NA 4g63 stroking using 4g69 crankshaft and hyundai theta II GDI (G4KJ) 88 bore piston

[RSS]

Hi there,
I got a SOCH 16 valve 2g carbureted 4g63 (galant 1993). I'm in tight budget and I have not access a lot of parts.
I'm trying to build NA Stroker DOCH 4g63, I got DOCH head and It's ok.
My problem Is about stroking,
I can buy 4g69 crankshaft (there is NO other option for me) and with that crankshaft I have to use low compression height piston. for me, there is just one option, hyundai 2.4 theta II GDI (G4KJ) pistons. these pistons are 88 mm bore, 22 mm pin, 28.5 mm compression height. some guy around me used that pistons and He says It's ok, His engine is running for more than two years. What's your opinion about using 88 mm bore piston in 4g63 2g? Is it safe?
Regards,

 

[Spleen8urLSX]

That would be machining roughly 3mm out of each cylinder on a 4g63 if those pistons are indeed an 88mm bore diameter, I would say the local who told you he did that either has no clue what he actually has or he’s lying as that wouldn’t be a wise thing to do.

 

[bastarddsm]

It'll probably run, but the cylinder is going to be thin. I ran a block turbo at 86mm. I broke the cylinderwall at 700whp. The pieces were around 3mm thick, so going to 88 you'd be down to 2mm thick.

I think the biggest problem is headgasket. IDK where you'll get one that size.

Depending on stroke, look into k20 or k24 pistons.....

 

[RSS]

That would be machining roughly 3mm out of each cylinder on a 4g63 if those pistons are indeed an 88mm bore diameter, I would say the local who told you he did that either has no clue what he actually has or he’s lying as that wouldn’t be a wise thing to do.

You are right but there are aftermarket pistons with 87.5 bore for turbo application

It'll probably run, but the cylinder is going to be thin. I ran a block turbo at 86mm. I broke the cylinderwall at 700whp. The pieces were around 3mm thick, so going to 88 you'd be down to 2mm thick.

I think the biggest problem is headgasket. IDK where you'll get one that size.

Depending on stroke, look into k20 or k24 pistons.....

You built a turbo engine with 700 whp, but mine will be natural aspirated around 200 hp, what do you think about this?
K24 bore is 87.5mm and k20 bore is 89 mm
I can make custom head gasket.

 

[Spleen8urLSX]

You are right but there are aftermarket pistons with 87.5 bore for turbo application

No one is offering 87.5mm bore pistons for the 4g63, if you seen those somewhere they weren’t for a 4g63. The largest offered are 86mm as again, aside from it being a bad idea, you’d be hard pressed to find a machinist willing to take 2.5mm out of the cylinder bore. As far as making a head gasket I’m curious on that one, what do you plan to do cut it out of gasket paper? Also not going to end well. I’m sorry if these aren’t the answers you’re looking for but it sounds like you only want to hear the answers you’re looking for, what you’re looking to do flat out isn’t realistic, you asked for opinions and whys and we gave them.

Also might I add, pistons for these are universal between the turbo and na applications. No reason you can’t use pistons listed for “turbo application” in an na engine if desired.

 

[DSMPT]

Hi there,
I got a SOCH 16 valve 2g carbureted 4g63 (galant 1993). I'm in tight budget and I have not access a lot of parts.
I'm trying to build NA Stroker DOCH 4g63, I got DOCH head and It's ok.
My problem Is about stroking,
I can buy 4g69 crankshaft (there is NO other option for me) and with that crankshaft I have to use low compression height piston. for me, there is just one option, hyundai 2.4 theta II GDI (G4KJ) pistons. these pistons are 88 mm bore, 22 mm pin, 28.5 mm compression height. some guy around me used that pistons and He says It's ok, His engine is running for more than two years. What's your opinion about using 88 mm bore piston in 4g63 2g? Is it safe?
Regards,

Piston size, wrist pin diameter and compression height are not the only things you should consider. There are more things that you should consider and make sure about before buying parts. Besides the cylinder wall thickness, at least about the static compression, piston to valve clearance, clearance between wrist pin boss and rod small end, thrust side of the pistons, etc. P.S. normally GDI pistons have totally different piston top shape.
I don't know how tight your budget is but please keep in mind at least you would probably need some extra money for machining or customizing. I have a similar setup in my 2.3L 2g to your plan, the Hyundai G4KF Genesis coupe turbo pistons with a 4g64 100mm stroke crank and the stock 7 bolt rods in a 4g63 block. 86.00mm is standard for those pistons but I modified the pistons and rods a little bit.

 

[bastarddsm]

You are right but there are aftermarket pistons with 87.5 bore for turbo application


You built a turbo engine with 700 whp, but mine will be natural aspirated around 200 hp, what do you think about this?
K24 bore is 87.5mm and k20 bore is 89 mm
I can make custom head gasket.

You are mistaken. K20 is 86, and k24 is 87. The compression height is taller so you will need to machine piston dome some.

No one is offering 87.5mm bore pistons for the 4g63, if you seen those somewhere they weren’t for a 4g63. The largest offered are 86mm as again, aside from it being a bad idea, you’d be hard pressed to find a machinist willing to take 2.5mm out of the cylinder bore. As far as making a head gasket I’m curious on that one, what do you plan to do cut it out of gasket paper? Also not going to end well. I’m sorry if these aren’t the answers you’re looking for but it sounds like you only want to hear the answers you’re looking for, what you’re looking to do flat out isn’t realistic, you asked for opinions and whys and we gave them.

Also might I add, pistons for these are universal between the turbo and na applications. No reason you can’t use pistons listed for “turbo application” in an na engine if desired.

Never say never. Wiseco had at least 0.080" over at one time, I think there was 0.100" over too. I think you can still get 60 overs marketed for a 63 and not standard 64.