Piston to valve Clearance?

[Halon]

.055" deck height + .051" HG? Dayum.

[gvr4]

Yeah. I'm not sure where the difference comes in... Evo 9's have a different deck height? Rod length? Or wrist pin height? Idk. Not sure if its worth the $600 it saved me over going with a MAP short block either...

[goodhart]

Sounds about right according to your thread here Brandon. Or at least not out of the ordinary for a DSM engine running Evo IX pistons.

http://www.mitsustyle.com/forums/showthread.php?t=32088

[gvr4]

Quench really comes into play on NA engines, but I would think that with the dynamic compression these mitsu engines are seeing, it doesn't have as much of an effect. Especially with dish pistons, there really isn't much quench area on the DSM pistons I've seen, whereas on my Trans Am, almost half the piston is quench area. On my Trans Am, with a -.001 deck and a thin gasket, quench height is at .032". Its details like that that let me run a nice streetable cam and still make the same power as guys running xe284's.


I'm still kinda shaking my head on how little actual information there is out there about these engines. I've been unable to find the stock dish cc on the IX pistons, but I finally did come across the number for milling the heads: 1cc per .007" milled. It would be nice if someone would take the time to publish all the numbers for various configurations, since basically you can mix and match parts from any of them to get OEM parts for any goals you have.

[sleepydsm]

Do you have have gray hair?

[gvr4]

Do you have have gray hair?

No.

Where do you work that your measuring parts down to 10 millionths?

[Halon]

Quench really comes into play on NA engines, but I would think that with the dynamic compression these mitsu engines are seeing, it doesn't have as much of an effect. Especially with dish pistons, there really isn't much quench area on the DSM pistons I've seen, whereas on my Trans Am, almost half the piston is quench area. On my Trans Am, with a -.001 deck and a thin gasket, quench height is at .032". Its details like that that let me run a nice streetable cam and still make the same power as guys running xe284's.


I'm still kinda shaking my head on how little actual information there is out there about these engines. I've been unable to find the stock dish cc on the IX pistons, but I finally did come across the number for milling the heads: 1cc per .007" milled. It would be nice if someone would take the time to publish all the numbers for various configurations, since basically you can mix and match parts from any of them to get OEM parts for any goals you have.

Magnus offers a piston with "an improved" quench design for the 4g63.

Other manufacturers design boosted engines with a more ideal quench band than mitsu does. I'm curious why others care and mitsu doesn't.

Did you measure deck height with the stock piston by chance? My notes were a 6 bolt would be closer to .015, but not sure how accurate that is. If so that means the evo 9 piston sits way lower.

Goodhart, yeah I agree his hg measurement is what id expect according to my post, but the .05 deck height surprised me. But the evo 9 deck height was around that, so I guess that just means these piston are that much shorter maybe. Kinda interesting.

[gvr4]

There could be a number of places that deck height difference could come in. Actual deck height (crank centerline to gasket surface), rod length (doubtful but who knows?), or compression height (wrist pin centerline to quench pad).

I didn't measure my old rotating assembly, but IIRC, it wasn't more than .02" in the hole.

[Pushit2.0]

At what point are you measuring PTV? To get an accurate number the motor would need to assembled and rotated over, I would have to look at my paper work but I think ptv will be closest on the exhaust stroke as the piston comes up on TDC.

The evo9 piston will be a 22mm wrist pin, did you have 1g rods machined for the bigger wrist pin? Or are they evo 9 rods?

If the piston is down the hole a little that's fine. When it sticks out is when you can have issues. Also what size valves, valve springs/ retainers, and what cams/cam gears?

I want to say my race motor was somewhere around .025" ptv on the exhaust side and I would shift at 10,000rpm.

[gvr4]

The rods were machined for the bigger wrist pin.

The reason it's my intake valves that are so close is that the evo valve reliefs are backwards compared to the dsm, so the exhaust is sitting in the intake valve relief, which is fine, but the other valve relief is smaller, so the intake valve can't fit inside its relief. So normally, you're right, the closest point would be when the piston is chasing the exhaust valve closed on the exhaust stroke.

What's your valvetrain like in your race motor? I'm running all stock stuff, so I think I'll keep my revs a little lower with that tight of clearance.