Mi16 Flattened Lifters

[dynacord 6 1 Cars]

hi,

 

The car is running with kent cams pt1603, CR about 11.5, the head has just been done (ported, etc.) new MLS head gasket and new valves. The limiter is at about 7800rpm and after apprx. 50-60kms heavy use, lost compression on one cylinder. When we took the head off, we saw one failed valve and one lifter has been flattened at the top, very strange.

 

Per specs, these cams should run on the standard springs and hydr. lifters (http://www.kentcams.com/product-details/284/Camshaft/Camshaft/PT1603-Competition-Suitable-for-XU9J4-engine/) (Mechanical lifters are a bit pricey, so wondering if buying new fresh standard ones will be okay? any advice on the reasons for this flattened lifter is appreciated.

 

regards, Alex

 

 

[petert 587]

You've pushed well beyond the limit of hydraulic lifters I'm afraid. Past 7500 they turn to mush. That valve has hit the piston and the lifter is well and truly stuffed. My advice is to regrind the hydraulic cams to a comparable solid grind and fit solid lifters.

[kyepan 291]

after market replacement lifters are s*ite, i had to bin a set as they were not correctly finished and picked up on the lifter bores...

 

Stick with standard refaced ones, or as peter says, for your application, solid, shims, and an oil way restrictor in the head.

 

Sounds like it's going to be an interesting engine once done! mega compression.

[dynacord 6 1 Cars]

thanks for the replies; the car made 161bhp@wheels and 180 and something nm with megasquirt 2.2 ECU

original lifters from opel (c20xe) are exactly the same diameter and size, a local guy could convert them to mech for much less money; i'm not sure if these will be strong enough, though

as a workaround, setting the limiter back to 7300 or maybe 7400 is a solution but i really liked how the car was pulling strong when changing gears on limiter (mi16 standard gearbox with quaife)

 

 

 

 

[welshpug 1,657]

there's no torque or power at 7800, so why rev it that far?!

 

was the cam timing confirmed? if its only making 180 Nm then its probably a bit retarded as my stock 155 engine makes 180 Nm.

[GilesW 41]

Based on that graph:

 

1) No point going past 7k

2) What's up with your torque curve?

 

That to me points to some mis-matched 'go faster' goodies, or some underlying problem with your engine.

[petert 587]

Also, if the valve has it the piston, it will be bent and the guide cracked.

[Rippthrough 98]

Based on that graph:

 

1) No point going past 7k

 

Really? Looks like a great big chunk of horsepower in the next gears-worth of point to me...

[GilesW 41]

Really?

At 6940 it seems to me horsepower is dropping off and the torque dropping through the floor.

If it were my engine I'd just see the extra stress of the higher revs not worth it and invest my time an effort smoothing the torque curve and potentially moving both up the rev range.

 

But perhaps that's just me.

[Rippthrough 98]

Whether it's dropping off or not, you're probably going to drop 2krpm in the next gear, if you can hold on to the redline in that graph that gives a whole lot more power at the wheels when you change...the power looks fairly flat right to 7400, I wouldn't want to change until around then really.

Edited April 1, 2014 by Rippthrough

[petert 587]

PT1603

max lift 10.82mm

advertised duration 290 degrees

@ 0.010" = 282 degrees

@ 0.040" = 241 degrees

 

As I said, just convert it to solids and you can sit up there all day long. If you stay with hydraulic lifters you'll just keep fixing it. I'd regrind the inlet to my 16S400A and the exhaust to 16S420. It has the correct CR for bigger cams so don't hold back. Just make sure the valve springs are up to it.

 

http://www.taylor-eng.com/xu9j4/16v_camgrinds.htm

[dynacord 6 1 Cars]

Hey guys, sorry for the late reply, actually the graph is not quite accurate (the dynamometer is not precise in regard to the rpms of the engine at all). Basically, it's showing with 500rpm or so less (6500 on the graph = 7000 on the engine). The torque curve looks bouncy because of the low air:fuel mixture at lower rpms (14:1, not really sure)

A guy experienced the same problem, and fitted stiffer valve springs and no problems afterward. I also think that mech lifters is the only reasonable way to go.

@petert - which lifters do you recommend? do you think converting standard ones to mechanical will be strong enough? Thanks.

 

regards, Alex

[petert 587]

Converting standard lifters is fine, if you're a competent machinist. From memory 14mm or 9/16" silver steel can be used. Otherwise, just buy a set of Arrow buckets and get some top hat shims. At $7 each, you wouldn't bother making them.

[voldo 1]

What valvesprings were you running? I think it is likely you have pumped the lifter up from valve float and tagged the piston.

[voldo 1]

To expand on my previous post, I believe the valve springs caused this issue, not the lifters.

I cannot see any mechanism that would cause a hydraulic lifter to pump up without the lifter losing contact with the valve - which is the valve springs job. If the lifter had collapsed in operation you would have impact damage on the bucket.