6 bolt 4g64 build question

[jasonlee]

I am just a little worried about boring the cylinders and how far to go safely.

would a .040 bore be safe with no worries of cylinder distortion or cracking a cylinder wall?

 

[Black94DSM]

Just have the machine shop bore it untill its round again. Dont over bore if its not needed. If .020 cleans it up, good. More material in there the better. Dont order your pistons untill the maching is done on the block.

 

[jasonlee]

the only reason i ask was i may have found a sweet deal on some pistons for cheap and they are .040

otherwise i would do as you suggested.

 

[Black94DSM]

There must be a reason why you found the sweet deal for a .040 piston. Sorry i dont have an answer for you though about going that large on the bore. Hopefully somebody will chime in. Just seems rather large for our motors.

 

[alexg1323]

mitsubishi offers there pistons in 1mm over. if the designers of the engine deem it ok for their engine than it must not be that bad.

 

[project_tsi]

.40 over is completely safe. I know of a few people running .60 over Wiseco's w/ no problems whatsoever. In fact, I have .40 over Wiseco's in my motor for the same reason you are asking, I got them at a gread deal. .40 over will couse no over heating issues like some have stated, granted your clearances are correct.

I believe .60 over is the max you can go on an overbore before the cylinder walls become to thin.

By going the smallest overbore you can only provides more safety down the road if the block needs to be bored again. But for me, that was not an issue, b/c frankly blocks are cheap and I have a few laying around if I needed to build another.

 

[99gst_racer]

Yes, Dan is correct.

One of my personal customers has built over 65 2.3L strokers since last year and they used .040 over Wiseco's in every build. They've never had any issues with that overbore.

 

[Suparata]

Just have the machine shop bore it untill its round again. Dont over bore if its not needed. If .020 cleans it up, good. More material in there the better. Dont order your pistons untill the maching is done on the block.

That’s a great post and that’s what should be done on MOST engines. However the question was if boring a 4G64 block .040” over is safe if I’m not mistaken. The answer to that is no. 87mm is the most I would go on a 2.4 block.
If the question is regarding a 2.0 block, it is OK but somebody needs to change the thread title.

 

[Injected]

That's a great post and that's what should be done on MOST engines. However the question was if boring a 4G64 block .040" over is safe if I'm not mistaken. The answer to that is no. 87mm is the most I would go on a 2.4 block.
If the question is regarding a 2.0 block, it is OK but somebody needs to change the thread title.

Correct me if I'm wrong, but since the 63 and 64 are the same casting, wouldn't bores of the same size yield the same structural characteristics (either okay or not). The cylinder walls will be the same thickness so long as the bores are equal.

 

[Rick@AP]

Correct me if I'm wrong, but since the 63 and 64 are the same casting, wouldn't bores of the same size yield the same structural characteristics (either okay or not). The cylinder walls will be the same thickness so long as the bores are equal.

Same block material between the two but not the same size pistons. To achive a stock sized 4g64 piston the 4g63 pistons would need to be 60 over.

 

[Injected]

Same block material between the two but not the same size pistons. To achive a stock sized 4g64 piston the 4g63 pistons would need to be 60 over.

This doesn't make sense at all to me. If the blocks are the same, then if the bore is smaller in the 63, the wall thickness would be greater.

 

[Rick@AP]

This doesn't make sense at all to me. If the blocks are the same, then if the bore is smaller in the 63, the wall thickness would be greater.

Reread what I said again slowly, same block MATERIAL. I never said the blocks were the same bore size.

The 4g64 has a larger bore and increased deck height than the 4g63 which would mean less material between the bores to work with.

To make this even simpler, imagine you recieved a 4g63 block and you found out from your machinst that the pistons in the block are 60 over standard. If you needed to bore the cylinder walls out to make them round again then you wouldn't be able to bore it out much larger because of the already thin walls due to the previous installation of the 60 over pistons.

Make sense?

 

[Injected]

Reread what I said again slowly, same block MATERIAL. I never said the blocks were the same bore size.

The 4g64 has a larger bore and increased deck height than the 4g63 which would mean less material between the bores to work with.

To make this even simpler, imagine you recieved a 4g63 block and you found out from your machinst that the pistons in the block are 60 over standard. If you needed to bore the cylinder walls out to make them round again then you wouldn't be able to bore it out much larger because of the already thin walls due to the previous installation of the 60 over pistons.

Make sense?

Not really, because you say that there is more deck height, which has nothing to do with the bore size.

Lets start from scratch...

From the factory, start with two blocks, one to be a 64 and the other to be a 63, they are identical otherwise in every way (which if true). The 63 block will have 6mm taken off of the head and recieve a bore of 85mm with the 88mm crank. The 64 will recieve the 100mm crank and an 86.5mm bore. This boring of the 64 is larger, creating less material between the two. To make up for the difference, the 63 can recieve an overbore and still be the same size as the 64. From this point on, the 64 and 63 have the same amount of material between the cylinders. .60 over on a 63 would be .40 over on a 64 which is the point where you want to stop on each block respectively.

I think we may be saying the same thing, but didn't understand eachother (dang internet).

Some seriously good info in this thread.

 

[Rick@AP]

I think we may be saying the same thing, but didn't understand eachother (dang internet).

! We are.

 

[steel_3d]

Except that a 60 over 4g63 is at 86.5mm bore, which is the standard bore for a 4g64. A 20 over 4g64 would be like an 80 over 4g63 and so on. 0.020" ~ 0.5mm.

I don't think anyone has confirmed whether the effective cylinder wall thickness at the same bore is the same on both blocks. Ie does a 60 over 4g63 have the same cylinder wall thickness as a standard bore 4g64, or is the 4g64 cast thicker to start with?

You also might run into issues with the gasket sealing surface between cylinders.

 

[Injected]

Except that a 60 over 4g63 is at 86.5mm bore, which is the standard bore for a 4g64. A 20 over 4g64 would be like an 80 over 4g63 and so on. 0.020" ~ 0.5mm.

I don't think anyone has confirmed whether the effective cylinder wall thickness at the same bore is the same on both blocks. Ie does a 60 over 4g63 have the same cylinder wall thickness as a standard bore 4g64, or is the 4g64 cast thicker to start with?

You also might run into issues with the gasket sealing surface between cylinders.

Good points. I guess until we have some hardcore measurements, we won't know. However the blocks came out of the same cast so if you bore them starting in the same location (which they are, thus the interchangeable cranks) then the same bore size in mm would yield the same cylinder wall thickness.

 

[jasonlee]

just wanted to give you guys an update on this..

the machining work is pretty much done.... cylinder bore size is now 3.445 (87.5mm) looks to be enough material in between the cylinders for the head gasket... thats .040 oversized on the 4g64. guess were gonna find out if its gonna hold, or crack the cylinder wall. eeeeekk

 

[fourreGsixty3]

Good luck. You should be fine. Personally I would have had it bored to the point where the cyl. walls were round once more, and then get pistons that would work with that. So that way you could still bore it out again if needed, but I guess if you have a handful of block lying around like Dan then it wouldn't really matter.

Dustin

 

[dherron]

You should not have any problem with a .040 over. Most people would bore it out 60 just to get the full 2.3 liter. I personal feel that this is the way to go because these blocks are a dime a dozen. I have 4 sitting at home with cranks if anyone needs them by the way. Not stroker cranks just 88s.

Everyone needs a stroker 6 bolt, the motor the 4g63 should have been.

 

[steel_3d]

You missed the fact that he started from a 4g64 which is already 60 over a 4g63.

You're taking a lot of material out going from 85mm on a stock 4g63 to 87.5 on this 4g64. Let us know how it works out

I would think your cylinder walls will be all warped. Did you measure it with a dial bore gauge? Even my 40 over 4g63 is all over the place. Bolt torques affect the cylinder walls a lot. Don't know if a stock bore would have been more stable, but I would think an 87.5mm bore would be kinda wobbly, if not ready to split