Anybody ever bored a 4g63 to 86.5mm

 

Hope to be useful

https://www.evolutionm.net/forums/ev...bore-safe.html

 

Thanks man, not much response on your thread either.

 

I know 86mm is the largest size recommended by most but has anybody done 86.5mm in a 2.0 evo block?

 

It is not recommended since the cylinder wall would be very thin and likely to crack, you run the same risk with 86mm but it has been done before. You can always sonic check your block for core shift to get an idea how thick your cylinder walls are. On a block .060 overbore i would suggest a full fill as well not something i would drive everyday for a long distance.

 

If nothing else it would be the last time for that block assuming it did work. After 86.5 its straight done. That being said several piston manufacturers have part numbers for 86.5mm pistons. IF you are doing it just to get more displacement I would do a 4G69/G9CS or a 4G64/G4CS with your stock crank.

 

This is what TTP said.


Yes, I have one right now ready to drop in an engine bay complete with Manley I-Beams to 1000hp, JE Pistons, ACL Race bearings, ready to go.
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Correct. 86.5mm is about as large as one would want to go. It should give you close if not right at a 2.1L with standard stroke Evo crank.

 

This is what i'm worried about, what kinda power is safe with 86.5 bore?

 

We are running over 700+whp 800+BHP on 86.5mm pistons.

 

Its hard to say what power is "safe" relative to bore size. Preignition is what will kill it, crack the block and its all over. We have seen blocks crack at 85mm, 85.5mm, solid filled blocks, 86.5-87mm 4G64s. All it takes is preignition, a meth failure of some kind, hydraulicking a piston, and you can (and we have) lose a block at 520whp. We have made 1100+ and been fine and then seen issues at 900.

Is it common, no. Does it happen? Yes.

 

4g63? or 4g64?

 

Maybe we can help you out a little better if you let us know your plans? DD/Track? Boost level? HP Goals? max RPM? Did you mess up your block? Power gains are going to be minimal from a .060 overbore compared to a .020 overbore. Questions for TTP Was there any bore distortion on the .060 overbore(ring sealing)? are these wet blocks? What is the cylinder wall thickness on average with the 86.5 bore 4g63?

 

The question is......Anybody ever used 86.5mm pistons in a 4g63? And if so, at what power level? TTP said they have done this up to 700whp, anybody else? I know most do not recommend this but what makes them say 86mm is as far as u should go? Have they tried 86.5? Do they know how much meat is left on the sleeve? Or are they just guessing?

 

I agree, what is the point of doing this for you? did you seize your motor and already need to get it bored? Or is it something you want to do just to make more power? If it’s about more power and your block is fine, you might want to think about other ways of making that power as the bore size is not going to automatically give you a huge HP gain.