 said:
Was the same crank used both times? Almost sounds like there is a blockage in the oil passage in the crank that feeds that rod bearing if it's the same rod that failed again.

No. Different crank. The one that is in the current motor was cleaned up and worked at machine shop.

Update though- started car to get off trailer, and no knock at all. Drove 20 miles, flogged it to 4500 rpm a couple times- no issues.

So thinking it is bad lifters/lash adjusters, not rod knock. Apparently the knock is very similar to rods. Took the oil pan off the last motor, and rods look fine. Bad lifters would explain valves not closing, power loss, and detonation (3 broke pistons in last motor). Was told this is more common in the 3 valve.

Will update after changing lifters.

Jonathan Villines · Jul 16, 2017

Ok.. changed lifters with no help. 2nd gear at 5000, valves sounded like they floated, lost power, engine shuttered for about 5 miles and leveled out. Power seemed to return. Valve springs?

Jonathan Villines · Jul 22, 2017

Someone? Anyone?

Valves Floating And Rod Knock???

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