Valve Clearance Differences Xu9J4/10J4 Vs Ux10J4Rs

[kyepan 291]

A convo between me and a couple of others has ground to a halt, we need a bit of info.

 

 

Why is there so much more valve to piston clearance on the xu9/10 when compared to the xu10j4rs gti-6 engine?

 

 

Piston cutouts on the xu9j4?

More lift as standard on the xu10j4rs?

Inclination of the valves?

 

this comes from a which head is better conversation... Better being less likely to drop a valve, or give oil surge.

 

Cheers

 

J

[welshpug 1,626]

Piston Valve Cutouts, massive difference in them, valve sizes are quite close, RS exhaust is slightly larger.

 

The MI valve sizes are the same as the J4R engine, a larger inlet smaller exhaust than the RS.

 

Valve timing isn't vastly different, milder on the RS, slightly lower peak lift.

[BlueBolt 156]

So to get the best of all worlds, you'd go for a J4R inlet, and RS out?? (regarding the valves)

And use J4R cams??

 

Or am I reading that wrong...

Edited April 30, 2012 by BlueBolt

[welshpug 1,626]

no, the R cams are VERY mild.

[BlueBolt 156]

no, the R cams are VERY mild.

 

Valves the right theory with some aftermarket aggressiveness for the cams?? Lol

[welshpug 1,626]

Depends really how far you're taking the engine build, but staying with the standard valve sizes saves a lot of time and money without sacrificing much if anything power wise.

 

 

Specifically you probably need to talk to Peter T and Sandy.

 

Regarding oil control, have a look at Sandy's EW thread

[petert 554]

Both engines have similar lift @ TDC with the standard cams but the Mi16 cams are significantly bigger.

 

The designers of the RS just need a good kick in the butt. Goodness know what they were thinking. They gave us a stick engine but left little room for aftermarket cam swaps. Another 1mm depth on the pockets would have been fantastic without robbing CR.

 

The Mi16 is well planned in that the allowable lift @ TDC matches the standard CR in terms of suitable cam upgrades.

 

The XU9J4/XU10J4 head is far more reliable, but of course retains too much oil.

Edited April 30, 2012 by petert

[welshpug 1,626]

Another 1mm depth on the pockets would have been fantastic without robbing CR.

 

like this