4g61t.org

im trying to find out the measurment from the centre of the piston pin to the top of the piston or what would be called the compression pin height for a 4g61 any help would be apreciated

1.25-1.30" or 31.75-33.02mm. That is as close as I could get by eye balling it. My piston and rod are still intact. But looks around 32mm.

Good luck.

_________________
1985 Mitsubishi Cordia
Build in progress

Biglady, can you measure from the top of the piston to the top of the wrist pin bore? A little math and we can have a little bit better number.

Keep in mind this is a turbo 4G61 piston.

I with my super old micrometers is looks like .8531" or 21.67mm from the top of the pin boss to the top of the piston. This is not accounting for the dish in the center of course. Just the outer rim of the piston.

_________________
1985 Mitsubishi Cordia
Build in progress

Well shit I thought the FSM would list wrist pin diameter. Could you measure that too?

21mm. Same as all the other Sirius 6 bolt motors.

_________________
1985 Mitsubishi Cordia
Build in progress

heaps of thanks for the help im trying to find a forged piston for the 4g61 just getting all the measurments for a start when i find somthing i will let everyone no.

I am not sure if you have one, or know anyone who does, but you can always send a piston to a manufacturer you want to use and have them copy it and set the compression to what you want. As well as the other piston options out there.

_________________
1985 Mitsubishi Cordia
Build in progress

I would love to just have custom set made but time is critical atm so if i can find somthing already of the shelf would suit butter, i just have to work out comp sizes etc now and go from there will keep everyone informed

_________________
Current
95 Mirage AWD - "HoboEvo" 1008 awhp 9.5@165
08 535ix 420awhp
06 C6 Z06- 600whp NA

i did see that but he has no other info to add doesnt no comp heights or final com ratio they are what im leaning towards useing. In his build thread he said he used custom pistons and was running 10.5-1 comp ratios ?that is probaly a little high for me im aiming for around 9.2-1.So i am looking into these pistons aswell as others that run lower than 9-1 to begin with.

Call CP. They should have the motor specs-and can run the numbers through their calculator to see what final compression will be. Also, they may have more than one piston compression option (different pistion cc')

_________________
Current
95 Mirage AWD - "HoboEvo" 1008 awhp 9.5@165
08 535ix 420awhp
06 C6 Z06- 600whp NA

I had Weisco make some 10:1 pistons for me. Big dome on them though, they stick way above deck height. I'm running a 16g at 12psi on 92oct and it runs fine with ecm link.

_________________
'89 Colt GT w/bigger than stock turbo
'91 Talon AWD w/bigger than stock turbo
'05 Dodge diesel w/bigger than stock turbo

Just a update I had cp some up fme flat tops with valve releifs cut in came in at 8.8-1 which is where I want it it will now become a 1.7 ltr I have also purchases a pte5857 ball bearing turbo on the advise off modern performance hope they no what are on about? Anyways will keep you updated